A
HISTORY OF SCIENCE
BY
HENRY SMITH WILLIAMS, M.D., LL.D.
ASSISTED BY
EDWARD H. WILLIAMS, M.D.

IN FIVE VOLUMES
VOLUME II.




CONTENTS

BOOK II

CHAPTER I. SCIENCE IN THE DARK AGE

CHAPTER II. MEDIAEVAL SCIENCE AMONG THE ARABIANS

CHAPTER III. MEDIAEVAL SCIENCE IN THE WEST

CHAPTER IV. THE NEW COSMOLOGY--COPERNICUS TO KEPLER AND GALILEO

CHAPTER V. GALILEO AND THE NEW PHYSICS

CHAPTER VI. TWO PSEUDO-SCIENCES--ALCHEMY AND ASTROLOGY

CHAPTER VII. FROM PARACELSUS TO HARVEY

CHAPTER VIII. MEDICINE IN THE SIXTEENTH AND SEVENTEENTH CENTURIES

CHAPTER IX. PHILOSOPHER-SCIENTISTS AND NEW INSTITUTIONS OF
LEARNING

CHAPTER X. THE SUCCESSORS OF GALILEO IN PHYSICAL SCIENCE

CHAPTER XI. NEWTON AND THE COMPOSITION OF LIGHT

CHAPTER XII. NEWTON AND THE LAW OF GRAVITATION

CHAPTER XIII. INSTRUMENTS OF PRECISION IN THE AGE OF NEWTON

CHAPTER XIV. PROGRESS IN ELECTRICITY FROM GILBERT AND VON
GUERICKE TO FRANKLIN

CHAPTER XV. NATURAL HISTORY TO THE TIME OF LINNAEUS

APPENDIX



A HISTORY OF SCIENCE

BOOK II

THE BEGINNINGS OF MODERN SCIENCE

The studies of the present book cover the progress of science
from the close of the Roman period in the fifth century A.D. to
about the middle of the eighteenth century. In tracing the course
of events through so long a period, a difficulty becomes
prominent which everywhere besets the historian in less degree--a
difficulty due to the conflict between the strictly chronological
and the topical method of treatment. We must hold as closely as
possible to the actual sequence of events, since, as already
pointed out, one discovery leads on to another. But, on the other
hand, progressive steps are taken contemporaneously in the
various fields of science, and if we were to attempt to introduce
these in strict chronological order we should lose all sense of
topical continuity.

Our method has been to adopt a compromise, following the course
of a single science in each great epoch to a convenient
stopping-point, and then turning back to bring forward the story
of another science. Thus, for example, we tell the story of
Copernicus and Galileo, bringing the record of cosmical and
mechanical progress down to about the middle of the seventeenth
century, before turning back to take up the physiological
progress of the fifteenth and sixteenth centuries. Once the
latter stream is entered, however, we follow it without
interruption to the time of Harvey and his contemporaries in the
middle of the seventeenth century, where we leave it to return to
the field of mechanics as exploited by the successors of Galileo,
who were also the predecessors and contemporaries of Newton.

In general, it will aid the reader to recall that, so far as
possible, we hold always to the same sequences of topical
treatment of contemporary events; as a rule we treat first the
cosmical, then the physical, then the biological sciences. The
same order of treatment will be held to in succeeding volumes.

Several of the very greatest of scientific generalizations are
developed in the period covered by the present book: for example,
the Copernican theory of the solar system, the true doctrine of
planetary motions, the laws of motion, the theory of the
circulation of the blood, and the Newtonian theory of
gravitation. The labors of the investigators of the early decades
of the eighteenth century, terminating with Franklin's discovery
of the nature of lightning and with the Linnaean classification
of plants and animals, bring us to the close of our second great
epoch; or, to put it otherwise, to the threshold of the modern
period,


I. SCIENCE IN THE DARK AGE

An obvious distinction between the classical and mediaeval epochs
may be found in the fact that the former produced, whereas the
latter failed to produce, a few great thinkers in each generation
who were imbued with that scepticism which is the foundation of
the investigating spirit; who thought for themselves and supplied
more or less rational explanations of observed phenomena. Could
we eliminate the work of some score or so of classical observers
and thinkers, the classical epoch would seem as much a dark age
as does the epoch that succeeded it.

But immediately we are met with the question: Why do no great
original investigators appear during all these later centuries?
We have already offered a part explanation in the fact that the
borders of civilization, where racial mingling naturally took
place, were peopled with semi-barbarians. But we must not forget
that in the centres of civilization all along there were many men
of powerful intellect. Indeed, it would violate the principle of
historical continuity to suppose that there was any sudden change
in the level of mentality of the Roman world at the close of the
classical period. We must assume, then, that the direction in
which the great minds turned was for some reason changed. Newton
is said to have alleged that he made his discoveries by
"intending" his mind in a certain direction continuously. It is
probable that the same explanation may be given of almost every
great scientific discovery. Anaxagoras could not have thought out
the theory of the moon's phases; Aristarchus could not have found
out the true mechanism of the solar system; Eratosthenes could
not have developed his plan for measuring the earth, had not each
of these investigators "intended" his mind persistently towards
the problems in question.

Nor can we doubt that men lived in every generation of the dark
age who were capable of creative thought in the field of science,
bad they chosen similarly to "intend" their minds in the right
direction. The difficulty was that they did not so choose. Their
minds had a quite different bent. They were under the spell of
different ideals; all their mental efforts were directed into
different channels. What these different channels were cannot be
in doubt--they were the channels of oriental ecclesiasticism. One
all-significant fact speaks volumes here. It is the fact that, as
Professor Robinson[1] points out, from the time of Boethius (died
524 or 525 A.D.) to that of Dante (1265-1321 A.D.) there was not
a single writer of renown in western Europe who was not a
professional churchman. All the learning of the time, then,
centred in the priesthood. We know that the same condition of
things pertained in Egypt, when science became static there. But,
contrariwise, we have seen that in Greece and early Rome the
scientific workers were largely physicians or professional
teachers; there was scarcely a professional theologian among
them.

Similarly, as we shall see in the Arabic world, where alone there
was progress in the mediaeval epoch, the learned men were, for
the most part, physicians. Now the meaning of this must be
self-evident. The physician naturally "intends" his mind towards
the practicalities. His professional studies tend to make him an
investigator of the operations of nature. He is usually a
sceptic, with a spontaneous interest in practical science. But
the theologian "intends" his mind away from practicalities and
towards mysticism. He is a professional believer in the
supernatural; he discounts the value of merely "natural"
phenomena. His whole attitude of mind is unscientific; the
fundamental tenets of his faith are based on alleged occurrences
which inductive science cannot admit--namely, miracles. And so
the minds "intended" towards the supernatural achieved only the
hazy mysticism of mediaeval thought. Instead of investigating
natural laws, they paid heed (as, for example, Thomas Aquinas
does in his Summa Theologia) to the "acts of angels," the
"speaking of angels," the "subordination of angels," the "deeds
of guardian angels," and the like. They disputed such important
questions as, How many angels can stand upon the point of a
needle? They argued pro and con as to whether Christ were coeval
with God, or whether he had been merely created "in the
beginning," perhaps ages before the creation of the world. How
could it be expected that science should flourish when the
greatest minds of the age could concern themselves with problems
such as these?

Despite our preconceptions or prejudices, there can be but one
answer to that question. Oriental superstition cast its blight
upon the fair field of science, whatever compensation it may or
may not have brought in other fields. But we must be on our guard
lest we overestimate or incorrectly estimate this influence.
Posterity, in glancing backward, is always prone to stamp any
given age of the past with one idea, and to desire to
characterize it with a single phrase; whereas in reality all ages
are diversified, and any generalization regarding an epoch is
sure to do that epoch something less or something more than
justice. We may be sure, then, that the ideal of ecclesiasticism
is not solely responsible for the scientific stasis of the dark
age. Indeed, there was another influence of a totally different
character that is too patent to be overlooked--the influence,
namely, of the economic condition of western Europe during this
period. As I have elsewhere pointed out,[2] Italy, the centre of
western civilization, was at this time impoverished, and hence
could not provide the monetary stimulus so essential to artistic
and scientific no less than to material progress. There were no
patrons of science and literature such as the Ptolemies of that
elder Alexandrian day. There were no great libraries; no colleges
to supply opportunities and afford stimuli to the rising
generation. Worst of all, it became increasingly difficult to
secure books.

This phase of the subject is often overlooked. Yet a moment's
consideration will show its importance. How should we fare to-day
if no new scientific books were being produced, and if the
records of former generations were destroyed? That is what
actually happened in Europe during the Middle Ages. At an earlier
day books were made and distributed much more abundantly than is
sometimes supposed. Bookmaking had, indeed, been an important
profession in Rome, the actual makers of books being slaves who
worked under the direction of a publisher. It was through the
efforts of these workers that the classical works in Greek and
Latin were multiplied and disseminated. Unfortunately the climate
of Europe does not conduce to the indefinite preservation of a
book; hence very few remnants of classical works have come down
to us in the original from a remote period. The rare exceptions
are certain papyrus fragments, found in Egypt, some of which are
Greek manuscripts dating from the third century B.C. Even from
these sources the output is meagre; and the only other repository
of classical books is a single room in the buried city of
Herculaneum, which contained several hundred manuscripts, mostly
in a charred condition, a considerable number of which, however,
have been unrolled and found more or less legible. This library
in the buried city was chiefly made up of philosophical works,
some of which were quite unknown to the modern world until
discovered there.

But this find, interesting as it was from an archaeological
stand-point, had no very important bearing on our knowledge of
the literature of antiquity. Our chief dependence for our
knowledge of that literature must still be placed in such copies
of books as were made in the successive generations.
Comparatively few of the extant manuscripts are older than the
tenth century of our era. It requires but a momentary
consideration of the conditions under which ancient books were
produced to realize how slow and difficult the process was before
the invention of printing. The taste of the book-buying public
demanded a clearly written text, and in the Middle Ages it became
customary to produce a richly ornamented text as well. The script
employed being the prototype of the modern printed text, it will
be obvious that a scribe could produce but a few pages at best in
a day. A large work would therefore require the labor of a scribe
for many months or even for several years. We may assume, then,
that it would be a very flourishing publisher who could produce a
hundred volumes all told per annum; and probably there were not
many publishers at any given time, even in the period of Rome's
greatest glory, who had anything like this output.

As there was a large number of authors in every generation of the
classical period, it follows that most of these authors must have
been obliged to content themselves with editions numbering very
few copies; and it goes without saying that the greater number of
books were never reproduced in what might be called a second
edition. Even books that retained their popularity for several
generations would presently fail to arouse sufficient interest to
be copied; and in due course such works would pass out of
existence altogether. Doubtless many hundreds of books were thus
lost before the close of the classical period, the names of their
authors being quite forgotten, or preserved only through a chance
reference; and of course the work of elimination went on much
more rapidly during the Middle Ages, when the interest in
classical literature sank to so low an ebb in the West. Such
collections of references and quotations as the Greek Anthology
and the famous anthologies of Stobaeus and Athanasius and
Eusebius give us glimpses of a host of writers--more than seven
hundred are quoted by Stobaeus--a very large proportion of whom
are quite unknown except through these brief excerpts from their
lost works.

Quite naturally the scientific works suffered at least as largely
as any others in an age given over to ecclesiastical dreamings.
Yet in some regards there is matter for surprise as to the works
preserved. Thus, as we have seen, the very extensive works of
Aristotle on natural history, and the equally extensive natural
history of Pliny, which were preserved throughout this period,
and are still extant, make up relatively bulky volumes. These
works seem to have interested the monks of the Middle Ages, while
many much more important scientific books were allowed to perish.
A considerable bulk of scientific literature was also preserved
through the curious channels of Arabic and Armenian translations.
Reference has already been made to the Almagest of Ptolemy,
which, as we have seen, was translated into Arabic, and which was
at a later day brought by the Arabs into western Europe and (at
the instance of Frederick II of Sicily) translated out of their
language into mediaeval Latin.

It remains to inquire, however, through what channels the Greek
works reached the Arabs themselves. To gain an answer to this
question we must follow the stream of history from its Roman
course eastward to the new seat of the Roman empire in Byzantium.
Here civilization centred from about the fifth century A.D., and
here the European came in contact with the civilization of the
Syrians, the Persians, the Armenians, and finally of the Arabs.
The Byzantines themselves, unlike the inhabitants of western
Europe, did not ignore the literature of old Greece; the Greek
language became the regular speech of the Byzantine people, and
their writers made a strenuous effort to perpetuate the idiom and
style of the classical period. Naturally they also made
transcriptions of the classical authors, and thus a great mass of
literature was preserved, while the corresponding works were
quite forgotten in western Europe.

Meantime many of these works were translated into Syriac,
Armenian, and Persian, and when later on the Byzantine
civilization degenerated, many works that were no longer to be
had in the Greek originals continued to be widely circulated in
Syriac, Persian, Armenian, and, ultimately, in Arabic
translations. When the Arabs started out in their conquests,
which carried them through Egypt and along the southern coast of
the Mediterranean, until they finally invaded Europe from the
west by way of Gibraltar, they carried with them their
translations of many a Greek classical author, who was introduced
anew to the western world through this strange channel.

We are told, for example, that Averrhoes, the famous commentator
of Aristotle, who lived in Spain in the twelfth century, did not
know a word of Greek and was obliged to gain his knowledge of the
master through a Syriac translation; or, as others alleged
(denying that he knew even Syriac), through an Arabic version
translated from the Syriac. We know, too, that the famous
chronology of Eusebius was preserved through an Armenian
translation; and reference has more than once been made to the
Arabic translation of Ptolemy's great work, to which we still
apply its Arabic title of Almagest.

The familiar story that when the Arabs invaded Egypt they burned
the Alexandrian library is now regarded as an invention of later
times. It seems much more probable that the library bad been
largely scattered before the coming of the Moslems. Indeed, it
has even been suggested that the Christians of an earlier day
removed the records of pagan thought. Be that as it may, the
famous Alexandrian library had disappeared long before the
revival of interest in classical learning. Meanwhile, as we have
said, the Arabs, far from destroying the western literature, were
its chief preservers. Partly at least because of their regard for
the records of the creative work of earlier generations of alien
peoples, the Arabs were enabled to outstrip their contemporaries.
For it cannot be in doubt that, during that long stretch of time
when the western world was ignoring science altogether or at most
contenting itself with the casual reading of Aristotle and Pliny,
the Arabs had the unique distinction of attempting original
investigations in science. To them were due all important
progressive steps which were made in any scientific field
whatever for about a thousand years after the time of Ptolemy and
Galen. The progress made even by the Arabs during this long
period seems meagre enough, yet it has some significant features.
These will now demand our attention.



II. MEDIAEVAL SCIENCE AMONG THE ARABIANS

The successors of Mohammed showed themselves curiously receptive
of the ideas of the western people whom they conquered. They came
in contact with the Greeks in western Asia and in Egypt, and, as
has been said, became their virtual successors in carrying
forward the torch of learning. It must not be inferred, however,
that the Arabian scholars, as a class, were comparable to their
predecessors in creative genius. On the contrary, they retained
much of the conservative oriental spirit. They were under the
spell of tradition, and, in the main, what they accepted from the
Greeks they regarded as almost final in its teaching. There were,
however, a few notable exceptions among their men of science, and
to these must be ascribed several discoveries of some importance.

The chief subjects that excited the interest and exercised the
ingenuity of the Arabian scholars were astronomy, mathematics,
and medicine. The practical phases of all these subjects were
given particular attention. Thus it is well known that our
so-called Arabian numerals date from this period. The
revolutionary effect of these characters, as applied to practical
mathematics, can hardly be overestimated; but it is generally
considered, and in fact was admitted by the Arabs themselves,
that these numerals were really borrowed from the Hindoos, with
whom the Arabs came in contact on the east. Certain of the Hindoo
alphabets, notably that of the Battaks of Sumatra, give us clews
to the originals of the numerals. It does not seem certain,
however, that the Hindoos employed these characters according to
the decimal system, which is the prime element of their
importance. Knowledge is not forthcoming as to just when or by
whom such application was made. If this was an Arabic innovation,
it was perhaps the most important one with which that nation is
to be credited. Another mathematical improvement was the
introduction into trigonometry of the sine--the half-chord of the
double arc--instead of the chord of the arc itself which the
Greek astronomers had employed. This improvement was due to the
famous Albategnius, whose work in other fields we shall examine
in a moment.

Another evidence of practicality was shown in the Arabian method
of attempting to advance upon Eratosthenes' measurement of the
earth. Instead of trusting to the measurement of angles, the
Arabs decided to measure directly a degree of the earth's
surface--or rather two degrees. Selecting a level plain in
Mesopotamia for the experiment, one party of the surveyors
progressed northward, another party southward, from a given point
to the distance of one degree of arc, as determined by
astronomical observations. The result found was fifty-six miles
for the northern degree, and fifty-six and two-third miles for
the southern. Unfortunately, we do not know the precise length of
the mile in question, and therefore cannot be assured as to the
accuracy of the measurement. It is interesting to note, however,
that the two degrees were found of unequal lengths, suggesting
that the earth is not a perfect sphere--a suggestion the validity
of which was not to be put to the test of conclusive measurements
until about the close of the eighteenth century. The Arab
measurement was made in the time of Caliph Abdallah al-Mamun, the
son of the famous Harun-al-Rashid. Both father and son were
famous for their interest in science. Harun-al-Rashid was, it
will be recalled, the friend of Charlemagne. It is said that he
sent that ruler, as a token of friendship, a marvellous clock
which let fall a metal ball to mark the hours. This mechanism,
which is alleged to have excited great wonder in the West,
furnishes yet another instance of Arabian practicality.

Perhaps the greatest of the Arabian astronomers was Mohammed ben
Jabir Albategnius, or El-batani, who was born at Batan, in
Mesopotamia, about the year 850 A.D., and died in 929.
Albategnius was a student of the Ptolemaic astronomy, but he was
also a practical observer. He made the important discovery of the
motion of the solar apogee. That is to say, he found that the
position of the sun among the stars, at the time of its greatest
distance from the earth, was not what it had been in the time of
Ptolemy. The Greek astronomer placed the sun in longitude 65
degrees, but Albategnius found it in longitude 82 degrees, a
distance too great to be accounted for by inaccuracy of
measurement. The modern inference from this observation is that
the solar system is moving through space; but of course this
inference could not well be drawn while the earth was regarded as
the fixed centre of the universe.

In the eleventh century another Arabian discoverer, Arzachel,
observing the sun to be less advanced than Albategnius had found
it, inferred incorrectly that the sun had receded in the mean
time. The modern explanation of this observation is that the
measurement of Albategnius was somewhat in error, since we know
that the sun's motion is steadily progressive. Arzachel, however,
accepting the measurement of his predecessor, drew the false
inference of an oscillatory motion of the stars, the idea of the
motion of the solar system not being permissible. This assumed
phenomenon, which really has no existence in point of fact, was
named the "trepidation of the fixed stars," and was for centuries
accepted as an actual phenomenon. Arzachel explained this
supposed phenomenon by assuming that the equinoctial points, or
the points of intersection of the equator and the ecliptic,
revolve in circles of eight degrees' radius. The first points of
Aries and Libra were supposed to describe the circumference of
these circles in about eight hundred years. All of which
illustrates how a difficult and false explanation may take the
place of a simple and correct one. The observations of later
generations have shown conclusively that the sun's shift of
position is regularly progressive, hence that there is no
"trepidation" of the stars and no revolution of the equinoctial
points.

If the Arabs were wrong as regards this supposed motion of the
fixed stars, they made at least one correct observation as to the
inequality of motion of the moon. Two inequalities of the motion
of this body were already known. A third, called the moon's
variation, was discovered by an Arabian astronomer who lived at
Cairo and observed at Bagdad in 975, and who bore the formidable
name of Mohammed Aboul Wefaal-Bouzdjani. The inequality of motion
in question, in virtue of which the moon moves quickest when she
is at new or full, and slowest at the first and third quarter,
was rediscovered by Tycho Brahe six centuries later; a fact which
in itself evidences the neglect of the Arabian astronomer's
discovery by his immediate successors.

In the ninth and tenth centuries the Arabian city of Cordova, in
Spain, was another important centre of scientific influence.
There was a library of several hundred thousand volumes here, and
a college where mathematics and astronomy were taught. Granada,
Toledo, and Salamanca were also important centres, to which
students flocked from western Europe. It was the proximity of
these Arabian centres that stimulated the scientific interests of
Alfonso X. of Castile, at whose instance the celebrated Alfonsine
tables were constructed. A familiar story records that Alfonso,
pondering the complications of the Ptolemaic cycles and
epicycles, was led to remark that, had he been consulted at the
time of creation, he could have suggested a much better and
simpler plan for the universe. Some centuries were to elapse
before Copernicus was to show that it was not the plan of the
universe, but man's interpretation of it, that was at fault.

Another royal personage who came under Arabian influence was
Frederick II. of Sicily--the "Wonder of the World," as he was
called by his contemporaries. The Almagest of Ptolemy was
translated into Latin at his instance, being introduced to the
Western world through this curious channel. At this time it
became quite usual for the Italian and Spanish scholars to
understand Arabic although they were totally ignorant of Greek.

In the field of physical science one of the most important of the
Arabian scientists was Alhazen. His work, published about the
year 1100 A.D., had great celebrity throughout the mediaeval
period. The original investigations of Alhazen had to do largely
with optics. He made particular studies of the eye itself, and
the names given by him to various parts of the eye, as the
vitreous humor, the cornea, and the retina, are still retained by
anatomists. It is known that Ptolemy had studied the refraction
of light, and that he, in common with his immediate predecessors,
was aware that atmospheric refraction affects the apparent
position of stars near the horizon. Alhazen carried forward these
studies, and was led through them to make the first recorded
scientific estimate of the phenomena of twilight and of the
height of the atmosphere. The persistence of a glow in the
atmosphere after the sun has disappeared beneath the horizon is
so familiar a phenomenon that the ancient philosophers seem not
to have thought of it as requiring an explanation. Yet a moment's
consideration makes it clear that, if light travels in straight
lines and the rays of the sun were in no wise deflected, the
complete darkness of night should instantly succeed to day when
the sun passes below the horizon. That this sudden change does
not occur, Alhazen explained as due to the reflection of light by
the earth's atmosphere.

Alhazen appears to have conceived the atmosphere as a sharply
defined layer, and, assuming that twilight continues only so long
as rays of the sun reflected from the outer surface of this layer
can reach the spectator at any given point, he hit upon a means
of measurement that seemed to solve the hitherto inscrutable
problem as to the atmospheric depth. Like the measurements of
Aristarchus and Eratosthenes, this calculation of Alhazen is
simple enough in theory. Its defect consists largely in the
difficulty of fixing its terms with precision, combined with the
further fact that the rays of the sun, in taking the slanting
course through the earth's atmosphere, are really deflected from
a straight line in virtue of the constantly increasing density of
the air near the earth's surface. Alhazen must have been aware of
this latter fact, since it was known to the later Alexandrian
astronomers, but he takes no account of it in the present
measurement. The diagram will make the method of Alhazen clear.

His important premises are two: first, the well-recognized fact
that, when light is reflected from any surface, the angle of
incidence is equal to the angle of reflection; and, second, the
much more doubtful observation that twilight continues until such
time as the sun, according to a simple calculation, is nineteen
degrees below the horizon. Referring to the diagram, let the
inner circle represent the earth's surface, the outer circle the
limits of the atmosphere, C being the earth's centre, and RR
radii of the earth. Then the observer at the point A will
continue to receive the reflected rays of the sun until that body
reaches the point S, which is, according to the hypothesis,
nineteen degrees below the horizon line of the observer at A.
This horizon line, being represented by AH, and the sun's ray by
SM, the angle HMS is an angle of nineteen degrees. The
complementary angle SMA is, obviously, an angle of (180-19) one
hundred and sixty-one degrees. But since M is the reflecting
surface and the angle of incidence equals the angle of
reflection, the angle AMC is an angle of one-half of one hundred
and sixty-one degrees, or eighty degrees and thirty minutes. Now
this angle AMC, being known, the right-angled triangle MAC is
easily resolved, since the side AC of that triangle, being the
radius of the earth, is a known dimension. Resolution of this
triangle gives us the length of the hypotenuse MC, and the
difference between this and the radius (AC), or CD, is obviously
the height of the atmosphere (h), which was the measurement
desired. According to the calculation of Alhazen, this h, or the
height of the atmosphere, represents from twenty to thirty miles.
The modern computation extends this to about fifty miles. But,
considering the various ambiguities that necessarily attended the
experiment, the result was a remarkably close approximation to
the truth.

Turning from physics to chemistry, we find as perhaps the
greatest Arabian name that of Geber, who taught in the College of
Seville in the first half of the eighth century. The most
important researches of this really remarkable experimenter had
to do with the acids. The ancient world had had no knowledge of
any acid more powerful than acetic. Geber, however, vastly
increased the possibilities of chemical experiment by the
discovery of sulphuric, nitric, and nitromuriatic acids. He made
use also of the processes of sublimation and filtration, and his
works describe the water bath and the chemical oven. Among the
important chemicals which he first differentiated is oxide of
mercury, and his studies of sulphur in its various compounds have
peculiar interest. In particular is this true of his observation
that, tinder certain conditions of oxidation, the weight of a
metal was lessened.

From the record of these studies in the fields of astronomy,
physics, and chemistry, we turn to a somewhat extended survey of
the Arabian advances in the field of medicine.


ARABIAN MEDICINE

The influence of Arabian physicians rested chiefly upon their use
of drugs rather than upon anatomical knowledge. Like the
mediaeval Christians, they looked with horror on dissection of
the human body; yet there were always among them investigators
who turned constantly to nature herself for hidden truths, and
were ready to uphold the superiority of actual observation to
mere reading. Thus the physician Abd el-Letif, while in Egypt,
made careful studies of a mound of bones containing more than
twenty thousand skeletons. While examining these bones he
discovered that the lower jaw consists of a single bone, not of
two, as had been taught by Galen. He also discovered several
other important mistakes in Galenic anatomy, and was so impressed
with his discoveries that he contemplated writing a work on
anatomy which should correct the great classical authority's
mistakes.

It was the Arabs who invented the apothecary, and their
pharmacopoeia, issued from the hospital at Gondisapor, and
elaborated from time to time, formed the basis for Western
pharmacopoeias. Just how many drugs originated with them, and how
many were borrowed from the Hindoos, Jews, Syrians, and Persians,
cannot be determined. It is certain, however, that through them
various new and useful drugs, such as senna, aconite, rhubarb,
camphor, and mercury, were handed down through the Middle Ages,
and that they are responsible for the introduction of alcohol in
the field of therapeutics.

In mediaeval Europe, Arabian science came to be regarded with
superstitious awe, and the works of certain Arabian physicians
were exalted to a position above all the ancient writers. In
modern times, however, there has been a reaction and a tendency
to depreciation of their work. By some they are held to be mere
copyists or translators of Greek books, and in no sense original
investigators in medicine. Yet there can be little doubt that
while the Arabians did copy and translate freely, they also
originated and added considerably to medical knowledge. It is
certain that in the time when Christian monarchs in western
Europe were paying little attention to science or education, the
caliphs and vizirs were encouraging physicians and philosophers,
building schools, and erecting libraries and hospitals. They made
at least a creditable effort to uphold and advance upon the
scientific standards of an earlier age.

The first distinguished Arabian physician was Harets ben Kaladah,
who received his education in the Nestonian school at Gondisapor,
about the beginning of the seventh century. Notwithstanding the
fact that Harets was a Christian, he was chosen by Mohammed as
his chief medical adviser, and recommended as such to his
successor, the Caliph Abu Bekr. Thus, at the very outset, the
science of medicine was divorced from religion among the
Arabians; for if the prophet himself could employ the services of
an unbeliever, surely others might follow his example. And that
this example was followed is shown in the fact that many
Christian physicians were raised to honorable positions by
succeeding generations of Arabian monarchs. This broad-minded
view of medicine taken by the Arabs undoubtedly assisted as much
as any one single factor in upbuilding the science, just as the
narrow and superstitious view taken by Western nations helped to
destroy it.

The education of the Arabians made it natural for them to
associate medicine with the natural sciences, rather than with
religion. An Arabian savant was supposed to be equally well
educated in philosophy, jurisprudence, theology, mathematics, and
medicine, and to practise law, theology, and medicine with equal
skill upon occasion. It is easy to understand, therefore, why
these religious fanatics were willing to employ unbelieving
physicians, and their physicians themselves to turn to the
scientific works of Hippocrates and Galen for medical
instruction, rather than to religious works. Even Mohammed
himself professed some knowledge of medicine, and often relied
upon this knowledge in treating ailments rather than upon prayers
or incantations. He is said, for example, to have recommended and
applied the cautery in the case of a friend who, when suffering
from angina, had sought his aid.

The list of eminent Arabian physicians is too long to be given
here, but some of them are of such importance in their influence
upon later medicine that they cannot be entirely ignored. One of
the first of these was Honain ben Isaac (809-873 A.D.), a
Christian Arab of Bagdad. He made translations of the works of
Hippocrates, and practised the art along the lines indicated by
his teachings and those of Galen. He is considered the greatest
translator of the ninth century and one of the greatest
philosophers of that period.

Another great Arabian physician, whose work was just beginning as
Honain's was drawing to a close, was Rhazes (850-923 A.D.), who
during his life was no less noted as a philosopher and musician
than as a physician. He continued the work of Honain, and
advanced therapeutics by introducing more extensive use of
chemical remedies, such as mercurial ointments, sulphuric acid,
and aqua vitae. He is also credited with being the first
physician to describe small-pox and measles accurately.

While Rhazes was still alive another Arabian, Haly Abbas (died
about 994), was writing his famous encyclopaedia of medicine,
called The Royal Book. But the names of all these great
physicians have been considerably obscured by the reputation of
Avicenna (980-1037), the Arabian "Prince of Physicians," the
greatest name in Arabic medicine, and one of the most remarkable
men in history. Leclerc says that "he was perhaps never surpassed
by any man in brilliancy of intellect and indefatigable
activity." His career was a most varied one. He was at all times
a boisterous reveller, but whether flaunting gayly among the
guests of an emir or biding in some obscure apothecary cellar,
his work of philosophical writing was carried on steadily. When a
friendly emir was in power, he taught and wrote and caroused at
court; but between times, when some unfriendly ruler was supreme,
he was hiding away obscurely, still pouring out his great mass of
manuscripts. In this way his entire life was spent.

By his extensive writings he revived and kept alive the best of
the teachings of the Greek physicians, adding to them such
observations as he had made in anatomy, physiology, and materia
medica. Among his discoveries is that of the contagiousness of
pulmonary tuberculosis. His works for several centuries continued
to be looked upon as the highest standard by physicians, and he
should undoubtedly be credited with having at least retarded the
decline of mediaeval medicine.

But it was not the Eastern Arabs alone who were active in the
field of medicine. Cordova, the capital of the western caliphate,
became also a great centre of learning and produced several great
physicians. One of these, Albucasis (died in 1013 A.D.), is
credited with having published the first illustrated work on
surgery, this book being remarkable in still another way, in that
it was also the first book, since classical times, written from
the practical experience of the physician, and not a mere
compilation of ancient authors. A century after Albucasis came
the great physician Avenzoar (1113-1196), with whom he divides
about equally the medical honors of the western caliphate. Among
Avenzoar's discoveries was that of the cause of "itch"--a little
parasite, "so small that he is hardly visible." The discovery of
the cause of this common disease seems of minor importance now,
but it is of interest in medical history because, had Avenzoar's
discovery been remembered a hundred years ago, "itch struck in"
could hardly have been considered the cause of three-fourths of
all diseases, as it was by the famous Hahnemann.

The illustrious pupil of Avenzoar, Averrhoes, who died in 1198
A.D., was the last of the great Arabian physicians who, by
rational conception of medicine, attempted to stem the flood of
superstition that was overwhelming medicine. For a time he
succeeded; but at last the Moslem theologians prevailed, and he
was degraded and banished to a town inhabited only by the
despised Jews.


ARABIAN HOSPITALS

To early Christians belong the credit of having established the
first charitable institutions for caring for the sick; but their
efforts were soon eclipsed by both Eastern and Western
Mohammedans. As early as the eighth century the Arabs had begun
building hospitals, but the flourishing time of hospital building
seems to have begun early in the tenth century. Lady Seidel, in
918 A.D., opened a hospital at Bagdad, endowed with an amount
corresponding to about three hundred pounds sterling a month.
Other similar hospitals were erected in the years immediately
following, and in 977 the Emir Adad-adaula established an
enormous institution with a staff of twenty-four medical
officers. The great physician Rhazes is said to have selected the
site for one of these hospitals by hanging pieces of meat in
various places about the city, selecting the site near the place
at which putrefaction was slowest in making its appearance. By
the middle of the twelfth century there were something like sixty
medical institutions in Bagdad alone, and these institutions were
free to all patients and supported by official charity.

The Emir Nureddin, about the year 1160, founded a great hospital
at Damascus, as a thank-offering for his victories over the
Crusaders. This great institution completely overshadowed all the
earlier Moslem hospitals in size and in the completeness of its
equipment. It was furnished with facilities for teaching, and was
conducted for several centuries in a lavish manner, regardless of
expense. But little over a century after its foundation the fame
of its methods of treatment led to the establishment of a larger
and still more luxurious institution--the Mansuri hospital at
Cairo. It seems that a certain sultan, having been cured by
medicines from the Damascene hospital, determined to build one of
his own at Cairo which should eclipse even the great Damascene
institution.

In a single year (1283-1284) this hospital was begun and
completed. No efforts were spared in hurrying on the good work,
and no one was exempt from performing labor on the building if he
chanced to pass one of the adjoining streets. It was the order of
the sultan that any person passing near could be impressed into
the work, and this order was carried out to the letter, noblemen
and beggars alike being forced to lend a hand. Very naturally,
the adjacent thoroughfares became unpopular and practically
deserted, but still the holy work progressed rapidly and was
shortly completed.

This immense structure is said to have contained four courts,
each having a fountain in the centre; lecture-halls, wards for
isolating certain diseases, and a department that corresponded to
the modern hospital's "out-patient" department. The yearly
endowment amounted to something like the equivalent of one
hundred and twenty-five thousand dollars. A novel feature was a
hall where musicians played day and night, and another where
story-tellers were employed, so that persons troubled with
insomnia were amused and melancholiacs cheered. Those of a
religious turn of mind could listen to readings of the Koran,
conducted continuously by a staff of some fifty chaplains. Each
patient on leaving the hospital received some gold pieces, that
he need not be obliged to attempt hard labor at once.

In considering the astonishing tales of these sumptuous Arabian
institutions, it should be borne in mind that our accounts of
them are, for the most part, from Mohammedan sources.
Nevertheless, there can be little question that they were
enormous institutions, far surpassing any similar institutions in
western Europe. The so-called hospitals in the West were, at this
time, branches of monasteries under supervision of the monks, and
did not compare favorably with the Arabian hospitals.

But while the medical science of the Mohammedans greatly
overshadowed that of the Christians during this period, it did
not completely obliterate it. About the year 1000 A.D. came into
prominence the Christian medical school at Salerno, situated on
the Italian coast, some thirty miles southeast of Naples. Just
how long this school had been in existence, or by whom it was
founded, cannot be determined, but its period of greatest
influence was the eleventh, twelfth, and thirteenth centuries.
The members of this school gradually adopted Arabic medicine,
making use of many drugs from the Arabic pharmacopoeia, and this
formed one of the stepping-stones to the introduction of Arabian
medicine all through western Europe.

It was not the adoption of Arabian medicines, however, that has
made the school at Salerno famous both in rhyme and prose, but
rather the fact that women there practised the healing art.
Greatest among them was Trotula, who lived in the eleventh
century, and whose learning is reputed to have equalled that of
the greatest physicians of the day. She is accredited with a work
on Diseases of Women, still extant, and many of her writings on
general medical subjects were quoted through two succeeding
centuries. If we may judge from these writings, she seemed to
have had many excellent ideas as to the proper methods of
treating diseases, but it is difficult to determine just which of
the writings credited to her are in reality hers. Indeed, the
uncertainty is even greater than this implies, for, according to
some writers, "Trotula" is merely the title of a book. Such an
authority as Malgaigne, however, believed that such a woman
existed, and that the works accredited to her are authentic. The
truth of the matter may perhaps never be fully established, but
this at least is certain--the tradition in regard to Trotula
could never have arisen had not women held a far different
position among the Arabians of this period from that accorded
them in contemporary Christendom.



III. MEDIAEVAL SCIENCE IN THE WEST

We have previously referred to the influence of the Byzantine
civilization in transmitting the learning of antiquity across the
abysm of the dark age. It must be admitted, however, that the
importance of that civilization did not extend much beyond the
task of the common carrier. There were no great creative
scientists in the later Roman empire of the East any more than in
the corresponding empire of the West. There was, however, one
field in which the Byzantine made respectable progress and
regarding which their efforts require a few words of special
comment. This was the field of medicine.

The Byzantines of this time could boast of two great medical men,
Aetius of Amida (about 502-575 A.D.) and Paul of Aegina (about
620-690). The works of Aetius were of value largely because they
recorded the teachings of many of his eminent predecessors, but
he was not entirely lacking in originality, and was perhaps the
first physician to mention diphtheria, with an allusion to some
observations of the paralysis of the palate which sometimes
follows this disease.

Paul of Aegina, who came from the Alexandrian school about a
century later, was one of those remarkable men whose ideas are
centuries ahead of their time. This was particularly true of Paul
in regard to surgery, and his attitude towards the supernatural
in the causation and treatment of diseases. He was essentially a
surgeon, being particularly familiar with military surgery, and
some of his descriptions of complicated and difficult operations
have been little improved upon even in modern times. In his books
he describes such operations as the removal of foreign bodies
from the nose, ear, and esophagus; and he recognizes foreign
growths such as polypi in the air-passages, and gives the method
of their removal. Such operations as tracheotomy, tonsellotomy,
bronchotomy, staphylotomy, etc., were performed by him, and he
even advocated and described puncture of the abdominal cavity,
giving careful directions as to the location in which such
punctures should be made. He advocated amputation of the breast
for the cure of cancer, and described extirpation of the uterus.
Just how successful this last operation may have been as
performed by him does not appear; but he would hardly have
recommended it if it had not been sometimes, at least,
successful. That he mentions it at all, however, is significant,
as this difficult operation is considered one of the great
triumphs of modern surgery.

But Paul of Aegina is a striking exception to the rule among
Byzantine surgeons, and as he was their greatest, so he was also
their last important surgeon. The energies of all Byzantium were
so expended in religious controversies that medicine, like the
other sciences, was soon relegated to a place among the other
superstitions, and the influence of the Byzantine school was
presently replaced by that of the conquering Arabians.


THIRTEENTH-CENTURY MEDICINE

The thirteenth century marks the beginning of a gradual change in
medicine, and a tendency to leave the time-worn rut of
superstitious dogmas that so long retarded the progress of
science. It is thought that the great epidemics which raged
during the Middle Ages acted powerfully in diverting the medical
thought of the times into new and entirely different channels. It
will be remembered that the teachings of Galen were handed
through mediaeval times as the highest and best authority on the
subject of all diseases. When, however, the great epidemics made
their appearance, the medical men appealed to the works of Galen
in vain for enlightenment, as these works, having been written
several centuries before the time of the plagues, naturally
contained no information concerning them. It was evident,
therefore, that on this subject, at least, Galen was not
infallible; and it would naturally follow that, one fallible
point having been revealed, others would be sought for. In other
words, scepticism in regard to accepted methods would be aroused,
and would lead naturally, as such scepticism usually does, to
progress. The devastating effects of these plagues, despite
prayers and incantations, would arouse doubt in the minds of many
as to the efficacy of superstitious rites and ceremonies in
curing diseases. They had seen thousands and tens of thousands of
their fellow-beings swept away by these awful scourges. They had
seen the ravages of these epidemics continue for months or even
years, notwithstanding the fact that multitudes of God-fearing
people prayed hourly that such ravages might be checked. And they
must have observed also that when even very simple rules of
cleanliness and hygiene were followed there was a diminution in
the ravages of the plague, even without the aid of incantations.
Such observations as these would have a tendency to awaken a
suspicion in the minds of many of the physicians that disease was
not a manifestation of the supernatural, but a natural
phenomenon, to be treated by natural methods.

But, be the causes what they may, it is a fact that the
thirteenth century marks a turning-point, or the beginning of an
attitude of mind which resulted in bringing medicine to a much
more rational position. Among the thirteenth-century physicians,
two men are deserving of special mention. These are Arnald of
Villanova (1235-1312) and Peter of Abano (1250-1315). Both these
men suffered persecution for expressing their belief in natural,
as against the supernatural, causes of disease, and at one time
Arnald was obliged to flee from Barcelona for declaring that the
"bulls" of popes were human works, and that "acts of charity were
dearer to God than hecatombs." He was also accused of alchemy.
Fleeing from persecution, he finally perished by shipwreck.

Arnald was the first great representative of the school of
Montpellier. He devoted much time to the study of chemicals, and
was active in attempting to re-establish the teachings of
Hippocrates and Galen. He was one of the first of a long line of
alchemists who, for several succeeding centuries, expended so
much time and energy in attempting to find the "elixir of life."
The Arab discovery of alcohol first deluded him into the belief
that the "elixir" had at last been found; but later he discarded
it and made extensive experiments with brandy, employing it in
the treatment of certain diseases--the first record of the
administration of this liquor as a medicine. Arnald also revived
the search for some anaesthetic that would produce insensibility
to pain in surgical operations. This idea was not original with
him, for since very early times physicians had attempted to
discover such an anaesthetic, and even so early a writer as
Herodotus tells how the Scythians, by inhalation of the vapors of
some kind of hemp, produced complete insensibility. It may have
been these writings that stimulated Arnald to search for such an
anaesthetic. In a book usually credited to him, medicines are
named and methods of administration described which will make the
patient insensible to pain, so that "he may be cut and feel
nothing, as though he were dead." For this purpose a mixture of
opium, mandragora, and henbane is to be used. This mixture was
held at the patient's nostrils much as ether and chloroform are
administered by the modern surgeon. The method was modified by
Hugo of Lucca (died in 1252 or 1268), who added certain other
narcotics, such as hemlock, to the mixture, and boiled a new
sponge in this decoction. After boiling for a certain time, this
sponge was dried, and when wanted for use was dipped in hot water
and applied to the nostrils.

Just how frequently patients recovered from the administration of
such a combination of powerful poisons does not appear, but the
percentage of deaths must have been very high, as the practice
was generally condemned. Insensibility could have been produced
only by swallowing large quantities of the liquid, which dripped
into the nose and mouth when the sponge was applied, and a lethal
quantity might thus be swallowed. The method was revived, with
various modifications, from time to time, but as often fell into
disuse. As late as 1782 it was sometimes attempted, and in that
year the King of Poland is said to have been completely
anaesthetized and to have recovered, after a painless amputation
had been performed by the surgeons.

Peter of Abano was one of the first great men produced by the
University of Padua. His fate would have been even more tragic
than that of the shipwrecked Arnald had he not cheated the
purifying fagots of the church by dying opportunely on the eve of
his execution for heresy. But if his spirit had cheated the
fanatics, his body could not, and his bones were burned for his
heresy. He had dared to deny the existence of a devil, and had
suggested that the case of a patient who lay in a trance for
three days might help to explain some miracles, like the raising
of Lazarus.

His great work was Conciliator Differentiarum, an attempt to
reconcile physicians and philosophers. But his researches were
not confined to medicine, for he seems to have had an inkling of
the hitherto unknown fact that air possesses weight, and his
calculation of the length of the year at three hundred and
sixty-five days, six hours, and four minutes, is exceptionally
accurate for the age in which he lived. He was probably the first
of the Western writers to teach that the brain is the source of
the nerves, and the heart the source of the vessels. From this it
is seen that he was groping in the direction of an explanation of
the circulation of the blood, as demonstrated by Harvey three
centuries later.

The work of Arnald and Peter of Abano in "reviving" medicine was
continued actively by Mondino (1276-1326) of Bologna, the
"restorer of anatomy," and by Guy of Chauliac: (born about 1300),
the "restorer of surgery." All through the early Middle Ages
dissections of human bodies had been forbidden, and even
dissection of the lower animals gradually fell into disrepute
because physicians detected in such practices were sometimes
accused of sorcery. Before the close of the thirteenth century,
however, a reaction had begun, physicians were protected, and
dissections were occasionally sanctioned by the ruling monarch.
Thus Emperor Frederick H. (1194-1250 A.D.)--whose services to
science we have already had occasion to mention--ordered that at
least one human body should be dissected by physicians in his
kingdom every five years. By the time of Mondino dissections were
becoming more frequent, and he himself is known to have dissected
and demonstrated several bodies. His writings on anatomy have
been called merely plagiarisms of Galen, but in all probability
be made many discoveries independently, and on the whole, his
work may be taken as more advanced than Galen's. His description
of the heart is particularly accurate, and he seems to have come
nearer to determining the course of the blood in its circulation
than any of his predecessors. In this quest he was greatly
handicapped by the prevailing belief in the idea that
blood-vessels must contain air as well as blood, and this led him
to assume that one of the cavities of the heart contained
"spirits," or air. It is probable, however, that his accurate
observations, so far as they went, were helpful stepping-stones
to Harvey in his discovery of the circulation.

Guy of Chauliac, whose innovations in surgery reestablished that
science on a firm basis, was not only one of the most cultured,
but also the most practical surgeon of his time. He had great
reverence for the works of Galen, Albucasis, and others of his
noted predecessors; but this reverence did not blind him to their
mistakes nor prevent him from using rational methods of treatment
far in advance of theirs. His practicality is shown in some of
his simple but useful inventions for the sick-room, such as the
device of a rope, suspended from the ceiling over the bed, by
which a patient may move himself about more easily; and in some
of his improvements in surgical dressings, such as stiffening
bandages by dipping them in the white of an egg so that they are
held firmly. He treated broken limbs in the suspended cradle
still in use, and introduced the method of making "traction" on a
broken limb by means of a weight and pulley, to prevent deformity
through shortening of the member. He was one of the first
physicians to recognize the utility of spectacles, and
recommended them in cases not amenable to treatment with lotions
and eye-waters. In some of his surgical operations, such as
trephining for fracture of the skull, his technique has been
little improved upon even in modern times. In one of these
operations he successfully removed a portion of a man's brain.


Surgery was undoubtedly stimulated greatly at this period by the
constant wars. Lay physicians, as a class, had been looked down
upon during the Dark Ages; but with the beginning of the return
to rationalism, the services of surgeons on the battle-field, to
remove missiles from wounds, and to care for wounds and apply
dressings, came to be more fully appreciated. In return for his
labors the surgeon was thus afforded better opportunities for
observing wounds and diseases, which led naturally to a gradual
improvement in surgical methods.


FIFTEENTH-CENTURY MEDICINE

The thirteenth and fourteenth centuries had seen some slight
advancement in the science of medicine; at least, certain
surgeons and physicians, if not the generality, had made
advances; but it was not until the fifteenth century that the
general revival of medical learning became assured. In this
movement, naturally, the printing-press played an all-important
part. Medical books, hitherto practically inaccessible to the
great mass of physicians, now became common, and this output of
reprints of Greek and Arabic treatises revealed the fact that
many of the supposed true copies were spurious. These discoveries
very naturally aroused all manner of doubt and criticism, which
in turn helped in the development of independent thought.

A certain manuscript of the great Cornelius Celsus, the De
Medicine, which had been lost for many centuries, was found in
the church of St. Ambrose, at Milan, in 1443, and was at once put
into print. The effect of the publication of this book, which had
lain in hiding for so many centuries, was a revelation, showing
the medical profession how far most of their supposed true copies
of Celsus had drifted away from the original. The indisputable
authenticity of this manuscript, discovered and vouched for by
the man who shortly after became Pope Nicholas V., made its
publication the more impressive. The output in book form of other
authorities followed rapidly, and the manifest discrepancies
between such teachers as Celsus, Hippocrates, Galen, and Pliny
heightened still more the growing spirit of criticism.

These doubts resulted in great controversies as to the proper
treatment of certain diseases, some physicians following
Hippocrates, others Galen or Celsus, still others the Arabian
masters. One of the most bitter of these contests was over the
question of "revulsion," and "derivation"--that is, whether in
cases of pleurisy treated by bleeding, the venesection should be
made at a point distant from the seat of the disease, as held by
the "revulsionists," or at a point nearer and on the same side of
the body, as practised by the "derivationists." That any great
point for discussion could be raised in the fifteenth or
sixteenth centuries on so simple a matter as it seems to-day
shows how necessary to the progress of medicine was the discovery
of the circulation of the blood made by Harvey two centuries
later. After Harvey's discovery no such discussion could have
been possible, because this discovery made it evident that as far
as the general effect upon the circulation is concerned, it made
little difference whether the bleeding was done near a diseased
part or remote from it. But in the sixteenth century this
question was the all-absorbing one among the doctors. At one time
the faculty of Paris condemned "derivation"; but the supporters
of this method carried the war still higher, and Emperor Charles
V. himself was appealed to. He reversed the decision of the Paris
faculty, and decided in favor of "derivation." His decision was
further supported by Pope Clement VII., although the discussion
dragged on until cut short by Harvey's discovery.

But a new form of injury now claimed the attention of the
surgeons, something that could be decided by neither Greek nor
Arabian authors, as the treatment of gun-shot wounds was, for
obvious reasons, not given in their writings. About this time,
also, came the great epidemics, "the sweating sickness" and
scurvy; and upon these subjects, also, the Greeks and Arabians
were silent. John of Vigo, in his book, the Practica Copiosa,
published in 1514, and repeated in many editions, became the
standard authority on all these subjects, and thus supplanted the
works of the ancient writers.

According to Vigo, gun-shot wounds differed from the wounds made
by ordinary weapons--that is, spear, arrow, sword, or axe--in
that the bullet, being round, bruised rather than cut its way
through the tissues; it burned the flesh; and, worst of all, it
poisoned it. Vigo laid especial stress upon treating this last
condition, recommending the use of the cautery or the oil of
elder, boiling hot. It is little wonder that gun-shot wounds were
so likely to prove fatal. Yet, after all, here was the germ of
the idea of antisepsis.


NEW BEGINNINGS IN GENERAL SCIENCE

We have dwelt thus at length on the subject of medical science,
because it was chiefly in this field that progress was made in
the Western world during the mediaeval period, and because these
studies furnished the point of departure for the revival all
along the line. It will be understood, however, from what was
stated in the preceding chapter, that the Arabian influences in
particular were to some extent making themselves felt along other
lines. The opportunity afforded a portion of the Western
world--notably Spain and Sicily --to gain access to the
scientific ideas of antiquity through Arabic translations could
not fail of influence. Of like character, and perhaps even more
pronounced in degree, was the influence wrought by the Byzantine
refugees, who, when Constantinople began to be threatened by the
Turks, migrated to the West in considerable numbers, bringing
with them a knowledge of Greek literature and a large number of
precious works which for centuries had been quite forgotten or
absolutely ignored in Italy. Now Western scholars began to take
an interest in the Greek language, which had been utterly
neglected since the beginning of the Middle Ages. Interesting
stories are told of the efforts made by such men as Cosmo de'
Medici to gain possession of classical manuscripts. The revival
of learning thus brought about had its first permanent influence
in the fields of literature and art, but its effect on science
could not be long delayed. Quite independently of the Byzantine
influence, however, the striving for better intellectual things
had manifested itself in many ways before the close of the
thirteenth century. An illustration of this is found in the
almost simultaneous development of centres of teaching, which
developed into the universities of Italy, France, England, and, a
little later, of Germany.

The regular list of studies that came to be adopted everywhere
comprised seven nominal branches, divided into two groups--the
so-called quadrivium, comprising music, arithmetic, geometry, and
astronomy; and the trivium comprising grammar, rhetoric, and
logic. The vagueness of implication of some of these branches
gave opportunity to the teacher for the promulgation of almost
any knowledge of which he might be possessed, but there can be no
doubt that, in general, science had but meagre share in the
curriculum. In so far as it was given representation, its chief
field must have been Ptolemaic astronomy. The utter lack of
scientific thought and scientific method is illustrated most
vividly in the works of the greatest men of that period--such men
as Albertus Magnus, Thomas Aquinas, Bonaventura, and the hosts of
other scholastics of lesser rank. Yet the mental awakening
implied in their efforts was sure to extend to other fields, and
in point of fact there was at least one contemporary of these
great scholastics whose mind was intended towards scientific
subjects, and who produced writings strangely at variance in tone
and in content with the others. This anachronistic thinker was
the English monk, Roger Bacon.


ROGER BACON

Bacon was born in 1214 and died in 1292. By some it is held that
he was not appreciated in his own time because he was really a
modern scientist living in an age two centuries before modern
science or methods of modern scientific thinking were known. Such
an estimate, however, is a manifest exaggeration of the facts,
although there is probably a grain of truth in it withal. His
learning certainly brought him into contact with the great
thinkers of the time, and his writings caused him to be
imprisoned by his fellow-churchmen at different times, from which
circumstances we may gather that he was advanced thinker, even if
not a modern scientist.

Although Bacon was at various times in durance, or under
surveillance, and forbidden to write, he was nevertheless a
marvellously prolific writer, as is shown by the numerous books
and unpublished manuscripts of his still extant. His
master-production was the Opus Majus. In Part IV. of this work he
attempts to show that all sciences rest ultimately on
mathematics; but Part V., which treats of perspective, is of
particular interest to modern scientists, because in this he
discusses reflection and refraction, and the properties of
mirrors and lenses. In this part, also, it is evident that he is
making use of such Arabian writers as Alkindi and Alhazen, and
this is of especial interest, since it has been used by his
detractors, who accuse him of lack of originality, to prove that
his seeming inventions and discoveries were in reality
adaptations of the Arab scientists. It is difficult to determine
just how fully such criticisms are justified. It is certain,
however, that in this part he describes the anatomy of the eye
with great accuracy, and discusses mirrors and lenses.

The magnifying power of the segment of a glass sphere had been
noted by Alhazen, who had observed also that the magnification
was increased by increasing the size of the segment used. Bacon
took up the discussion of the comparative advantages of segments,
and in this discussion seems to show that he understood how to
trace the progress of the rays of light through a spherical
transparent body, and how to determine the place of the image. He
also described a method of constructing a telescope, but it is by
no means clear that he had ever actually constructed such an
instrument. It is also a mooted question as to whether his
instructions as to the construction of such an instrument would
have enabled any one to construct one. The vagaries of the names
of terms as he uses them allow such latitude in interpretation
that modern scientists are not agreed as to the practicability of
Bacon's suggestions. For example, he constantly refers to force
under such names as virtus, species, imago, agentis, and a score
of other names, and this naturally gives rise to the great
differences in the interpretations of his writings, with
corresponding differences in estimates of them.

The claim that Bacon originated the use of lenses, in the form of
spectacles, cannot be proven. Smith has determined that as early
as the opening years of the fourteenth century such lenses were
in use, but this proves nothing as regards Bacon's connection
with their invention. The knowledge of lenses seems to be very
ancient, if we may judge from the convex lens of rock crystal
found by Layard in his excavations at Nimrud. There is nothing to
show, however, that the ancients ever thought of using them to
correct defects of vision. Neither, apparently, is it feasible to
determine whether the idea of such an application originated with
Bacon.

Another mechanical discovery about which there has been a great
deal of discussion is Bacon's supposed invention of gunpowder. It
appears that in a certain passage of his work he describes the
process of making a substance that is, in effect, ordinary
gunpowder; but it is more than doubtful whether he understood the
properties of the substance he describes. It is fairly well
established, however, that in Bacon's time gunpowder was known to
the Arabs, so that it should not be surprising to find references
made to it in Bacon's work, since there is reason to believe that
he constantly consulted Arabian writings.

The great merit of Bacon's work, however, depends on the
principles taught as regards experiment and the observation of
nature, rather than on any single invention. He had the
all-important idea of breaking with tradition. He championed
unfettered inquiry in every field of thought. He had the instinct
of a scientific worker--a rare instinct indeed in that age. Nor
need we doubt that to the best of his opportunities he was
himself an original investigator.


LEONARDO DA VINCI

The relative infertility of Bacon's thought is shown by the fact
that he founded no school and left no trace of discipleship. The
entire century after his death shows no single European name that
need claim the attention of the historian of science. In the
latter part of the fifteenth century, however, there is evidence
of a renaissance of science no less than of art. The German
Muller became famous under the latinized named of Regio Montanus
(1437-1472), although his actual scientific attainments would
appear to have been important only in comparison with the utter
ignorance of his contemporaries. The most distinguished worker of
the new era was the famous Italian Leonardo da Vinci--a man who
has been called by Hamerton the most universal genius that ever
lived. Leonardo's position in the history of art is known to
every one. With that, of course, we have no present concern; but
it is worth our while to inquire at some length as to the famous
painter's accomplishments as a scientist.

From a passage in the works of Leonardo, first brought to light
by Venturi,[1] it would seem that the great painter anticipated
Copernicus in determining the movement of the earth. He made
mathematical calculations to prove this, and appears to have
reached the definite conclusion that the earth does move--or what
amounts to the same thing, that the sun does not move. Muntz is
authority for the statement that in one of his writings he
declares, "Il sole non si mouve"--the sun does not move.[2]

Among his inventions is a dynamometer for determining the
traction power of machines and animals, and his experiments with
steam have led some of his enthusiastic partisans to claim for
him priority to Watt in the invention of the steam-engine. In
these experiments, however, Leonardo seems to have advanced
little beyond Hero of Alexandria and his steam toy. Hero's
steam-engine did nothing but rotate itself by virtue of escaping
jets of steam forced from the bent tubes, while Leonardo's
"steam-engine" "drove a ball weighing one talent over a distance
of six stadia." In a manuscript now in the library of the
Institut de France, Da Vinci describes this engine minutely. The
action of this machine was due to the sudden conversion of small
quantities of water into steam ("smoke," as he called it) by
coming suddenly in contact with a heated surface in a proper
receptacle, the rapidly formed steam acting as a propulsive force
after the manner of an explosive. It is really a steam-gun,
rather than a steam-engine, and it is not unlikely that the study
of the action of gunpowder may have suggested it to Leonardo.

It is believed that Leonardo is the true discoverer of the
camera-obscura, although the Neapolitan philosopher, Giambattista
Porta, who was not born until some twenty years after the death
of Leonardo, is usually credited with first describing this
device. There is little doubt, however, that Da Vinci understood
the principle of this mechanism, for he describes how such a
camera can be made by cutting a small, round hole through the
shutter of a darkened room, the reversed image of objects outside
being shown on the opposite wall.

Like other philosophers in all ages, he had observed a great
number of facts which he was unable to explain correctly. But
such accumulations of scientific observations are always
interesting, as showing how many centuries of observation
frequently precede correct explanation. He observed many facts
about sounds, among others that blows struck upon a bell produced
sympathetic sounds in a bell of the same kind; and that striking
the string of a lute produced vibration in corresponding strings
of lutes strung to the same pitch. He knew, also, that sounds
could be heard at a distance at sea by listening at one end of a
tube, the other end of which was placed in the water; and that
the same expedient worked successfully on land, the end of the
tube being placed against the ground.

The knowledge of this great number of unexplained facts is often
interpreted by the admirers of Da Vinci, as showing an almost
occult insight into science many centuries in advance of his
time. Such interpretations, however, are illusive. The
observation, for example, that a tube placed against the ground
enables one to hear movements on the earth at a distance, is not
in itself evidence of anything more than acute scientific
observation, as a similar method is in use among almost every
race of savages, notably the American Indians. On the other hand,
one is inclined to give credence to almost any story of the
breadth of knowledge of the man who came so near anticipating
Hutton, Lyell, and Darwin in his interpretation of the geological
records as he found them written on the rocks.

It is in this field of geology that Leonardo is entitled to the
greatest admiration by modern scientists. He had observed the
deposit of fossil shells in various strata of rocks, even on the
tops of mountains, and he rejected once for all the theory that
they had been deposited there by the Deluge. He rightly
interpreted their presence as evidence that they had once been
deposited at the bottom of the sea. This process he assumed bad
taken hundreds and thousands of centuries, thus tacitly rejecting
the biblical tradition as to the date of the creation.

Notwithstanding the obvious interest that attaches to the
investigations of Leonardo, it must be admitted that his work in
science remained almost as infertile as that of his great
precursor, Bacon. The really stimulative work of this generation
was done by a man of affairs, who knew little of theoretical
science except in one line, but who pursued that one practical
line until he achieved a wonderful result. This man was
Christopher Columbus. It is not necessary here to tell the trite
story of his accomplishment. Suffice it that his practical
demonstration of the rotundity of the earth is regarded by most
modern writers as marking an epoch in history. With the year of
his voyage the epoch of the Middle Ages is usually regarded as
coming to an end. It must not be supposed that any very sudden
change came over the aspect of scholarship of the time, but the
preliminaries of great things had been achieved, and when
Columbus made his famous voyage in 1492, the man was already
alive who was to bring forward the first great vitalizing thought
in the field of pure science that the Western world had
originated for more than a thousand years. This man bore the name
of Kopernik, or in its familiar Anglicized form, Copernicus. His
life work and that of his disciples will claim our attention in
the succeeding chapter.



IV. THE NEW COSMOLOGY--COPERNICUS TO KEPLER AND GALILEO

We have seen that the Ptolemaic astronomy, which was the accepted
doctrine throughout the Middle Ages, taught that the earth is
round. Doubtless there was a popular opinion current which
regarded the earth as flat, but it must be understood that this
opinion had no champions among men of science during the Middle
Ages. When, in the year 1492, Columbus sailed out to the west on
his memorable voyage, his expectation of reaching India had full
scientific warrant, however much it may have been scouted by
certain ecclesiastics and by the average man of the period.
Nevertheless, we may well suppose that the successful voyage of
Columbus, and the still more demonstrative one made about thirty
years later by Magellan, gave the theory of the earth's rotundity
a certainty it could never previously have had. Alexandrian
geographers had measured the size of the earth, and had not
hesitated to assert that by sailing westward one might reach
India. But there is a wide gap between theory and practice, and
it required the voyages of Columbus and his successors to bridge
that gap.

After the companions of Magellan completed the circumnavigation
of the globe, the general shape of our earth would, obviously,
never again be called in question. But demonstration of the
sphericity of the earth had, of course, no direct bearing upon
the question of the earth's position in the universe. Therefore
the voyage of Magellan served to fortify, rather than to dispute,
the Ptolemaic theory. According to that theory, as we have seen,
the earth was supposed to lie immovable at the centre of the
universe; the various heavenly bodies, including the sun,
revolving about it in eccentric circles. We have seen that
several of the ancient Greeks, notably Aristarchus, disputed this
conception, declaring for the central position of the sun in the
universe, and the motion of the earth and other planets about
that body. But this revolutionary theory seemed so opposed to the
ordinary observation that, having been discountenanced by
Hipparchus and Ptolemy, it did not find a single important
champion for more than a thousand years after the time of the
last great Alexandrian astronomer.

The first man, seemingly, to hark back to the Aristarchian
conception in the new scientific era that was now dawning was the
noted cardinal, Nikolaus of Cusa, who lived in the first half of
the fifteenth century, and was distinguished as a philosophical
writer and mathematician. His De Docta Ignorantia expressly
propounds the doctrine of the earth's motion. No one, however,
paid the slightest attention to his suggestion, which, therefore,
merely serves to furnish us with another interesting illustration
of the futility of propounding even a correct hypothesis before
the time is ripe to receive it--particularly if the hypothesis is
not fully fortified by reasoning based on experiment or
observation.

The man who was destined to put forward the theory of the earth's
motion in a way to command attention was born in 1473, at the
village of Thorn, in eastern Prussia. His name was Nicholas
Copernicus. There is no more famous name in the entire annals of
science than this, yet posterity has never been able fully to
establish the lineage of the famous expositor of the true
doctrine of the solar system. The city of Thorn lies in a
province of that border territory which was then under control of
Poland, but which subsequently became a part of Prussia. It is
claimed that the aspects of the city were essentially German, and
it is admitted that the mother of Copernicus belonged to that
race. The nationality of the father is more in doubt, but it is
urged that Copernicus used German as his mother-tongue. His great
work was, of course, written in Latin, according to the custom of
the time; but it is said that, when not employing that language,
he always wrote in German. The disputed nationality of Copernicus
strongly suggests that he came of a mixed racial lineage, and we
are reminded again of the influences of those ethnical minglings
to which we have previously more than once referred. The
acknowledged centres of civilization towards the close of the
fifteenth century were Italy and Spain. Therefore, the birthplace
of Copernicus lay almost at the confines of civilization,
reminding us of that earlier period when Greece was the centre of
culture, but when the great Greek thinkers were born in Asia
Minor and in Italy.

As a young man, Copernicus made his way to Vienna to study
medicine, and subsequently he journeyed into Italy and remained
there many years, About the year 1500 he held the chair of
mathematics in a college at Rome. Subsequently he returned to his
native land and passed his remaining years there, dying at
Domkerr, in Frauenburg, East Prussia, in the year 1543.

It would appear that Copernicus conceived the idea of the
heliocentric system of the universe while he was a comparatively
young man, since in the introduction to his great work, which he
addressed to Pope Paul III., he states that he has pondered his
system not merely nine years, in accordance with the maxim of
Horace, but well into the fourth period of nine years. Throughout
a considerable portion of this period the great work of
Copernicus was in manuscript, but it was not published until the
year of his death. The reasons for the delay are not very fully
established. Copernicus undoubtedly taught his system throughout
the later decades of his life. He himself tells us that he had
even questioned whether it were not better for him to confine
himself to such verbal teaching, following thus the example of
Pythagoras. Just as his life was drawing to a close, he decided
to pursue the opposite course, and the first copy of his work is
said to have been placed in his hands as he lay on his deathbed.

The violent opposition which the new system met from
ecclesiastical sources led subsequent commentators to suppose
that Copernicus had delayed publication of his work through fear
of the church authorities. There seems, however, to be no direct
evidence for this opinion. It has been thought significant that
Copernicus addressed his work to the pope. It is, of course,
quite conceivable that the aged astronomer might wish by this
means to demonstrate that he wrote in no spirit of hostility to
the church. His address to the pope might have been considered as
a desirable shield precisely because the author recognized that
his work must needs meet with ecclesiastical criticism. Be that
as it may, Copernicus was removed by death from the danger of
attack, and it remained for his disciples of a later generation
to run the gauntlet of criticism and suffer the charges of
heresy.

The work of Copernicus, published thus in the year 1543 at
Nuremberg, bears the title De Orbium Coelestium Revolutionibus.

It is not necessary to go into details as to the cosmological
system which Copernicus advocated, since it is familiar to every
one. In a word, he supposed the sun to be the centre of all the
planetary motions, the earth taking its place among the other
planets, the list of which, as known at that time, comprised
Mercury, Venus, the Earth, Mars, Jupiter, and Saturn. The fixed
stars were alleged to be stationary, and it was necessary to
suppose that they are almost infinitely distant, inasmuch as they
showed to the observers of that time no parallax; that is to say,
they preserved the same apparent position when viewed from the
opposite points of the earth's orbit.

But let us allow Copernicus to speak for himself regarding his
system, His exposition is full of interest. We quote first the
introduction just referred to, in which appeal is made directly
to the pope.

"I can well believe, most holy father, that certain people, when
they hear of my attributing motion to the earth in these books of
mine, will at once declare that such an opinion ought to be
rejected. Now, my own theories do not please me so much as not to
consider what others may judge of them. Accordingly, when I began
to reflect upon what those persons who accept the stability of
the earth, as confirmed by the opinion of many centuries, would
say when I claimed that the earth moves, I hesitated for a long
time as to whether I should publish that which I have written to
demonstrate its motion, or whether it would not be better to
follow the example of the Pythagoreans, who used to hand down the
secrets of philosophy to their relatives and friends only in oral
form. As I well considered all this, I was almost impelled to put
the finished work wholly aside, through the scorn I had reason to
anticipate on account of the newness and apparent contrariness to
reason of my theory.

"My friends, however, dissuaded me from such a course and
admonished me that I ought to publish my book, which had lain
concealed in my possession not only nine years, but already into
four times the ninth year. Not a few other distinguished and very
learned men asked me to do the same thing, and told me that I
ought not, on account of my anxiety, to delay any longer in
consecrating my work to the general service of mathematicians.

"But your holiness will perhaps not so much wonder that I have
dared to bring the results of my night labors to the light of
day, after having taken so much care in elaborating them, but is
waiting instead to hear how it entered my mind to imagine that
the earth moved, contrary to the accepted opinion of
mathematicians--nay, almost contrary to ordinary human
understanding. Therefore I will not conceal from your holiness
that what moved me to consider another way of reckoning the
motions of the heavenly bodies was nothing else than the fact
that the mathematicians do not agree with one another in their
investigations. In the first place, they are so uncertain about
the motions of the sun and moon that they cannot find out the
length of a full year. In the second place, they apply neither
the same laws of cause and effect, in determining the motions of
the sun and moon and of the five planets, nor the same proofs.
Some employ only concentric circles, others use eccentric and
epicyclic ones, with which, however, they do not fully attain the
desired end. They could not even discover nor compute the main
thing--namely, the form of the universe and the symmetry of its
parts. It was with them as if some should, from different places,
take hands, feet, head, and other parts of the body, which,
although very beautiful, were not drawn in their proper
relations, and, without making them in any way correspond, should
construct a monster instead of a human being.

"Accordingly, when I had long reflected on this uncertainty of
mathematical tradition, I took the trouble to read again the
books of all the philosophers I could get hold of, to see if some
one of them had not once believed that there were other motions
of the heavenly bodies. First I found in Cicero that Niceties had
believed in the motion of the earth. Afterwards I found in
Plutarch, likewise, that some others had held the same opinion.
This induced me also to begin to consider the movability of the
earth, and, although the theory appeared contrary to reason, I
did so because I knew that others before me had been allowed to
assume rotary movements at will, in order to explain the
phenomena of these celestial bodies. I was of the opinion that I,
too, might be permitted to see whether, by presupposing motion in
the earth, more reliable conclusions than hitherto reached could
not be discovered for the rotary motions of the spheres. And
thus, acting on the hypothesis of the motion which, in the
following book, I ascribe to the earth, and by long and continued
observations, I have finally discovered that if the motion of the
other planets be carried over to the relation of the earth and
this is made the basis for the rotation of every star, not only
will the phenomena of the planets be explained thereby, but also
the laws and the size of the stars; all their spheres and the
heavens themselves will appear so harmoniously connected that
nothing could be changed in any part of them without confusion in
the remaining parts and in the whole universe. I do not doubt
that clever and learned men will agree with me if they are
willing fully to comprehend and to consider the proofs which I
advance in the book before us. In order, however, that both the
learned and the unlearned may see that I fear no man's judgment,
I wanted to dedicate these, my night labors, to your holiness,
rather than to any one else, because you, even in this remote
corner of the earth where I live, are held to be the greatest in
dignity of station and in love for all sciences and for
mathematics, so that you, through your position and judgment, can
easily suppress the bites of slanderers, although the proverb
says that there is no remedy against the bite of calumny."


In chapter X. of book I., "On the Order of the Spheres," occurs a
more detailed presentation of the system, as follows:

"That which Martianus Capella, and a few other Latins, very well
knew, appears to me extremely noteworthy. He believed that Venus
and Mercury revolve about the sun as their centre and that they
cannot go farther away from it than the circles of their orbits
permit, since they do not revolve about the earth like the other
planets. According to this theory, then, Mercury's orbit would be
included within that of Venus, which is more than twice as great,
and would find room enough within it for its revolution.

"If, acting upon this supposition, we connect Saturn, Jupiter,
and Mars with the same centre, keeping in mind the greater extent
of their orbits, which include the earth's sphere besides those
of Mercury and Venus, we cannot fail to see the explanation of
the regular order of their motions. He is certain that Saturn,
Jupiter, and Mars are always nearest the earth when they rise in
the evening--that is, when they appear over against the sun, or
the earth stands between them and the sun--but that they are
farthest from the earth when they set in the evening--that is,
when we have the sun between them and the earth. This proves
sufficiently that their centre belongs to the sun and is the same
about which the orbits of Venus and Mercury circle. Since,
however, all have one centre, it is necessary for the space
intervening between the orbits of Venus and Mars to include the
earth with her accompanying moon and all that is beneath the
moon; for the moon, which stands unquestionably nearest the
earth, can in no way be separated from her, especially as there
is sufficient room for the moon in the aforesaid space. Hence we
do not hesitate to claim that the whole system, which includes
the moon with the earth for its centre, makes the round of that
great circle between the planets, in yearly motion about the sun,
and revolves about the centre of the universe, in which the sun
rests motionless, and that all which looks like motion in the sun
is explained by the motion of the earth. The extent of the
universe, however, is so great that, whereas the distance of the
earth from the sun is considerable in comparison with the size of
the other planetary orbits, it disappears when compared with the
sphere of the fixed stars. I hold this to be more easily
comprehensible than when the mind is confused by an almost
endless number of circles, which is necessarily the case with
those who keep the earth in the middle of the universe. Although
this may appear incomprehensible and contrary to the opinion of
many, I shall, if God wills, make it clearer than the sun, at
least to those who are not ignorant of mathematics.

"The order of the spheres is as follows: The first and lightest
of all the spheres is that of the fixed stars, which includes
itself and all others, and hence is motionless as the place in
the universe to which the motion and position of all other stars
is referred.

"Then follows the outermost planet, Saturn, which completes its
revolution around the sun in thirty years; next comes Jupiter
with a twelve years' revolution; then Mars, which completes its
course in two years. The fourth one in order is the yearly
revolution which includes the earth with the moon's orbit as an
epicycle. In the fifth place is Venus with a revolution of nine
months. The sixth place is taken by Mercury, which completes its
course in eighty days. In the middle of all stands the sun, and
who could wish to place the lamp of this most beautiful temple in
another or better place. Thus, in fact, the sun, seated upon the
royal throne, controls the family of the stars which circle
around him. We find in their order a harmonious connection which
cannot be found elsewhere. Here the attentive observer can see
why the waxing and waning of Jupiter seems greater than with
Saturn and smaller than with Mars, and again greater with Venus
than with Mercury. Also, why Saturn, Jupiter, and Mars are nearer
to the earth when they rise in the evening than when they
disappear in the rays of the sun. More prominently, however, is
it seen in the case of Mars, which when it appears in the heavens
at night, seems to equal Jupiter in size, but soon afterwards is
found among the stars of second magnitude. All of this results
from the same cause--namely, from the earth's motion. The fact
that nothing of this is to be seen in the case of the fixed stars
is a proof of their immeasurable distance, which makes even the
orbit of yearly motion or its counterpart invisible to us."[1]


The fact that the stars show no parallax had been regarded as an
important argument against the motion of the earth, and it was
still so considered by the opponents of the system of Copernicus.
It had, indeed, been necessary for Aristarchus to explain the
fact as due to the extreme distance of the stars; a perfectly
correct explanation, but one that implies distances that are
altogether inconceivable. It remained for nineteenth-century
astronomers to show, with the aid of instruments of greater
precision, that certain of the stars have a parallax. But long
before this demonstration had been brought forward, the system of
Copernicus had been accepted as a part of common knowledge.

While Copernicus postulated a cosmical scheme that was correct as
to its main features, he did not altogether break away from
certain defects of the Ptolemaic hypothesis. Indeed, he seems to
have retained as much of this as practicable, in deference to the
prejudice of his time. Thus he records the planetary orbits as
circular, and explains their eccentricities by resorting to the
theory of epicycles, quite after the Ptolemaic method. But now,
of course, a much more simple mechanism sufficed to explain the
planetary motions, since the orbits were correctly referred to
the central sun and not to the earth.

Needless to say, the revolutionary conception of Copernicus did
not meet with immediate acceptance. A number of prominent
astronomers, however, took it up almost at once, among these
being Rhaeticus, who wrote a commentary on the evolutions;
Erasmus Reinhold, the author of the Prutenic tables; Rothmann,
astronomer to the Landgrave of Hesse, and Maestlin, the
instructor of Kepler. The Prutenic tables, just referred to, so
called because of their Prussian origin, were considered an
improvement on the tables of Copernicus, and were highly esteemed
by the astronomers of the time. The commentary of Rhaeticus gives
us the interesting information that it was the observation of the
orbit of Mars and of the very great difference between his
apparent diameters at different times which first led Copernicus
to conceive the heliocentric idea. Of Reinhold it is recorded
that he considered the orbit of Mercury elliptical, and that he
advocated a theory of the moon, according to which her epicycle
revolved on an elliptical orbit, thus in a measure anticipating
one of the great discoveries of Kepler to which we shall refer
presently. The Landgrave of Hesse was a practical astronomer, who
produced a catalogue of fixed stars which has been compared with
that of Tycho Brahe. He was assisted by Rothmann and by Justus
Byrgius. Maestlin, the preceptor of Kepler, is reputed to have
been the first modern observer to give a correct explanation of
the light seen on portions of the moon not directly illumined by
the sun. He explained this as not due to any proper light of the
moon itself, but as light reflected from the earth. Certain of
the Greek philosophers, however, are said to have given the same
explanation, and it is alleged also that Leonardo da Vinci
anticipated Maestlin in this regard.[2]

While, various astronomers of some eminence thus gave support to
the Copernican system, almost from the beginning, it
unfortunately chanced that by far the most famous of the
immediate successors of Copernicus declined to accept the theory
of the earth's motion. This was Tycho Brahe, one of the greatest
observing astronomers of any age. Tycho Brahe was a Dane, born at
Knudstrup in the year 1546. He died in 1601 at Prague, in
Bohemia. During a considerable portion of his life he found a
patron in Frederick, King of Denmark, who assisted him to build a
splendid observatory on the Island of Huene. On the death of his
patron Tycho moved to Germany, where, as good luck would have it,
he came in contact with the youthful Kepler, and thus, no doubt,
was instrumental in stimulating the ambitions of one who in later
years was to be known as a far greater theorist than himself. As
has been said, Tycho rejected the Copernican theory of the
earth's motion. It should be added, however, that he accepted
that part of the Copernican theory which makes the sun the centre
of all the planetary motions, the earth being excepted. He thus
developed a system of his own, which was in some sort a
compromise between the Ptolemaic and the Copernican systems. As
Tycho conceived it, the sun revolves about the earth, carrying
with it the planets-Mercury, Venus, Mars, Jupiter, and Saturn,
which planets have the sun and not the earth as the centre of
their orbits. This cosmical scheme, it should be added, may be
made to explain the observed motions of the heavenly bodies, but
it involves a much more complex mechanism than is postulated by
the Copernican theory.

Various explanations have been offered of the conservatism which
held the great Danish astronomer back from full acceptance of the
relatively simple and, as we now know, correct Copernican
doctrine. From our latter-day point of view, it seems so much
more natural to accept than to reject the Copernican system, that
we find it difficult to put ourselves in the place of a
sixteenth-century observer. Yet if we recall that the traditional
view, having warrant of acceptance by nearly all thinkers of
every age, recorded the earth as a fixed, immovable body, we
shall see that our surprise should be excited rather by the
thinker who can break away from this view than by the one who
still tends to cling to it.

Moreover, it is useless to attempt to disguise the fact that
something more than a mere vague tradition was supposed to
support the idea of the earth's overshadowing importance in the
cosmical scheme. The sixteenth-century mind was overmastered by
the tenets of ecclesiasticism, and it was a dangerous heresy to
doubt that the Hebrew writings, upon which ecclesiasticism based
its claim, contained the last word regarding matters of science.
But the writers of the Hebrew text had been under the influence
of that Babylonian conception of the universe which accepted the
earth as unqualifiedly central--which, indeed, had never so much
as conceived a contradictory hypothesis; and so the Western
world, which had come to accept these writings as actually
supernatural in origin, lay under the spell of Oriental ideas of
a pre-scientific era. In our own day, no one speaking with
authority thinks of these Hebrew writings as having any
scientific weight whatever. Their interest in this regard is
purely antiquarian; hence from our changed point of view it seems
scarcely credible that Tycho Brahe can have been in earnest when
he quotes the Hebrew traditions as proof that the sun revolves
about the earth. Yet we shall see that for almost three centuries
after the time of Tycho, these same dreamings continued to be
cited in opposition to those scientific advances which new
observations made necessary; and this notwithstanding the fact
that the Oriental phrasing is, for the most part, poetically
ambiguous and susceptible of shifting interpretations, as the
criticism of successive generations has amply testified.

As we have said, Tycho Brahe, great observer as he was, could not
shake himself free from the Oriental incubus. He began his
objections, then, to the Copernican system by quoting the adverse
testimony of a Hebrew prophet who lived more than a thousand
years B.C. All of this shows sufficiently that Tycho Brahe was
not a great theorist. He was essentially an observer, but in this
regard he won a secure place in the very first rank. Indeed, he
was easily the greatest observing astronomer since Hipparchus,
between whom and himself there were many points of resemblance.
Hipparchus, it will be recalled, rejected the Aristarchian
conception of the universe just as Tycho rejected the conception
of Copernicus.

But if Tycho propounded no great generalizations, the list of
specific advances due to him is a long one, and some of these
were to prove important aids in the hands of later workers to the
secure demonstration of the Copernican idea. One of his most
important series of studies had to do with comets. Regarding
these bodies there had been the greatest uncertainty in the minds
of astronomers. The greatest variety of opinions regarding them
prevailed; they were thought on the one hand to be divine
messengers, and on the other to be merely igneous phenomena of
the earth's atmosphere. Tycho Brahe declared that a comet which
he observed in the year 1577 had no parallax, proving its extreme
distance. The observed course of the comet intersected the
planetary orbits, which fact gave a quietus to the long-mooted
question as to whether the Ptolemaic spheres were transparent
solids or merely imaginary; since the comet was seen to intersect
these alleged spheres, it was obvious that they could not be the
solid substance that they were commonly imagined to be, and this
fact in itself went far towards discrediting the Ptolemaic
system. It should be recalled, however, that this supposition of
tangible spheres for the various planetary and stellar orbits was
a mediaeval interpretation of Ptolemy's theory rather than an
interpretation of Ptolemy himself, there being nothing to show
that the Alexandrian astronomer regarded his cycles and epicycles
as other than theoretical.

An interesting practical discovery made by Tycho was his method
of determining the latitude of a place by means of two
observations made at an interval of twelve hours. Hitherto it had
been necessary to observe the sun's angle on the equinoctial
days, a period of six months being therefore required. Tycho
measured the angle of elevation of some star situated near the
pole, when on the meridian, and then, twelve hours later,
measured the angle of elevation of the same star when it again
came to the meridian at the opposite point of its apparent circle
about the polestar. Half the sum of these angles gives the
latitude of the place of observation.

As illustrating the accuracy of Tycho's observations, it may be
noted that he rediscovered a third inequality of the moon's
motion at its variation, he, in common with other European
astronomers, being then quite unaware that this inequality had
been observed by an Arabian astronomer. Tycho proved also that
the angle of inclination of the moon's orbit to the ecliptic is
subject to slight variation.

The very brilliant new star which shone forth suddenly in the
constellation of Cassiopeia in the year 1572, was made the object
of special studies by Tycho, who proved that the star had no
sensible parallax and consequently was far beyond the planetary
regions. The appearance of a new star was a phenomenon not
unknown to the ancients, since Pliny records that Hipparchus was
led by such an appearance to make his catalogue of the fixed
stars. But the phenomenon is sufficiently uncommon to attract
unusual attention. A similar phenomenon occurred in the year
1604, when the new star--in this case appearing in the
constellation of Serpentarius--was explained by Kepler as
probably proceeding from a vast combustion. This explanation--in
which Kepler is said to have followed. Tycho--is fully in accord
with the most recent theories on the subject, as we shall see in
due course. It is surprising to hear Tycho credited with so
startling a theory, but, on the other hand, such an explanation
is precisely what should be expected from the other astronomer
named. For Johann Kepler, or, as he was originally named, Johann
von Kappel, was one of the most speculative astronomers of any
age. He was forever theorizing, but such was the peculiar quality
of his mind that his theories never satisfied him for long unless
he could put them to the test of observation. Thanks to this
happy combination of qualities, Kepler became the discoverer of
three famous laws of planetary motion which lie at the very
foundation of modern astronomy, and which were to be largely
instrumental in guiding Newton to his still greater
generalization. These laws of planetary motion were vastly
important as corroborating the Copernican theory of the universe,
though their position in this regard was not immediately
recognized by contemporary thinkers. Let us examine with some
detail into their discovery, meantime catching a glimpse of the
life history of the remarkable man whose name they bear.


JOHANN KEPLER AND THE LAWS OF PLANETARY MOTION

Johann Kepler was born the 27th of December, 1571, in the little
town of Weil, in Wurtemburg. He was a weak, sickly child, further
enfeebled by a severe attack of small-pox. It would seem
paradoxical to assert that the parents of such a genius were
mismated, but their home was not a happy one, the mother being of
a nervous temperament, which perhaps in some measure accounted
for the genius of the child. The father led the life of a
soldier, and finally perished in the campaign against the Turks.
Young Kepler's studies were directed with an eye to the ministry.
After a preliminary training he attended the university at
Tubingen, where he came under the influence of the celebrated
Maestlin and became his life-long friend.

Curiously enough, it is recorded that at first Kepler had no
taste for astronomy or for mathematics. But the doors of the
ministry being presently barred to him, he turned with enthusiasm
to the study of astronomy, being from the first an ardent
advocate of the Copernican system. His teacher, Maestlin,
accepted the same doctrine, though he was obliged, for
theological reasons, to teach the Ptolemaic system, as also to
oppose the Gregorian reform of the calendar.

The Gregorian calendar, it should be explained, is so called
because it was instituted by Pope Gregory XIII., who put it into
effect in the year 1582, up to which time the so-called Julian
calendar, as introduced by Julius Caesar, had been everywhere
accepted in Christendom. This Julian calendar, as we have seen,
was a great improvement on preceding ones, but still lacked
something of perfection inasmuch as its theoretical day differed
appreciably from the actual day. In the course of fifteen hundred
years, since the time of Caesar, this defect amounted to a
discrepancy of about eleven days. Pope Gregory proposed to
correct this by omitting ten days from the calendar, which was
done in September, 1582. To prevent similar inaccuracies in the
future, the Gregorian calendar provided that once in four
centuries the additional day to make a leap-year should be
omitted, the date selected for such omission being the last year
of every fourth century. Thus the years 1500, 1900, and 2300,
A.D., would not be leap-years. By this arrangement an approximate
rectification of the calendar was effected, though even this does
not make it absolutely exact.

Such a rectification as this was obviously desirable, but there
was really no necessity for the omission of the ten days from the
calendar. The equinoctial day had shifted so that in the year
1582 it fell on the 10th of March and September. There was no
reason why it should not have remained there. It would greatly
have simplified the task of future historians had Gregory
contented himself with providing for the future stability of the
calendar without making the needless shift in question. We are so
accustomed to think of the 21st of March and 21st of September as
the natural periods of the equinox, that we are likely to forget
that these are purely arbitrary dates for which the 10th might
have been substituted without any inconvenience or inconsistency.

But the opposition to the new calendar, to which reference has
been made, was not based on any such considerations as these. It
was due, largely at any rate, to the fact that Germany at this
time was under sway of the Lutheran revolt against the papacy. So
effective was the opposition that the Gregorian calendar did not
come into vogue in Germany until the year 1699. It may be added
that England, under stress of the same manner of prejudice, held
out against the new reckoning until the year 1751, while Russia
does not accept it even now.

As the Protestant leaders thus opposed the papal attitude in a
matter of so practical a character as the calendar, it might
perhaps have been expected that the Lutherans would have had a
leaning towards the Copernican theory of the universe, since this
theory was opposed by the papacy. Such, however, was not the
case. Luther himself pointed out with great strenuousness, as a
final and demonstrative argument, the fact that Joshua commanded
the sun and not the earth to stand still; and his followers were
quite as intolerant towards the new teaching as were their
ultramontane opponents. Kepler himself was, at various times, to
feel the restraint of ecclesiastical opposition, though he was
never subjected to direct persecution, as was his friend and
contemporary, Galileo. At the very outset of Kepler's career
there was, indeed, question as to the publication of a work he
had written, because that work took for granted the truth of the
Copernican doctrine. This work appeared, however, in the year
1596. It bore the title Mysterium Cosmographium, and it attempted
to explain the positions of the various planetary bodies.
Copernicus had devoted much time to observation of the planets
with reference to measuring their distance, and his efforts had
been attended with considerable success. He did not, indeed, know
the actual distance of the sun, and, therefore, was quite unable
to fix the distance of any planet; but, on the other hand, he
determined the relative distance of all the planets then known,
as measured in terms of the sun's distance, with remarkable
accuracy.

With these measurements as a guide, Kepler was led to a very
fanciful theory, according to which the orbits of the five
principal planets sustain a peculiar relation to the five regular
solids of geometry. His theory was this: "Around the orbit of the
earth describe a dodecahedron--the circle comprising it will be
that of Mars; around Mars describe a tetrahedron--the circle
comprising it will be that of Jupiter; around Jupiter describe a
cube--the circle comprising it will be that of Saturn; now within
the earth's orbit inscribe an icosahedron--the inscribed circle
will be that of Venus; in the orbit of Venus inscribe an
octahedron --the circle inscribed will be that of Mercury."[3]

Though this arrangement was a fanciful one, which no one would
now recall had not the theorizer obtained subsequent fame on more
substantial grounds, yet it evidenced a philosophical spirit on
the part of the astronomer which, misdirected as it was in this
instance, promised well for the future. Tycho Brahe, to whom a
copy of the work was sent, had the acumen to recognize it as a
work of genius. He summoned the young astronomer to be his
assistant at Prague, and no doubt the association thus begun was
instrumental in determining the character of Kepler's future
work. It was precisely the training in minute observation that
could avail most for a mind which, like Kepler's, tended
instinctively to the formulation of theories. When Tycho Brahe
died, in 1601, Kepler became his successor. In due time he
secured access to all the unpublished observations of his great
predecessor, and these were of inestimable value to him in the
progress of his own studies.

Kepler was not only an ardent worker and an enthusiastic
theorizer, but he was an indefatigable writer, and it pleased him
to take the public fully into his confidence, not merely as to
his successes, but as to his failures. Thus his works elaborate
false theories as well as correct ones, and detail the
observations through which the incorrect guesses were refuted by
their originator. Some of these accounts are highly interesting,
but they must not detain us here. For our present purpose it must
suffice to point out the three important theories, which, as
culled from among a score or so of incorrect ones, Kepler was
able to demonstrate to his own satisfaction and to that of
subsequent observers. Stated in a few words, these theories,
which have come to bear the name of Kepler's Laws, are the
following:

1. That the planetary orbits are not circular, but elliptical,
the sun occupying one focus of the ellipses.

2. That the speed of planetary motion varies in different parts
of the orbit in such a way that an imaginary line drawn from the
sun to the planet--that is to say, the radius vector of the
planet's orbit--always sweeps the same area in a given time.


These two laws Kepler published as early as 1609. Many years more
of patient investigation were required before he found out the
secret of the relation between planetary distances and times of
revolution which his third law expresses. In 1618, however, he
was able to formulate this relation also, as follows:

3. The squares of the distance of the various planets from the
sun are proportional to the cubes of their periods of revolution
about the sun.


All these laws, it will be observed, take for granted the fact
that the sun is the centre of the planetary orbits. It must be
understood, too, that the earth is constantly regarded, in
accordance with the Copernican system, as being itself a member
of the planetary system, subject to precisely the same laws as
the other planets. Long familiarity has made these wonderful laws
of Kepler seem such a matter of course that it is difficult now
to appreciate them at their full value. Yet, as has been already
pointed out, it was the knowledge of these marvellously simple
relations between the planetary orbits that laid the foundation
for the Newtonian law of universal gravitation. Contemporary
judgment could not, of course, anticipate this culmination of a
later generation. What it could understand was that the first law
of Kepler attacked one of the most time-honored of metaphysical
conceptions--namely, the Aristotelian idea that the circle is the
perfect figure, and hence that the planetary orbits must be
circular. Not even Copernicus had doubted the validity of this
assumption. That Kepler dared dispute so firmly fixed a belief,
and one that seemingly had so sound a philosophical basis,
evidenced the iconoclastic nature of his genius. That he did not
rest content until he had demonstrated the validity of his
revolutionary assumption shows how truly this great theorizer
made his hypotheses subservient to the most rigid inductions.


GALILEO GALILEI

While Kepler was solving these riddles of planetary motion, there
was an even more famous man in Italy whose championship of the
Copernican doctrine was destined to give the greatest possible
publicity to the new ideas. This was Galileo Galilei, one of the
most extraordinary scientific observers of any age. Galileo was
born at Pisa, on the 18th of February (old style), 1564. The day
of his birth is doubly memorable, since on the same day the
greatest Italian of the preceding epoch, Michael Angelo, breathed
his last. Persons fond of symbolism have found in the coincidence
a forecast of the transit from the artistic to the scientific
epoch of the later Renaissance. Galileo came of an impoverished
noble family. He was educated for the profession of medicine, but
did not progress far before his natural proclivities directed him
towards the physical sciences. Meeting with opposition in Pisa,
he early accepted a call to the chair of natural philosophy in
the University of Padua, and later in life he made his home at
Florence. The mechanical and physical discoveries of Galileo will
claim our attention in another chapter. Our present concern is
with his contribution to the Copernican theory.

Galileo himself records in a letter to Kepler that he became a
convert to this theory at an early day. He was not enabled,
however, to make any marked contribution to the subject, beyond
the influence of his general teachings, until about the year
1610. The brilliant contributions which he made were due largely
to a single discovery--namely, that of the telescope. Hitherto
the astronomical observations had been made with the unaided eye.
Glass lenses had been known since the thirteenth century, but,
until now, no one had thought of their possible use as aids to
distant vision. The question of priority of discovery has never
been settled. It is admitted, however, that the chief honors
belong to the opticians of the Netherlands.

As early as the year 1590 the Dutch optician Zacharias Jensen
placed a concave and a convex lens respectively at the ends of a
tube about eighteen inches long, and used this instrument for the
purpose of magnifying small objects--producing, in short, a crude
microscope. Some years later, Johannes Lippershey, of whom not
much is known except that he died in 1619, experimented with a
somewhat similar combination of lenses, and made the startling
observation that the weather-vane on a distant church-steeple
seemed to be brought much nearer when viewed through the lens.
The combination of lenses he employed is that still used in the
construction of opera-glasses; the Germans still call such a
combination a Dutch telescope.

Doubtless a large number of experimenters took the matter up and
the fame of the new instrument spread rapidly abroad. Galileo,
down in Italy, heard rumors of this remarkable contrivance,
through the use of which it was said "distant objects might be
seen as clearly as those near at hand." He at once set to work to
construct for himself a similar instrument, and his efforts were
so far successful that at first he "saw objects three times as
near and nine times enlarged." Continuing his efforts, he
presently so improved his glass that objects were enlarged almost
a thousand times and made to appear thirty times nearer than when
seen with the naked eye. Naturally enough, Galileo turned this
fascinating instrument towards the skies, and he was almost
immediately rewarded by several startling discoveries. At the
very outset, his magnifying-glass brought to view a vast number
of stars that are invisible to the naked eye, and enabled the
observer to reach the conclusion that the hazy light of the Milky
Way is merely due to the aggregation of a vast number of tiny
stars.

Turning his telescope towards the moon, Galileo found that body
rough and earth-like in contour, its surface covered with
mountains, whose height could be approximately measured through
study of their shadows. This was disquieting, because the current
Aristotelian doctrine supposed the moon, in common with the
planets, to be a perfectly spherical, smooth body. The
metaphysical idea of a perfect universe was sure to be disturbed
by this seemingly rough workmanship of the moon. Thus far,
however, there was nothing in the observations of Galileo to bear
directly upon the Copernican theory; but when an inspection was
made of the planets the case was quite different. With the aid of
his telescope, Galileo saw that Venus, for example, passes
through phases precisely similar to those of the moon, due, of
course, to the same cause. Here, then, was demonstrative evidence
that the planets are dark bodies reflecting the light of the sun,
and an explanation was given of the fact, hitherto urged in
opposition to the Copernican theory, that the inferior planets do
not seem many times brighter when nearer the earth than when in
the most distant parts of their orbits; the explanation being, of
course, that when the planets are between the earth and the sun
only a small portion of their illumined surfaces is visible from
the earth.

On inspecting the planet Jupiter, a still more striking
revelation was made, as four tiny stars were observed to occupy
an equatorial position near that planet, and were seen, when
watched night after night, to be circling about the planet,
precisely as the moon circles about the earth. Here, obviously,
was a miniature solar system--a tangible object-lesson in the
Copernican theory. In honor of the ruling Florentine house of the
period, Galileo named these moons of Jupiter, Medicean stars.

Turning attention to the sun itself, Galileo observed on the
surface of that luminary a spot or blemish which gradually
changed its shape, suggesting that changes were taking place in
the substance of the sun--changes obviously incompatible with the
perfect condition demanded by the metaphysical theorists. But
however disquieting for the conservative, the sun's spots served
a most useful purpose in enabling Galileo to demonstrate that the
sun itself revolves on its axis, since a given spot was seen to
pass across the disk and after disappearing to reappear in due
course. The period of rotation was found to be about twenty-four
days.

It must be added that various observers disputed priority of
discovery of the sun's spots with Galileo. Unquestionably a
sun-spot had been seen by earlier observers, and by them mistaken
for the transit of an inferior planet. Kepler himself had made
this mistake. Before the day of the telescope, he had viewed the
image of the sun as thrown on a screen in a camera-obscura, and
had observed a spot on the disk which be interpreted as
representing the planet Mercury, but which, as is now known, must
have been a sun-spot, since the planetary disk is too small to
have been revealed by this method. Such observations as these,
however interesting, cannot be claimed as discoveries of the
sun-spots. It is probable, however, that several discoverers
(notably Johann Fabricius) made the telescopic observation of the
spots, and recognized them as having to do with the sun's
surface, almost simultaneously with Galileo. One of these
claimants was a Jesuit named Scheiner, and the jealousy of this
man is said to have had a share in bringing about that
persecution to which we must now refer.

There is no more famous incident in the history of science than
the heresy trial through which Galileo was led to the nominal
renunciation of his cherished doctrines. There is scarcely
another incident that has been commented upon so variously. Each
succeeding generation has put its own interpretation on it. The
facts, however, have been but little questioned. It appears that
in the year 1616 the church became at last aroused to the
implications of the heliocentric doctrine of the universe.
Apparently it seemed clear to the church authorities that the
authors of the Bible believed the world to be immovably fixed at
the centre of the universe. Such, indeed, would seem to be the
natural inference from various familiar phrases of the Hebrew
text, and what we now know of the status of Oriental science in
antiquity gives full warrant to this interpretation. There is no
reason to suppose that the conception of the subordinate place of
the world in the solar system had ever so much as occurred, even
as a vague speculation, to the authors of Genesis. In common with
their contemporaries, they believed the earth to be the
all-important body in the universe, and the sun a luminary placed
in the sky for the sole purpose of giving light to the earth.
There is nothing strange, nothing anomalous, in this view; it
merely reflects the current notions of Oriental peoples in
antiquity. What is strange and anomalous is the fact that the
Oriental dreamings thus expressed could have been supposed to
represent the acme of scientific knowledge. Yet such a hold had
these writings taken upon the Western world that not even a
Galileo dared contradict them openly; and when the church fathers
gravely declared the heliocentric theory necessarily false,
because contradictory to Scripture, there were probably few
people in Christendom whose mental attitude would permit them
justly to appreciate the humor of such a pronouncement. And,
indeed, if here and there a man might have risen to such an
appreciation, there were abundant reasons for the repression of
the impulse, for there was nothing humorous about the response
with which the authorities of the time were wont to meet the
expression of iconoclastic opinions. The burning at the stake of
Giordano Bruno, in the year 1600, was, for example, an
object-lesson well calculated to restrain the enthusiasm of other
similarly minded teachers.

Doubtless it was such considerations that explained the relative
silence of the champions of the Copernican theory, accounting for
the otherwise inexplicable fact that about eighty years elapsed
after the death of Copernicus himself before a single text-book
expounded his theory. The text-book which then appeared, under
date of 1622, was written by the famous Kepler, who perhaps was
shielded in a measure from the papal consequences of such
hardihood by the fact of residence in a Protestant country. Not
that the Protestants of the time favored the heliocentric
doctrine--we have already quoted Luther in an adverse sense--but
of course it was characteristic of the Reformation temper to
oppose any papal pronouncement, hence the ultramontane
declaration of 1616 may indirectly have aided the doctrine which
it attacked, by making that doctrine less obnoxious to Lutheran
eyes. Be that as it may, the work of Kepler brought its author
into no direct conflict with the authorities. But the result was
quite different when, in 1632, Galileo at last broke silence and
gave the world, under cover of the form of dialogue, an elaborate
exposition of the Copernican theory. Galileo, it must be
explained, had previously been warned to keep silent on the
subject, hence his publication doubly offended the authorities.
To be sure, he could reply that his dialogue introduced a
champion of the Ptolemaic system to dispute with the upholder of
the opposite view, and that, both views being presented with full
array of argument, the reader was left to reach a verdict for
himself, the author having nowhere pointedly expressed an
opinion. But such an argument, of course, was specious, for no
one who read the dialogue could be in doubt as to the opinion of
the author. Moreover, it was hinted that Simplicio, the character
who upheld the Ptolemaic doctrine and who was everywhere worsted
in the argument, was intended to represent the pope himself--a
suggestion which probably did no good to Galileo's cause.

The character of Galileo's artistic presentation may best be
judged from an example, illustrating the vigorous assault of
Salviati, the champion of the new theory, and the feeble retorts
of his conservative antagonist:

"Salviati. Let us then begin our discussion with the
consideration that, whatever motion may be attributed to the
earth, yet we, as dwellers upon it, and hence as participators in
its motion, cannot possibly perceive anything of it, presupposing
that we are to consider only earthly things. On the other hand,
it is just as necessary that this same motion belong apparently
to all other bodies and visible objects, which, being separated
from the earth, do not take part in its motion. The correct
method to discover whether one can ascribe motion to the earth,
and what kind of motion, is, therefore, to investigate and
observe whether in bodies outside the earth a perceptible motion
may be discovered which belongs to all alike. Because a movement
which is perceptible only in the moon, for instance, and has
nothing to do with Venus or Jupiter or other stars, cannot
possibly be peculiar to the earth, nor can its seat be anywhere
else than in the moon. Now there is one such universal movement
which controls all others--namely, that which the sun, moon, the
other planets, the fixed stars--in short, the whole universe,
with the single exception of the earth--appears to execute from
east to west in the space of twenty-four hours. This now, as it
appears at the first glance anyway, might just as well be a
motion of the earth alone as of all the rest of the universe with
the exception of the earth, for the same phenomena would result
from either hypothesis. Beginning with the most general, I will
enumerate the reasons which seem to speak in favor of the earth's
motion. When we merely consider the immensity of the starry
sphere in comparison with the smallness of the terrestrial ball,
which is contained many million times in the former, and then
think of the rapidity of the motion which completes a whole
rotation in one day and night, I cannot persuade myself how any
one can hold it to be more reasonable and credible that it is the
heavenly sphere which rotates, while the earth stands still.

"Simplicio. I do not well understand how that powerful motion may
be said to as good as not exist for the sun, the moon, the other
planets, and the innumerable host of fixed stars. Do you call
that nothing when the sun goes from one meridian to another,
rises up over this horizon and sinks behind that one, brings now
day, and now night; when the moon goes through similar changes,
and the other planets and fixed stars in the same way?

"Salviati. All the changes you mention are such only in respect
to the earth. To convince yourself of it, only imagine the earth
out of existence. There would then be no rising and setting of
the sun or of the moon, no horizon, no meridian, no day, no
night--in short, the said motion causes no change of any sort in
the relation of the sun to the moon or to any of the other
heavenly bodies, be they planets or fixed stars. All changes are
rather in respect to the earth; they may all be reduced to the
simple fact that the sun is first visible in China, then in
Persia, afterwards in Egypt, Greece, France, Spain, America,
etc., and that the same thing happens with the moon and the other
heavenly bodies. Exactly the same thing happens and in exactly
the same way if, instead of disturbing so large a part of the
universe, you let the earth revolve about itself. The difficulty
is, however, doubled, inasmuch as a second very important problem
presents itself. If, namely, that powerful motion is ascribed to
the heavens, it is absolutely necessary to regard it as opposed
to the individual motion of all the planets, every one of which
indubitably has its own very leisurely and moderate movement from
west to east. If, on the other hand, you let the earth move about
itself, this opposition of motion disappears.

"The improbability is tripled by the complete overthrow of that
order which rules all the heavenly bodies in which the revolving
motion is definitely established. The greater the sphere is in
such a case, so much longer is the time required for its
revolution; the smaller the sphere the shorter the time. Saturn,
whose orbit surpasses those of all the planets in size, traverses
it in thirty years. Jupiter[4] completes its smaller course in
twelve years, Mars in two; the moon performs its much smaller
revolution within a month. Just as clearly in the Medicean stars,
we see that the one nearest Jupiter completes its revolution in a
very short time--about forty-two hours; the next in about three
and one-half days, the third in seven, and the most distant one
in sixteen days. This rule, which is followed throughout, will
still remain if we ascribe the twenty-four-hourly motion to a
rotation of the earth. If, however, the earth is left motionless,
we must go first from the very short rule of the moon to ever
greater ones--to the two-yearly rule of Mars, from that to the
twelve-yearly one of Jupiter, from here to the thirty-yearly one
of Saturn, and then suddenly to an incomparably greater sphere,
to which also we must ascribe a complete rotation in twenty-four
hours. If, however, we assume a motion of the earth, the rapidity
of the periods is very well preserved; from the slowest sphere of
Saturn we come to the wholly motionless fixed stars. We also
escape thereby a fourth difficulty, which arises as soon as we
assume that there is motion in the sphere of the stars. I mean
the great unevenness in the movement of these very stars, some of
which would have to revolve with extraordinary rapidity in
immense circles, while others moved very slowly in small circles,
since some of them are at a greater, others at a less, distance
from the pole. That is likewise an inconvenience, for, on the one
hand, we see all those stars, the motion of which is indubitable,
revolve in great circles, while, on the other hand, there seems
to be little object in placing bodies, which are to move in
circles, at an enormous distance from the centre and then let
them move in very small circles. And not only are the size of the
different circles and therewith the rapidity of the movement very
different in the different fixed stars, but the same stars also
change their orbits and their rapidity of motion. Therein
consists the fifth inconvenience. Those stars, namely, which were
at the equator two thousand years ago, and hence described great
circles in their revolutions, must to-day move more slowly and in
smaller circles, because they are many degrees removed from it.
It will even happen, after not so very long a time, that one of
those which have hitherto been continually in motion will finally
coincide with the pole and stand still, but after a period of
repose will again begin to move. The other stars in the mean
while, which unquestionably move, all have, as was said, a great
circle for an orbit and keep this unchangeably.

"The improbability is further increased--this may be considered
the sixth inconvenience--by the fact that it is impossible to
conceive what degree of solidity those immense spheres must have,
in the depths of which so many stars are fixed so enduringly that
they are kept revolving evenly in spite of such difference of
motion without changing their respective positions. Or if,
according to the much more probable theory, the heavens are
fluid, and every star describes an orbit of its own, according to
what law then, or for what reason, are their orbits so arranged
that, when looked at from the earth, they appear to be contained
in one single sphere? To attain this it seems to me much easier
and more convenient to make them motionless instead of moving,
just as the paving-stones on the market-place, for instance,
remain in order more easily than the swarms of children running
about on them.

"Finally, the seventh difficulty: If we attribute the daily
rotation to the higher region of the heavens, we should have to
endow it with force and power sufficient to carry with it the
innumerable host of the fixed stars --every one a body of very
great compass and much larger than the earth--and all the
planets, although the latter, like the earth, move naturally in
an opposite direction. In the midst of all this the little earth,
single and alone, would obstinately and wilfully withstand such
force--a supposition which, it appears to me, has much against
it. I could also not explain why the earth, a freely poised body,
balancing itself about its centre, and surrounded on all sides by
a fluid medium, should not be affected by the universal rotation.
Such difficulties, however, do not confront us if we attribute
motion to the earth--such a small, insignificant body in
comparison with the whole universe, and which for that very
reason cannot exercise any power over the latter.

"Simplicio. You support your arguments throughout, it seems to
me, on the greater ease and simplicity with which the said
effects are produced. You mean that as a cause the motion of the
earth alone is just as satisfactory as the motion of all the rest
of the universe with the exception of the earth; you hold the
actual event to be much easier in the former case than in the
latter. For the ruler of the universe, however, whose might is
infinite, it is no less easy to move the universe than the earth
or a straw balm. But if his power is infinite, why should not a
greater, rather than a very small, part of it be revealed to me?

"Salviati. If I had said that the universe does not move on
account of the impotence of its ruler, I should have been wrong
and your rebuke would have been in order. I admit that it is just
as easy for an infinite power to move a hundred thousand as to
move one. What I said, however, does not refer to him who causes
the motion, but to that which is moved. In answer to your remark
that it is more fitting for an infinite power to reveal a large
part of itself rather than a little, I answer that, in relation
to the infinite, one part is not greater than another, if both
are finite. Hence it is unallowable to say that a hundred
thousand is a larger part of an infinite number than two,
although the former is fifty thousand times greater than the
latter. If, therefore, we consider the moving bodies, we must
unquestionably regard the motion of the earth as a much simpler
process than that of the universe; if, furthermore, we direct our
attention to so many other simplifications which may be reached
only by this theory, the daily movement of the earth must appear
much more probable than the motion of the universe without the
earth, for, according to Aristotle's just axiom, 'Frustra fit per
plura, quod potest fieri per p auciora' (It is vain to expend
many means where a few are sufficient)."[2]


The work was widely circulated, and it was received with an
interest which bespeaks a wide-spread undercurrent of belief in
the Copernican doctrine. Naturally enough, it attracted immediate
attention from the church authorities. Galileo was summoned to
appear at Rome to defend his conduct. The philosopher, who was
now in his seventieth year, pleaded age and infirmity. He had no
desire for personal experience of the tribunal of the
Inquisition; but the mandate was repeated, and Galileo went to
Rome. There, as every one knows, he disavowed any intention to
oppose the teachings of Scripture, and formally renounced the
heretical doctrine of the earth's motion. According to a tale
which so long passed current that every historian must still
repeat it though no one now believes it authentic, Galileo
qualified his renunciation by muttering to himself, "E pur si
muove" (It does move, none the less), as he rose to his feet and
retired from the presence of his persecutors. The tale is one of
those fictions which the dramatic sense of humanity is wont to
impose upon history, but, like most such fictions, it expresses
the spirit if not the letter of truth; for just as no one
believes that Galileo's lips uttered the phrase, so no one doubts
that the rebellious words were in his mind.

After his formal renunciation, Galileo was allowed to depart, but
with the injunction that he abstain in future from heretical
teaching. The remaining ten years of his life were devoted
chiefly to mechanics, where his experiments fortunately opposed
the Aristotelian rather than the Hebrew teachings. Galileo's
death occurred in 1642, a hundred years after the death of
Copernicus. Kepler had died thirteen years before, and there
remained no astronomer in the field who is conspicuous in the
history of science as a champion of the Copernican doctrine. But
in truth it might be said that the theory no longer needed a
champion. The researches of Kepler and Galileo had produced a
mass of evidence for the Copernican theory which amounted to
demonstration. A generation or two might be required for this
evidence to make itself everywhere known among men of science,
and of course the ecclesiastical authorities must be expected to
stand by their guns for a somewhat longer period. In point of
fact, the ecclesiastical ban was not technically removed by the
striking of the Copernican books from the list of the Index
Expurgatorius until the year 1822, almost two hundred years after
the date of Galileo's dialogue. But this, of course, is in no
sense a guide to the state of general opinion regarding the
theory. We shall gain a true gauge as to this if we assume that
the greater number of important thinkers had accepted the
heliocentric doctrine before the middle of the seventeenth
century, and that before the close of that century the old
Ptolemaic idea had been quite abandoned. A wonderful revolution
in man's estimate of the universe had thus been effected within
about two centuries after the birth of Copernicus.



V. GALILEO AND THE NEW PHYSICS

After Galileo had felt the strong hand of the Inquisition, in
1632, he was careful to confine his researches, or at least his
publications, to topics that seemed free from theological
implications. In doing so he reverted to the field of his
earliest studies --namely, the field of mechanics; and the
Dialoghi delle Nuove Scienze, which he finished in 1636, and
which was printed two years later, attained a celebrity no less
than that of the heretical dialogue that had preceded it. The
later work was free from all apparent heresies, yet perhaps it
did more towards the establishment of the Copernican doctrine,
through the teaching of correct mechanical principles, than the
other work had accomplished by a more direct method.

Galileo's astronomical discoveries were, as we have seen, in a
sense accidental; at least, they received their inception through
the inventive genius of another. His mechanical discoveries, on
the other hand, were the natural output of his own creative
genius. At the very beginning of his career, while yet a very
young man, though a professor of mathematics at Pisa, he had
begun that onslaught upon the old Aristotelian ideas which he was
to continue throughout his life. At the famous leaning tower in
Pisa, the young iconoclast performed, in the year 1590, one of
the most theatrical demonstrations in the history of science.
Assembling a multitude of champions of the old ideas, he proposed
to demonstrate the falsity of the Aristotelian doctrine that the
velocity of falling bodies is proportionate to their weight.
There is perhaps no fact more strongly illustrative of the temper
of the Middle Ages than the fact that this doctrine, as taught by
the Aristotelian philosopher, should so long have gone
unchallenged. Now, however, it was put to the test; Galileo
released a half-pound weight and a hundred-pound cannon-ball from
near the top of the tower, and, needless to say, they reached the
ground together. Of course, the spectators were but little
pleased with what they saw. They could not doubt the evidence of
their own senses as to the particular experiment in question;
they could suggest, however, that the experiment involved a
violation of the laws of nature through the practice of magic. To
controvert so firmly established an idea savored of heresy. The
young man guilty of such iconoclasm was naturally looked at
askance by the scholarship of his time. Instead of being
applauded, he was hissed, and he found it expedient presently to
retire from Pisa.

Fortunately, however, the new spirit of progress had made itself
felt more effectively in some other portions of Italy, and so
Galileo found a refuge and a following in Padua, and afterwards
in Florence; and while, as we have seen, he was obliged to curb
his enthusiasm regarding the subject that was perhaps nearest his
heart--the promulgation of the Copernican theory--yet he was
permitted in the main to carry on his experimental observations
unrestrained. These experiments gave him a place of unquestioned
authority among his contemporaries, and they have transmitted his
name to posterity as that of one of the greatest of experimenters
and the virtual founder of modern mechanical science. The
experiments in question range over a wide field; but for the most
part they have to do with moving bodies and with questions of
force, or, as we should now say, of energy. The experiment at the
leaning tower showed that the velocity of falling bodies is
independent of the weight of the bodies, provided the weight is
sufficient to overcome the resistance of the atmosphere. Later
experiments with falling bodies led to the discovery of laws
regarding the accelerated velocity of fall. Such velocities were
found to bear a simple relation to the period of time from the
beginning of the fall. Other experiments, in which balls were
allowed to roll down inclined planes, corroborated the
observation that the pull of gravitation gave a velocity
proportionate to the length of fall, whether such fall were
direct or in a slanting direction.

These studies were associated with observations on projectiles,
regarding which Galileo was the first to entertain correct
notions. According to the current idea, a projectile fired, for
example, from a cannon, moved in a straight horizontal line until
the propulsive force was exhausted, and then fell to the ground
in a perpendicular line. Galileo taught that the projectile
begins to fall at once on leaving the mouth of the cannon and
traverses a parabolic course. According to his idea, which is now
familiar to every one, a cannon-ball dropped from the level of
the cannon's muzzle will strike the ground simultaneously with a
ball fired horizontally from the cannon. As to the paraboloid
course pursued by the projectile, the resistance of the air is a
factor which Galileo could not accurately compute, and which
interferes with the practical realization of his theory. But this
is a minor consideration. The great importance of his idea
consists in the recognition that such a force as that of
gravitation acts in precisely the same way upon all unsupported
bodies, whether or not such bodies be at the same time acted upon
by a force of translation.

Out of these studies of moving bodies was gradually developed a
correct notion of several important general laws of
mechanics--laws a knowledge of which was absolutely essential to
the progress of physical science. The belief in the rotation of
the earth made necessary a clear conception that all bodies at
the surface of the earth partake of that motion quite
independently of their various observed motions in relation to
one another. This idea was hard to grasp, as an oft-repeated
argument shows. It was asserted again and again that, if the
earth rotates, a stone dropped from the top of a tower could not
fall at the foot of the tower, since the earth's motion would
sweep the tower far away from its original position while the
stone is in transit.

This was one of the stock arguments against the earth's motion,
yet it was one that could be refuted with the greatest ease by
reasoning from strictly analogous experiments. It might readily
be observed, for example, that a stone dropped from a moving cart
does not strike the ground directly below the point from which it
is dropped, but partakes of the forward motion of the cart. If
any one doubt this he has but to jump from a moving cart to be
given a practical demonstration of the fact that his entire body
was in some way influenced by the motion of translation.
Similarly, the simple experiment of tossing a ball from the deck
of a moving ship will convince any one that the ball partakes of
the motion of the ship, so that it can be manipulated precisely
as if the manipulator were standing on the earth. In short,
every-day experience gives us illustrations of what might be
called compound motion, which makes it seem altogether plausible
that, if the earth is in motion, objects at its surface will
partake of that motion in a way that does not interfere with any
other movements to which they may be subjected. As the Copernican
doctrine made its way, this idea of compound motion naturally
received more and more attention, and such experiments as those
of Galileo prepared the way for a new interpretation of the
mechanical principles involved.

The great difficulty was that the subject of moving bodies had
all along been contemplated from a wrong point of view. Since
force must be applied to an object to put it in motion, it was
perhaps not unnaturally assumed that similar force must continue
to be applied to keep the object in motion. When, for example, a
stone is thrown from the hand, the direct force applied
necessarily ceases as soon as the projectile leaves the hand. The
stone, nevertheless, flies on for a certain distance and then
falls to the ground. How is this flight of the stone to be
explained? The ancient philosophers puzzled more than a little
over this problem, and the Aristotelians reached the conclusion
that the motion of the hand had imparted a propulsive motion to
the air, and that this propulsive motion was transmitted to the
stone, pushing it on. Just how the air took on this propulsive
property was not explained, and the vagueness of thought that
characterized the time did not demand an explanation. Possibly
the dying away of ripples in water may have furnished, by
analogy, an explanation of the gradual dying out of the impulse
which propels the stone.

All of this was, of course, an unfortunate maladjustment of the
point of view. As every one nowadays knows, the air retards the
progress of the stone, enabling the pull of gravitation to drag
it to the earth earlier than it otherwise could. Were the
resistance of the air and the pull of gravitation removed, the
stone as projected from the hand would fly on in a straight line,
at an unchanged velocity, forever. But this fact, which is
expressed in what we now term the first law of motion, was
extremely difficult to grasp. The first important step towards it
was perhaps implied in Galileo's study of falling bodies. These
studies, as we have seen, demonstrated that a half-pound weight
and a hundred-pound weight fall with the same velocity. It is,
however, matter of common experience that certain bodies, as, for
example, feathers, do not fall at the same rate of speed with
these heavier bodies. This anomaly demands an explanation, and
the explanation is found in the resistance offered the relatively
light object by the air. Once the idea that the air may thus act
as an impeding force was grasped, the investigator of mechanical
principles had entered on a new and promising course.

Galileo could not demonstrate the retarding influence of air in
the way which became familiar a generation or two later; he could
not put a feather and a coin in a vacuum tube and prove that the
two would there fall with equal velocity, because, in his day,
the air-pump had not yet been invented. The experiment was made
only a generation after the time of Galileo, as we shall see;
but, meantime, the great Italian had fully grasped the idea that
atmospheric resistance plays a most important part in regard to
the motion of falling and projected bodies. Thanks largely to his
own experiments, but partly also to the efforts of others, he had
come, before the end of his life, pretty definitely to realize
that the motion of a projectile, for example, must be thought of
as inherent in the projectile itself, and that the retardation or
ultimate cessation of that motion is due to the action of
antagonistic forces. In other words, he had come to grasp the
meaning of the first law of motion. It remained, however, for the
great Frenchman Descartes to give precise expression to this law
two years after Galileo's death. As Descartes expressed it in his
Principia Philosophiae, published in 1644, any body once in
motion tends to go on in a straight line, at a uniform rate of
speed, forever. Contrariwise, a stationary body will remain
forever at rest unless acted on by some disturbing force.

This all-important law, which lies at the very foundation of all
true conceptions of mechanics, was thus worked out during the
first half of the seventeenth century, as the outcome of
numberless experiments for which Galileo's experiments with
failing bodies furnished the foundation. So numerous and so
gradual were the steps by which the reversal of view regarding
moving bodies was effected that it is impossible to trace them in
detail. We must be content to reflect that at the beginning of
the Galilean epoch utterly false notions regarding the subject
were entertained by the very greatest philosophers--by Galileo
himself, for example, and by Kepler--whereas at the close of that
epoch the correct and highly illuminative view had been attained.

We must now consider some other experiments of Galileo which led
to scarcely less-important results. The experiments in question
had to do with the movements of bodies passing down an inclined
plane, and with the allied subject of the motion of a pendulum.
The elaborate experiments of Galileo regarding the former subject
were made by measuring the velocity of a ball rolling down a
plane inclined at various angles. He found that the velocity
acquired by a ball was proportional to the height from which the
ball descended regardless of the steepness of the incline.
Experiments were made also with a ball rolling down a curved
gutter, the curve representing the are of a circle. These
experiments led to the study of the curvilinear motions of a
weight suspended by a cord; in other words, of the pendulum.

Regarding the motion of the pendulum, some very curious facts
were soon ascertained. Galileo found, for example, that a
pendulum of a given length performs its oscillations with the
same frequency though the arc described by the pendulum be varied
greatly.[1] He found, also, that the rate of oscillation for
pendulums of different lengths varies according to a simple law.
In order that one pendulum shall oscillate one-half as fast as
another, the length of the pendulums must be as four to one.
Similarly, by lengthening the pendulums nine times, the
oscillation is reduced to one-third, In other words, the rate of
oscillation of pendulums varies inversely as the square of their
length. Here, then, is a simple relation between the motions of
swinging bodies which suggests the relation which Kepler bad
discovered between the relative motions of the planets. Every
such discovery coming in this age of the rejuvenation of
experimental science had a peculiar force in teaching men the
all-important lesson that simple laws lie back of most of the
diverse phenomena of nature, if only these laws can be
discovered.

Galileo further observed that his pendulum might be constructed
of any weight sufficiently heavy readily to overcome the
atmospheric resistance, and that, with this qualification,
neither the weight nor the material had any influence upon the
time of oscillation, this being solely determined by the length
of the cord. Naturally, the practical utility of these
discoveries was not overlooked by Galileo. Since a pendulum of a
given length oscillates with unvarying rapidity, here is an
obvious means of measuring time. Galileo, however, appears not to
have met with any great measure of success in putting this idea
into practice. It remained for the mechanical ingenuity of
Huyghens to construct a satisfactory pendulum clock.

As a theoretical result of the studies of rolling and oscillating
bodies, there was developed what is usually spoken of as the
third law of motion--namely, the law that a given force operates
upon a moving body with an effect proportionate to its effect
upon the same body when at rest. Or, as Whewell states the law:
"The dynamical effect of force is as the statical effect; that
is, the velocity which any force generates in a given time, when
it puts the body in motion, is proportional to the pressure which
this same force produces in a body at rest."[2] According to the
second law of motion, each one of the different forces, operating
at the same time upon a moving body, produces the same effect as
if it operated upon the body while at rest.


STEVINUS AND THE LAW OF EQUILIBRIUM

It appears, then, that the mechanical studies of Galileo, taken
as a whole, were nothing less than revolutionary. They
constituted the first great advance upon the dynamic studies of
Archimedes, and then led to the secure foundation for one of the
most important of modern sciences. We shall see that an important
company of students entered the field immediately after the time
of Galileo, and carried forward the work he had so well begun.
But before passing on to the consideration of their labors, we
must consider work in allied fields of two men who were
contemporaries of Galileo and whose original labors were in some
respects scarcely less important than his own. These men are the
Dutchman Stevinus, who must always be remembered as a co-laborer
with Galileo in the foundation of the science of dynamics, and
the Englishman Gilbert, to whom is due the unqualified praise of
first subjecting the phenomenon of magnetism to a strictly
scientific investigation.

Stevinus was born in the year 1548, and died in 1620. He was a
man of a practical genius, and he attracted the attention of his
non-scientific contemporaries, among other ways, by the
construction of a curious land-craft, which, mounted on wheels,
was to be propelled by sails like a boat. Not only did he write a
book on this curious horseless carriage, but he put his idea into
practical application, producing a vehicle which actually
traversed the distance between Scheveningen and Petton, with no
fewer than twenty-seven passengers, one of them being Prince
Maurice of Orange. This demonstration was made about the year
1600. It does not appear, however, that any important use was
made of the strange vehicle; but the man who invented it put his
mechanical ingenuity to other use with better effect. It was he
who solved the problem of oblique forces, and who discovered the
important hydrostatic principle that the pressure of fluids is
proportionate to their depth, without regard to the shape of the
including vessel.

The study of oblique forces was made by Stevinus with the aid of
inclined planes. His most demonstrative experiment was a very
simple one, in which a chain of balls of equal weight was hung
from a triangle; the triangle being so constructed as to rest on
a horizontal base, the oblique sides bearing the relation to each
other of two to one. Stevinus found that his chain of balls just
balanced when four balls were on the longer side and two on the
shorter and steeper side. The balancing of force thus brought
about constituted a stable equilibrium, Stevinus being the first
to discriminate between such a condition and the unbalanced
condition called unstable equilibrium. By this simple experiment
was laid the foundation of the science of statics. Stevinus had a
full grasp of the principle which his experiment involved, and he
applied it to the solution of oblique forces in all directions.
Earlier investigations of Stevinus were published in 1608. His
collected works were published at Leyden in 1634.

This study of the equilibrium of pressure of bodies at rest led
Stevinus, not unnaturally, to consider the allied subject of the
pressure of liquids. He is to be credited with the explanation of
the so-called hydrostatic paradox. The familiar modern experiment
which illustrates this paradox is made by inserting a long
perpendicular tube of small caliber into the top of a tight
barrel. On filling the barrel and tube with water, it is possible
to produce a pressure which will burst the barrel, though it be a
strong one, and though the actual weight of water in the tube is
comparatively insignificant. This illustrates the fact that the
pressure at the bottom of a column of liquid is proportionate to
the height of the column, and not to its bulk, this being the
hydrostatic paradox in question. The explanation is that an
enclosed fluid under pressure exerts an equal force upon all
parts of the circumscribing wall; the aggregate pressure may,
therefore, be increased indefinitely by increasing the surface.
It is this principle, of course, which is utilized in the
familiar hydrostatic press. Theoretical explanations of the
pressure of liquids were supplied a generation or two later by
numerous investigators, including Newton, but the practical
refoundation of the science of hydrostatics in modern times dates
from the experiments of Stevinus.


GALILEO AND THE EQUILIBRIUM OF FLUIDS

Experiments of an allied character, having to do with the
equilibrium of fluids, exercised the ingenuity of Galileo. Some
of his most interesting experiments have to do with the subject
of floating bodies. It will be recalled that Archimedes, away
back in the Alexandrian epoch, had solved the most important
problems of hydrostatic equilibrium. Now, however, his
experiments were overlooked or forgotten, and Galileo was obliged
to make experiments anew, and to combat fallacious views that
ought long since to have been abandoned. Perhaps the most
illuminative view of the spirit of the times can be gained by
quoting at length a paper of Galileo's, in which he details his
own experiments with floating bodies and controverts the views of
his opponents. The paper has further value as illustrating
Galileo's methods both as experimenter and as speculative
reasoner.

The current view, which Galileo here undertakes to refute,
asserts that water offers resistance to penetration, and that
this resistance is instrumental in determining whether a body
placed in water will float or sink. Galileo contends that water
is non-resistant, and that bodies float or sink in virtue of
their respective weights. This, of course, is merely a
restatement of the law of Archimedes. But it remains to explain
the fact that bodies of a certain shape will float, while bodies
of the same material and weight, but of a different shape, will
sink. We shall see what explanation Galileo finds of this anomaly
as we proceed.

In the first place, Galileo makes a cone of wood or of wax, and
shows that when it floats with either its point or its base in
the water, it displaces exactly the same amount of fluid,
although the apex is by its shape better adapted to overcome the
resistance of the water, if that were the cause of buoyancy.
Again, the experiment may be varied by tempering the wax with
filings of lead till it sinks in the water, when it will be found
that in any figure the same quantity of cork must be added to it
to raise the surface.

"But," says Galileo, "this silences not my antagonists; they say
that all the discourse hitherto made by me imports little to
them, and that it serves their turn; that they have demonstrated
in one instance, and in such manner and figure as pleases them
best --namely, in a board and in a ball of ebony--that one when
put into the water sinks to the bottom, and that the other stays
to swim on the top; and the matter being the same, and the two
bodies differing in nothing but in figure, they affirm that with
all perspicuity they have demonstrated and sensibly manifested
what they undertook. Nevertheless, I believe, and think I can
prove, that this very experiment proves nothing against my
theory. And first, it is false that the ball sinks and the board
not; for the board will sink, too, if you do to both the figures
as the words of our question require; that is, if you put them
both in the water; for to be in the water implies to be placed in
the water, and by Aristotle's own definition of place, to be
placed imports to be environed by the surface of the ambient
body; but when my antagonists show the floating board of ebony,
they put it not into the water, but upon the water; where, being
detained by a certain impediment (of which more anon), it is
surrounded, partly with water, partly with air, which is contrary
to our agreement, for that was that bodies should be in the
water, and not part in the water, part in the air.

"I will not omit another reason, founded also upon experience,
and, if I deceive not myself, conclusive against the notion that
figure, and the resistance of the water to penetration, have
anything to do with the buoyancy of bodies. Choose a piece of
wood or other matter, as, for instance, walnut-wood, of which a
ball rises from the bottom of the water to the surface more
slowly than a ball of ebony of the same size sinks, so that,
clearly, the ball of ebony divides the water more readily in
sinking than the ball of wood does in rising. Then take a board
of walnut-tree equal to and like the floating one of my
antagonists; and if it be true that this latter floats by reason
of the figure being unable to penetrate the water, the other of
walnut-tree, without a question, if thrust to the bottom, ought
to stay there, as having the same impeding figure, and being less
apt to overcome the said resistance of the water. But if we find
by experience that not only the thin board, but every other
figure of the same walnut-tree, will return to float, as
unquestionably we shall, then I must desire my opponents to
forbear to attribute the floating of the ebony to the figure of
the board, since the resistance of the water is the same in
rising as in sinking, and the force of ascension of the
walnut-tree is less than the ebony's force for going to the
bottom.

"Now let us return to the thin plate of gold or silver, or the
thin board of ebony, and let us lay it lightly upon the water, so
that it may stay there without sinking, and carefully observe the
effect. It will appear clearly that the plates are a considerable
matter lower than the surface of the water, which rises up and
makes a kind of rampart round them on every side. But if it has
already penetrated and overcome the continuity of the water, and
is of its own nature heavier than the water, why does it not
continue to sink, but stop and suspend itself in that little
dimple that its weight has made in the water? My answer is,
because in sinking till its surface is below the water, which
rises up in a bank round it, it draws after and carries along
with it the air above it, so that that which, in this case,
descends in the water is not only the board of ebony or the plate
of iron, but a compound of ebony and air, from which composition
results a solid no longer specifically heavier than the water, as
was the ebony or gold alone. But, gentlemen, we want the same
matter; you are to alter nothing but the shape, and, therefore,
have the goodness to remove this air, which may be done simply by
washing the surface of the board, for the water having once got
between the board and the air will run together, and the ebony
will go to the bottom; and if it does not, you have won the day.

"But methinks I hear some of my antagonists cunningly opposing
this, and telling me that they will not on any account allow
their boards to be wetted, because the weight of the water so
added, by making it heavier than it was before, draws it to the
bottom, and that the addition of new weight is contrary to our
agreement, which was that the matter should be the same.

"To this I answer, first, that nobody can suppose bodies to be
put into the water without their being wet, nor do I wish to do
more to the board than you may do to the ball. Moreover, it is
not true that the board sinks on account of the weight of the
water added in the washing; for I will put ten or twenty drops on
the floating board, and so long as they stand separate it shall
not sink; but if the board be taken out and all that water wiped
off, and the whole surface bathed with one single drop, and put
it again upon the water, there is no question but it will sink,
the other water running to cover it, being no longer hindered by
the air. In the next place, it is altogether false that water can
in any way increase the weight of bodies immersed in it, for
water has no weight in water, since it does not sink. Now just as
he who should say that brass by its own nature sinks, but that
when formed into the shape of a kettle it acquires from that
figure the virtue of lying in water without sinking, would say
what is false, because that is not purely brass which then is put
into the water, but a compound of brass and air; so is it neither
more nor less false that a thin plate of brass or ebony swims by
virtue of its dilated and broad figure. Also, I cannot omit to
tell my opponents that this conceit of refusing to bathe the
surface of the board might beget an opinion in a third person of
a poverty of argument on their side, especially as the
conversation began about flakes of ice, in which it would be
simple to require that the surfaces should be kept dry; not to
mention that such pieces of ice, whether wet or dry, always
float, and so my antagonists say, because of their shape.

"Some may wonder that I affirm this power to be in the air of
keeping plate of brass or silver above water, as if in a certain
sense I would attribute to the air a kind of magnetic virtue for
sustaining heavy bodies with which it is in contact. To satisfy
all these doubts I have contrived the following experiment to
demonstrate how truly the air does support these bodies; for I
have found, when one of these bodies which floats when placed
lightly on the water is thoroughly bathed and sunk to the bottom,
that by carrying down to it a little air without otherwise
touching it in the least, I am able to raise and carry it back to
the top, where it floats as before. To this effect, I take a ball
of wax, and with a little lead make it just heavy enough to sink
very slowly to the bottom, taking care that its surface be quite
smooth and even. This, if put gently into the water, submerges
almost entirely, there remaining visible only a little of the
very top, which, so long as it is joined to the air, keeps the
ball afloat; but if we take away the contact of the air by
wetting this top, the ball sinks to the bottom and remains there.
Now to make it return to the surface by virtue of the air which
before sustained it, thrust into the water a glass with the mouth
downward, which will carry with it the air it contains, and move
this down towards the ball until you see, by the transparency of
the glass, that the air has reached the top of it; then gently
draw the glass upward, and you will see the ball rise, and
afterwards stay on the top of the water, if you carefully part
the glass and water without too much disturbing it."[3]

It will be seen that Galileo, while holding in the main to a
correct thesis, yet mingles with it some false ideas. At the very
outset, of course, it is not true that water has no resistance to
penetration; it is true, however, in the sense in which Galileo
uses the term--that is to say, the resistance of the water to
penetration is not the determining factor ordinarily in deciding
whether a body sinks or floats. Yet in the case of the flat body
it is not altogether inappropriate to say that the water resists
penetration and thus supports the body. The modern physicist
explains the phenomenon as due to surface-tension of the fluid.
Of course, Galileo's disquisition on the mixing of air with the
floating body is utterly fanciful. His experiments were
beautifully exact; his theorizing from them was, in this
instance, altogether fallacious. Thus, as already intimated, his
paper is admirably adapted to convey a double lesson to the
student of science.


WILLIAM GILBERT AND THE STUDY OF MAGNETISM

It will be observed that the studies of Galileo and Stevinus were
chiefly concerned with the force of gravitation. Meanwhile, there
was an English philosopher of corresponding genius, whose
attention was directed towards investigation of the equally
mysterious force of terrestrial magnetism. With the doubtful
exception of Bacon, Gilbert was the most distinguished man of
science in England during the reign of Queen Elizabeth. He was
for many years court physician, and Queen Elizabeth ultimately
settled upon him a pension that enabled him to continue his
researches in pure science.

His investigations in chemistry, although supposed to be of great
importance, are mostly lost; but his great work, De Magnete, on
which he labored for upwards of eighteen years, is a work of
sufficient importance, as Hallam says, "to raise a lasting
reputation for its author." From its first appearance it created
a profound impression upon the learned men of the continent,
although in England Gilbert's theories seem to have been somewhat
less favorably received. Galileo freely expressed his admiration
for the work and its author; Bacon, who admired the author, did
not express the same admiration for his theories; but Dr.
Priestley, later, declared him to be "the father of modern
electricity."

Strangely enough, Gilbert's book had never been translated into
English, or apparently into any other language, until recent
years, although at the time of its publication certain learned
men, unable to read the book in the original, had asked that it
should be. By this neglect, or oversight, a great number of
general readers as well as many scientists, through succeeding
centuries, have been deprived of the benefit of writings that
contained a good share of the fundamental facts about magnetism
as known to-day.

Gilbert was the first to discover that the earth is a great
magnet, and he not only gave the name of "pole" to the
extremities of the magnetic needle, but also spoke of these
"poles" as north and south pole, although he used these names in
the opposite sense from that in which we now use them, his south
pole being the extremity which pointed towards the north, and
vice versa. He was also first to make use of the terms "electric
force," "electric emanations," and "electric attractions."

It is hardly necessary to say that some of the views taken by
Gilbert, many of his theories, and the accuracy of some of his
experiments have in recent times been found to be erroneous. As a
pioneer in an unexplored field of science, however, his work is
remarkably accurate. "On the whole," says Dr. John Robinson,
"this performance contains more real information than any writing
of the age in which he lived, and is scarcely exceeded by any
that has appeared since."[4]

In the preface to his work Gilbert says: "Since in the discovery
of secret things, and in the investigation of hidden causes,
stronger reasons are obtained from sure experiments and
demonstrated arguments than from probable conjectures and the
opinions of philosophical speculators of the common sort,
therefore, to the end of that noble substance of that great
loadstone, our common mother (the earth), still quite unknown,
and also that the forces extraordinary and exalted of this globe
may the better be understood, we have decided, first, to begin
with the common stony and ferruginous matter, and magnetic
bodies, and the part of the earth that we may handle and may
perceive with senses, and then to proceed with plain magnetic
experiments, and to penetrate to the inner parts of the
earth."[5]

Before taking up the demonstration that the earth is simply a
giant loadstone, Gilbert demonstrated in an ingenious way that
every loadstone, of whatever size, has definite and fixed poles.
He did this by placing the stone in a metal lathe and converting
it into a sphere, and upon this sphere demonstrated how the poles
can be found. To this round loadstone he gave the name of
terrella--that is, little earth.

"To find, then, poles answering to the earth," he says, "take in
your hand the round stone, and lay on it a needle or a piece of
iron wire: the ends of the wire move round their middle point,
and suddenly come to a standstill. Now, with ochre or with chalk,
mark where the wire lies still and sticks. Then move the middle
or centre of the wire to another spot, and so to a third and
fourth, always marking the stone along the length of the wire
where it stands still; the lines so marked will exhibit meridian
circles, or circles like meridians, on the stone or terrella; and
manifestly they will all come together at the poles of the stone.
The circle being continued in this way, the poles appear, both
the north and the south, and betwixt these, midway, we may draw a
large circle for an equator, as is done by the astronomer in the
heavens and on his spheres, and by the geographer on the
terrestrial globe."[6]

Gilbert had tried the familiar experiment of placing the
loadstone on a float in water, and observed that the poles always
revolved until they pointed north and south, which he explained
as due to the earth's magnetic attraction. In this same
connection he noticed that a piece of wrought iron mounted on a
cork float was attracted by other metals to a slight degree, and
he observed also that an ordinary iron bar, if suspended
horizontally by a thread, assumes invariably a north and south
direction. These, with many other experiments of a similar
nature, convinced him that the earth "is a magnet and a
loadstone," which he says is a "new and till now unheard-of view
of the earth."

Fully to appreciate Gilbert's revolutionary views concerning the
earth as a magnet, it should be remembered that numberless
theories to explain the action of the electric needle had been
advanced. Columbus and Paracelsus, for example, believed that the
magnet was attracted by some point in the heavens, such as a
magnetic star. Gilbert himself tells of some of the beliefs that
had been held by his predecessors, many of whom he declares
"wilfully falsify." One of his first steps was to refute by
experiment such assertions as that of Cardan, that "a wound by a
magnetized needle was painless"; and also the assertion of
Fracastoni that loadstone attracts silver; or that of Scalinger,
that the diamond will attract iron; and the statement of
Matthiolus that "iron rubbed with garlic is no longer attracted
to the loadstone."

Gilbert made extensive experiments to explain the dipping of the
needle, which had been first noticed by William Norman. His
deduction as to this phenomenon led him to believe that this was
also explained by the magnetic attraction of the earth, and to
predict where the vertical dip would be found. These deductions
seem the more wonderful because at the time he made them the dip
had just been discovered, and had not been studied except at
London. His theory of the dip was, therefore, a scientific
prediction, based on a preconceived hypothesis. Gilbert found the
dip to be 72 degrees at London; eight years later Hudson found
the dip at 75 degrees 22' north latitude to be 89 degrees 30';
but it was not until over two hundred years later, in 1831, that
the vertical dip was first observed by Sir James Ross at about 70
degrees 5' north latitude, and 96 degrees 43' west longitude.
This was not the exact point assumed by Gilbert, and his
scientific predictions, therefore, were not quite correct; but
such comparatively slight and excusable errors mar but little the
excellence of his work as a whole.

A brief epitome of some of his other important discoveries
suffices to show that the exalted position in science accorded
him by contemporaries, as well as succeeding generations of
scientists, was well merited. He was first to distinguish between
magnetism and electricity, giving the latter its name. He
discovered also the "electrical charge," and pointed the way to
the discovery of insulation by showing that the charge could be
retained some time in the excited body by covering it with some
non-conducting substance, such as silk; although, of course,
electrical conduction can hardly be said to have been more than
vaguely surmised, if understood at all by him. The first
electrical instrument ever made, and known as such, was invented
by him, as was also the first magnetometer, and the first
electrical indicating device. Although three centuries have
elapsed since his death, the method of magnetizing iron first
introduced by him is in common use to-day.

He made exhaustive experiments with a needle balanced on a pivot
to see how many substances he could find which, like amber, on
being rubbed affected the needle. In this way he discovered that
light substances were attracted by alum, mica, arsenic,
sealing-wax, lac sulphur, slags, beryl, amethyst, rock-crystal,
sapphire, jet, carbuncle, diamond, opal, Bristol stone, glass,
glass of antimony, gum-mastic, hard resin, rock-salt, and, of
course, amber. He discovered also that atmospheric conditions
affected the production of electricity, dryness being unfavorable
and moisture favorable.

Galileo's estimate of this first electrician is the verdict of
succeeding generations. "I extremely admire and envy this
author," he said. "I think him worthy of the greatest praise for
the many new and true observations which he has made, to the
disgrace of so many vain and fabling authors."


STUDIES OF LIGHT, HEAT, AND ATMOSPHERIC PRESSURE

We have seen that Gilbert was by no means lacking in versatility,
yet the investigations upon which his fame is founded were all
pursued along one line, so that the father of magnetism may be
considered one of the earliest of specialists in physical
science. Most workers of the time, on the other band, extended
their investigations in many directions. The sum total of
scientific knowledge of that day had not bulked so large as to
exclude the possibility that one man might master it all. So we
find a Galileo, for example, making revolutionary discoveries in
astronomy, and performing fundamental experiments in various
fields of physics. Galileo's great contemporary, Kepler, was
almost equally versatile, though his astronomical studies were of
such pre-eminent importance that his other investigations sink
into relative insignificance. Yet he performed some notable
experiments in at least one department of physics. These
experiments had to do with the refraction of light, a subject
which Kepler was led to investigate, in part at least, through
his interest in the telescope.

We have seen that Ptolemy in the Alexandrian time, and Alhazen,
the Arab, made studies of refraction. Kepler repeated their
experiments, and, striving as always to generalize his
observations, he attempted to find the law that governed the
observed change of direction which a ray of light assumes in
passing from one medium to another. Kepler measured the angle of
refraction by means of a simple yet ingenious trough-like
apparatus which enabled him to compare readily the direct and
refracted rays. He discovered that when a ray of light passes
through a glass plate, if it strikes the farther surface of the
glass at an angle greater than 45 degrees it will be totally
refracted instead of passing through into the air. He could not
well fail to know that different mediums refract light
differently, and that for the same medium the amount of light
valies with the change in the angle of incidence. He was not
able, however, to generalize his observations as he desired, and
to the last the law that governs refraction escaped him. It
remained for Willebrord Snell, a Dutchman, about the year 1621,
to discover the law in question, and for Descartes, a little
later, to formulate it. Descartes, indeed, has sometimes been
supposed to be the discoverer of the law. There is reason to
believe that he based his generalizations on the experiment of
Snell, though he did not openly acknowledge his indebtedness. The
law, as Descartes expressed it, states that the sine of the angle
of incidence bears a fixed ratio to the sine of the angle of
refraction for any given medium. Here, then, was another
illustration of the fact that almost infinitely varied phenomena
may be brought within the scope of a simple law. Once the law had
been expressed, it could be tested and verified with the greatest
ease; and, as usual, the discovery being made, it seems
surprising that earlier investigators--in particular so sagacious
a guesser as Kepler--should have missed it.

Galileo himself must have been to some extent a student of light,
since, as we have seen, he made such notable contributions to
practical optics through perfecting the telescope; but he seems
not to have added anything to the theory of light. The subject of
heat, however, attracted his attention in a somewhat different
way, and he was led to the invention of the first contrivance for
measuring temperatures. His thermometer was based on the
afterwards familiar principle of the expansion of a liquid under
the influence of heat; but as a practical means of measuring
temperature it was a very crude affair, because the tube that
contained the measuring liquid was exposed to the air, hence
barometric changes of pressure vitiated the experiment. It
remained for Galileo's Italian successors of the Accademia del
Cimento of Florence to improve upon the apparatus, after the
experiments of Torricelli--to which we shall refer in a
moment--had thrown new light on the question of atmospheric
pressure. Still later the celebrated Huygens hit upon the idea of
using the melting and the boiling point of water as fixed points
in a scale of measurements, which first gave definiteness to
thermometric tests.


TORRICELLI

In the closing years of his life Galileo took into his family, as
his adopted disciple in science, a young man, Evangelista
Torricelli (1608-1647), who proved himself, during his short
lifetime, to be a worthy follower of his great master. Not only
worthy on account of his great scientific discoveries, but
grateful as well, for when he had made the great discovery that
the "suction" made by a vacuum was really nothing but air
pressure, and not suction at all, he regretted that so important
a step in science might not have been made by his great teacher,
Galileo, instead of by himself. "This generosity of Torricelli,"
says Playfair, "was, perhaps, rarer than his genius: there are
more who might have discovered the suspension of mercury in the
barometer than who would have been willing to part with the honor
of the discovery to a master or a friend."

Torricelli's discovery was made in 1643, less than two years
after the death of his master. Galileo had observed that water
will not rise in an exhausted tube, such as a pump, to a height
greater than thirty-three feet, but he was never able to offer a
satisfactory explanation of the principle. Torricelli was able to
demonstrate that the height at which the water stood depended
upon nothing but its weight as compared with the weight of air.
If this be true, it is evident that any fluid will be supported
at a definite height, according to its relative weight as
compared with air. Thus mercury, which is about thirteen times
more dense than water, should only rise to one-thirteenth the
height of a column of water--that is, about thirty inches.
Reasoning in this way, Torricelli proceeded to prove that his
theory was correct. Filling a long tube, closed at one end, with
mercury, he inverted the tube with its open orifice in a vessel
of mercury. The column of mercury fell at once, but at a height
of about thirty inches it stopped and remained stationary, the
pressure of the air on the mercury in the vessel maintaining it
at that height. This discovery was a shattering blow to the old
theory that had dominated that field of physics for so many
centuries. It was completely revolutionary to prove that, instead
of a mysterious something within the tube being responsible for
the suspension of liquids at certain heights, it was simply the
ordinary atmospheric pressure mysterious enough, it is
true--pushing upon them from without. The pressure exerted by the
atmosphere was but little understood at that time, but
Torricelli's discovery aided materially in solving the mystery.
The whole class of similar phenomena of air pressure, which had
been held in the trammel of long-established but false doctrines,
was now reduced to one simple law, and the door to a solution of
a host of unsolved problems thrown open.

It had long been suspected and believed that the density of the
atmosphere varies at certain times. That the air is sometimes
"heavy" and at other times "light" is apparent to the senses
without scientific apparatus for demonstration. It is evident,
then, that Torricelli's column of mercury should rise and fall
just in proportion to the lightness or heaviness of the air. A
short series of observations proved that it did so, and with
those observations went naturally the observations as to changes
in the weather. It was only necessary, therefore, to scratch a
scale on the glass tube, indicating relative atmospheric
pressures, and the Torricellian barometer was complete.

Such a revolutionary theory and such an important discovery were,
of course, not to be accepted without controversy, but the feeble
arguments of the opponents showed how untenable the old theory
had become. In 1648 Pascal suggested that if the theory of the
pressure of air upon the mercury was correct, it could be
demonstrated by ascending a mountain with the mercury tube. As
the air was known to get progressively lighter from base to
summit, the height of the column should be progressively lessened
as the ascent was made, and increase again on the descent into
the denser air. The experiment was made on the mountain called
the Puy-de-Dome, in Auvergne, and the column of mercury fell and
rose progressively through a space of about three inches as the
ascent and descent were made.

This experiment practically sealed the verdict on the new theory,
but it also suggested something more. If the mercury descended to
a certain mark on the scale on a mountain-top whose height was
known, why was not this a means of measuring the heights of all
other elevations? And so the beginning was made which, with
certain modifications and corrections in details, is now the
basis of barometrical measurements of heights.

In hydraulics, also, Torricelli seems to have taken one of the
first steps. He did this by showing that the water which issues
from a hole in the side or bottom of a vessel does so at the same
velocity as that which a body would acquire by falling from the
level of the surface of the water to that of the orifice. This
discovery was of the greatest importance to a correct
understanding of the science of the motions of fluids. He also
discovered the valuable mechanical principle that if any number
of bodies be connected so that by their motion there is neither
ascent nor descent of their centre of gravity, these bodies are
in equilibrium.

Besides making these discoveries, he greatly improved the
microscope and the telescope, and invented a simple microscope
made of a globule of glass. In 1644 he published a tract on the
properties of the cycloid in which he suggested a solution of the
problem of its quadrature. As soon as this pamphlet appeared its
author was accused by Gilles Roberval (1602-1675) of having
appropriated a solution already offered by him. This led to a
long debate, during which Torricelli was seized with a fever,
from the effects of which he died, in Florence, October 25, 1647.
There is reason to believe, however, that while Roberval's
discovery was made before Torricelli's, the latter reached his
conclusions independently.



VI. TWO PSEUDO-SCIENCES--ALCHEMY AND ASTROLOGY

In recent chapters we have seen science come forward with
tremendous strides. A new era is obviously at hand. But we shall
misconceive the spirit of the times if we fail to understand that
in the midst of all this progress there was still room for
mediaeval superstition and for the pursuit of fallacious ideals.
Two forms of pseudo-science were peculiarly prevalent --alchemy
and astrology. Neither of these can with full propriety be called
a science, yet both were pursued by many of the greatest
scientific workers of the period. Moreover, the studies of the
alchemist may with some propriety be said to have laid the
foundation for the latter-day science of chemistry; while
astrology was closely allied to astronomy, though its relations
to that science are not as intimate as has sometimes been
supposed.

Just when the study of alchemy began is undetermined. It was
certainly of very ancient origin, perhaps Egyptian, but its most
flourishing time was from about the eighth century A.D. to the
eighteenth century. The stories of the Old Testament formed a
basis for some of the strange beliefs regarding the properties of
the magic "elixir," or "philosopher's stone." Alchemists believed
that most of the antediluvians, perhaps all of them, possessed a
knowledge of this stone. How, otherwise, could they have
prolonged their lives to nine and a half centuries? And Moses was
surely a first-rate alchemist, as is proved by the story of the
Golden Calf.[1] After Aaron had made the calf of gold, Moses
performed the much more difficult task of grinding it to powder
and "strewing it upon the waters," thus showing that he had
transmuted it into some lighter substance.

But antediluvians and Biblical characters were not the only
persons who were thought to have discovered the coveted.
"elixir." Hundreds of aged mediaeval chemists were credited with
having made the discovery, and were thought to be living on
through the centuries by its means. Alaies de Lisle, for example,
who died in 1298, at the age of 110, was alleged to have been at
the point of death at the age of fifty, but just at this time he
made the fortunate discovery of the magic stone, and so continued
to live in health and affluence for sixty years more. And De
Lisle was but one case among hundreds.

An aged and wealthy alchemist could claim with seeming
plausibility that he was prolonging his life by his magic;
whereas a younger man might assert that, knowing the great
secret, he was keeping himself young through the centuries. In
either case such a statement, or rumor, about a learned and
wealthy alchemist was likely to be believed, particularly among
strangers; and as such a man would, of course, be the object of
much attention, the claim was frequently made by persons seeking
notoriety. One of the most celebrated of these impostors was a
certain Count de Saint-Germain, who was connected with the court
of Louis XV. His statements carried the more weight because,
having apparently no means of maintenance, he continued to live
in affluence year after year--for two thousand years, as he
himself admitted--by means of the magic stone. If at any time his
statements were doubted, he was in the habit of referring to his
valet for confirmation, this valet being also under the influence
of the elixir of life.

"Upon one occasion his master was telling a party of ladies and
gentlemen, at dinner, some conversation he had had in Palestine,
with King Richard I., of England, whom he described as a very
particular friend of his. Signs of astonishment and incredulity
were visible on the faces of the company, upon which
Saint-Germain very coolly turned to his servant, who stood behind
his chair, and asked him if he had not spoken the truth. 'I
really cannot say,' replied the man, without moving a muscle;
'you forget, sir, I have been only five hundred years in your
service.' 'Ah, true,' said his master, 'I remember now; it was a
little before your time!' "[2]

In the time of Saint-Germain, only a little over a century ago,
belief in alchemy had almost disappeared, and his extraordinary
tales were probably regarded in the light of amusing stories.
Still there was undoubtedly a lingering suspicion in the minds of
many that this man possessed some peculiar secret. A few
centuries earlier his tales would hardly have been questioned,
for at that time the belief in the existence of this magic
something was so strong that the search for it became almost a
form of mania; and once a man was seized with it, lie gambled
away health, position, and life itself in pursuing the coveted
stake. An example of this is seen in Albertus Magnus, one of the
most learned men of his time, who it is said resigned his
position as bishop of Ratisbon in order that he might pursue his
researches in alchemy.

If self-sacrifice was not sufficient to secure the prize, crime
would naturally follow, for there could be no limit to the price
of the stakes in this game. The notorious Marechal de Reys,
failing to find the coveted stone by ordinary methods of
laboratory research, was persuaded by an impostor that if he
would propitiate the friendship of the devil the secret would be
revealed. To this end De Reys began secretly capturing young
children as they passed his castle and murdering them. When he
was at last brought to justice it was proved that he had murdered
something like a hundred children within a period of three years.
So, at least, runs one version of the story of this perverted
being.

Naturally monarchs, constantly in need of funds, were interested
in these alchemists. Even sober England did not escape, and
Raymond Lully, one of the most famous of the thirteenth and
fourteenth century alchemists, is said to have been secretly
invited by King Edward I. (or II.) to leave Milan and settle in
England. According to some accounts, apartments were assigned to
his use in the Tower of London, where he is alleged to have made
some six million pounds sterling for the monarch, out of iron,
mercury, lead, and pewter.

Pope John XXII., a friend and pupil of the alchemist Arnold de
Villeneuve, is reported to have learned the secrets of alchemy
from his master. Later he issued two bulls against "pretenders"
in the art, which, far from showing his disbelief, were cited by
alchemists as proving that he recognized pretenders as distinct
from true masters of magic.

To moderns the attitude of mind of the alchemist is difficult to
comprehend. It is, perhaps, possible to conceive of animals or
plants possessing souls, but the early alchemist attributed the
same thing--or something kin to it--to metals also. Furthermore,
just as plants germinated from seeds, so metals were supposed to
germinate also, and hence a constant growth of metals in the
ground. To prove this the alchemist cited cases where previously
exhausted gold-mines were found, after a lapse of time, to
contain fresh quantities of gold. The "seed" of the remaining
particles of gold had multiplied and increased. But this
germinating process could only take place under favorable
conditions, just as the seed of a plant must have its proper
surroundings before germinating; and it was believed that the
action of the philosopher's stone was to hasten this process, as
man may hasten the growth of plants by artificial means. Gold was
looked upon as the most perfect metal, and all other metals
imperfect, because not yet "purified." By some alchemists they
were regarded as lepers, who, when cured of their leprosy, would
become gold. And since nature intended that all things should be
perfect, it was the aim of the alchemist to assist her in this
purifying process, and incidentally to gain wealth and prolong
his life.

By other alchemists the process of transition from baser metals
into gold was conceived to be like a process of ripening fruit.
The ripened product was gold, while the green fruit, in various
stages of maturity, was represented by the base metals. Silver,
for example, was more nearly ripe than lead; but the difference
was only one of "digestion," and it was thought that by further
"digestion" lead might first become silver and eventually gold.
In other words, Nature had not completed her work, and was
wofully slow at it at best; but man, with his superior faculties,
was to hasten the process in his laboratories--if he could but
hit upon the right method of doing so.

It should not be inferred that the alchemist set about his task
of assisting nature in a haphazard way, and without training in
the various alchemic laboratory methods. On the contrary, he
usually served a long apprenticeship in the rudiments of his
calling. He was obliged to learn, in a general way, many of the
same things that must be understood in either chemical or
alchemical laboratories. The general knowledge that certain
liquids vaporize at lower temperatures than others, and that the
melting-points of metals differ greatly, for example, was just as
necessary to alchemy as to chemistry. The knowledge of the gross
structure, or nature, of materials was much the same to the
alchemist as to the chemist, and, for that matter, many of the
experiments in calcining, distilling, etc., were practically
identical.

To the alchemist there were three principles--salt, sulphur, and
mercury--and the sources of these principles were the four
elements--earth, water, fire, and air. These four elements were
accountable for every substance in nature. Some of the
experiments to prove this were so illusive, and yet apparently so
simple, that one is not surprised that it took centuries to
disprove them. That water was composed of earth and air seemed
easily proven by the simple process of boiling it in a
tea-kettle, for the residue left was obviously an earthy
substance, whereas the steam driven off was supposed to be air.
The fact that pure water leaves no residue was not demonstrated
until after alchemy had practically ceased to exist. It was
possible also to demonstrate that water could be turned into fire
by thrusting a red-hot poker under a bellglass containing a dish
of water. Not only did the quantity of water diminish, but, if a
lighted candle was thrust under the glass, the contents ignited
and burned, proving, apparently, that water had been converted
into fire. These, and scores of other similar experiments, seemed
so easily explained, and to accord so well with the "four
elements" theory, that they were seldom questioned until a later
age of inductive science.

But there was one experiment to which the alchemist pinned his
faith in showing that metals could be "killed" and "revived,"
when proper means were employed. It had been known for many
centuries that if any metal, other than gold or silver, were
calcined in an open crucible, it turned, after a time, into a
peculiar kind of ash. This ash was thought by the alchemist to
represent the death of the metal. But if to this same ash a few
grains of wheat were added and heat again applied to the
crucible, the metal was seen to "rise from its ashes" and resume
its original form--a well-known phenomenon of reducing metals
from oxides by the use of carbon, in the form of wheat, or, for
that matter, any other carbonaceous substance. Wheat was,
therefore, made the symbol of the resurrection of the life
eternal. Oats, corn, or a piece of charcoal would have "revived"
the metals from the ashes equally well, but the mediaeval
alchemist seems not to have known this. However, in this
experiment the metal seemed actually to be destroyed and
revivified, and, as science had not as yet explained this
striking phenomenon, it is little wonder that it deceived the
alchemist.

Since the alchemists pursued their search of the magic stone in
such a methodical way, it would seem that they must have some
idea of the appearance of the substance they sought. Probably
they did, each according to his own mental bias; but, if so, they
seldom committed themselves to writing, confining their
discourses largely to speculations as to the properties of this
illusive substance. Furthermore, the desire for secrecy would
prevent them from expressing so important a piece of information.
But on the subject of the properties, if not on the appearance of
the "essence," they were voluminous writers. It was supposed to
be the only perfect substance in existence, and to be confined in
various substances, in quantities proportionate to the state of
perfection of the substance. Thus, gold being most nearly perfect
would contain more, silver less, lead still less, and so on. The
"essence" contained in the more nearly perfect metals was thought
to be more potent, a very small quantity of it being capable of
creating large quantities of gold and of prolonging life
indefinitely.

It would appear from many of the writings of the alchemists that
their conception of nature and the supernatural was so confused
and entangled in an inexplicable philosophy that they themselves
did not really understand the meaning of what they were
attempting to convey. But it should not be forgotten that alchemy
was kept as much as possible from the ignorant general public,
and the alchemists themselves had knowledge of secret words and
expressions which conveyed a definite meaning to one of their
number, but which would appear a meaningless jumble to an
outsider. Some of these writers declared openly that their
writings were intended to convey an entirely erroneous
impression, and were sent out only for that purpose.

However, while it may have been true that the vagaries of their
writings were made purposely, the case is probably more correctly
explained by saying that the very nature of the art made definite
statements impossible. They were dealing with something that did
not exist--could not exist. Their attempted descriptions became,
therefore, the language of romance rather than the language of
science.

But if the alchemists themselves were usually silent as to the
appearance of the actual substance of the philosopher's stone,
there were numberless other writers who were less reticent. By
some it was supposed to be a stone, by others a liquid or elixir,
but more commonly it was described as a black powder. It also
possessed different degrees of efficiency according to its
degrees of purity, certain forms only possessing the power of
turning base metals into gold, while others gave eternal youth
and life or different degrees of health. Thus an alchemist, who
had made a partial discovery of this substance, could prolong
life a certain number of years only, or, possessing only a small
and inadequate amount of the magic powder, he was obliged to give
up the ghost when the effect of this small quantity had passed
away.

This belief in the supernatural power of the philosopher's stone
to prolong life and heal diseases was probably a later phase of
alchemy, possibly developed by attempts to connect the power of
the mysterious essence with Biblical teachings. The early Roman
alchemists, who claimed to be able to transmute metals, seem not
to have made other claims for their magic stone.

By the fifteenth century the belief in the philosopher's stone
had become so fixed that governments began to be alarmed lest
some lucky possessor of the secret should flood the country with
gold, thus rendering the existing coin of little value. Some
little consolation was found in the thought that in case all the
baser metals were converted into gold iron would then become the
"precious metal," and would remain so until some new
philosopher's stone was found to convert gold back into iron--a
much more difficult feat, it was thought. However, to be on the
safe side, the English Parliament, in 1404, saw fit to pass an
act declaring the making of gold and silver to be a felony.
Nevertheless, in 1455, King Henry VI. granted permission to
several "knights, citizens of London, chemists, and monks" to
find the philosopher's stone, or elixir, that the crown might
thus be enabled to pay off its debts. The monks and ecclesiastics
were supposed to be most likely to discover the secret process,
since "they were such good artists in transubstantiating bread
and wine."

In Germany the emperors Maximilian I., Rudolf II., and Frederick
II. gave considerable attention to the search, and the example
they set was followed by thousands of their subjects. It is said
that some noblemen developed the unpleasant custom of inviting to
their courts men who were reputed to have found the stone, and
then imprisoning the poor alchemists until they had made a
certain quantity of gold, stimulating their activity with
tortures of the most atrocious kinds. Thus this danger of being
imprisoned and held for ransom until some fabulous amount of gold
should be made became the constant menace of the alchemist. It
was useless for an alchemist to plead poverty once it was noised
about that he had learned the secret. For how could such a man be
poor when, with a piece of metal and a few grains of magic
powder, he was able to provide himself with gold? It was,
therefore, a reckless alchemist indeed who dared boast that he
had made the coveted discovery.

The fate of a certain indiscreet alchemist, supposed by many to
have been Seton, a Scotchman, was not an uncommon one. Word
having been brought to the elector of Saxony that this alchemist
was in Dresden and boasting of his powers, the elector caused him
to be arrested and imprisoned. Forty guards were stationed to see
that he did not escape and that no one visited him save the
elector himself. For some time the elector tried by argument and
persuasion to penetrate his secret or to induce him to make a
certain quantity of gold; but as Seton steadily refused, the rack
was tried, and for several months he suffered torture, until
finally, reduced to a mere skeleton, be was rescued by a rival
candidate of the elector, a Pole named Michael Sendivogins, who
drugged the guards. However, before Seton could be "persuaded" by
his new captor, he died of his injuries.

But Sendivogins was also ambitious in alchemy, and, since Seton
was beyond his reach, he took the next best step and married his
widow. From her, as the story goes, he received an ounce of black
powder--the veritable philosopher's stone. With this he
manufactured great quantities of gold, even inviting Emperor
Rudolf II. to see him work the miracle. That monarch was so
impressed that he caused a tablet to be inserted in the wall of
the room in which he had seen the gold made.

Sendivogins had learned discretion from the misfortune of Seton,
so that he took the precaution of concealing most of the precious
powder in a secret chamber of his carriage when he travelled,
having only a small quantity carried by his steward in a gold
box. In particularly dangerous places, he is said to have
exchanged clothes with his coachman, making the servant take his
place in the carriage while he mounted the box.


About the middle of the seventeenth century alchemy took such
firm root in the religious field that it became the basis of the
sect known as the Rosicrucians. The name was derived from the
teaching of a German philosopher, Rosenkreutz, who, having been
healed of a dangerous illness by an Arabian supposed to possess
the philosopher's stone, returned home and gathered about him a
chosen band of friends, to whom he imparted the secret. This sect
came rapidly into prominence, and for a short time at least
created a sensation in Europe, and at the time were credited with
having "refined and spiritualized" alchemy. But by the end of the
seventeenth century their number had dwindled to a mere handful,
and henceforth they exerted little influence.

Another and earlier religious sect was the Aureacrucians, founded
by Jacob Bohme, a shoemaker, born in Prussia in 1575. According
to his teachings the philosopher's stone could be discovered by a
diligent search of the Old and the New Testaments, and more
particularly the Apocalypse, which contained all the secrets of
alchemy. This sect found quite a number of followers during the
life of Bohme, but gradually died out after his death; not,
however, until many of its members had been tortured for heresy,
and one at least, Kuhlmann, of Moscow, burned as a sorcerer.

The names of the different substances that at various times were
thought to contain the large quantities of the "essence" during
the many centuries of searching for it, form a list of
practically all substances that were known, discovered, or
invented during the period. Some believed that acids contained
the substance; others sought it in minerals or in animal or
vegetable products; while still others looked to find it among
the distilled "spirits"--the alcoholic liquors and distilled
products. On the introduction of alcohol by the Arabs that
substance became of all-absorbing interest, and for a long time
allured the alchemist into believing that through it they were
soon to be rewarded. They rectified and refined it until
"sometimes it was so strong that it broke the vessels containing
it," but still it failed in its magic power. Later, brandy was
substituted for it, and this in turn discarded for more recent
discoveries.

There were always, of course, two classes of alchemists: serious
investigators whose honesty could not be questioned, and clever
impostors whose legerdemain was probably largely responsible for
the extended belief in the existence of the philosopher's stone.
Sometimes an alchemist practised both, using the profits of his
sleight-of-hand to procure the means of carrying on his serious
alchemical researches. The impostures of some of these jugglers
deceived even the most intelligent and learned men of the time,
and so kept the flame of hope constantly burning. The age of cold
investigation had not arrived, and it is easy to understand how
an unscrupulous mediaeval Hermann or Kellar might completely
deceive even the most intelligent and thoughtful scholars. In
scoffing at the credulity of such an age, it should not be
forgotten that the "Keely motor" was a late nineteenth-century
illusion.

But long before the belief in the philosopher's stone had died
out, the methods of the legerdemain alchemist had been
investigated and reported upon officially by bodies of men
appointed to make such investigations, although it took several
generations completely to overthrow a superstition that had been
handed down through several thousand years. In April of 1772
Monsieur Geoffroy made a report to the Royal Academy of Sciences,
at Paris, on the alchemic cheats principally of the sixteenth and
seventeenth centuries. In this report he explains many of the
seemingly marvellous feats of the unscrupulous alchemists. A very
common form of deception was the use of a double-bottomed
crucible. A copper or brass crucible was covered on the inside
with a layer of wax, cleverly painted so as to resemble the
ordinary metal. Between this layer of wax and the bottom of the
crucible, however, was a layer of gold dust or silver. When the
alchemist wished to demonstrate his power, he had but to place
some mercury or whatever substance he chose in the crucible, heat
it, throw in a grain or two of some mysterious powder, pronounce
a few equally mysterious phrases to impress his audience, and,
behold, a lump of precious metal would be found in the bottom of
his pot. This was the favorite method of mediocre performers, but
was, of course, easily detected.

An equally successful but more difficult way was to insert
surreptitiously a lump of metal into the mixture, using an
ordinary crucible. This required great dexterity, but was
facilitated by the use of many mysterious ceremonies on the part
of the operator while performing, just as the modern vaudeville
performer diverts the attention of the audience to his right hand
while his left is engaged in the trick. Such ceremonies were not
questioned, for it was the common belief that the whole process
"lay in the spirit as much as in the substance," many, as we have
seen, regarding the whole process as a divine manifestation.

Sometimes a hollow rod was used for stirring the mixture in the
crucible, this rod containing gold dust, and having the end
plugged either with wax or soft metal that was easily melted.
Again, pieces of lead were used which had been plugged with lumps
of gold carefully covered over; and a very simple and impressive
demonstration was making use of a nugget of gold that had been
coated over with quicksilver and tarnished so as to resemble lead
or some base metal. When this was thrown into acid the coating
was removed by chemical action, leaving the shining metal in the
bottom of the vessel. In order to perform some of these tricks,
it is obvious that the alchemist must have been well supplied
with gold, as some of them, when performing before a royal
audience, gave the products to their visitors. But it was always
a paying investment, for once his reputation was established the
gold-maker found an endless variety of ways of turning his
alleged knowledge to account, frequently amassing great wealth.

Some of the cleverest of the charlatans often invited royal or
other distinguished guests to bring with them iron nails to be
turned into gold ones. They were transmuted in the alchemist's
crucible before the eyes of the visitors, the juggler adroitly
extracting the iron nail and inserting a gold one without
detection. It mattered little if the converted gold nail differed
in size and shape from the original, for this change in shape
could be laid to the process of transmutation; and even the very
critical were hardly likely to find fault with the exchange thus
made. Furthermore, it was believed that gold possessed the
property of changing its bulk under certain conditions, some of
the more conservative alchemists maintaining that gold was only
increased in bulk, not necessarily created, by certain forms of
the magic stone. Thus a very proficient operator was thought to
be able to increase a grain of gold into a pound of pure metal,
while one less expert could only double, or possibly treble, its
original weight.

The actual number of useful discoveries resulting from the
efforts of the alchemists is considerable, some of them of
incalculable value. Roger Bacon, who lived in the thirteenth
century, while devoting much of his time to alchemy, made such
valuable discoveries as the theory, at least, of the telescope,
and probably gunpowder. Of this latter we cannot be sure that the
discovery was his own and that he had not learned of it through
the source of old manuscripts. But it is not impossible nor
improbable that he may have hit upon the mixture that makes the
explosives while searching for the philosopher's stone in his
laboratory. "Von Helmont, in the same pursuit, discoverd the
properties of gas," says Mackay; "Geber made discoveries in
chemistry, which were equally important; and Paracelsus, amid his
perpetual visions of the transmutation of metals, found that
mercury was a remedy for one of the most odious and excruciating
of all the diseases that afflict humanity."' As we shall see a
little farther on, alchemy finally evolved into modern chemistry,
but not until it had passed through several important
transitional stages.


ASTROLOGY

In a general way modern astronomy may be considered as the
outgrowth of astrology, just as modern chemistry is the result of
alchemy. It is quite possible, however, that astronomy is the
older of the two; but astrology must have developed very shortly
after. The primitive astronomer, having acquired enough knowledge
from his observations of the heavenly bodies to make correct
predictions, such as the time of the coming of the new moon,
would be led, naturally, to believe that certain predictions
other than purely astronomical ones could be made by studying the
heavens. Even if the astronomer himself did not believe this,
some of his superstitious admirers would; for to the unscientific
mind predictions of earthly events would surely seem no more
miraculous than correct predictions as to the future movements of
the sun, moon, and stars. When astronomy had reached a stage of
development so that such things as eclipses could be predicted
with anything like accuracy, the occult knowledge of the
astronomer would be unquestioned. Turning this apparently occult
knowledge to account in a mercenary way would then be the
inevitable result, although it cannot be doubted that many of the
astrologers, in all ages, were sincere in their beliefs.

Later, as the business of astrology became a profitable one,
sincere astronomers would find it expedient to practise astrology
as a means of gaining a livelihood. Such a philosopher as Kepler
freely admitted that he practised astrology "to keep from
starving," although he confessed no faith in such predictions.
"Ye otherwise philosophers," he said, "ye censure this daughter
of astronomy beyond her deserts; know ye not that she must
support her mother by her charms."

Once astrology had become an established practice, any
considerable knowledge of astronomy was unnecessary, for as it
was at best but a system of good guessing as to future events,
clever impostors could thrive equally well without troubling to
study astronomy. The celebrated astrologers, however, were
usually astronomers as well, and undoubtedly based many of their
predictions on the position and movements of the heavenly bodies.
Thus, the casting of a horoscope that is, the methods by which
the astrologers ascertained the relative position of the heavenly
bodies at the time of a birth--was a simple but fairly exact
procedure. Its basis was the zodiac, or the path traced by the
sun in his yearly course through certain constellations. At the
moment of the birth of a child, the first care of the astrologer
was to note the particular part of the zodiac that appeared on
the horizon. The zodiac was then divided into "houses"--that is,
into twelve spaces--on a chart. In these houses were inserted the
places of the planets, sun, and moon, with reference to the
zodiac. When this chart was completed it made a fairly correct
diagram of the heavens and the position of the heavenly bodies as
they would appear to a person standing at the place of birth at a
certain time.

Up to this point the process was a simple one of astronomy. But
the next step--the really important one--that of interpreting
this chart, was the one which called forth the skill and
imagination of the astrologer. In this interpretation, not in his
mere observations, lay the secret of his success. Nor did his
task cease with simply foretelling future events that were to
happen in the life of the newly born infant. He must not only
point out the dangers, but show the means whereby they could be
averted, and his prophylactic measures, like his predictions,
were alleged to be based on his reading of the stars.

But casting a horoscope at the time of births was, of course,
only a small part of the astrologer's duty. His offices were
sought by persons of all ages for predictions as to their
futures, the movements of an enemy, where to find stolen goods,
and a host of everyday occurrences. In such cases it is more than
probable that the astrologers did very little consulting of the
stars in making their predictions. They became expert
physiognomists and excellent judges of human nature, and were
thus able to foretell futures with the same shrewdness and by the
same methods as the modern "mediums," palmists, and
fortune-tellers. To strengthen belief in their powers, it became
a common thing for some supposedly lost document of the
astrologer to be mysteriously discovered after an important
event, this document purporting to foretell this very event. It
was also a common practice with astrologers to retain, or have
access to, their original charts, cleverly altering them from
time to time to fit conditions.

The dangers attendant upon astrology were of such a nature that
the lot of the astrologer was likely to prove anything but an
enviable one. As in the case of the alchemist, the greater the
reputation of an astrologer the greater dangers he was likely to
fall into. If he became so famous that he was employed by kings
or noblemen, his too true or too false prophecies were likely to
bring him into disrepute--even to endanger his life.

Throughout the dark age the astrologers flourished, but the
sixteenth and seventeenth centuries were the golden age of these
impostors. A skilful astrologer was as much an essential to the
government as the highest official, and it would have been a bold
monarch, indeed, who would undertake any expedition of importance
unless sanctioned by the governing stars as interpreted by these
officials.

It should not be understood, however, that belief in astrology
died with the advent of the Copernican doctrine. It did become
separated from astronomy very shortly after, to be sure, and
undoubtedly among the scientists it lost much of its prestige.
But it cannot be considered as entirely passed away, even to-day,
and even if we leave out of consideration street-corner
"astrologers" and fortune-tellers, whose signs may be seen in
every large city, there still remains quite a large class of
relatively intelligent people who believe in what they call "the
science of astrology." Needless to say, such people are not found
among the scientific thinkers; but it is significant that
scarcely a year passes that some book or pamphlet is not
published by some ardent believer in astrology, attempting to
prove by the illogical dogmas characteristic of unscientific
thinkers that astrology is a science. The arguments contained in
these pamphlets are very much the same as those of the
astrologers three hundred years ago, except that they lack the
quaint form of wording which is one of the features that lends
interest to the older documents. These pamphlets need not be
taken seriously, but they are interesting as exemplifying how
difficult it is, even in an age of science, to entirely stamp out
firmly established superstitions. Here are some of the arguments
advanced in defence of astrology, taken from a little brochure
entitled "Astrology Vindicated," published in 1898: It will be
found that a person born when the Sun is in twenty degrees
Scorpio has the left ear as his exceptional feature and the nose
(Sagittarius) bent towards the left ear. A person born when the
Sun is in any of the latter degrees of Taurus, say the
twenty-fifth degree, will have a small, sharp, weak chin, curved
up towards Gemini, the two vertical lines on the upper lip."[4]
The time was when science went out of its way to prove that such
statements were untrue; but that time is past, and such writers
are usually classed among those energetic but misguided persons
who are unable to distinguish between logic and sophistry.


In England, from the time of Elizabeth to the reign of William
and Mary, judicial astrology was at its height. After the great
London fire, in 1666, a committee of the House of Commons
publicly summoned the famous astrologer, Lilly, to come before
Parliament and report to them on his alleged prediction of the
calamity that had befallen the city. Lilly, for some reason best
known to himself, denied having made such a prediction, being, as
he explained, "more interested in determining affairs of much
more importance to the future welfare of the country." Some of
the explanations of his interpretations will suffice to show
their absurdities, which, however, were by no means regarded as
absurdities at that time, for Lilly was one of the greatest
astrologers of his day. He said that in 1588 a prophecy had been
printed in Greek characters which foretold exactly the troubles
of England between the years 1641. and 1660. "And after him shall
come a dreadful dead man," ran the prophecy, "and with him a
royal G of the best blood in the world, and he shall have the
crown and shall set England on the right way and put out all
heresies. His interpretation of this was that, "Monkery being
extinguished above eighty or ninety years, and the Lord General's
name being Monk, is the dead man. The royal G or C (it is gamma
in the Greek, intending C in the Latin, being the third letter in
the alphabet) is Charles II., who, for his extraction, may be
said to be of the best blood of the world."[5]

This may be taken as a fair sample of Lilly's interpretations of
astrological prophesies, but many of his own writings, while
somewhat more definite and direct, are still left sufficiently
vague to allow his skilful interpretations to set right an
apparent mistake. One of his famous documents was "The Starry
Messenger," a little pamphlet purporting to explain the
phenomenon of a "strange apparition of three suns" that were seen
in London on November 19, 1644---the anniversary of the birth of
Charles I., then the reigning monarch. This phenomenon caused a
great stir among the English astrologers, coming, as it did, at a
time of great political disturbance. Prophecies were numerous,
and Lilly's brochure is only one of many that appeared at that
time, most of which, however, have been lost. Lilly, in his
preface, says: "If there be any of so prevaricate a judgment as
to think that the apparition of these three Suns doth intimate no
Novelle thing to happen in our own Climate, where they were
manifestly visible, I shall lament their indisposition, and
conceive their brains to be shallow, and voyde of understanding
humanity, or notice of common History."

Having thus forgiven his few doubting readers, who were by no
means in the majority in his day, he takes up in review the
records of the various appearances of three suns as they have
occurred during the Christian era, showing how such phenomena
have governed certain human events in a very definite manner.
Some of these are worth recording.

"Anno 66. A comet was seen, and also three Suns: In which yeer,
Florus President of the Jews was by them slain. Paul writes to
Timothy. The Christians are warned by a divine Oracle, and depart
out of Jerusalem. Boadice a British Queen, killeth seventy
thousand Romans. The Nazareni, a scurvie Sect, begun, that
boasted much of Revelations and Visions. About a year after Nero
was proclaimed enemy to the State of Rome."

Again, "Anno 1157, in September, there were seen three Suns
together, in as clear weather as could be: And a few days after,
in the same month, three Moons, and, in the Moon that stood in
the middle, a white Crosse. Sueno, King of Denmark, at a great
Feast, killeth Canutus: Sueno is himself slain, in pursuit of
Waldemar. The Order of Eremites, according to the rule of Saint
Augustine, begun this year; and in the next, the Pope submits to
the Emperour: (was not this miraculous?) Lombardy was also
adjudged to the Emperour."

Continuing this list of peculiar phenomena he comes down to
within a few years of his own time.

"Anno 1622, three Suns appeared at Heidelberg. The woful
Calamities that have ever since fallen upon the Palatinate, we
are all sensible of, and of the loss of it, for any thing I see,
for ever, from the right Heir. Osman the great Turk is strangled
that year; and Spinola besiegeth Bergen up Zoom, etc."

Fortified by the enumeration of these past events, he then
proceeds to make his deductions. "Only this I must tell thee," he
writes, "that the interpretation I write is, I conceive, grounded
upon probable foundations; and who lives to see a few years over
his head, will easily perceive I have unfolded as much as was fit
to discover, and that my judgment was not a mile and a half from
truth."

There is a great significance in this "as much as was fit to
discover"--a mysterious something that Lilly thinks it expedient
not to divulge. But, nevertheless, one would imagine that he was
about to make some definite prediction about Charles I., since
these three suns appeared upon his birthday and surely must
portend something concerning him. But after rambling on through
many pages of dissertations upon planets and prophecies, he
finally makes his own indefinite prediction.

"O all you Emperors, Kings, Princes, Rulers and Magistrates of
Europe, this unaccustomed Apparition is like the Handwriting in
Daniel to some of you; it premonisheth you, above all other
people, to make your peace with God in time. You shall every one
of you smart, and every one of you taste (none excepted) the
heavie hand of God, who will strengthen your subjects with
invincible courage to suppress your misgovernments and
Oppressions in Church or Common-wealth; . . . Those words are
general: a word for my own country of England. . . . Look to
yourselves; here's some monstrous death towards you. But to whom?
wilt thou say. Herein we consider the Signe, Lord thereof, and
the House; The Sun signifies in that Royal Signe, great ones; the
House signifies captivity, poison, Treachery: From which is
derived thus much, That some very great man, what King, Prince,
Duke, or the like, I really affirm I perfectly know not, shall, I
say, come to some such untimely end."[6]

Here is shown a typical example of astrological prophecy, which
seems to tell something or nothing, according to the point of
view of the reader. According to a believer in astrology, after
the execution of Charles I., five years later, this could be made
to seem a direct and exact prophecy. For example, he says: "You
Kings, Princes, etc., ... it premonisheth you ... to make your
peace with God.... Look to yourselves; here's some monstrous
death towards you. ... That some very great man, what King,
Prince, . shall, I say, come to such untimely end."

But by the doubter the complete prophecy could be shown to be
absolutely indefinite, and applicable as much to the king of
France or Spain as to Charles I., or to any king in the future,
since no definite time is stated. Furthermore, Lilly distinctly
states, "What King, Prince, Duke, or the like, I really affirm I
perfectly know not"--which last, at least, was a most truthful
statement. The same ingenuity that made "Gen. Monk" the "dreadful
dead man," could easily make such a prediction apply to the
execution of Charles I. Such a definite statement that, on such
and such a day a certain number of years in the future, the
monarch of England would be beheaded--such an exact statement can
scarcely be found in any of the works on astrology. It should be
borne in mind, also, that Lilly was of the Cromwell party and
opposed to the king.

After the death of Charles I., Lilly admitted that the monarch
had given him a thousand pounds to cast his horoscope. "I advised
him," says Lilly, "to proceed eastwards; he went west, and all
the world knows the result." It is an unfortunate thing for the
cause of astrology that Lilly failed to mention this until after
the downfall of the monarch. In fact, the sudden death, or
decline in power, of any monarch, even to-day, brings out the
perennial post-mortem predictions of astrologers.

We see how Lilly, an opponent of the king, made his so-called
prophecy of the disaster of the king and his army. At the same
time another celebrated astrologer and rival of Lilly, George
Wharton, also made some predictions about the outcome of the
eventful march from Oxford. Wharton, unlike Lilly, was a follower
of the king's party, but that, of course, should have had no
influence in his "scientific" reading of the stars. Wharton's
predictions are much less verbose than Lilly's, much more
explicit, and, incidentally, much more incorrect in this
particular instance. "The Moon Lady of the 12," he wrote, "and
moving betwixt the 8 degree, 34 min., and 21 degree, 26 min. of
Aquarius, gives us to understand that His Majesty shall receive
much contentment by certain Messages brought him from foreign
parts; and that he shall receive some sudden and unexpected
supply of . . . by the means of some that assimilate the
condition of his Enemies: And withal this comfort; that His
Majesty shall be exceeding successful in Besieging Towns,
Castles, or Forts, and in persuing the enemy.

"Mars his Sextile to the Sun, Lord of the Ascendant (which
happeneth the 18 day of May) will encourage our Soldiers to
advance with much alacrity and cheerfulness of spirit; to show
themselves gallant in the most dangerous attempt.... And now to
sum up all: It is most apparent to every impartial and ingenuous
judgment; That although His Majesty cannot expect to be secured
from every trivial disaster that may befall his army, either by
the too much Presumption, Ignorance, or Negligence of some
particular Persons (which is frequently incident and unavoidable
in the best of Armies), yet the several positions of the Heavens
duly considered and compared among themselves, as well in the
prefixed Scheme as at the Quarterly Ingresses, do generally
render His Majesty and his whole Army unexpectedly victorious and
successful in all his designs; Believe it (London), thy Miseries
approach, they are like to be many, great, and grievous, and not
to be diverted, unless thou seasonably crave Pardon of God for
being Nurse to this present Rebellion, and speedily submit to thy
Prince's Mercy; Which shall be the daily Prayer of Geo.
Wharton."[7]

In the light of after events, it is probable that Wharton's stock
as an astrologer was not greatly enhanced by this document, at
least among members of the Royal family. Lilly's book, on the
other hand, became a favorite with the Parliamentary army.

After the downfall and death of Napoleon there were unearthed
many alleged authentic astrological documents foretelling his
ruin. And on the death of George IV., in 1830, there appeared a
document (unknown, as usual, until that time) purporting to
foretell the death of the monarch to the day, and this without
the astrologer knowing that his horoscope was being cast for a
monarch. A full account of this prophecy is told, with full
belief, by Roback, a nineteenth-century astrologer. He says:

"In the year 1828, a stranger of noble mien, advanced in life,
but possessing the most bland manners, arrived at the abode of a
celebrated astrologer in London," asking that the learned man
foretell his future. "The astrologer complied with the request of
the mysterious visitor, drew forth his tables, consulted his
ephemeris, and cast the horoscope or celestial map for the hour
and the moment of the inquiry, according to the established rules
of his art.

"The elements of his calculation were adverse, and a feeling of
gloom cast a shade of serious thought, if not dejection, over his
countenance.

" 'You are of high rank,' said the astrologer, as he calculated
and looked on the stranger, 'and of illustrious title.' The
stranger made a graceful inclination of the head in token of
acknowledgment of the complimentary remarks, and the astrologer
proceeded with his mission.

"The celestial signs were ominous of calamity to the stranger,
who, probably observing a sudden change in the countenance of the
astrologer, eagerly inquired what evil or good fortune had been
assigned him by the celestial orbs.

'To the first part of your inquiry,' said the astrologer, 'I can
readily reply. You have been a favorite of fortune; her smiles on
you have been abundant, her frowns but few; you have had, perhaps
now possess, wealth and power; the impossibility of their
accomplishment is the only limit to the fulfilment of your
desires.' "

" 'You have spoken truly of the past,' said the stranger. 'I have
full faith in your revelations of the future: what say you of my
pilgrimage in this life--is it short or long?'

" 'I regret,' replied the astrologer, in answer to this inquiry,
'to be the herald of ill, though TRUE, fortune; your sojourn on
earth will be short.'

" 'How short?' eagerly inquired the excited and anxious stranger.

" 'Give me a momentary truce,' said the astrologer; 'I will
consult the horoscope, and may possibly find some mitigating
circumstances.'

"Having cast his eyes over the celestial map, and paused for some
moments, he surveyed the countenance of the stranger with great
sympathy, and said, 'I am sorry that I can find no planetary
influences that oppose your destiny--your death will take place
in two years.'

"The event justified the astrologic prediction: George IV. died
on May 18, 1830, exactly two years from the day on which he had
visited the astrologer."[8]

This makes a very pretty story, but it hardly seems like occult
insight that an astrologer should have been able to predict an
early death of a man nearly seventy years old, or to have guessed
that his well-groomed visitor "had, perhaps now possesses, wealth
and power." Here again, however, the point of view of each
individual plays the governing part in determining the importance
of such a document. To the scientist it proves nothing; to the
believer in astrology, everything. The significant thing is that
it appeared shortly AFTER the death of the monarch.


On the Continent astrologers were even more in favor than in
England. Charlemagne, and some of his immediate successors, to be
sure, attempted to exterminate them, but such rulers as Louis XI.
and Catherine de' Medici patronized and encouraged them, and it
was many years after the time of Copernicus before their
influence was entirely stamped out even in official life. There
can be no question that what gave the color of truth to many of
the predictions was the fact that so many of the prophecies of
sudden deaths and great conflagrations were known to have come
true--in many instances were made to come true by the astrologer
himself. And so it happened that when the prediction of a great
conflagration at a certain time culminated in such a
conflagration, many times a second but less-important burning
took place, in which the ambitious astrologer, or his followers,
took a central part about a stake, being convicted of
incendiarism, which they had committed in order that their
prophecies might be fulfilled.

But, on the other hand, these predictions were sometimes turned
to account by interested friends to warn certain persons of
approaching dangers.

For example, a certain astrologer foretold the death of Prince
Alexander de' Medici. He not only foretold the death, but
described so minutely the circumstances that would attend it, and
gave such a correct description of the assassin who should murder
the prince, that he was at once suspected of having a hand in the
assassination. It developed later, however, that such was
probably not the case; but that some friend of Prince Alexander,
knowing of the plot to take his life, had induced the astrologer
to foretell the event in order that the prince might have timely
warning and so elude the conspirators.

The cause of the decline of astrology was the growing prevalence
of the new spirit of experimental science. Doubtless the most
direct blow was dealt by the Copernican theory. So soon as this
was established, the recognition of the earth's subordinate place
in the universe must have made it difficult for astronomers to be
longer deceived by such coincidences as had sufficed to convince
the observers of a more credulous generation. Tycho Brahe was,
perhaps, the last astronomer of prominence who was a
conscientious practiser of the art of the astrologer.



VII. FROM PARACELSUS TO HARVEY

PARACELSUS

In the year 1526 there appeared a new lecturer on the platform at
the University at Basel--a small, beardless, effeminate-looking
person--who had already inflamed all Christendom with his
peculiar philosophy, his revolutionary methods of treating
diseases, and his unparalleled success in curing them. A man who
was to be remembered in after-time by some as the father of
modern chemistry and the founder of modern medicine; by others as
madman, charlatan, impostor; and by still others as a combination
of all these. This soft-cheeked, effeminate, woman-hating man,
whose very sex has been questioned, was Theophrastus von
Hohenheim, better known as Paracelsus (1493-1541).

To appreciate his work, something must be known of the life of
the man. He was born near Maria-Einsiedeln, in Switzerland, the
son of a poor physician of the place. He began the study of
medicine under the instruction of his father, and later on came
under the instruction of several learned churchmen. At the age of
sixteen he entered the University of Basel, but, soon becoming
disgusted with the philosophical teachings of the time, he
quitted the scholarly world of dogmas and theories and went to
live among the miners in the Tyrol, in order that he might study
nature and men at first hand. Ordinary methods of study were
thrown aside, and he devoted his time to personal
observation--the only true means of gaining useful knowledge, as
he preached and practised ever after. Here he became familiar
with the art of mining, learned the physical properties of
minerals, ores, and metals, and acquired some knowledge of
mineral waters. More important still, he came in contact with
such diseases, wounds, and injuries as miners are subject to, and
he tried his hand at the practical treatment of these conditions,
untrammelled by the traditions of a profession in which his
training had been so scant.

Having acquired some empirical skill in treating diseases,
Paracelsus set out wandering from place to place all over Europe,
gathering practical information as he went, and learning more and
more of the medicinal virtues of plants and minerals. His
wanderings covered a period of about ten years, at the end of
which time he returned to Basel, where he was soon invited to
give a course of lectures in the university.

These lectures were revolutionary in two respects--they were
given in German instead of time-honored Latin, and they were
based upon personal experience rather than upon the works of such
writers as Galen and Avicenna. Indeed, the iconoclastic teacher
spoke with open disparagement of these revered masters, and
openly upbraided his fellow-practitioners for following their
tenets. Naturally such teaching raised a storm of opposition
among the older physicians, but for a time the unparalleled
success of Paracelsus in curing diseases more than offset his
unpopularity. Gradually, however, his bitter tongue and his
coarse personality rendered him so unpopular, even among his
patients, that, finally, his liberty and life being jeopardized,
he was obliged to flee from Basel, and became a wanderer. He
lived for brief periods in Colmar, Nuremberg, Appenzell, Zurich,
Pfeffers, Augsburg, and several other cities, until finally at
Salzburg his eventful life came to a close in 1541. His enemies
said that he had died in a tavern from the effects of a
protracted debauch; his supporters maintained that he had been
murdered at the instigation of rival physicians and apothecaries.

But the effects of his teachings had taken firm root, and
continued to spread after his death. He had shown the fallibility
of many of the teachings of the hitherto standard methods of
treating diseases, and had demonstrated the advantages of
independent reasoning based on observation. In his Magicum he
gives his reasons for breaking with tradition. "I did," he says,
"embrace at the beginning these doctrines, as my adversaries
(followers of Galen) have done, but since I saw that from their
procedures nothing resulted but death, murder, stranglings,
anchylosed limbs, paralysis, and so forth, that they held most
diseases incurable. . . . therefore have I quitted this wretched
art, and sought for truth in any other direction. I asked myself
if there were no such thing as a teacher in medicine, where could
I learn this art best? Nowhere better than the open book of
nature, written with God's own finger." We shall see, however,
that this "book of nature" taught Paracelsus some very strange
lessons. Modesty was not one of these. "Now at this time," he
declares, "I, Theophrastus Paracelsus, Bombast, Monarch of the
Arcana, was endowed by God with special gifts for this end, that
every searcher after this supreme philosopher's work may be
forced to imitate and to follow me, be he Italian, Pole, Gaul,
German, or whatsoever or whosoever he be. Come hither after me,
all ye philosophers, astronomers, and spagirists. . . . I will
show and open to you ... this corporeal regeneration."[1]

Paracelsus based his medical teachings on four "pillars"
--philosophy, astronomy, alchemy, and virtue of the physician--a
strange-enough equipment surely, and yet, properly interpreted,
not quite so anomalous as it seems at first blush. Philosophy was
the "gate of medicine," whereby the physician entered rightly
upon the true course of learning; astronomy, the study of the
stars, was all-important because "they (the stars) caused disease
by their exhalations, as, for instance, the sun by excessive
heat"; alchemy, as he interpreted it, meant the improvement of
natural substances for man's benefit; while virtue in the
physician was necessary since "only the virtuous are permitted to
penetrate into the innermost nature of man and the universe."

All his writings aim to promote progress in medicine, and to hold
before the physician a grand ideal of his profession. In this his
views are wide and far-reaching, based on the relationship which
man bears to nature as a whole; but in his sweeping condemnations
he not only rejected Galenic therapeutics and Galenic anatomy,
but condemned dissections of any kind. He laid the cause of all
diseases at the door of the three mystic elements--salt, sulphur,
and mercury. In health he supposed these to be mingled in the
body so as to be indistinguishable; a slight separation of them
produced disease; and death he supposed to be the result of their
complete separation. The spiritual agencies of diseases, he said,
had nothing to do with either angels or devils, but were the
spirits of human beings.

He believed that all food contained poisons, and that the
function of digestion was to separate the poisonous from the
nutritious. In the stomach was an archaeus, or alchemist, whose
duty was to make this separation. In digestive disorders the
archaeus failed to do this, and the poisons thus gaining access
to the system were "coagulated" and deposited in the joints and
various other parts of the body. Thus the deposits in the kidneys
and tartar on the teeth were formed; and the stony deposits of
gout were particularly familiar examples of this. All this is
visionary enough, yet it shows at least a groping after rational
explanations of vital phenomena.

Like most others of his time, Paracelsus believed firmly in the
doctrine of "signatures"--a belief that every organ and part of
the body had a corresponding form in nature, whose function was
to heal diseases of the organ it resembled. The vagaries of this
peculiar doctrine are too numerous and complicated for lengthy
discussion, and varied greatly from generation to generation. In
general, however, the theory may be summed up in the words of
Paracelsus: "As a woman is known by her shape, so are the
medicines." Hence the physicians were constantly searching for
some object of corresponding shape to an organ of the body. The
most natural application of this doctrine would be the use of the
organs of the lower animals for the treatment of the
corresponding diseased organs in man. Thus diseases of the heart
were to be treated with the hearts of animals, liver disorders
with livers, and so on. But this apparently simple form of
treatment had endless modifications and restrictions, for not all
animals were useful. For example, it was useless to give the
stomach of an ox in gastric diseases when the indication in such
cases was really for the stomach of a rat. Nor were the organs of
animals the only "signatures" in nature. Plants also played a
very important role, and the herb-doctors devoted endless labor
to searching for such plants. Thus the blood-root, with its red
juice, was supposed to be useful in blood diseases, in stopping
hemorrhage, or in subduing the redness of an inflammation.

Paracelsus's system of signatures, however, was so complicated by
his theories of astronomy and alchemy that it is practically
beyond comprehension. It is possible that he himself may have
understood it, but it is improbable that any one else did--as
shown by the endless discussions that have taken place about it.
But with all the vagaries of his theories he was still rational
in his applications, and he attacked to good purpose the
complicated "shot-gun" prescriptions of his contemporaries,
advocating more simple methods of treatment.

The ever-fascinating subject of electricity, or, more
specifically, "magnetism," found great favor with him, and with
properly adjusted magnets he claimed to be able to cure many
diseases. In epilepsy and lockjaw, for example, one had but to
fasten magnets to the four extremities of the body, and then,
"when the proper medicines were given," the cure would be
effected. The easy loop-hole for excusing failure on the ground
of improper medicines is obvious, but Paracelsus declares that
this one prescription is of more value than "all the humoralists
have ever written or taught."

Since Paracelsus condemned the study of anatomy as useless, he
quite naturally regarded surgery in the same light. In this he
would have done far better to have studied some of his
predecessors, such as Galen, Paul of Aegina, and Avicenna. But
instead of "cutting men to pieces," he taught that surgeons would
gain more by devoting their time to searching for the universal
panacea which would cure all diseases, surgical as well as
medical. In this we detect a taint of the popular belief in the
philosopher's stone and the magic elixir of life, his belief in
which have been stoutly denied by some of his followers. He did
admit, however, that one operation alone was perhaps
permissible--lithotomy, or the "cutting for stone."

His influence upon medicine rests undoubtedly upon his
revolutionary attitude, rather than on any great or new
discoveries made by him. It is claimed by many that he brought
prominently into use opium and mercury, and if this were
indisputably proven his services to medicine could hardly be
overestimated. Unfortunately, however, there are good grounds for
doubting that he was particularly influential in reintroducing
these medicines. His chief influence may perhaps be summed up in
a single phrase--he overthrew old traditions.

To Paracelsus's endeavors, however, if not to the actual products
of his work, is due the credit of setting in motion the chain of
thought that developed finally into scientific chemistry. Nor can
the ultimate aim of the modern chemist seek a higher object than
that of this sixteenth-century alchemist, who taught that "true
alchemy has but one aim and object, to extract the quintessence
of things, and to prepare arcana, tinctures, and elixirs which
may restore to man the health and soundness he has lost."


THE GREAT ANATOMISTS

About the beginning of the sixteenth century, while Paracelsus
was scoffing at the study of anatomy as useless, and using his
influence against it, there had already come upon the scene the
first of the great anatomists whose work was to make the century
conspicuous in that branch of medicine.

The young anatomist Charles etienne (1503-1564) made one of the
first noteworthy discoveries, pointing out for the first time
that the spinal cord contains a canal, continuous throughout its
length. He also made other minor discoveries of some importance,
but his researches were completely overshadowed and obscured by
the work of a young Fleming who came upon the scene a few years
later, and who shone with such brilliancy in the medical world
that he obscured completely the work of his contemporary until
many years later. This young physician, who was destined to lead
such an eventful career and meet such an untimely end as a martyr
to science, was Andrew Vesalius (1514-1564), who is called the
"greatest of anatomists." At the time he came into the field
medicine was struggling against the dominating Galenic teachings
and the theories of Paracelsus, but perhaps most of all against
the superstitions of the time. In France human dissections were
attended with such dangers that the young Vesalius transferred
his field of labors to Italy, where such investigations were
covertly permitted, if not openly countenanced.

From the very start the young Fleming looked askance at the
accepted teachings of the day, and began a series of independent
investigations based upon his own observations. The results of
these investigations he gave in a treatise on the subject which
is regarded as the first comprehensive and systematic work on
human anatomy. This remarkable work was published in the author's
twenty-eighth or twenty-ninth year. Soon after this Vesalius was
invited as imperial physician to the court of Emperor Charles V.
He continued to act in the same capacity at the court of Philip
II., after the abdication of his patron. But in spite of this
royal favor there was at work a factor more powerful than the
influence of the monarch himself--an instrument that did so much
to retard scientific progress, and by which so many lives were
brought to a premature close.

Vesalius had received permission from the kinsmen of a certain
grandee to perform an autopsy. While making his observations the
heart of the outraged body was seen to palpitate--so at least it
was reported. This was brought immediately to the attention of
the Inquisition, and it was only by the intervention of the king
himself that the anatomist escaped the usual fate of those
accused by that tribunal. As it was, he was obliged to perform a
pilgrimage to the Holy Land. While returning from this he was
shipwrecked, and perished from hunger and exposure on the island
of Zante.

At the very time when the anatomical writings of Vesalius were
startling the medical world, there was living and working
contemporaneously another great anatomist, Eustachius (died
1574), whose records of his anatomical investigations were ready
for publication only nine years after the publication of the work
of Vesalius. Owing to the unfortunate circumstances of the
anatomist, however, they were never published during his
lifetime--not, in fact, until 1714. When at last they were given
to the world as Anatomical Engravings, they showed conclusively
that Eustachius was equal, if not superior to Vesalius in his
knowledge of anatomy. It has been said of this remarkable
collection of engravings that if they had been published when
they were made in the sixteenth century, anatomy would have been
advanced by at least two centuries. But be this as it may, they
certainly show that their author was a most careful dissector and
observer.

Eustachius described accurately for the first time certain
structures of the middle ear, and rediscovered the tube leading
from the ear to the throat that bears his name. He also made
careful studies of the teeth and the phenomena of first and
second dentition. He was not baffled by the minuteness of
structures and where he was unable to study them with the naked
eye he used glasses for the purpose, and resorted to macerations
and injections for the study of certain complicated structures.
But while the fruit of his pen and pencil were lost for more than
a century after his death, the effects of his teachings were not;
and his two pupils, Fallopius and Columbus, are almost as well
known to-day as their illustrious teacher. Columbus (1490-1559)
did much in correcting the mistakes made in the anatomy of the
bones as described by Vesalius. He also added much to the science
by giving correct accounts of the shape and cavities of the
heart, and made many other discoveries of minor importance.
Fallopius (1523-1562) added considerably to the general knowledge
of anatomy, made several discoveries in the anatomy of the ear,
and also several organs in the abdominal cavity.

At this time a most vitally important controversy was in progress
as to whether or not the veins of the bodies were supplied with
valves, many anatomists being unable to find them. etienne had
first described these structures, and Vesalius had confirmed his
observations. It would seem as if there could be no difficulty in
settling the question as to the fact of such valves being present
in the vessels, for the demonstration is so simple that it is now
made daily by medical students in all physiological laboratories
and dissecting-rooms. But many of the great anatomists of the
sixteenth century were unable to make this demonstration, even
when it had been brought to their attention by such an authority
as Vesalius. Fallopius, writing to Vesalius on the subject in
1562, declared that he was unable to find such valves. Others,
however, such as Eustachius and Fabricius (1537-1619), were more
successful, and found and described these structures. But the
purpose served by these valves was entirely misinterpreted. That
they act in preventing the backward flow of the blood in the
veins on its way to the heart, just as the valves of the heart
itself prevent regurgitation, has been known since the time of
Harvey; but the best interpretation that could be given at that
time, even by such a man as Fabricius, was that they acted in
retarding the flow of the blood as it comes from the heart, and
thus prevent its too rapid distribution throughout the body. The
fact that the blood might have been going towards the heart,
instead of coming from it, seems never to have been considered
seriously until demonstrated so conclusively by Harvey.

Of this important and remarkable controversy over the valves in
veins, Withington has this to say: "This is truly a marvellous
story. A great Galenic anatomist is first to give a full and
correct description of the valves and their function, but fails
to see that any modification of the old view as to the motion of
the blood is required. Two able dissectors carefully test their
action by experiment, and come to a result. the exact reverse of
the truth. Urged by them, the two foremost anatomists of the age
make a special search for valves and fail to find them. Finally,
passing over lesser peculiarities, an aged and honorable
professor, who has lived through all this, calmly asserts that no
anatomist, ancient or modern, has ever mentioned valves in veins
till he discovered them in 1574!"[2]

Among the anatomists who probably discovered these valves was
Michael Servetus (1511-1553); but if this is somewhat in doubt,
it is certain that he discovered and described the pulmonary
circulation, and had a very clear idea of the process of
respiration as carried on in the lungs. The description was
contained in a famous document sent to Calvin in 1545--a document
which the reformer carefully kept for seven years in order that
he might make use of some of the heretical statements it
contained to accomplish his desire of bringing its writer to the
stake. The awful fate of Servetus, the interesting character of
the man, and the fact that he came so near to anticipating the
discoveries of Harvey make him one of the most interesting
figures in medical history.

In this document which was sent to Calvin, Servetus rejected the
doctrine of natural, vital, and animal spirits, as contained in
the veins, arteries, and nerves respectively, and made the
all-important statement that the fluids contained in veins and
arteries are the same. He showed also that the blood is "purged
from fume" and purified by respiration in the lungs, and declared
that there is a new vessel in the lungs, "formed out of vein and
artery." Even at the present day there is little to add to or
change in this description of Servetus's.

By keeping this document, pregnant with advanced scientific
views, from the world, and in the end only using it as a means of
destroying its author, the great reformer showed the same
jealousy in retarding scientific progress as had his arch-enemies
of the Inquisition, at whose dictates Vesalius became a martyr to
science, and in whose dungeons etienne perished.


THE COMING OF HARVEY

The time was ripe for the culminating discovery of the
circulation of the blood; but as yet no one had determined the
all-important fact that there are two currents of blood in the
body, one going to the heart, one coming from it. The valves in
the veins would seem to show conclusively that the venous current
did not come from the heart, and surgeons must have observed
thousands of times the every-day phenomenon of congested veins at
the distal extremity of a limb around which a ligature or
constriction of any kind had been placed, and the simultaneous
depletion of the vessels at the proximal points above the
ligature. But it should be remembered that inductive science was
in its infancy. This was the sixteenth, not the nineteenth
century, and few men had learned to put implicit confidence in
their observations and convictions when opposed to existing
doctrines. The time was at hand, however, when such a man was to
make his appearance, and, as in the case of so many revolutionary
doctrines in science, this man was an Englishman. It remained for
William Harvey (1578-1657) to solve the great mystery which had
puzzled the medical world since the beginning of history; not
only to solve it, but to prove his case so conclusively and so
simply that for all time his little booklet must he handed down
as one of the great masterpieces of lucid and almost faultless
demonstration.

Harvey, the son of a prosperous Kentish yeoman, was born at
Folkestone. His education was begun at the grammar-school of
Canterbury, and later he became a pensioner of Caius College,
Cambridge. Soon after taking his degree of B.A., at the age of
nineteen, he decided upon the profession of medicine, and went to
Padua as a pupil of Fabricius and Casserius. Returning to England
at the age of twenty-four, he soon after (1609) obtained the
reversion of the post of physician to St. Bartholomew's Hospital,
his application being supported by James I. himself. Even at this
time he was a popular physician, counting among his patients such
men as Francis Bacon. In 1618 he was appointed physician
extraordinary to the king, and, a little later, physician in
ordinary. He was in attendance upon Charles I. at the battle of
Edgehill, in 1642, where, with the young Prince of Wales and the
Duke of York, after seeking shelter under a hedge, he drew a book
out of his pocket and, forgetful of the battle, became absorbed
in study, until finally the cannon-balls from the enemy's
artillery made him seek a more sheltered position.

On the fall of Charles I. he retired from practice, and lived in
retirement with his brother. He was then well along in years, but
still pursued his scientific researches with the same vigor as
before, directing his attention chiefly to the study of
embryology. On June 3, 1657, he was attacked by paralysis and
died, in his eightieth year. He had lived to see his theory of
the circulation accepted, several years before, by all the
eminent anatomists of the civilized world.

A keenness in the observation of facts, characteristic of the
mind of the man, had led Harvey to doubt the truth of existing
doctrines as to the phenomena of the circulation. Galen had
taught that "the arteries are filled, like bellows, because they
are expanded," but Harvey thought that the action of spurting
blood from a severed vessel disproved this. For the spurting was
remittant, "now with greater, now with less impetus," and its
greater force always corresponded to the expansion (diastole),
not the contraction (systole) of the vessel. Furthermore, it was
evident that contraction of the heart and the arteries was not
simultaneous, as was commonly taught, because in that case there
would be no marked propulsion of the blood in any direction; and
there was no gainsaying the fact that the blood was forcibly
propelled in a definite direction, and that direction away from
the heart.

Harvey's investigations led him to doubt also the accepted theory
that there was a porosity in the septum of tissue that divides
the two ventricles of the heart. It seemed unreasonable to
suppose that a thick fluid like the blood could find its way
through pores so small that they could not be demonstrated by any
means devised by man. In evidence that there could be no such
openings he pointed out that, since the two ventricles contract
at the same time, this process would impede rather than
facilitate such an intra-ventricular passage of blood. But what
seemed the most conclusive proof of all was the fact that in the
foetus there existed a demonstrable opening between the two
ventricles, and yet this is closed in the fully developed heart.
Why should Nature, if she intended that blood should pass between
the two cavities, choose to close this opening and substitute
microscopic openings in place of it? It would surely seem more
reasonable to have the small perforations in the thin, easily
permeable membrane of the foetus, and the opening in the adult
heart, rather than the reverse. From all this Harvey drew his
correct conclusions, declaring earnestly, "By Hercules, there ARE
no such porosities, and they cannot be demonstrated."

Having convinced himself that no intra-ventricular opening
existed, he proceeded to study the action of the heart itself,
untrammelled by too much faith in established theories, and, as
yet, with no theory of his own. He soon discovered that the
commonly accepted theory of the heart striking against the
chest-wall during the period of relaxation was entirely wrong,
and that its action was exactly the reverse of this, the heart
striking the chest-wall during contraction. Having thus disproved
the accepted theory concerning the heart's action, he took up the
subject of the action of arteries, and soon was able to
demonstrate by vivisection that the contraction of the arteries
was not simultaneous with contractions of the heart. His
experiments demonstrated that these vessels were simply elastic
tubes whose pulsations were "nothing else than the impulse of the
blood within them." The reason that the arterial pulsation was
not simultaneous with the heart-beat he found to be because of
the time required to carry the impulse along the tube,

By a series of further careful examinations and experiments,
which are too extended to be given here, he was soon able further
to demonstrate the action and course of the blood during the
contractions of the heart. His explanations were practically the
same as those given to-day--first the contraction of the auricle,
sending blood into the ventricle; then ventricular contraction,
making the pulse, and sending the blood into the arteries. He had
thus demonstrated what had not been generally accepted before,
that the heart was an organ for the propulsion of blood. To make
such a statement to-day seems not unlike the sober announcement
that the earth is round or that the sun does not revolve about
it. Before Harvey's time, however, it was considered as an organ
that was "in some mysterious way the source of vitality and
warmth, as an animated crucible for the concoction of blood and
the generation of vital spirits."[3]

In watching the rapid and ceaseless contractions of the heart,
Harvey was impressed with the fact that, even if a very small
amount of blood was sent out at each pulsation, an enormous
quantity must pass through the organ in a day, or even in an
hour. Estimating the size of the cavities of the heart, and
noting that at least a drachm must be sent out with each
pulsation, it was evident that the two thousand beats given by a
very slow human heart in an hour must send out some forty pounds
of blood--more than twice the amount in the entire body. The
question was, what became of it all? For it should be remembered
that the return of the blood by the veins was unknown, and
nothing like a "circulation" more than vaguely conceived even by
Harvey himself. Once it could be shown that the veins were
constantly returning blood to the heart, the discovery that the
blood in some way passes from the arteries to the veins was only
a short step. Harvey, by resorting to vivisections of lower
animals and reptiles, soon demonstrated beyond question the fact
that the veins do carry the return blood. "But this, in
particular, can be shown clearer than daylight," says Harvey.
"The vena cava enters the heart at an inferior portion, while the
artery passes out above. Now if the vena cava be taken up with
forceps or the thumb and finger, and the course of the blood
intercepted for some distance below the heart, you will at once
see it almost emptied between the fingers and the heart, the
blood being exhausted by the heart's pulsation, the heart at the
same time becoming much paler even in its dilatation, smaller in
size, owing to the deficiency of blood, and at length languid in
pulsation, as if about to die. On the other hand, when you
release the vein the heart immediately regains its color and
dimensions. After that, if you leave the vein free and tie and
compress the arteries at some distance from the heart, you will
see, on the contrary, their included portion grow excessively
turgid, the heart becoming so beyond measure, assuming a dark-red
color, even to lividity, and at length so overloaded with blood
as to seem in danger of suffocation; but when the obstruction is
removed it returns to its normal condition, in size, color, and
movement."[4]

This conclusive demonstration that the veins return the blood to
the heart must have been most impressive to Harvey, who had been
taught to believe that the blood current in the veins pursued an
opposite course, and must have tended to shake his faith in all
existing doctrines of the day.

His next step was the natural one of demonstrating that the blood
passes from the arteries to the veins. He demonstrated
conclusively that this did occur, but for once his rejection of
the ancient writers and one modern one was a mistake. For Galen
had taught, and had attempted to demonstrate, that there are sets
of minute vessels connecting the arteries and the veins; and
Servetus had shown that there must be such vessels, at least in
the lungs.

However, the little flaw in the otherwise complete demonstration
of Harvey detracts nothing from the main issue at stake. It was
for others who followed to show just how these small vessels
acted in effecting the transfer of the blood from artery to vein,
and the grand general statement that such a transfer does take
place was, after all, the all-important one, and the exact method
of how it takes place a detail. Harvey's experiments to
demonstrate that the blood passes from the arteries to the veins
are so simply and concisely stated that they may best be given in
his own words.

"I have here to cite certain experiments," he wrote, "from which
it seems obvious that the blood enters a limb by the arteries,
and returns from it by the veins; that the arteries are the
vessels carrying the blood from the heart, and the veins the
returning channels of the blood to the heart; that in the limbs
and extreme parts of the body the blood passes either by
anastomosis from the arteries into the veins, or immediately by
the pores of the flesh, or in both ways, as has already been said
in speaking of the passage of the blood through the lungs; whence
it appears manifest that in the circuit the blood moves from
thence hither, and hence thither; from the centre to the
extremities, to wit, and from the extreme parts back again to the
centre. Finally, upon grounds of circulation, with the same
elements as before, it will be obvious that the quantity can
neither be accounted for by the ingesta, nor yet be held
necessary to nutrition.

"Now let any one make an experiment on the arm of a man, either
using such a fillet as is employed in blood-letting or grasping
the limb tightly with his hand, the best subject for it being one
who is lean, and who has large veins, and the best time after
exercise, when the body is warm, the pulse is full, and the blood
carried in large quantities to the extremities, for all then is
more conspicuous; under such circumstances let a ligature be
thrown about the extremity and drawn as tightly as can be borne:
it will first be perceived that beyond the ligature neither in
the wrist nor anywhere else do the arteries pulsate, that at the
same time immediately above the ligature the artery begins to
rise higher at each diastole, to throb more violently, and to
swell in its vicinity with a kind of tide, as if it strove to
break through and overcome the obstacle to its current; the
artery here, in short, appears as if it were permanently full.
The hand under such circumstances retains its natural color and
appearances; in the course of time it begins to fall somewhat in
temperature, indeed, but nothing is DRAWN into it.

"After the bandage has been kept on some short time in this way,
let it be slackened a little, brought to the state or term of
middling tightness which is used in bleeding, and it will be seen
that the whole hand and arm will instantly become deeply suffused
and distended, injected, gorged with blood, DRAWN, as it is said,
by this middling ligature, without pain, or heat, or any horror
of a vacuum, or any other cause yet indicated.

"As we have noted, in connection with the tight ligature, that
the artery above the bandage was distended and pulsated, not
below it, so, in the case of the moderately tight bandage, on the
contrary, do we find that the veins below, never above, the
fillet swell and become dilated, while the arteries shrink; and
such is the degree of distention of the veins here that it is
only very strong pressure that will force the blood beyond the
fillet and cause any of the veins in the upper part of the arm to
rise.

"From these facts it is easy for any careful observer to learn
that the blood enters an extremity by the arteries; for when they
are effectively compressed nothing is DRAWN to the member; the
hand preserves its color; nothing flows into it, neither is it
distended; but when the pressure is diminished, as it is with the
bleeding fillet, it is manifest that the blood is instantly
thrown in with force, for then the hand begins to swell; which is
as much as to say that when the arteries pulsate the blood is
flowing through them, as it is when the moderately tight ligature
is applied; but when they do not pulsate, or when a tight
ligature is used, they cease from transmitting anything; they are
only distended above the part where the ligature is applied. The
veins again being compressed, nothing can flow through them; the
certain indication of which is that below the ligature they are
much more tumid than above it, and than they usually appear when
there is no bandage upon the arm.

"It therefore plainly appears that the ligature prevents the
return of the blood through the veins to the parts above it, and
maintains those beneath it in a state of permanent distention.
But the arteries, in spite of the pressure, and under the force
and impulse of the heart, send on the blood from the internal
parts of the body to the parts beyond the bandage."[5]


This use of ligatures is very significant, because, as shown, a
very tight ligature stops circulation in both arteries and veins,
while a loose one, while checking the circulation in the veins,
which lie nearer the surface and are not so directly influenced
by the force of the heart, does not stop the passage of blood in
the arteries, which are usually deeply imbedded in the tissues,
and not so easily influenced by pressure from without.

The last step of Harvey's demonstration was to prove that the
blood does flow along the veins to the heart, aided by the valves
that had been the cause of so much discussion and dispute between
the great sixteenth-century anatomists. Harvey not only
demonstrated the presence of these valves, but showed
conclusively, by simple experiments, what their function was,
thus completing his demonstration of the phenomena of the
circulation.

The final ocular demonstration of the passage of the blood from
the arteries to the veins was not to be made until four years
after Harvey's death. This process, which can be observed easily
in the web of a frog's foot by the aid of a low-power lens, was
first demonstrated by Marcello Malpighi (1628-1694) in 1661. By
the aid of a lens he first saw the small "capillary" vessels
connecting the veins and arteries in a piece of dried lung.
Taking his cue from this, he examined the lung of a turtle, and
was able to see in it the passage of the corpuscles through these
minute vessels, making their way along these previously unknown
channels from the arteries into the veins on their journey back
to the heart. Thus the work of Harvey, all but complete, was made
absolutely entire by the great Italian. And all this in a single
generation.


LEEUWENHOEK DISCOVERS BACTERIA

The seventeenth century was not to close, however, without
another discovery in science, which, when applied to the
causation of disease almost two centuries later, revolutionized
therapeutics more completely than any one discovery. This was the
discovery of microbes, by Antonius von Leeuwenhoek (1632-1723),
in 1683. Von Leeuwenhoek discovered that "in the white matter
between his teeth" there were millions of microscopic
"animals"--more, in fact, than "there were human beings in the
united Netherlands," and all "moving in the most delightful
manner." There can be no question that he saw them, for we can
recognize in his descriptions of these various forms of little
"animals" the four principal forms of microbes--the long and
short rods of bacilli and bacteria, the spheres of micrococci,
and the corkscrew spirillum.

The presence of these microbes in his mouth greatly annoyed
Antonius, and he tried various methods of getting rid of them,
such as using vinegar and hot coffee. In doing this he little
suspected that he was anticipating modern antiseptic surgery by a
century and three-quarters, and to be attempting what antiseptic
surgery is now able to accomplish. For the fundamental principle
of antisepsis is the use of medicines for ridding wounds of
similar microscopic organisms. Von Leenwenhoek was only
temporarily successful in his attempts, however, and took
occasion to communicate his discovery to the Royal Society of
England, hoping that they would be "interested in this novelty."
Probably they were, but not sufficiently so for any member to
pursue any protracted investigations or reach any satisfactory
conclusions, and the whole matter was practically forgotten until
the middle of the nineteenth century.



VIII. MEDICINE IN THE SIXTEENTH AND SEVENTEENTH CENTURIES

Of the half-dozen surgeons who were prominent in the sixteenth
century, Ambroise Pare (1517-1590), called the father of French
surgery, is perhaps the most widely known. He rose from the
position of a common barber to that of surgeon to three French
monarchs, Henry II., Francis II., and Charles IX. Some of his
mottoes are still first principles of the medical man. Among
others are: "He who becomes a surgeon for the sake of money, and
not for the sake of knowledge, will accomplish nothing"; and "A
tried remedy is better than a newly invented." On his statue is
his modest estimate of his work in caring for the wounded, "Je le
pansay, Dieu le guarit"--I dressed him, God cured him.

It was in this dressing of wounds on the battlefield that he
accidentally discovered how useless and harmful was the terribly
painful treatment of applying boiling oil to gunshot wounds as
advocated by John of Vigo. It happened that after a certain
battle, where there was an unusually large number of casualties,
Pare found, to his horror, that no more boiling oil was available
for the surgeons, and that he should be obliged to dress the
wounded by other simpler methods. To his amazement the results
proved entirely satisfactory, and from that day he discarded the
hot-oil treatment.

As Pare did not understand Latin he wrote his treatises in
French, thus inaugurating a custom in France that was begun by
Paracelsus in Germany half a century before. He reintroduced the
use of the ligature in controlling hemorrhage, introduced the
"figure of eight" suture in the operation for hare-lip, improved
many of the medico-legal doctrines, and advanced the practice of
surgery generally. He is credited with having successfully
performed the operation for strangulated hernia, but he probably
borrowed it from Peter Franco (1505-1570), who published an
account of this operation in 1556. As this operation is
considered by some the most important operation in surgery, its
discoverer is entitled to more than passing notice, although he
was despised and ignored by the surgeons of his time.

Franco was an illiterate travelling lithotomist--a class of
itinerant physicians who were very generally frowned down by the
regular practitioners of medicine. But Franco possessed such
skill as an operator, and appears to have been so earnest in the
pursuit of what he considered a legitimate calling, that he
finally overcame the popular prejudice and became one of the
salaried surgeons of the republic of Bern. He was the first
surgeon to perform the suprapubic lithotomy operation--the
removal of stone through the abdomen instead of through the
perineum. His works, while written in an illiterate style, give
the clearest descriptions of any of the early modern writers.

As the fame of Franco rests upon his operation for prolonging
human life, so the fame of his Italian contemporary, Gaspar
Tagliacozzi (1545-1599), rests upon his operation for increasing
human comfort and happiness by restoring amputated noses. At the
time in which he lived amputation of the nose was very common,
partly from disease, but also because a certain pope had fixed
the amputation of that member as the penalty for larceny.
Tagliacozzi probably borrowed his operation from the East; but he
was the first Western surgeon to perform it and describe it. So
great was the fame of his operations that patients flocked to him
from all over Europe, and each "went away with as many noses as
he liked." Naturally, the man who directed his efforts to
restoring structures that bad been removed by order of the Church
was regarded in the light of a heretic by many theologians; and
though he succeeded in cheating the stake or dungeon, and died a
natural death, his body was finally cast out of the church in
which it had been buried.

In the sixteenth century Germany produced a surgeon, Fabricius
Hildanes (1560-1639), whose work compares favorably with that of
Pare, and whose name would undoubtedly have been much better
known had not the circumstances of the time in which he lived
tended to obscure his merits. The blind followers of Paracelsus
could see nothing outside the pale of their master's teachings,
and the disastrous Thirty Years' War tended to obscure and retard
all scientific advances in Germany. Unlike many of his
fellow-surgeons, Hildanes was well versed in Latin and Greek;
and, contrary to the teachings of Paracelsus, he laid particular
stress upon the necessity of the surgeon having a thorough
knowledge of anatomy. He had a helpmate in his wife, who was also
something of a surgeon, and she is credited with having first
made use of the magnet in removing particles of metal from the
eye. Hildanes tells of a certain man who had been injured by a
small piece of steel in the cornea, which resisted all his
efforts to remove it. After observing Hildanes' fruitless efforts
for a time, it suddenly occurred to his wife to attempt to make
the extraction with a piece of loadstone. While the physician
held open the two lids, his wife attempted to withdraw the steel
with the magnet held close to the cornea, and after several
efforts she was successful--which Hildanes enumerates as one of
the advantages of being a married man.

Hildanes was particularly happy in his inventions of surgical
instruments, many of which were designed for locating and
removing the various missiles recently introduced in warfare.


The seventeenth century, which was such a flourishing one for
anatomy and physiology, was not as productive of great surgeons
or advances in surgery as the sixteenth had been or the
eighteenth was to be. There was a gradual improvement all along
the line, however, and much of the work begun by such surgeons as
Pare and Hildanes was perfected or improved. Perhaps the most
progressive surgeon of the century was an Englishman, Richard
Wiseman (1625-1686), who, like Harvey, enjoyed royal favor, being
in the service of all the Stuart kings. He was the first surgeon
to advocate primary amputation, in gunshot wounds, of the limbs,
and also to introduce the treatment of aneurisms by compression;
but he is generally rated as a conservative operator, who favored
medication rather than radical operations, where possible.

In Italy, Marcus Aurelius Severinus (1580-1656) and Peter
Marchettis (1589-1675) were the leading surgeons of their nation.
Like many of his predecessors in Europe, Severinus ran amuck with
the Holy Inquisition and fled from Naples. But the waning of the
powerful arm of the Church is shown by the fact that he was
brought back by the unanimous voice of the grateful citizens, and
lived in safety despite the frowns of the theologians.


The sixteenth century cannot be said to have added much of
importance in the field of practical medicine, and, as in the
preceding and succeeding centuries, was at best only struggling
along in the wake of anatomy, physiology, and surgery. In the
seventeenth century, however, at least one discovery in
therapeutics was made that has been an inestimable boon to
humanity ever since. This was the introduction of cinchona bark
(from which quinine is obtained) in 1640. But this century was
productive of many medical SYSTEMS, and could boast of many great
names among the medical profession, and, on the whole, made
considerably more progress than the preceding century.

Of the founders of medical systems, one of the most widely known
is Jan Baptista van Helmont (1578-1644), an eccentric genius who
constructed a system of medicine of his own and for a time
exerted considerable influence. But in the end his system was
destined to pass out of existence, not very long after the death
of its author. Van Helmont was not only a physician, but was
master of all the other branches of learning of the time, taking
up the study of medicine and chemistry as an after-thought, but
devoting himself to them with the greatest enthusiasm once he had
begun his investigations. His attitude towards existing doctrines
was as revolutionary as that of Paracelsus, and he rejected the
teachings of Galen and all the ancient writers, although
retaining some of the views of Paracelsus. He modified the
archaeus of Paracelsus, and added many complications to it. He
believed the whole body to be controlled by an archaeus influus,
the soul by the archaei insiti, and these in turn controlled by
the central archeus. His system is too elaborate and complicated
for full explanation, but its chief service to medicine was in
introducing new chemical methods in the preparation of drugs. In
this way he was indirectly connected with the establishment of
the Iatrochemical school. It was he who first used the word
"gas"--a word coined by him, along with many others that soon
fell into disuse.

The principles of the Iatrochemical school were the use of
chemical medicines, and a theory of pathology different from the
prevailing "humoral" pathology. The founder of this school was
Sylvius (Franz de le Boe, 1614-1672), professor of medicine at
Leyden. He attempted to establish a permanent system of medicine
based on the newly discovered theory of the circulation and the
new chemistry, but his name is remembered by medical men because
of the fissure in the brain (fissure of Sylvius) that bears it.
He laid great stress on the cause of fevers and other diseases as
originating in the disturbances of the process of fermentation in
the stomach. The doctrines of Sylvius spread widely over the
continent, but were not generally accepted in England until
modified by Thomas Willis (1622-1675), whose name, like that of
Sylvius, is perpetuated by a structure in the brain named after
him, the circle of Willis. Willis's descriptions of certain
nervous diseases, and an account of diabetes, are the first
recorded, and added materially to scientific medicine. These
schools of medicine lasted until the end of the seventeenth
century, when they were finally overthrown by Sydenham.

The Iatrophysical school (also called iatromathematical,
iatromechanical, or physiatric) was founded on theories of
physiology, probably by Borelli, of Naples (1608-1679), although
Sanctorius; Sanctorius, a professor at Padua, was a precursor, if
not directly interested in establishing it. Sanctorius discovered
the fact that an "insensible perspiration" is being given off by
the body continually, and was amazed to find that loss of weight
in this way far exceeded the loss of weight by all other
excretions of the body combined. He made this discovery by means
of a peculiar weighing-machine to which a chair was attached, and
in which he spent most of his time. Very naturally he
overestimated the importance of this discovery, but it was,
nevertheless, of great value in pointing out the hygienic
importance of the care of the skin. He also introduced a
thermometer which he advocated as valuable in cases of fever, but
the instrument was probably not his own invention, but borrowed
from his friend Galileo.

Harvey's discovery of the circulation of the blood laid the
foundation of the Iatrophysical school by showing that this vital
process was comparable to a hydraulic system. In his On the
Motive of Animals, Borelli first attempted to account for the
phenomena of life and diseases on these principles. The
iatromechanics held that the great cause of disease is due to
different states of elasticity of the solids of the body
interfering with the movements of the fluids, which are
themselves subject to changes in density, one or both of these
conditions continuing to cause stagnation or congestion. The
school thus founded by Borelli was the outcome of the unbounded
enthusiasm, with its accompanying exaggeration of certain
phenomena with the corresponding belittling of others that
naturally follows such a revolutionary discovery as that of
Harvey. Having such a founder as the brilliant Italian Borelli,
it was given a sufficient impetus by his writings to carry it
some distance before it finally collapsed. Some of the
exaggerated mathematical calculations of Borelli himself are
worth noting. Each heart-beat, as he calculated it, overcomes a
resistance equal to one hundred and eighty thousand pounds;--the
modern physiologist estimates its force at from five to nine
ounces!


THOMAS SYDENHAM

But while the Continent was struggling with these illusive
"systems," and dabbling in mystic theories that were to scarcely
outlive the men who conceived

them, there appeared in England--the "land of common-sense," as a
German scientist has called it--"a cool, clear, and unprejudiced
spirit," who in the golden age of systems declined "to be like
the man who builds the chambers of the upper story of his house
before he had laid securely the foundation walls."[1] This man
was Thomas Sydenham (1624-1689), who, while the great Harvey was
serving the king as surgeon, was fighting as a captain in the
parliamentary army. Sydenham took for his guide the teachings of
Hippocrates, modified to suit the advances that had been made in
scientific knowledge since the days of the great Greek, and
established, as a standard, observation and experience. He cared
little for theory unless confirmed by practice, but took the
Hippocratic view that nature cured diseases, assisted by the
physician. He gave due credit, however, to the importance of the
part played by the assistant. As he saw it, medicine could be
advanced in three ways: (1) "By accurate descriptions or natural
histories of diseases; (2) by establishing a fixed principle or
method of treatment, founded upon experience; (3) by searching
for specific remedies, which he believes must exist in
considerable numbers, though he admits that the only one yet
discovered is Peruvian bark."[2] As it happened, another equally
specific remedy, mercury, when used in certain diseases, was
already known to him, but he evidently did not recognize it as
such.

The influence on future medicine of Sydenham's teachings was most
pronounced, due mostly to his teaching of careful observation. To
most physicians, however, he is now remembered chiefly for his
introduction of the use of laudanum, still considered one of the
most valuable remedies of modern pharmacopoeias. The German gives
the honor of introducing this preparation to Paracelsus, but the
English-speaking world will always believe that the credit should
be given to Sydenham.



IX. PHILOSOPHER-SCIENTISTS AND NEW INSTITUTIONS OF LEARNING

We saw that in the old Greek days there was no sharp line of
demarcation between the field of the philosopher and that of the
scientist. In the Hellenistic epoch, however, knowledge became
more specialized, and our recent chapters have shown us
scientific investigators whose efforts were far enough removed
from the intangibilities of the philosopher. It must not be
overlooked, however, that even in the present epoch there were
men whose intellectual efforts were primarily directed towards
the subtleties of philosophy, yet who had also a penchant for
strictly scientific imaginings, if not indeed for practical
scientific experiments. At least three of these men were of
sufficient importance in the history of the development of
science to demand more than passing notice. These three are the
Englishman Francis Bacon (1561-1626), the Frenchman Rene
Descartes (1596-1650); and the German Gottfried Leibnitz
(1646-1716). Bacon, as the earliest path-breaker, showed the way,
theoretically at least, in which the sciences should be studied;
Descartes, pursuing the methods pointed out by Bacon, carried the
same line of abstract reason into practice as well; while
Leibnitz, coming some years later, and having the advantage of
the wisdom of his two great predecessors, was naturally
influenced by both in his views of abstract scientific
principles.

Bacon's career as a statesman and his faults and misfortunes as a
man do not concern us here. Our interest in him begins with his
entrance into Trinity College, Cambridge, where he took up the
study of all the sciences taught there at that time. During the
three years he became more and more convinced that science was
not being studied in a profitable manner, until at last, at the
end of his college course, he made ready to renounce the old
Aristotelian methods of study and advance his theory of inductive
study. For although he was a great admirer of Aristotle's work,
he became convinced that his methods of approaching study were
entirely wrong.

"The opinion of Aristotle," he says, in his De Argumentum
Scientiarum, "seemeth to me a negligent opinion, that of those
things which exist by nature nothing can be changed by custom;
using for example, that if a stone be thrown ten thousand times
up it will not learn to ascend; and that by often seeing or
hearing we do not learn to see or hear better. For though this
principle be true in things wherein nature is peremptory (the
reason whereof we cannot now stand to discuss), yet it is
otherwise in things wherein nature admitteth a latitude. For he
might see that a straight glove will come more easily on with
use; and that a wand will by use bend otherwise than it grew; and
that by use of the voice we speak louder and stronger; and that
by use of enduring heat or cold we endure it the better, and the
like; which latter sort have a nearer resemblance unto that
subject of manners he handleth than those instances which he
allegeth."[1]

These were his opinions, formed while a young man in college,
repeated at intervals through his maturer years, and reiterated
and emphasized in his old age. Masses of facts were to be
obtained by observing nature at first hand, and from such
accumulations of facts deductions were to be made. In short,
reasoning was to be from the specific to the general, and not
vice versa.

It was by his teachings alone that Bacon thus contributed to the
foundation of modern science; and, while he was constantly
thinking and writing on scientific subjects, he contributed
little in the way of actual discoveries. "I only sound the
clarion," he said, "but I enter not the battle."

The case of Descartes, however, is different. He both sounded the
clarion and entered into the fight. He himself freely
acknowledges his debt to Bacon for his teachings of inductive
methods of study, but modern criticism places his work on the
same plane as that of the great Englishman. "If you lay hold of
any characteristic product of modern ways of thinking," says
Huxley, "either in the region of philosophy or in that of
science, you find the spirit of that thought, if not its form,
has been present in the mind of the great Frenchman."[2]

Descartes, the son of a noble family of France, was educated by
Jesuit teachers. Like Bacon, he very early conceived the idea
that the methods of teaching and studying science were wrong, but
be pondered the matter well into middle life before putting into
writing his ideas of philosophy and science. Then, in his
Discourse Touching the Method of Using One's Reason Rightly and
of Seeking Scientific Truth, he pointed out the way of seeking
after truth. His central idea in this was to emphasize the
importance of DOUBT, and avoidance of accepting as truth anything
that does not admit of absolute and unqualified proof. In
reaching these conclusions he had before him the striking
examples of scientific deductions by Galileo, and more recently
the discovery of the circulation of the blood by Harvey. This
last came as a revelation to scientists, reducing this seemingly
occult process, as it did, to the field of mechanical phenomena.
The same mechanical laws that governed the heavenly bodies, as
shown by Galileo, governed the action of the human heart, and,
for aught any one knew, every part of the body, and even the mind
itself.

Having once conceived this idea, Descartes began a series of
dissections and experiments upon the lower animals, to find, if
possible, further proof of this general law. To him the human
body was simply a machine, a complicated mechanism, whose
functions were controlled just as any other piece of machinery.
He compared the human body to complicated machinery run by
water-falls and complicated pipes. "The nerves of the machine
which I am describing," he says, "may very well be compared to
the pipes of these waterworks; its muscles and its tendons to the
other various engines and springs which seem to move them; its
animal spirits to the water which impels them, of which the heart
is the fountain; while the cavities of the brain are the central
office. Moreover, respiration and other such actions as are
natural and usual in the body, and which depend on the course of
the spirits, are like the movements of a clock, or a mill, which
may be kept up by the ordinary flow of water."[3]

In such passages as these Descartes anticipates the ideas of
physiology of the present time. He believed that the functions
are performed by the various organs of the bodies of animals and
men as a mechanism, to which in man was added the soul. This soul
he located in the pineal gland, a degenerate and presumably
functionless little organ in the brain. For years Descartes's
idea of the function of this gland was held by many
physiologists, and it was only the introduction of modern
high-power microscopy that reduced this also to a mere mechanism,
and showed that it is apparently the remains of a Cyclopean eye
once common to man's remote ancestors.

Descartes was the originator of a theory of the movements of the
universe by a mechanical process--the Cartesian theory of
vortices--which for several decades after its promulgation
reigned supreme in science. It is the ingenuity of this theory,
not the truth of its assertions, that still excites admiration,
for it has long since been supplanted. It was certainly the best
hitherto advanced--the best "that the observations of the age
admitted," according to D'Alembert.

According to this theory the infinite universe is full of matter,
there being no such thing as a vacuum. Matter, as Descartes
believed, is uniform in character throughout the entire universe,
and since motion cannot take place in any part of a space
completely filled, without simultaneous movement in all other
parts, there are constant more or less circular movements,
vortices, or whirlpools of particles, varying, of course, in size
and velocity. As a result of this circular movement the particles
of matter tend to become globular from contact with one another.
Two species of matter are thus formed, one larger and globular,
which continue their circular motion with a constant tendency to
fly from the centre of the axis of rotation, the other composed
of the clippings resulting from the grinding process. These
smaller "filings" from the main bodies, becoming smaller and
smaller, gradually lose their velocity and accumulate in the
centre of the vortex. This collection of the smaller matter in
the centre of the vortex constitutes the sun or star, while the
spherical particles propelled in straight lines from the centre
towards the circumference of the vortex produce the phenomenon of
light radiating from the central star. Thus this matter becomes
the atmosphere revolving around the accumulation at the centre.
But the small particles being constantly worn away from the
revolving spherical particles in the vortex, become entangled in
their passage, and when they reach the edge of the inner strata
of solar dust they settle upon it and form what we call
sun-spots. These are constantly dissolved and reformed, until
sometimes they form a crust round the central nucleus.

As the expansive force of the star diminishes in the course of
time, it is encroached upon by neighboring vortices. If the part
of the encroaching star be of a less velocity than the star which
it has swept up, it will presently lose its hold, and the smaller
star pass out of range, becoming a comet. But if the velocity of
the vortex into which the incrusted star settles be equivalent to
that of the surrounded vortex, it will hold it as a captive,
still revolving and "wrapt in its own firmament." Thus the
several planets of our solar system have been captured and held
by the sun-vortex, as have the moon and other satellites.

But although these new theories at first created great enthusiasm
among all classes of philosophers and scientists, they soon came
under the ban of the Church. While no actual harm came to
Descartes himself, his writings were condemned by the Catholic
and Protestant churches alike. The spirit of philosophical
inquiry he had engendered, however, lived on, and is largely
responsible for modern philosophy.

In many ways the life and works of Leibnitz remind us of Bacon
rather than Descartes. His life was spent in filling high
political positions, and his philosophical and scientific
writings were by-paths of his fertile mind. He was a theoretical
rather than a practical scientist, his contributions to science
being in the nature of philosophical reasonings rather than
practical demonstrations. Had he been able to withdraw from
public life and devote himself to science alone, as Descartes
did, he would undoubtedly have proved himself equally great as a
practical worker. But during the time of his greatest activity in
philosophical fields, between the years 1690 and 1716, he was all
the time performing extraordinary active duties in entirely
foreign fields. His work may be regarded, perhaps, as doing for
Germany in particular what Bacon's did for England and the rest
of the world in general.

Only a comparatively small part of his philosophical writings
concern us here. According to his theory of the ultimate elements
of the universe, the entire universe is composed of individual
centres, or monads. To these monads he ascribed numberless
qualities by which every phase of nature may be accounted. They
were supposed by him to be percipient, self-acting beings, not
under arbitrary control of the deity, and yet God himself was the
original monad from which all the rest are generated. With this
conception as a basis, Leibnitz deduced his doctrine of
pre-established harmony, whereby the numerous independent
substances composing the world are made to form one universe. He
believed that by virtue of an inward energy monads develop
themselves spontaneously, each being independent of every other.
In short, each monad is a kind of deity in itself--a microcosm
representing all the great features of the macrocosm.

It would be impossible clearly to estimate the precise value of
the stimulative influence of these philosophers upon the
scientific thought of their time. There was one way, however, in
which their influence was made very tangible--namely, in the
incentive they gave to the foundation of scientific societies.


SCIENTIFIC SOCIETIES

At the present time, when the elements of time and distance are
practically eliminated in the propagation of news, and when cheap
printing has minimized the difficulties of publishing scientific
discoveries, it is difficult to understand the isolated position
of the scientific investigation of the ages that preceded steam
and electricity. Shut off from the world and completely out of
touch with fellow-laborers perhaps only a few miles away, the
investigators were naturally seriously handicapped; and
inventions and discoveries were not made with the same rapidity
that they would undoubtedly have been had the same men been
receiving daily, weekly, or monthly communications from
fellow-laborers all over the world, as they do to-day. Neither
did they have the advantage of public or semi-public
laboratories, where they were brought into contact with other
men, from whom to gather fresh trains of thought and receive the
stimulus of their successes or failures. In the natural course of
events, however, neighbors who were interested in somewhat
similar pursuits, not of the character of the rivalry of trade or
commerce, would meet more or less frequently and discuss their
progress. The mutual advantages of such intercourse would be at
once appreciated; and it would be but a short step from the
casual meeting of two neighborly scientists to the establishment
of "societies," meeting at fixed times, and composed of members
living within reasonable travelling distance. There would,
perhaps, be the weekly or monthly meetings of men in a limited
area; and as the natural outgrowth of these little local
societies, with frequent meetings, would come the formation of
larger societies, meeting less often, where members travelled a
considerable distance to attend. And, finally, with increased
facilities for communication and travel, the great international
societies of to-day would be produced--the natural outcome of the
neighborly meetings of the primitive mediaeval investigators.

In Italy, at about the time of Galileo, several small societies
were formed. One of the most important of these was the Lyncean
Society, founded about the year 1611, Galileo himself being a
member. This society was succeeded by the Accademia del Cimento,
at Florence, in 1657, which for a time flourished, with such a
famous scientist as Torricelli as one of its members.

In England an impetus seems to have been given by Sir Francis
Bacon's writings in criticism and censure of the systern of
teaching in colleges. It is supposed that his suggestions as to
what should be the aims of a scientific society led eventually to
the establishment of the Royal Society. He pointed out how little
had really been accomplished by the existing institutions of
learning in advancing science, and asserted that little good
could ever come from them while their methods of teaching
remained unchanged. He contended that the system which made the
lectures and exercises of such a nature that no deviation from
the established routine could be thought of was pernicious. But
he showed that if any teacher had the temerity to turn from the
traditional paths, the daring pioneer was likely to find
insurmountable obstacles placed in the way of his advancement.
The studies were "imprisoned" within the limits of a certain set
of authors, and originality in thought or teaching was to be
neither contemplated nor tolerated.

The words of Bacon, given in strong and unsparing terms of
censure and condemnation, but nevertheless with perfect
justification, soon bore fruit. As early as the year 1645 a small
company of scientists had been in the habit of meeting at some
place in London to discuss philosophical and scientific subjects
for mental advancement. In 1648, owing to the political
disturbances of the time, some of the members of these meetings
removed to Oxford, among them Boyle, Wallis, and Wren, where the
meetings were continued, as were also the meetings of those left
in London. In 1662, however, when the political situation bad
become more settled, these two bodies of men were united under a
charter from Charles II., and Bacon's ideas were practically
expressed in that learned body, the Royal Society of London. And
it matters little that in some respects Bacon's views were not
followed in the practical workings of the society, or that the
division of labor in the early stages was somewhat different than
at present. The aim of the society has always been one for the
advancement of learning; and if Bacon himself could look over its
records, he would surely have little fault to find with the aid
it has given in carrying out his ideas for the promulgation of
useful knowledge.

Ten years after the charter was granted to the Royal Society of
London, Lord Bacon's words took practical effect in Germany, with
the result that the Academia Naturae Curiosorum was founded,
under the leadership of Professor J. C. Sturm. The early labors
of this society were devoted to a repetition of the most notable
experiments of the time, and the work of the embryo society was
published in two volumes, in 1672 and 1685 respectively, which
were practically text-books of the physics of the period. It was
not until 1700 that Frederick I. founded the Royal Academy of
Sciences at Berlin, after the elaborate plan of Leibnitz, who was
himself the first president.

Perhaps the nearest realization of Bacon's ideal, however, is in
the Royal Academy of Sciences at Paris, which was founded in 1666
under the administration of Colbert, during the reign of Louis
XIV. This institution not only recognized independent members,
but had besides twenty pensionnaires who received salaries from
the government. In this way a select body of scientists were
enabled to pursue their investigations without being obliged to
"give thought to the morrow" for their sustenance. In return they
were to furnish the meetings with scientific memoirs, and once a
year give an account of the work they were engaged upon. Thus a
certain number of the brightest minds were encouraged to devote
their entire time to scientific research, "delivered alike from
the temptations of wealth or the embarrassments of poverty." That
such a plan works well is amply attested by the results emanating
from the French academy. Pensionnaires in various branches of
science, however, either paid by the state or by learned
societies, are no longer confined to France.

Among the other early scientific societies was the Imperial
Academy of Sciences at St. Petersburg, projected by Peter the
Great, and established by his widow, Catharine I., in 1725; and
also the Royal Swedish Academy, incorporated in 1781, and
counting among its early members such men as the celebrated
Linnaeus. But after the first impulse had resulted in a few
learned societies, their manifest advantage was so evident that
additional numbers increased rapidly, until at present almost
every branch of every science is represented by more or less
important bodies; and these are, individually and collectively,
adding to knowledge and stimulating interest in the many fields
of science, thus vindicating Lord Bacon's asseverations that
knowledge could be satisfactorily promulgated in this manner.



X. THE SUCCESSORS OF GALILEO IN PHYSICAL SCIENCE

We have now to witness the diversified efforts of a company of
men who, working for the most part independently, greatly added
to the data of the physical sciences--such men as Boyle, Huygens,
Von Gericke, and Hooke. It will be found that the studies of
these men covered the whole field of physical sciences as then
understood--the field of so-called natural philosophy. We shall
best treat these successors of Galileo and precursors of Newton
somewhat biographically, pointing out the correspondences and
differences between their various accomplishments as we proceed.
It will be noted in due course that the work of some of them was
anticipatory of great achievements of a later century.


ROBERT BOYLE (1627-1691)

Some of Robert Boyle's views as to the possible structure of
atmospheric air will be considered a little farther on in this
chapter, but for the moment we will take up the consideration of
some of his experiments upon that as well as other gases. Boyle
was always much interested in alchemy, and carried on extensive
experiments in attempting to accomplish the transmutation of
metals; but he did not confine himself to these experiments,
devoting himself to researches in all the fields of natural
philosophy. He was associated at Oxford with a company of
scientists, including Wallis and Wren, who held meetings and made
experiments together, these gatherings being the beginning, as
mentioned a moment ago, of what finally became the Royal Society.
It was during this residence at Oxford that many of his valuable
researches upon air were made, and during this time be invented
his air-pump, now exhibited in the Royal Society rooms at
Burlington House.[1]

His experiments to prove the atmospheric pressure are most
interesting and conclusive. "Having three small, round glass
bubbles, blown at the flame of a lamp, about the size of
hazel-nuts," he says, "each of them with a short, slender stem,
by means whereof they were so exactly poised in water that a very
small change of weight would make them either emerge or sink; at
a time when the atmosphere was of convenient weight, I put them
into a wide-mouthed glass of common water, and leaving them in a
quiet place, where they were frequently in my eye, I observed
that sometimes they would be at the top of the water, and remain
there for several days, or perhaps weeks, together, and sometimes
fall to the bottom, and after having continued there for some
time rise again. And sometimes they would rise or fall as the air
was hot or cold."[2]

It was in the course of these experiments that the observations
made by Boyle led to the invention of his "statical barometer,"
the mercurial barometer having been invented, as we have seen, by
Torricelli, in 1643. In describing this invention he says:
"Making choice of a large, thin, and light glass bubble, blown at
the flame of a lamp, I counterpoised it with a metallic weight,
in a pair of scales that were suspended in a frame, that would
turn with the thirtieth part of a grain. Both the frame and the
balance were then placed near a good barometer, whence I might
learn the present weight of the atmosphere; when, though the
scales were unable to show all the variations that appeared in
the mercurial barometer, yet they gave notice of those that
altered the height of the mercury half a quarter of an inch."[3]
A fairly sensitive barometer, after all. This statical barometer
suggested several useful applications to the fertile imagination
of its inventor, among others the measuring of mountain-peaks, as
with the mercurial barometer, the rarefication of the air at the
top giving a definite ratio to the more condensed air in the
valley.

Another of his experiments was made to discover the atmospheric
pressure to the square inch. After considerable difficulty he
determined that the relative weight of a cubic inch of water and
mercury was about one to fourteen, and computing from other known
weights he determined that "when a column of quicksilver thirty
inches high is sustained in the barometer, as it frequently
happens, a column of air that presses upon an inch square near
the surface of the earth must weigh about fifteen avoirdupois
pounds."[4] As the pressure of air at the sea-level is now
estimated at 14.7304 pounds to the square inch, it will be seen
that Boyle's calculation was not far wrong.

From his numerous experiments upon the air, Boyle was led to
believe that there were many "latent qualities" due to substances
contained in it that science had as yet been unable to fathom,
believing that there is "not a more heterogeneous body in the
world." He believed that contagious diseases were carried by the
air, and suggested that eruptions of the earth, such as those
made by earthquakes, might send up "venomous exhalations" that
produced diseases. He suggested also that the air might play an
important part in some processes of calcination, which, as we
shall see, was proved to be true by Lavoisier late in the
eighteenth century. Boyle's notions of the exact chemical action
in these phenomena were of course vague and indefinite, but he
had observed that some part was played by the air, and he was
right in supposing that the air "may have a great share in
varying the salts obtainable from calcined vitriol."[5]

Although he was himself such a painstaking observer of facts, he
had the fault of his age of placing too much faith in hear-say
evidence of untrained observers. Thus, from the numerous stories
he heard concerning the growth of metals in previously exhausted
mines, he believed that the air was responsible for producing
this growth--in which he undoubtedly believed. The story of a
tin-miner that, in his own time, after a lapse of only
twenty-five years, a heap, of earth previously exhausted of its
ore became again even more richly impregnated than before by
lying exposed to the air, seems to have been believed by the
philosopher.

As Boyle was an alchemist, and undoubtedly believed in the
alchemic theory that metals have "spirits" and various other
qualities that do not exist, it is not surprising that he was
credulous in the matter of beliefs concerning peculiar phenomena
exhibited by them. Furthermore, he undoubtedly fell into the
error common to "specialists," or persons working for long
periods of time on one subject--the error of over-enthusiasm in
his subject. He had discovered so many remarkable qualities in
the air that it is not surprising to find that he attributed to
it many more that he could not demonstrate.

Boyle's work upon colors, although probably of less importance
than his experiments and deductions upon air, show that he was in
the van as far as the science of his day was concerned. As he
points out, the schools of his time generally taught that "color
is a penetrating quality, reaching to the innermost part of the
substance," and, as an example of this, sealing-wax was cited,
which could be broken into minute bits, each particle retaining
the same color as its fellows or the original mass. To refute
this theory, and to show instances to the contrary, Boyle, among
other things, shows that various colors--blue, red, yellow--may
be produced upon tempered steel, and yet the metal within "a
hair's-breadth of its surface" have none of these colors.
Therefore, he was led to believe that color, in opaque bodies at
least, is superficial.

"But before we descend to a more particular consideration of our
subject," he says, " 'tis proper to observe that colors may be
regarded either as a quality residing in bodies to modify light
after a particular manner, or else as light itself so modified as
to strike upon the organs of sight, and cause the sensation we
call color; and that this latter is the more proper acceptation
of the word color will appear hereafter. And indeed it is the
light itself, which after a certain manner, either mixed with
shades or other-wise, strikes our eyes and immediately produces
that motion in the organ which gives us the color of an
object."[6]

In examining smooth and rough surfaces to determine the cause of
their color, he made use of the microscope, and pointed out the
very obvious example of the difference in color of a rough and a
polished piece of the same block of stone. He used some striking
illustrations of the effect of light and the position of the eye
upon colors. "Thus the color of plush or velvet will appear
various if you stroke part of it one way and part another, the
posture of the particular threads in regard to the light, or the
eye, being thereby varied. And 'tis observable that in a field of
ripe corn, blown upon by the wind, there will appear waves of a
color different from that of the rest of the corn, because the
wind, by depressing some of the ears more than others, causes one
to reflect more light from the lateral and strawy parts than
another."[7] His work upon color, however, as upon light, was
entirely overshadowed by the work of his great fellow-countryman
Newton.

Boyle's work on electricity was a continuation of Gilbert's, to
which he added several new facts. He added several substances to
Gilbert's list of "electrics," experimented on smooth and rough
surfaces in exciting of electricity, and made the important
discovery that amber retained its attractive virtue after the
friction that excited it bad ceased. "For the attrition having
caused an intestine motion in its parts," he says, "the heat
thereby excited ought not to cease as soon as ever the rubbing is
over, but to continue capable of emitting effluvia for some time
afterwards, longer or shorter according to the goodness of the
electric and the degree of the commotion made; all which, joined
together, may sometimes make the effect considerable; and by this
means, on a warm day, I, with a certain body not bigger than a
pea, but very vigorously attractive, moved a steel needle, freely
poised, about three minutes after I had left off rubbing it."[8]


MARIOTTE AND VON GUERICKE

Working contemporaneously with Boyle, and a man whose name is
usually associated with his as the propounder of the law of
density of gases, was Edme Mariotte (died 1684), a native of
Burgundy. Mariotte demonstrated that but for the resistance of
the atmosphere, all bodies, whether light or heavy, dense or
thin, would fall with equal rapidity, and he proved this by the
well-known "guinea-and-feather" experiment. Having exhausted the
air from a long glass tube in which a guinea piece and a feather
had been placed, he showed that in the vacuum thus formed they
fell with equal rapidity as often as the tube was reversed. From
his various experiments as to the pressure of the atmosphere he
deduced the law that the density and elasticity of the atmosphere
are precisely proportional to the compressing force (the law of
Boyle and Mariotte). He also ascertained that air existed in a
state of mechanical mixture with liquids, "existing between their
particles in a state of condensation." He made many other
experiments, especially on the collision of bodies, but his most
important work was upon the atmosphere.

But meanwhile another contemporary of Boyle and Mariotte was
interesting himself in the study of the atmosphere, and had made
a wonderful invention and a most striking demonstration. This was
Otto von Guericke (1602-1686), Burgomaster of Magdeburg, and
councillor to his "most serene and potent Highness" the elector
of that place. When not engrossed with the duties of public
office, he devoted his time to the study of the sciences,
particularly pneumatics and electricity, both then in their
infancy. The discoveries of Galileo, Pascal, and Torricelli
incited him to solve the problem of the creation of a vacuum--a
desideratum since before the days of Aristotle. His first
experiments were with a wooden pump and a barrel of water, but he
soon found that with such porous material as wood a vacuum could
not be created or maintained. He therefore made use of a globe of
copper, with pump and stop-cock; and with this he was able to
pump out air almost as easily as water. Thus, in 1650, the
air-pump was invented. Continuing his experiments upon vacuums
and atmospheric pressure with his newly discovered pump, he made
some startling discoveries as to the enormous pressure exerted by
the air.

It was not his intention, however, to demonstrate his newly
acquired knowledge by words or theories alone, nor by mere
laboratory experiments; but he chose instead an open field, to
which were invited Emperor Ferdinand III., and all the princes of
the Diet at Ratisbon. When they were assembled he produced two
hollow brass hemispheres about two feet in diameter, and placing
their exactly fitting surfaces together, proceeded to pump out
the air from their hollow interior, thus causing them to stick
together firmly in a most remarkable way, apparently without
anything holding them. This of itself was strange enough; but now
the worthy burgomaster produced teams of horses, and harnessing
them to either side of the hemispheres, attempted to pull the
adhering brasses apart. Five, ten, fifteen teams--thirty horses,
in all--were attached; but pull and tug as they would they could
not separate the firmly clasped hemispheres. The enormous
pressure of the atmosphere had been most strikingly demonstrated.

But it is one thing to demonstrate, another to convince; and many
of the good people of Magdeburg shook their heads over this
"devil's contrivance," and predicted that Heaven would punish the
Herr Burgomaster, as indeed it had once by striking his house
with lightning and injuring some of his infernal contrivances.
They predicted his future punishment, but they did not molest
him, for to his fellow-citizens, who talked and laughed, drank
and smoked with him, and knew him for the honest citizen that he
was, he did not seem bewitched at all. And so he lived and worked
and added other facts to science, and his brass hemispheres were
not destroyed by fanatical Inquisitors, but are still preserved
in the royal library at Berlin.

In his experiments with his air-pump he discovered many things
regarding the action of gases, among others, that animals cannot
live in a vacuum. He invented the anemoscope and the air-balance,
and being thus enabled to weight the air and note the changes
that preceded storms and calms, he was able still further to
dumfound his wondering fellow-Magde-burgers by more or less
accurate predictions about the weather.

Von Guericke did not accept Gilbert's theory that the earth was a
great magnet, but in his experiments along lines similar to those
pursued by Gilbert, he not only invented the first electrical
machine, but discovered electrical attraction and repulsion. The
electrical machine which he invented consisted of a sphere of
sulphur mounted on an iron axis to imitate the rotation of the
earth, and which, when rubbed, manifested electrical reactions.
When this globe was revolved and stroked with the dry hand it was
found that it attached to it "all sorts of little fragments, like
leaves of gold, silver, paper, etc." "Thus this globe," he says,
"when brought rather near drops of water causes them to swell and
puff up. It likewise attracts air, smoke, etc."[9] Before the
time of Guericke's demonstrations, Cabaeus had noted that chaff
leaped back from an "electric," but he did not interpret the
phenomenon as electrical repulsion. Von Guericke, however,
recognized it as such, and refers to it as what he calls
"expulsive virtue." "Even expulsive virtue is seen in this
globe," he says, "for it not only attracts, but also REPELS again
from itself little bodies of this sort, nor does it receive them
until they have touched something else." It will be observed from
this that he was very close to discovering the discharge of the
electrification of attracted bodies by contact with some other
object, after which they are reattracted by the electric.

He performed a most interesting experiment with his sulphur globe
and a feather, and in doing so came near anticipating Benjamin
Franklin in his discovery of the effects of pointed conductors in
drawing off the discharge. Having revolved and stroked his globe
until it repelled a bit of down, he removed the globe from its
rack and advancing it towards the now repellent down, drove it
before him about the room. In this chase he observed that the
down preferred to alight against "the points of any object
whatsoever." He noticed that should the down chance to be driven
within a few inches of a lighted candle, its attitude towards the
globe suddenly changed, and instead of running away from it, it
now "flew to it for protection" --the charge on the down having
been dissipated by the hot air. He also noted that if one face of
a feather had been first attracted and then repelled by the
sulphur ball, that the surface so affected was always turned
towards the globe; so that if the positions of the two were
reversed, the sides of the feather reversed also.

Still another important discovery, that of electrical conduction,
was made by Von Guericke. Until his discovery no one had observed
the transference of electricity from one body to another,
although Gilbert had some time before noted that a rod rendered
magnetic at one end became so at the other. Von Guericke's
experiments were made upon a linen thread with his sulphur globe,
which, he says, "having been previously excited by rubbing, can
exercise likewise its virtue through a linen thread an ell or
more long, and there attract something." But this discovery, and
his equally important one that the sulphur ball becomes luminous
when rubbed, were practically forgotten until again brought to
notice by the discoveries of Francis Hauksbee and Stephen Gray
early in the eighteenth century. From this we may gather that Von
Guericke himself did not realize the import of his discoveries,
for otherwise he would certainly have carried his investigations
still further. But as it was he turned his attention to other
fields of research.


ROBERT HOOKE

A slender, crooked, shrivelled-limbed, cantankerous little man,
with dishevelled hair and haggard countenance, bad-tempered and
irritable, penurious and dishonest, at least in his claims for
priority in discoveries--this is the picture usually drawn, alike
by friends and enemies, of Robert Hooke (1635-1703), a man with
an almost unparalleled genius for scientific discoveries in
almost all branches of science. History gives few examples so
striking of a man whose really great achievements in science
would alone have made his name immortal, and yet who had the
pusillanimous spirit of a charlatan--an almost insane mania, as
it seems--for claiming the credit of discoveries made by others.
This attitude of mind can hardly be explained except as a mania:
it is certainly more charitable so to regard it. For his own
discoveries and inventions were so numerous that a few more or
less would hardly have added to his fame, as his reputation as a
philosopher was well established. Admiration for his ability and
his philosophical knowledge must always be marred by the
recollection of his arrogant claims to the discoveries of other
philosophers.

It seems pretty definitely determined that Hooke should be
credited with the invention of the balance-spring for regulating
watches; but for a long time a heated controversy was waged
between Hooke and Huygens as to who was the real inventor. It
appears that Hooke conceived the idea of the balance-spring,
while to Huygens belongs the credit of having adapted the COILED
spring in a working model. He thus made practical Hooke's
conception, which is without value except as applied by the
coiled spring; but, nevertheless, the inventor, as well as the
perfector, should receive credit. In this controversy, unlike
many others, the blame cannot be laid at Hooke's door.

Hooke was the first curator of the Royal Society, and when
anything was to be investigated, usually invented the mechanical
devices for doing so. Astronomical apparatus, instruments for
measuring specific weights, clocks and chronometers, methods of
measuring the velocity of falling bodies, freezing and boiling
points, strength of gunpowder, magnetic instruments--in short,
all kinds of ingenious mechanical devices in all branches of
science and mechanics. It was he who made the famous air-pump of
Robert Boyle, based on Boyle's plans. Incidentally, Hooke claimed
to be the inventor of the first air-pump himself, although this
claim is now entirely discredited.

Within a period of two years he devised no less than thirty
different methods of flying, all of which, of course, came to
nothing, but go to show the fertile imagination of the man, and
his tireless energy. He experimented with electricity and made
some novel suggestions upon the difference between the electric
spark and the glow, although on the whole his contributions in
this field are unimportant. He also first pointed out that the
motions of the heavenly bodies must be looked upon as a
mechanical problem, and was almost within grasping distance of
the exact theory of gravitation, himself originating the idea of
making use of the pendulum in measuring gravity. Likewise, he
first proposed the wave theory of light; although it was Huygens
who established it on its present foundation.

Hooke published, among other things, a book of plates and
descriptions of his Microscopical Observations, which gives an
idea of the advance that had already been made in microscopy in
his time. Two of these plates are given here, which, even in this
age of microscopy, are both interesting and instructive. These
plates are made from prints of Hooke's original copper plates,
and show that excellent lenses were made even at that time. They
illustrate, also, how much might have been accomplished in the
field of medicine if more attention had been given to microscopy
by physicians. Even a century later, had physicians made better
use of their microscopes, they could hardly have overlooked such
an easily found parasite as the itch mite, which is quite as
easily detected as the cheese mite, pictured in Hooke's book.

In justice to Hooke, and in extenuation of his otherwise
inexcusable peculiarities of mind, it should be remembered that
for many years he suffered from a painful and wasting disease.
This may have affected his mental equilibrium, without
appreciably affecting his ingenuity. In his own time this
condition would hardly have been considered a disease; but
to-day, with our advanced ideas as to mental diseases, we should
be more inclined to ascribe his unfortunate attitude of mind to a
pathological condition, rather than to any manifestation of
normal mentality. From this point of view his mental deformity
seems not unlike that of Cavendish's, later, except that in the
case of Cavendish it manifested itself as an abnormal
sensitiveness instead of an abnormal irritability.


CHRISTIAN HUYGENS

If for nothing else, the world is indebted to the man who
invented the pendulum clock, Christian Huygens (1629-1695), of
the Hague, inventor, mathematician, mechanician, astronomer, and
physicist. Huygens was the descendant of a noble and
distinguished family, his father, Sir Constantine Huygens, being
a well-known poet and diplomatist. Early in life young Huygens
began his career in the legal profession, completing his
education in the juridical school at Breda; but his taste for
mathematics soon led him to neglect his legal studies, and his
aptitude for scientific researches was so marked that Descartes
predicted great things of him even while he was a mere tyro in
the field of scientific investigation.

One of his first endeavors in science was to attempt an
improvement of the telescope. Reflecting upon the process of
making lenses then in vogue, young Huygens and his brother
Constantine attempted a new method of grinding and polishing,
whereby they overcame a great deal of the spherical and chromatic
aberration. With this new telescope a much clearer field of
vision was obtained, so much so that Huygens was able to detect,
among other things, a hitherto unknown satellite of Saturn. It
was these astronomical researches that led him to apply the
pendulum to regulate the movements of clocks. The need for some
more exact method of measuring time in his observations of the
stars was keenly felt by the young astronomer, and after several
experiments along different lines, Huygens hit upon the use of a
swinging weight; and in 1656 made his invention of the pendulum
clock. The year following, his clock was presented to the
states-general. Accuracy as to time is absolutely essential in
astronomy, but until the invention of Huygens's clock there was
no precise, nor even approximately precise, means of measuring
short intervals.

Huygens was one of the first to adapt the micrometer to the
telescope--a mechanical device on which all the nice
determination of minute distances depends. He also took up the
controversy against Hooke as to the superiority of telescopic
over plain sights to quadrants, Hooke contending in favor of the
plain. In this controversy, the subject of which attracted wide
attention, Huygens was completely victorious; and Hooke, being
unable to refute Huygens's arguments, exhibited such irritability
that he increased his already general unpopularity. All of the
arguments for and against the telescope sight are too numerous to
be given here. In contending in its favor Huygens pointed out
that the unaided eye is unable to appreciate an angular space in
the sky less than about thirty seconds. Even in the best quadrant
with a plain sight, therefore, the altitude must be uncertain by
that quantity. If in place of the plain sight a telescope is
substituted, even if it magnify only thirty times, it will enable
the observer to fix the position to one second, with
progressively increased accuracy as the magnifying power of the
telescope is increased. This was only one of the many telling
arguments advanced by Huygens.

In the field of optics, also, Huygens has added considerably to
science, and his work, Dioptrics, is said to have been a favorite
book with Newton. During the later part of his life, however,
Huygens again devoted himself to inventing and constructing
telescopes, grinding the lenses, and devising, if not actually
making, the frame for holding them. These telescopes were of
enormous lengths, three of his object-glasses, now in possession
of the Royal Society, being of 123, 180, and 210 feet focal
length respectively. Such instruments, if constructed in the
ordinary form of the long tube, were very unmanageable, and to
obviate this Huygens adopted the plan of dispensing with the tube
altogether, mounting his lenses on long poles manipulated by
machinery. Even these were unwieldy enough, but the difficulties
of manipulation were fully compensated by the results obtained.

It had been discovered, among other things, that in oblique
refraction light is separated into colors. Therefore, any small
portion of the convex lens of the telescope, being a prism, the
rays proceed to the focus, separated into prismatic colors, which
make the image thus formed edged with a fringe of color and
indistinct. But, fortunately for the early telescope makers, the
degree of this aberration is independent of the focal length of
the lens; so that, by increasing this focal length and using the
appropriate eye-piece, the image can be greatly magnified, while
the fringe of colors remains about the same as when a less
powerful lens is used. Hence the advantage of Huygens's long
telescope. He did not confine his efforts to simply lengthening
the focal length of his telescopes, however, but also added to
their efficiency by inventing an almost perfect achromatic
eye-piece.

In 1663 he was elected a fellow of the Royal Society of London,
and in 1669 he gave to that body a concise statement of the laws
governing the collision of elastic bodies. Although the same
views had been given by Wallis and Wren a few weeks earlier,
there is no doubt that Huygens's views were reached
independently; and it is probable that he had arrived at his
conclusions several years before. In the Philosophical
Transactions for 1669 it is recorded that the society, being
interested in the laws of the principles of motion, a request was
made that M. Huygens, Dr. Wallis, and Sir Christopher Wren submit
their views on the subject. Wallis submitted his paper first,
November 15, 1668. A month later, December 17th, Wren imparted to
the society his laws as to the nature of the collision of bodies.
And a few days later, January 5, 1669, Huygens sent in his "Rules
Concerning the Motion of Bodies after Mutual Impulse." Although
Huygens's report was received last, he was anticipated by such a
brief space of time, and his views are so clearly stated--on the
whole rather more so than those of the other two--that we give
them in part here:


"1. If a hard body should strike against a body equally hard at
rest, after contact the former will rest and the latter acquire a
velocity equal to that of the moving body.

"2. But if that other equal body be likewise in motion, and
moving in the same direction, after contact they will move with
reciprocal velocities.

"3. A body, however great, is moved by a body however small
impelled with any velocity whatsoever.

"5. The quantity of motion of two bodies may be either increased
or diminished by their shock; but the same quantity towards the
same part remains, after subtracting the quantity of the contrary
motion.

"6. The sum of the products arising from multiplying the mass of
any hard body into the squares of its velocity is the same both
before and after the stroke.

"7. A hard body at rest will receive a greater quantity of motion
from another hard body, either greater or less than itself, by
the interposition of any third body of a mean quantity, than if
it was immediately struck by the body itself; and if the
interposing body be a mean proportional between the other two,
its action upon the quiescent body will be the greatest of
all."[10]


This was only one of several interesting and important
communications sent to the Royal Society during his lifetime. One
of these was a report on what he calls "Pneumatical Experiments."
"Upon including in a vacuum an insect resembling a beetle, but
somewhat larger," he says, "when it seemed to be dead, the air
was readmitted, and soon after it revived; putting it again in
the vacuum, and leaving it for an hour, after which the air was
readmitted, it was observed that the insect required a longer
time to recover; including it the third time for two days, after
which the air was admitted, it was ten hours before it began to
stir; but, putting it in a fourth time, for eight days, it never
afterwards recovered.... Several birds, rats, mice, rabbits, and
cats were killed in a vacuum, but if the air was admitted before
the engine was quite exhausted some of them would recover; yet
none revived that had been in a perfect vacuum.... Upon putting
the weight of eighteen grains of powder with a gauge into a
receiver that held several pounds of water, and firing the
powder, it raised the mercury an inch and a half; from which it
appears that there is one-fifth of air in gunpowder, upon the
supposition that air is about one thousand times lighter than
water; for in this experiment the mercury rose to the eighteenth
part of the height at which the air commonly sustains it, and
consequently the weight of eighteen grains of powder yielded air
enough to fill the eighteenth part of a receiver that contained
seven pounds of water; now this eighteenth part contains
forty-nine drachms of water; wherefore the air, that takes up an
equal space, being a thousand times lighter, weighs
one-thousandth part of forty-nine drachms, which is more than
three grains and a half; it follows, therefore, that the weight
of eighteen grains of powder contains more than three and a half
of air, which is about one-fifth of eighteen grains...."

From 1665 to 1681, accepting the tempting offer made him through
Colbert, by Louis XIV., Huygens pursued his studies at the
Bibliotheque du Roi as a resident of France. Here he published
his Horologium Oscillatorium, dedicated to the king, containing,
among other things, his solution of the problem of the "centre of
oscillation." This in itself was an important step in the history
of mechanics. Assuming as true that the centre of gravity of any
number of interdependent bodies cannot rise higher than the point
from which it falls, he reached correct conclusions as to the
general principle of the conservation of vis viva, although he
did not actually prove his conclusions. This was the first
attempt to deal with the dynamics of a system. In this work,
also, was the true determination of the relation between the
length of a pendulum and the time of its oscillation.

In 1681 he returned to Holland, influenced, it is believed, by
the attitude that was being taken in France against his religion.
Here he continued his investigations, built his immense
telescopes, and, among other things, discovered "polarization,"
which is recorded in Traite de la Lumiere, published at Leyden in
1690. Five years later he died, bequeathing his manuscripts to
the University of Leyden. It is interesting to note that he never
accepted Newton's theory of gravitation as a universal property
of matter.



XI. NEWTON AND THE COMPOSITION OF LIGHT

Galileo, that giant in physical science of the early seventeenth
century, died in 1642. On Christmas day of the same year there
was born in England another intellectual giant who was destined
to carry forward the work of Copernicus, Kepler, and Galileo to a
marvellous consummation through the discovery of the great
unifying law in accordance with which the planetary motions are
performed. We refer, of course, to the greatest of English
physical scientists, Isaac Newton, the Shakespeare of the
scientific world. Born thus before the middle of the seventeenth
century, Newton lived beyond the first quarter of the eighteenth
(1727). For the last forty years of that period his was the
dominating scientific personality of the world. With full
propriety that time has been spoken of as the "Age of Newton."

Yet the man who was to achieve such distinction gave no early
premonition of future greatness. He was a sickly child from
birth, and a boy of little seeming promise. He was an indifferent
student, yet, on the other hand, he cared little for the common
amusements of boyhood. He early exhibited, however, a taste for
mechanical contrivances, and spent much time in devising
windmills, water-clocks, sun-dials, and kites. While other boys
were interested only in having kites that would fly, Newton--at
least so the stories of a later time would have us
understand--cared more for the investigation of the seeming
principles involved, or for testing the best methods of attaching
the strings, or the best materials to be used in construction.

Meanwhile the future philosopher was acquiring a taste for
reading and study, delving into old volumes whenever he found an
opportunity. These habits convinced his relatives that it was
useless to attempt to make a farmer of the youth, as had been
their intention. He was therefore sent back to school, and in the
summer of 1661 he matriculated at Trinity College, Cambridge.
Even at college Newton seems to have shown no unusual mental
capacity, and in 1664, when examined for a scholarship by Dr.
Barrow, that gentleman is said to have formed a poor opinion of
the applicant. It is said that the knowledge of the estimate
placed upon his abilities by his instructor piqued Newton, and
led him to take up in earnest the mathematical studies in which
he afterwards attained such distinction. The study of Euclid and
Descartes's "Geometry" roused in him a latent interest in
mathematics, and from that time forward his investigations were
carried on with enthusiasm. In 1667 he was elected Fellow of
Trinity College, taking the degree of M.A. the following spring.

It will thus appear that Newton's boyhood and early manhood were
passed during that troublous time in British political annals
which saw the overthrow of Charles I., the autocracy of Cromwell,
and the eventual restoration of the Stuarts. His maturer years
witnessed the overthrow of the last Stuart and the reign of the
Dutchman, William of Orange. In his old age he saw the first of
the Hanoverians mount the throne of England. Within a decade of
his death such scientific path-finders as Cavendish, Black, and
Priestley were born--men who lived on to the close of the
eighteenth century. In a full sense, then, the age of Newton
bridges the gap from that early time of scientific awakening
under Kepler and Galileo to the time which we of the twentieth
century think of as essentially modern.


THE COMPOSITION OF WHITE LIGHT

In December, 1672, Newton was elected a Fellow of the Royal
Society, and at this meeting a paper describing his invention of
the refracting telescope was read. A few days later he wrote to
the secretary, making some inquiries as to the weekly meetings of
the society, and intimating that he had an account of an
interesting discovery that he wished to lay before the society.
When this communication was made public, it proved to be an
explanation of the discovery of the composition of white light.
We have seen that the question as to the nature of color had
commanded the attention of such investigators as Huygens, but
that no very satisfactory solution of the question had been
attained. Newton proved by demonstrative experiments that white
light is composed of the blending of the rays of diverse colors,
and that the color that we ascribe to any object is merely due to
the fact that the object in question reflects rays of that color,
absorbing the rest. That white light is really made up of many
colors blended would seem incredible had not the experiments by
which this composition is demonstrated become familiar to every
one. The experiments were absolutely novel when Newton brought
them forward, and his demonstration of the composition of light
was one of the most striking expositions ever brought to the
attention of the Royal Society. It is hardly necessary to add
that, notwithstanding the conclusive character of Newton's work,
his explanations did not for a long time meet with general
acceptance.

Newton was led to his discovery by some experiments made with an
ordinary glass prism applied to a hole in the shutter of a
darkened room, the refracted rays of the sunlight being received
upon the opposite wall and forming there the familiar spectrum.
"It was a very pleasing diversion," he wrote, "to view the vivid
and intense colors produced thereby; and after a time, applying
myself to consider them very circumspectly, I became surprised to
see them in varying form, which, according to the received laws
of refraction, I expected should have been circular. They were
terminated at the sides with straight lines, but at the ends the
decay of light was so gradual that it was difficult to determine
justly what was their figure, yet they seemed semicircular.

"Comparing the length of this colored spectrum with its breadth,
I found it almost five times greater; a disproportion so
extravagant that it excited me to a more than ordinary curiosity
of examining from whence it might proceed. I could scarce think
that the various thicknesses of the glass, or the termination
with shadow or darkness, could have any influence on light to
produce such an effect; yet I thought it not amiss, first, to
examine those circumstances, and so tried what would happen by
transmitting light through parts of the glass of divers
thickness, or through holes in the window of divers bigness, or
by setting the prism without so that the light might pass through
it and be refracted before it was transmitted through the hole;
but I found none of those circumstances material. The fashion of
the colors was in all these cases the same.

"Then I suspected whether by any unevenness of the glass or other
contingent irregularity these colors might be thus dilated. And
to try this I took another prism like the former, and so placed
it that the light, passing through them both, might be refracted
contrary ways, and so by the latter returned into that course
from which the former diverted it. For, by this means, I thought,
the regular effects of the first prism would be destroyed by the
second prism, but the irregular ones more augmented by the
multiplicity of refractions. The event was that the light, which
by the first prism was diffused into an oblong form, was by the
second reduced into an orbicular one with as much regularity as
when it did not all pass through them. So that, whatever was the
cause of that length, 'twas not any contingent irregularity.

"I then proceeded to examine more critically what might be
effected by the difference of the incidence of rays coming from
divers parts of the sun; and to that end measured the several
lines and angles belonging to the image. Its distance from the
hole or prism was 22 feet; its utmost length 13 1/4 inches; its
breadth 2 5/8; the diameter of the hole 1/4 of an inch; the angle
which the rays, tending towards the middle of the image, made
with those lines, in which they would have proceeded without
refraction, was 44 degrees 56'; and the vertical angle of the
prism, 63 degrees 12'. Also the refractions on both sides of the
prism--that is, of the incident and emergent rays--were, as near
as I could make them, equal, and consequently about 54 degrees
4'; and the rays fell perpendicularly upon the wall. Now,
subducting the diameter of the hole from the length and breadth
of the image, there remains 13 inches the length, and 2 3/8 the
breadth, comprehended by those rays, which, passing through the
centre of the said hole, which that breadth subtended, was about
31', answerable to the sun's diameter; but the angle which its
length subtended was more than five such diameters, namely 2
degrees 49'.

"Having made these observations, I first computed from them the
refractive power of the glass, and found it measured by the ratio
of the sines 20 to 31. And then, by that ratio, I computed the
refractions of two rays flowing from opposite parts of the sun's
discus, so as to differ 31' in their obliquity of incidence, and
found that the emergent rays should have comprehended an angle of
31', as they did, before they were incident.

"But because this computation was founded on the hypothesis of
the proportionality of the sines of incidence and refraction,
which though by my own experience I could not imagine to be so
erroneous as to make that angle but 31', which in reality was 2
degrees 49', yet my curiosity caused me again to make my prism.
And having placed it at my window, as before, I observed that by
turning it a little about its axis to and fro, so as to vary its
obliquity to the light more than an angle of 4 degrees or 5
degrees, the colors were not thereby sensibly translated from
their place on the wall, and consequently by that variation of
incidence the quantity of refraction was not sensibly varied. By
this experiment, therefore, as well as by the former computation,
it was evident that the difference of the incidence of rays
flowing from divers parts of the sun could not make them after
decussation diverge at a sensibly greater angle than that at
which they before converged; which being, at most, but about 31'
or 32', there still remained some other cause to be found out,
from whence it could be 2 degrees 49'."

All this caused Newton to suspect that the rays, after their
trajection through the prism, moved in curved rather than in
straight lines, thus tending to be cast upon the wall at
different places according to the amount of this curve. His
suspicions were increased, also, by happening to recall that a
tennis-ball sometimes describes such a curve when "cut" by a
tennis-racket striking the ball obliquely.

"For a circular as well as a progressive motion being
communicated to it by the stroke," he says, "its parts on that
side where the motions conspire must press and beat the
contiguous air more violently than on the other, and there excite
a reluctancy and reaction of the air proportionately greater. And
for the same reason, if the rays of light should possibly be
globular bodies, and by their oblique passage out of one medium
into another acquire a circulating motion, they ought to feel the
greater resistance from the ambient ether on that side where the
motions conspire, and thence be continually bowed to the other.
But notwithstanding this plausible ground of suspicion, when I
came to examine it I could observe no such curvity in them. And,
besides (which was enough for my purpose), I observed that the
difference 'twixt the length of the image and diameter of the
hole through which the light was transmitted was proportionable
to their distance.

"The gradual removal of these suspicions at length led me to the
experimentum crucis, which was this: I took two boards, and,
placing one of them close behind the prism at the window, so that
the light must pass through a small hole, made in it for the
purpose, and fall on the other board, which I placed at about
twelve feet distance, having first made a small hole in it also,
for some of the incident light to pass through. Then I placed
another prism behind this second board, so that the light
trajected through both the boards might pass through that also,
and be again refracted before it arrived at the wall. This done,
I took the first prism in my hands and turned it to and fro
slowly about its axis, so much as to make the several parts of
the image, cast on the second board, successively pass through
the hole in it, that I might observe to what places on the wall
the second prism would refract them. And I saw by the variation
of these places that the light, tending to that end of the image
towards which the refraction of the first prism was made, did in
the second prism suffer a refraction considerably greater than
the light tending to the other end. And so the true cause of the
length of that image was detected to be no other than that LIGHT
consists of RAYS DIFFERENTLY REFRANGIBLE, which, without any
respect to a difference in their incidence, were, according to
their degrees of refrangibility, transmitted towards divers parts
of the wall."[1]


THE NATURE OF COLOR

Having thus proved the composition of light, Newton took up an
exhaustive discussion as to colors, which cannot be entered into
at length here. Some of his remarks on the subject of compound
colors, however, may be stated in part. Newton's views are of
particular interest in this connection, since, as we have already
pointed out, the question as to what constituted color could not
be agreed upon by the philosophers. Some held that color was an
integral part of the substance; others maintained that it was
simply a reflection from the surface; and no scientific
explanation had been generally accepted. Newton concludes his
paper as follows:

"I might add more instances of this nature, but I shall conclude
with the general one that the colors of all natural bodies have
no other origin than this, that they are variously qualified to
reflect one sort of light in greater plenty than another. And
this I have experimented in a dark room by illuminating those
bodies with uncompounded light of divers colors. For by that
means any body may be made to appear of any color. They have
there no appropriate color, but ever appear of the color of the
light cast upon them, but yet with this difference, that they are
most brisk and vivid in the light of their own daylight color.
Minium appeareth there of any color indifferently with which 'tis
illustrated, but yet most luminous in red; and so Bise appeareth
indifferently of any color with which 'tis illustrated, but yet
most luminous in blue. And therefore Minium reflecteth rays of
any color, but most copiously those indued with red; and
consequently, when illustrated with daylight--that is, with all
sorts of rays promiscuously blended--those qualified with red
shall abound most in the reflected light, and by their prevalence
cause it to appear of that color. And for the same reason, Bise,
reflecting blue most copiously, shall appear blue by the excess
of those rays in its reflected light; and the like of other
bodies. And that this is the entire and adequate cause of their
colors is manifest, because they have no power to change or alter
the colors of any sort of rays incident apart, but put on all
colors indifferently with which they are enlightened."[2]

This epoch-making paper aroused a storm of opposition. Some of
Newton's opponents criticised his methods, others even doubted
the truth of his experiments. There was one slight mistake in
Newton's belief that all prisms would give a spectrum of exactly
the same length, and it was some time before he corrected this
error. Meanwhile he patiently met and answered the arguments of
his opponents until he began to feel that patience was no longer
a virtue. At one time he even went so far as to declare that,
once he was "free of this business," he would renounce scientific
research forever, at least in a public way. Fortunately for the
world, however, he did not adhere to this determination, but went
on to even greater discoveries--which, it may be added, involved
still greater controversies.

In commenting on Newton's discovery of the composition of light,
Voltaire said: "Sir Isaac Newton has demonstrated to the eye, by
the bare assistance of a prism, that light is a composition of
colored rays, which, being united, form white color. A single ray
is by him divided into seven, which all fall upon a piece of
linen or a sheet of white paper, in their order one above the
other, and at equal distances. The first is red, the second
orange, the third yellow, the fourth green, the fifth blue, the
sixth indigo, the seventh a violet purple. Each of these rays
transmitted afterwards by a hundred other prisms will never
change the color it bears; in like manner as gold, when
completely purged from its dross, will never change afterwards in
the crucible."[3]



XII. NEWTON AND THE LAW OF GRAVITATION

We come now to the story of what is by common consent the
greatest of scientific achievements. The law of universal
gravitation is the most far-reaching principle as yet discovered.
It has application equally to the minutest particle of matter and
to the most distant suns in the universe, yet it is amazing in
its very simplicity. As usually phrased, the law is this: That
every particle of matter in the universe attracts every other
particle with a force that varies directly with the mass of the
particles and inversely as the squares of their mutual distance.
Newton did not vault at once to the full expression of this law,
though he had formulated it fully before he gave the results of
his investigations to the world. We have now to follow the steps
by which he reached this culminating achievement.

At the very beginning we must understand that the idea of
universal gravitation was not absolutely original with Newton.
Away back in the old Greek days, as we have seen, Anaxagoras
conceived and clearly expressed the idea that the force which
holds the heavenly bodies in their orbits may be the same that
operates upon substances at the surface of the earth. With
Anaxagoras this was scarcely more than a guess. After his day the
idea seems not to have been expressed by any one until the
seventeenth century's awakening of science. Then the
consideration of Kepler's Third Law of planetary motion suggested
to many minds perhaps independently the probability that the
force hitherto mentioned merely as centripetal, through the
operation of which the planets are held in their orbits is a
force varying inversely as the square of the distance from the
sun. This idea had come to Robert Hooke, to Wren, and perhaps to
Halley, as well as to Newton; but as yet no one had conceived a
method by which the validity of the suggestion might be tested.
It was claimed later on by Hooke that he had discovered a method
demonstrating the truth of the theory of inverse squares, and
after the full announcement of Newton's discovery a heated
controversy was precipitated in which Hooke put forward his
claims with accustomed acrimony. Hooke, however, never produced
his demonstration, and it may well be doubted whether he had
found a method which did more than vaguely suggest the law which
the observations of Kepler had partially revealed. Newton's great
merit lay not so much in conceiving the law of inverse squares as
in the demonstration of the law. He was led to this demonstration
through considering the orbital motion of the moon. According to
the familiar story, which has become one of the classic myths of
science, Newton was led to take up the problem through observing
the fall of an apple. Voltaire is responsible for the story,
which serves as well as another; its truth or falsity need not in
the least concern us. Suffice it that through pondering on the
familiar fact of terrestrial gravitation, Newton was led to
question whether this force which operates so tangibly here at
the earth's surface may not extend its influence out into the
depths of space, so as to include, for example, the moon.
Obviously some force pulls the moon constantly towards the earth;
otherwise that body would fly off at a tangent and never return.
May not this so-called centripetal force be identical with
terrestrial gravitation? Such was Newton's query. Probably many
another man since Anaxagoras had asked the same question, but
assuredly Newton was the first man to find an answer.

The thought that suggested itself to Newton's mind was this: If
we make a diagram illustrating the orbital course of the moon for
any given period, say one minute, we shall find that the course
of the moon departs from a straight line during that period by a
measurable distance--that: is to say, the moon has been virtually
pulled towards the earth by an amount that is represented by the
difference between its actual position at the end of the minute
under observation and the position it would occupy had its course
been tangential, as, according to the first law of motion, it
must have been had not some force deflected it towards the earth.
Measuring the deflection in question--which is equivalent to the
so-called versed sine of the arc traversed--we have a basis for
determining the strength of the deflecting force. Newton
constructed such a diagram, and, measuring the amount of the
moon's departure from a tangential rectilinear course in one
minute, determined this to be, by his calculation, thirteen feet.
Obviously, then, the force acting upon the moon is one that would
cause that body to fall towards the earth to the distance of
thirteen feet in the first minute of its fall. Would such be the
force of gravitation acting at the distance of the moon if the
power of gravitation varies inversely as the square of the
distance? That was the tangible form in which the problem
presented itself to Newton. The mathematical solution of the
problem was simple enough. It is based on a comparison of the
moon's distance with the length of the earth's radius. On making
this calculation, Newton found that the pull of gravitation--if
that were really the force that controls the moon--gives that
body a fall of slightly over fifteen feet in the first minute,
instead of thirteen feet. Here was surely a suggestive
approximation, yet, on the other band, the discrepancy seemed to
be too great to warrant him in the supposition that he had found
the true solution. He therefore dismissed the matter from his
mind for the time being, nor did he return to it definitely for
some years.

{illustration caption =  DIAGRAM TO ILLUSTRATE NEWTON'S LAW OF
GRAVITATION (E represents the earth and A the moon. Were the
earth's pull on the moon to cease, the moon's inertia would cause
it to take the tangential course, AB. On the other hand, were the
moon's motion to be stopped for an instant, the moon would fall
directly towards the earth, along the line AD. The moon's actual
orbit, resulting from these component forces, is AC. Let AC
represent the actual flight of the moon in one minute. Then BC,
which is obviously equal to AD, represents the distance which the
moon virtually falls towards the earth in one minute. Actual
computation, based on measurements of the moon's orbit, showed
this distance to be about fifteen feet. Another computation
showed that this is the distance that the moon would fall towards
the earth under the influence of gravity, on the supposition that
the force of gravity decreases inversely with the square of the
distance; the basis of comparison being furnished by falling
bodies at the surface of the earth. Theory and observations thus
coinciding, Newton was justified in declaring that the force that
pulls the moon towards the earth and keeps it in its orbit, is
the familiar force of gravity, and that this varies inversely as
the square of the distance.)}

It was to appear in due time that Newton's hypothesis was
perfectly valid and that his method of attempted demonstration
was equally so. The difficulty was that the earth's proper
dimensions were not at that time known. A wrong estimate of the
earth's size vitiated all the other calculations involved, since
the measurement of the moon's distance depends upon the
observation of the parallax, which cannot lead to a correct
computation unless the length of the earth's radius is accurately
known. Newton's first calculation was made as early as 1666, and
it was not until 1682 that his attention was called to a new and
apparently accurate measurement of a degree of the earth's
meridian made by the French astronomer Picard. The new
measurement made a degree of the earth's surface 69.10 miles,
instead of sixty miles.

Learning of this materially altered calculation as to the earth's
size, Newton was led to take up again his problem of the falling
moon. As he proceeded with his computation, it became more and
more certain that this time the result was to harmonize with the
observed facts. As the story goes, he was so completely
overwhelmed with emotion that he was forced to ask a friend to
complete the simple calculation. That story may well be true,
for, simple though the computation was, its result was perhaps
the most wonderful demonstration hitherto achieved in the entire
field of science. Now at last it was known that the force of
gravitation operates at the distance of the moon, and holds that
body in its elliptical orbit, and it required but a slight effort
of the imagination to assume that the force which operates
through such a reach of space extends its influence yet more
widely. That such is really the case was demonstrated presently
through calculations as to the moons of Jupiter and by similar
computations regarding the orbital motions of the various
planets. All results harmonizing, Newton was justified in
reaching the conclusion that gravitation is a universal property
of matter. It remained, as we shall see, for nineteenth-century
scientists to prove that the same force actually operates upon
the stars, though it should be added that this demonstration
merely fortified a belief that had already found full acceptance.

Having thus epitomized Newton's discovery, we must now take up
the steps of his progress somewhat in detail, and state his
theories and their demonstration in his own words. Proposition
IV., theorem 4, of his Principia is as follows:

"That the moon gravitates towards the earth and by the force of
gravity is continually drawn off from a rectilinear motion and
retained in its orbit.

"The mean distance of the moon from the earth, in the syzygies in
semi-diameters of the earth, is, according to Ptolemy and most
astronomers, 59; according to Vendelin and Huygens, 60; to
Copernicus, 60 1/3; to Street, 60 2/3; and to Tycho, 56 1/2. But
Tycho, and all that follow his tables of refractions, making the
refractions of the sun and moon (altogether against the nature of
light) to exceed the refractions of the fixed stars, and that by
four or five minutes NEAR THE HORIZON, did thereby increase the
moon's HORIZONTAL parallax by a like number of minutes, that is,
by a twelfth or fifteenth part of the whole parallax. Correct
this error and the distance will become about 60 1/2
semi-diameters of the earth, near to what others have assigned.
Let us assume the mean distance of 60 diameters in the syzygies;
and suppose one revolution of the moon, in respect to the fixed
stars, to be completed in 27d. 7h. 43', as astronomers have
determined; and the circumference of the earth to amount to
123,249,600 Paris feet, as the French have found by mensuration.
And now, if we imagine the moon, deprived of all motion, to be
let go, so as to descend towards the earth with the impulse of
all that force by which (by Cor. Prop. iii.) it is retained in
its orb, it will in the space of one minute of time describe in
its fall 15 1/12 Paris feet. For the versed sine of that arc
which the moon, in the space of one minute of time, would by its
mean motion describe at the distance of sixty semi-diameters of
the earth, is nearly 15 1/12 Paris feet, or more accurately 15
feet, 1 inch, 1 line 4/9. Wherefore, since that force, in
approaching the earth, increases in the reciprocal-duplicate
proportion of the distance, and upon that account, at the surface
of the earth, is 60 x 60 times greater than at the moon, a body
in our regions, falling with that force, ought in the space of
one minute of time to describe 60 x 60 x 15 1/12 Paris feet; and
in the space of one second of time, to describe 15 1/12 of those
feet, or more accurately, 15 feet, 1 inch, 1 line 4/9. And with
this very force we actually find that bodies here upon earth do
really descend; for a pendulum oscillating seconds in the
latitude of Paris will be 3 Paris feet, and 8 lines 1/2 in
length, as Mr. Huygens has observed. And the space which a heavy
body describes by falling in one second of time is to half the
length of the pendulum in the duplicate ratio of the
circumference of a circle to its diameter (as Mr. Huygens has
also shown), and is therefore 15 Paris feet, 1 inch, 1 line 4/9.
And therefore the force by which the moon is retained in its
orbit is that very same force which we commonly call gravity;
for, were gravity another force different from that, then bodies
descending to the earth with the joint impulse of both forces
would fall with a double velocity, and in the space of one second
of time would describe 30 1/6 Paris feet; altogether against
experience."[1]

All this is beautifully clear, and its validity has never in
recent generations been called in question; yet it should be
explained that the argument does not amount to an actually
indisputable demonstration. It is at least possible that the
coincidence between the observed and computed motion of the moon
may be a mere coincidence and nothing more. This probability,
however, is so remote that Newton is fully justified in
disregarding it, and, as has been said, all subsequent
generations have accepted the computation as demonstrative.

Let us produce now Newton's further computations as to the other
planetary bodies, passing on to his final conclusion that gravity
is a universal force.

          "PROPOSITION V., THEOREM V.

"That the circumjovial planets gravitate towards Jupiter; the
circumsaturnal towards Saturn; the circumsolar towards the sun;
and by the forces of their gravity are drawn off from rectilinear
motions, and retained in curvilinear orbits.


"For the revolutions of the circumjovial planets about Jupiter,
of the circumsaturnal about Saturn, and of Mercury and Venus and
the other circumsolar planets about the sun, are appearances of
the same sort with the revolution of the moon about the earth;
and therefore, by Rule ii., must be owing to the same sort of
causes; especially since it has been demonstrated that the forces
upon which those revolutions depend tend to the centres of
Jupiter, of Saturn, and of the sun; and that those forces, in
receding from Jupiter, from Saturn, and from the sun, decrease in
the same proportion, and according to the same law, as the force
of gravity does in receding from the earth.

"COR. 1.--There is, therefore, a power of gravity tending to all
the planets; for doubtless Venus, Mercury, and the rest are
bodies of the same sort with Jupiter and Saturn. And since all
attraction (by Law iii.) is mutual, Jupiter will therefore
gravitate towards all his own satellites, Saturn towards his, the
earth towards the moon, and the sun towards all the primary
planets.

"COR. 2.--The force of gravity which tends to any one planet is
reciprocally as the square of the distance of places from the
planet's centre.

"COR. 3.--All the planets do mutually gravitate towards one
another, by Cor. 1 and 2, and hence it is that Jupiter and
Saturn, when near their conjunction, by their mutual attractions
sensibly disturb each other's motions. So the sun disturbs the
motions of the moon; and both sun and moon disturb our sea, as we
shall hereafter explain.

          "SCHOLIUM

"The force which retains the celestial bodies in their orbits has
been hitherto called centripetal force; but it being now made
plain that it can be no other than a gravitating force, we shall
hereafter call it gravity. For the cause of the centripetal force
which retains the moon in its orbit will extend itself to all the
planets by Rules i., ii., and iii.

          "PROPOSITION VI., THEOREM VI.

"That all bodies gravitate towards every planet; and that the
weights of the bodies towards any the same planet, at equal
distances from the centre of the planet, are proportional to the
quantities of matter which they severally contain.


"It has been now a long time observed by others that all sorts of
heavy bodies (allowance being made for the inability of
retardation which they suffer from a small power of resistance in
the air) descend to the earth FROM EQUAL HEIGHTS in equal times;
and that equality of times we may distinguish to a great accuracy
by help of pendulums. I tried the thing in gold, silver, lead,
glass, sand, common salt, wood, water, and wheat. I provided two
wooden boxes, round and equal: I filled the one with wood, and
suspended an equal weight of gold (as exactly as I could) in the
centre of oscillation of the other. The boxes hanging by eleven
feet, made a couple of pendulums exactly equal in weight and
figure, and equally receiving the resistance of the air. And,
placing the one by the other, I observed them to play together
forward and backward, for a long time, with equal vibrations. And
therefore the quantity of matter in gold was to the quantity of
matter in the wood as the action of the motive force (or vis
motrix) upon all the gold to the action of the same upon all the
wood--that is, as the weight of the one to the weight of the
other: and the like happened in the other bodies. By these
experiments, in bodies of the same weight, I could manifestly
have discovered a difference of matter less than the thousandth
part of the whole, had any such been. But, without all doubt, the
nature of gravity towards the planets is the same as towards the
earth. For, should we imagine our terrestrial bodies removed to
the orb of the moon, and there, together with the moon, deprived
of all motion, to be let go, so as to fall together towards the
earth, it is certain, from what we have demonstrated before,
that, in equal times, they would describe equal spaces with the
moon, and of consequence are to the moon, in quantity and matter,
as their weights to its weight.

"Moreover, since the satellites of Jupiter perform their
revolutions in times which observe the sesquiplicate proportion
of their distances from Jupiter's centre, their accelerative
gravities towards Jupiter will be reciprocally as the square of
their distances from Jupiter's centre--that is, equal, at equal
distances. And, therefore, these satellites, if supposed to fall
TOWARDS JUPITER from equal heights, would describe equal spaces
in equal times, in like manner as heavy bodies do on our earth.
And, by the same argument, if the circumsolar planets were
supposed to be let fall at equal distances from the sun, they
would, in their descent towards the sun, describe equal spaces in
equal times. But forces which equally accelerate unequal bodies
must be as those bodies--that is to say, the weights of the
planets (TOWARDS THE SUN must be as their quantities of matter.
Further, that the weights of Jupiter and his satellites towards
the sun are proportional to the several quantities of their
matter, appears from the exceedingly regular motions of the
satellites. For if some of these bodies were more strongly
attracted to the sun in proportion to their quantity of matter
than others, the motions of the satellites would be disturbed by
that inequality of attraction. If at equal distances from the sun
any satellite, in proportion to the quantity of its matter, did
gravitate towards the sun with a force greater than Jupiter in
proportion to his, according to any given proportion, suppose d
to e; then the distance between the centres of the sun and of the
satellite's orbit would be always greater than the distance
between the centres of the sun and of Jupiter nearly in the
subduplicate of that proportion: as by some computations I have
found. And if the satellite did gravitate towards the sun with a
force, lesser in the proportion of e to d, the distance of the
centre of the satellite's orb from the sun would be less than the
distance of the centre of Jupiter from the sun in the
subduplicate of the same proportion. Therefore, if at equal
distances from the sun, the accelerative gravity of any satellite
towards the sun were greater or less than the accelerative
gravity of Jupiter towards the sun by one-one-thousandth part of
the whole gravity, the distance of the centre of the satellite's
orbit from the sun would be greater or less than the distance of
Jupiter from the sun by one one-two-thousandth part of the whole
distance--that is, by a fifth part of the distance of the utmost
satellite from the centre of Jupiter; an eccentricity of the
orbit which would be very sensible. But the orbits of the
satellites are concentric to Jupiter, and therefore the
accelerative gravities of Jupiter and of all its satellites
towards the sun, at equal distances from the sun, are as their
several quantities of matter; and the weights of the moon and of
the earth towards the sun are either none, or accurately
proportional to the masses of matter which they contain.

"COR. 5.--The power of gravity is of a different nature from the
power of magnetism; for the magnetic attraction is not as the
matter attracted. Some bodies are attracted more by the magnet;
others less; most bodies not at all. The power of magnetism in
one and the same body may be increased and diminished; and is
sometimes far stronger, for the quantity of matter, than the
power of gravity; and in receding from the magnet decreases not
in the duplicate, but almost in the triplicate proportion of the
distance, as nearly as I could judge from some rude observations.


          "PROPOSITION VII., THEOREM VII.

"That there is a power of gravity tending to all bodies,
proportional to the several quantities of matter which they
contain.


That all the planets mutually gravitate one towards another we
have proved before; as well as that the force of gravity towards
every one of them considered apart, is reciprocally as the square
of the distance of places from the centre of the planet. And
thence it follows, that the gravity tending towards all the
planets is proportional to the matter which they contain.

"Moreover, since all the parts of any planet A gravitates towards
any other planet B; and the gravity of every part is to the
gravity of the whole as the matter of the part is to the matter
of the whole; and to every action corresponds a reaction;
therefore the planet B will, on the other hand, gravitate towards
all the parts of planet A, and its gravity towards any one part
will be to the gravity towards the whole as the matter of the
part to the matter of the whole. Q.E.D.


"HENCE IT WOULD APPEAR THAT the force of the whole must arise
from the force of the component parts."


Newton closes this remarkable Book iii. with the following words:

"Hitherto we have explained the phenomena of the heavens and of
our sea by the power of gravity, but have not yet assigned the
cause of this power. This is certain, that it must proceed from a
cause that penetrates to the very centre of the sun and planets,
without suffering the least diminution of its force; that
operates not according to the quantity of the surfaces of the
particles upon which it acts (as mechanical causes used to do),
but according to the quantity of solid matter which they contain,
and propagates its virtue on all sides to immense distances,
decreasing always in the duplicate proportions of the distances.
Gravitation towards the sun is made up out of the gravitations
towards the several particles of which the body of the sun is
composed; and in receding from the sun decreases accurately in
the duplicate proportion of the distances as far as the orb of
Saturn, as evidently appears from the quiescence of the aphelions
of the planets; nay, and even to the remotest aphelions of the
comets, if those aphelions are also quiescent. But hitherto I
have not been able to discover the cause of those properties of
gravity from phenomena, and I frame no hypothesis; for whatever
is not deduced from the phenomena is to be called an hypothesis;
and hypotheses, whether metaphysical or physical, whether of
occult qualities or mechanical, have no place in experimental
philosophy. . . . And to us it is enough that gravity does really
exist, and act according to the laws which we have explained, and
abundantly serves to account for all the motions of the celestial
bodies and of our sea."[2]


The very magnitude of the importance of the theory of universal
gravitation made its general acceptance a matter of considerable
time after the actual discovery. This opposition had of course
been foreseen by Newton, and, much as be dreaded controversy, he
was prepared to face it and combat it to the bitter end. He knew
that his theory was right; it remained for him to convince the
world of its truth. He knew that some of his contemporary
philosophers would accept it at once; others would at first
doubt, question, and dispute, but finally accept; while still
others would doubt and dispute until the end of their days. This
had been the history of other great discoveries; and this will
probably be the history of most great discoveries for all time.
But in this case the discoverer lived to see his theory accepted
by practically all the great minds of his time.

Delambre is authority for the following estimate of Newton by
Lagrange. "The celebrated Lagrange," he says, "who frequently
asserted that Newton was the greatest genius that ever existed,
used to add--'and the most fortunate, for we cannot find MORE
THAN ONCE a system of the world to establish.' " With pardonable
exaggeration the admiring followers of the great generalizer
pronounced this epitaph:

 "Nature and Nature's laws lay hid in night;
  God said `Let Newton be!' and all was light."



XIII. INSTRUMENTS OF PRECISION IN THE AGE OF NEWTON

During the Newtonian epoch there were numerous important
inventions of scientific instruments, as well as many
improvements made upon the older ones. Some of these discoveries
have been referred to briefly in other places, but their
importance in promoting scientific investigation warrants a
fuller treatment of some of the more significant.

Many of the errors that had arisen in various scientific
calculations before the seventeenth century may be ascribed to
the crudeness and inaccuracy in the construction of most
scientific instruments. Scientists had not as yet learned that an
approach to absolute accuracy was necessary in every
investigation in the field of science, and that such accuracy
must be extended to the construction of the instruments used in
these investigations and observations. In astronomy it is obvious
that instruments of delicate exactness are most essential; yet
Tycho Brahe, who lived in the sixteenth century, is credited with
being the first astronomer whose instruments show extreme care in
construction.

It seems practically settled that the first telescope was
invented in Holland in 1608; but three men, Hans Lippershey,
James Metius, and Zacharias Jansen, have been given the credit of
the invention at different times. It would seem from certain
papers, now in the library of the University of Leyden, and
included in Huygens's papers, that Lippershey was probably the
first to invent a telescope and to describe his invention. The
story is told that Lippershey, who was a spectacle-maker,
stumbled by accident upon the discovery that when two lenses are
held at a certain distance apart, objects at a distance appear
nearer and larger. Having made this discovery, be fitted two
lenses with a tube so as to maintain them at the proper distance,
and thus constructed the first telescope.

It was Galileo, however, as referred to in a preceding chapter,
who first constructed a telescope based on his knowledge of the
laws of refraction. In 1609, having heard that an instrument had
been invented, consisting of two lenses fixed in a tube, whereby
objects were made to appear larger and nearer, he set about
constructing such an instrument that should follow out the known
effects of refraction. His first telescope, made of two lenses
fixed in a lead pipe, was soon followed by others of improved
types, Galileo devoting much time and labor to perfecting lenses
and correcting errors. In fact, his work in developing the
instrument was so important that the telescope came gradually to
be known as the "Galilean telescope."

In the construction of his telescope Galileo made use of a convex
and a concave lens; but shortly after this Kepler invented an
instrument in which both the lenses used were convex. This
telescope gave a much larger field of view than the Galilean
telescope, but did not give as clear an image, and in consequence
did not come into general use until the middle of the seventeenth
century. The first powerful telescope of this type was made by
Huygens and his brother. It was of twelve feet focal length, and
enabled Huygens to discover a new satellite of Saturn, and to
determine also the true explanation of Saturn's ring.

It was Huygens, together with Malvasia and Auzout, who first
applied the micrometer to the telescope, although the inventor of
the first micrometer was William Gascoigne, of Yorkshire, about
1636. The micrometer as used in telescopes enables the observer
to measure accurately small angular distances. Before the
invention of the telescope such measurements were limited to the
angle that could be distinguished by the naked eye, and were, of
course, only approximately accurate. Even very careful observers,
such as Tycho Brahe, were able to obtain only fairly accurate
results. But by applying Gascoigne's invention to the telescope
almost absolute accuracy became at once possible. The principle
of Gascoigne's micrometer was that of two pointers lying
parallel, and in this position pointing to zero. These were
arranged so that the turning of a single screw separated or
approximated them at will, and the angle thus formed could be
determined with absolute accuracy.

Huygens's micrometer was a slip of metal of variable breadth
inserted at the focus of the telescope. By observing at what
point this exactly covered an object under examination, and
knowing the focal length of the telescope and the width of the
metal, he could then deduce the apparent angular breadth of the
object. Huygens discovered also that an object placed in the
common focus of the two lenses of a Kepler telescope appears
distinct and clearly defined. The micrometers of Malvasia, and
later of Auzout and Picard, are the development of this
discovery. Malvasia's micrometer, which he described in 1662,
consisted of fine silver wires placed at right-angles at the
focus of his telescope.

As telescopes increased in power, however, it was found that even
the finest wire, or silk filaments, were much too thick for
astronomical observations, as they obliterated the image, and so,
finally, the spider-web came into use and is still used in
micrometers and other similar instruments. Before that time,
however, the fine crossed wires had revolutionized astronomical
observations. "We may judge how great was the improvement which
these contrivances introduced into the art of observing," says
Whewell, "by finding that Hevelius refused to adopt them because
they would make all the old observations of no value. He had
spent a laborious and active life in the exercise of the old
methods, and could not bear to think that all the treasures which
he had accumulated had lost their worth by the discovery of a new
mine of richer ones."[1]

Until the time of Newton, all the telescopes in use were either
of the Galilean or Keplerian type, that is, refractors. But about
the year 1670 Newton constructed his first reflecting telescope,
which was greatly superior to, although much smaller than, the
telescopes then in use. He was led to this invention by his
experiments with light and colors. In 1671 he presented to the
Royal Society a second and somewhat larger telescope, which he
had made; and this type of instrument was little improved upon
until the introduction of the achromatic telescope, invented by
Chester Moor Hall in 1733.

As is generally known, the element of accurate measurements of
time plays an important part in the measurements of the movements
of the heavenly bodies. In fact, one was scarcely possible
without the other, and as it happened it was the same man,
Huygens, who perfected Kepler's telescope and invented the
pendulum clock. The general idea had been suggested by Galileo;
or, better perhaps, the equal time occupied by the successive
oscillations of the pendulum had been noted by him. He had not
been able, however, to put this discovery to practical account.
But in 1656 Huygens invented the necessary machinery for
maintaining the motion of the pendulum and perfected several
accurate clocks. These clocks were of invaluable assistance to
the astronomers, affording as they did a means of keeping time
"more accurate than the sun itself." When Picard had corrected
the variation caused by heat and cold acting upon the pendulum
rod by combining metals of different degrees of expansibility, a
high degree of accuracy was possible.

But while the pendulum clock was an unequalled stationary
time-piece, it was useless in such unstable situations as, for
example, on shipboard. But here again Huygens played a prominent
part by first applying the coiled balance-spring for regulating
watches and marine clocks. The idea of applying a spring to the
balance-wheel was not original with Huygens, however, as it had
been first conceived by Robert Hooke; but Huygens's application
made practical Hooke's idea. In England the importance of
securing accurate watches or marine clocks was so fully
appreciated that a reward of L20,000 sterling was offered by
Parliament as a stimulus to the inventor of such a time-piece.
The immediate incentive for this offer was the obvious fact that
with such an instrument the determination of the longitude of
places would be much simplified. Encouraged by these offers, a
certain carpenter named Harrison turned his attention to the
subject of watch-making, and, after many years of labor, in 1758
produced a spring time-keeper which, during a sea-voyage
occupying one hundred and sixty-one days, varied only one minute
and five seconds. This gained for Harrison a reward Of L5000
sterling at once, and a little later L10,000 more, from
Parliament.

While inventors were busy with the problem of accurate
chronometers, however, another instrument for taking longitude at
sea had been invented. This was the reflecting quadrant, or
sextant, as the improved instrument is now called, invented by
John Hadley in 1731, and independently by Thomas Godfrey, a poor
glazier of Philadelphia, in 1730. Godfrey's invention, which was
constructed on the same principle as that of the Hadley
instrument, was not generally recognized until two years after
Hadley's discovery, although the instrument was finished and
actually in use on a sea-voyage some months before Hadley
reported his invention. The principle of the sextant, however,
seems to have been known to Newton, who constructed an instrument
not very unlike that of Hadley; but this invention was lost sight
of until several years after the philosopher's death and some
time after Hadley's invention.

The introduction of the sextant greatly simplified taking
reckonings at sea as well as facilitating taking the correct
longitude of distant places. Before that time the mariner was
obliged to depend upon his compass, a cross-staff, or an
astrolabe, a table of the sun's declination and a correction for
the altitude of the polestar, and very inadequate and incorrect
charts. Such were the instruments used by Columbus and Vasco da
Gama and their immediate successors.

During the Newtonian period the microscopes generally in use were
those constructed of simple lenses, for although compound
microscopes were known, the difficulties of correcting aberration
had not been surmounted, and a much clearer field was given by
the simple instrument. The results obtained by the use of such
instruments, however, were very satisfactory in many ways. By
referring to certain plates in this volume, which reproduce
illustrations from Robert Hooke's work on the microscope, it will
be seen that quite a high degree of effectiveness had been
attained. And it should be recalled that Antony von Leeuwenboek,
whose death took place shortly before Newton's, had discovered
such micro-organisms as bacteria, had seen the blood corpuscles
in circulation, and examined and described other microscopic
structures of the body.



XIV. PROGRESS IN ELECTRICITY FROM GILBERT AND VON GUERICKE TO
FRANKLIN

We have seen how Gilbert, by his experiments with magnets, gave
an impetus to the study of magnetism and electricity. Gilbert
himself demonstrated some facts and advanced some theories, but
the system of general laws was to come later. To this end the
discovery of electrical repulsion, as well as attraction, by Von
Guericke, with his sulphur ball, was a step forward; but
something like a century passed after Gilbert's beginning before
anything of much importance was done in the field of electricity.

In 1705, however, Francis Hauksbee began a series of experiments
that resulted in some startling demonstrations. For many years it
had been observed that a peculiar light was seen sometimes in the
mercurial barometer, but Hauksbee and the other scientific
investigators supposed the radiance to be due to the mercury in a
vacuum, brought about, perhaps, by some agitation. That this
light might have any connection with electricity did not, at
first, occur to Hauksbee any more than it had to his
predecessors. The problem that interested him was whether the
vacuum in the tube of the barometer was essential to the light;
and in experimenting to determine this, he invented his
"mercurial fountain." Having exhausted the air in a receiver
containing some mercury, he found that by allowing air to rush
through the mercury the metal became a jet thrown in all
directions against the sides of the vessel, making a great,
flaming shower, "like flashes of lightning," as he said. But it
seemed to him that there was a difference between this light and
the glow noted in the barometer. This was a bright light, whereas
the barometer light was only a glow. Pondering over this,
Hauksbee tried various experiments, revolving pieces of amber,
flint, steel, and other substances in his exhausted air-pump
receiver, with negative, or unsatisfactory, results. Finally, it
occurred to him to revolve an exhausted glass tube itself.
Mounting such a globe of glass on an axis so that it could be
revolved rapidly by a belt running on a large wheel, he found
that by holding his fingers against the whirling globe a purplish
glow appeared, giving sufficient light so that coarse print could
be read, and the walls of a dark room sensibly lightened several
feet away. As air was admitted to the globe the light gradually
diminished, and it seemed to him that this diminished glow was
very similar in appearance to the pale light seen in the
mercurial barometer. Could it be that it was the glass, and not
the mercury, that caused it? Going to a barometer he proceeded to
rub the glass above the column of mercury over the vacuum,
without disturbing the mercury, when, to his astonishment, the
same faint light, to all appearances identical with the glow seen
in the whirling globe, was produced.

Turning these demonstrations over in his mind, he recalled the
well-known fact that rubbed glass attracted bits of paper,
leaf-brass, and other light substances, and that this phenomenon
was supposed to be electrical. This led him finally to determine
the hitherto unsuspected fact, that the glow in the barometer was
electrical as was also the glow seen in his whirling globe.
Continuing his investigations, he soon discovered that solid
glass rods when rubbed produced the same effects as the tube. By
mere chance, happening to hold a rubbed tube to his cheek, he
felt the effect of electricity upon the skin like "a number of
fine, limber hairs," and this suggested to him that, since the
mysterious manifestation was so plain, it could be made to show
its effects upon various substances. Suspending some woollen
threads over the whirling glass cylinder, he found that as soon
as he touched the glass with his hands the threads, which were
waved about by the wind of the revolution, suddenly straightened
themselves in a peculiar manner, and stood in a radical position,
pointing to the axis of the cylinder.

Encouraged by these successes, he continued his experiments with
breathless expectancy, and soon made another important discovery,
that of "induction," although the real significance of this
discovery was not appreciated by him or, for that matter, by any
one else for several generations following. This discovery was
made by placing two revolving cylinders within an inch of each
other, one with the air exhausted and the other unexhausted.
Placing his hand on the unexhausted tube caused the light to
appear not only upon it, but on the other tube as well. A little
later he discovered that it is not necessary to whirl the
exhausted tube to produce this effect, but simply to place it in
close proximity to the other whirling cylinder.

These demonstrations of Hauksbee attracted wide attention and
gave an impetus to investigators in the field of electricity; but
still no great advance was made for something like a quarter of a
century. Possibly the energies of the scientists were exhausted
for the moment in exploring the new fields thrown open to
investigation by the colossal work of Newton.


THE EXPERIMENTS OF STEPHEN GRAY

In 1729 Stephen Gray (died in 1736), an eccentric and irascible
old pensioner of the Charter House in London, undertook some
investigations along lines similar to those of Hauksbee. While
experimenting with a glass tube for producing electricity, as
Hauksbee had done, he noticed that the corks with which he had
stopped the ends of the tube to exclude the dust, seemed to
attract bits of paper and leaf-brass as well as the glass itself.
He surmised at once that this mysterious electricity, or
"virtue," as it was called, might be transmitted through other
substances as it seemed to be through glass.

"Having by me an ivory ball of about one and three-tenths of an
inch in diameter," he writes, "with a hole through it, this I
fixed upon a fir-stick about four inches long, thrusting the
other end into the cork, and upon rubbing the tube found that the
ball attracted and repelled the feather with more vigor than the
cork had done, repeating its attractions and repulsions for many
times together. I then fixed the ball on longer sticks, first
upon one of eight inches, and afterwards upon one of twenty-four
inches long, and found the effect the same. Then I made use of
iron, and then brass wire, to fix the ball on, inserting the
other end of the wire in the cork, as before, and found that the
attraction was the same as when the fir-sticks were made use of,
and that when the feather was held over against any part of the
wire it was attracted by it; but though it was then nearer the
tube, yet its attraction was not so strong as that of the ball.
When the wire of two or three feet long was used, its vibrations,
caused by the rubbing of the tube, made it somewhat troublesome
to be managed. This put me to thinking whether, if the ball was
hung by a pack-thread and suspended by a loop on the tube, the
electricity would not be carried down the line to the ball; I
found it to succeed accordingly; for upon suspending the ball on
the tube by a pack-thread about three feet long, when the tube
had been excited by rubbing, the ivory ball attracted and
repelled the leaf-brass over which it was held as freely as it
had done when it was suspended on sticks or wire, as did also a
ball of cork, and another of lead that weighed one pound and a
quarter."

Gray next attempted to determine what other bodies would attract
the bits of paper, and for this purpose he tried coins, pieces of
metal, and even a tea-kettle, "both empty and filled with hot or
cold water"; but he found that the attractive power appeared to
be the same regardless of the substance used.

"I next proceeded," he continues, "to try at what greater
distances the electric virtues might be carried, and having by me
a hollow walking-cane, which I suppose was part of a fishing-rod,
two feet seven inches long, I cut the great end of it to fit into
the bore of the tube, into which it went about five inches; then
when the cane was put into the end of the tube, and this excited,
the cane drew the leaf-brass to the height of more than two
inches, as did also the ivory ball, when by a cork and stick it
had been fixed to the end of the cane.... With several pieces of
Spanish cane and fir-sticks I afterwards made a rod, which,
together with the tube, was somewhat more than eighteen feet
long, which was the greatest length I could conveniently use in
my chamber, and found the attraction very nearly, if not
altogether, as strong as when the ball was placed on the shorter
rods."

This experiment exhausted the capacity of his small room, but on
going to the country a little later he was able to continue his
experiments. "To a pole of eighteen feet there was tied a line of
thirty-four feet in length, so that the pole and line together
were fifty-two feet. With the pole and tube I stood in the
balcony, the assistant below in the court, where he held the
board with the leaf-brass on it. Then the tube being excited, as
usual, the electric virtue passed from the tube up the pole and
down the line to the ivory ball, which attracted the leaf-brass,
and as the ball passed over it in its vibrations the leaf-brass
would follow it till it was carried off the board."

Gray next attempted to send the electricity over a line suspended
horizontally. To do this he suspended the pack-thread by pieces
of string looped over nails driven into beams for that purpose.
But when thus suspended he found that the ivory ball no longer
excited the leaf-brass, and he guessed correctly that the
explanation of this lay in the fact that "when the electric
virtue came to the loop that was suspended on the beam it went up
the same to the beam," none of it reaching the ball. As we shall
see from what follows, however, Gray had not as yet determined
that certain substances will conduct electricity while others
will not. But by a lucky accident he made the discovery that
silk, for example, was a poor conductor, and could be turned to
account in insulating the conducting-cord.

A certain Mr. Wheler had become much interested in the old
pensioner and his work, and, as a guest at the Wheler house, Gray
had been repeating some of his former experiments with the
fishing-rod, line, and ivory ball. He had finally exhausted the
heights from which these experiments could be made by climbing to
the clock-tower and exciting bits of leaf-brass on the ground
below.

"As we had no greater heights here," he says, "Mr. Wheler was
desirous to try whether we could not carry the electric virtue
horizontally. I then told him of the attempt I had made with that
design, but without success, telling him the method and materials
made use of, as mentioned above. He then proposed a silk line to
support the line by which the electric virtue was to pass. I told
him it might do better upon account of its smallness; so that
there would be less virtue carried from the line of
communication.

"The first experiment was made in the matted gallery, July 2,
1729, about ten in the morning. About four feet from the end of
the gallery there was a cross line that was fixed by its ends to
each side of the gallery by two nails; the middle part of the
line was silk, the rest at each end pack-thread; then the line to
which the ivory ball was hung and by which the electric virtue
was to be conveyed to it from the tube, being eighty and one-half
feet in length, was laid on the cross silk line, so that the ball
hung about nine feet below it. Then the other end of the line was
by a loop suspended on the glass cane, and the leaf-brass held
under the ball on a piece of white paper; when, the tube being
rubbed, the ball attracted the leaf-brass, and kept it suspended
on it for some time."

This experiment succeeded so well that the string was lengthened
until it was some two hundred and ninety-three feet long; and
still the attractive force continued, apparently as strong as
ever. On lengthening the string still more, however, the extra
weight proved too much for the strength of the silk
suspending-thread. "Upon this," says Gray, "having brought with
me both brass and iron wire, instead of the silk we put up small
iron wire; but this was too weak to bear the weight of the line.
We then took brass wire of a somewhat larger size than that of
iron. This supported our line of communication; but though the
tube was well rubbed, yet there was not the least motion or
attraction given by the ball, neither with the great tube, which
we made use of when we found the small solid cane to be
ineffectual; by which we were now convinced that the success we
had before depended upon the lines that supported the line of
communication being silk, and not upon their being small, as
before trial I had imagined it might be; the same effect
happening here as it did when the line that is to convey the
electric virtue is supported by pack-thread."

Soon after this Gray and his host suspended a pack-thread six
hundred and sixty-six feet long on poles across a field, these
poles being slightly inclined so that the thread could be
suspended from the top by small silk cords, thus securing the
necessary insulation. This pack-thread line, suspended upon poles
along which Gray was able to transmit the electricity, is very
suggestive of the modern telegraph, but the idea of signalling or
making use of it for communicating in any way seems not to have
occurred to any one at that time. Even the successors of Gray who
constructed lines some thousands of feet long made no attempt to
use them for anything but experimental purposes--simply to test
the distances that the current could be sent. Nevertheless, Gray
should probably be credited with the discovery of two of the most
important properties of electricity--that it can be conducted and
insulated, although, as we have seen, Gilbert and Von Guericke
had an inkling of both these properties.


EXPERIMENTS OF CISTERNAY DUFAY

So far England had produced the two foremost workers in
electricity. It was now France's turn to take a hand, and,
through the efforts of Charles Francois de Cisternay Dufay, to
advance the science of electricity very materially. Dufay was a
highly educated savant, who had been soldier and diplomat
betimes, but whose versatility and ability as a scientist is
shown by the fact that he was the only man who had ever
contributed to the annals of the academy investigations in every
one of the six subjects admitted by that institution as worthy of
recognition. Dufay upheld his reputation in this new field of
science, making many discoveries and correcting many mistakes of
former observers. In this work also he proved himself a great
diplomat by remaining on terms of intimate friendship with Dr.
Gray--a thing that few people were able to do.

Almost his first step was to overthrow the belief that certain
bodies are "electrics" and others "non-electrics"--that is, that
some substances when rubbed show certain peculiarities in
attracting pieces of paper and foil which others do not. Dufay
proved that all bodies possess this quality in a certain degree.

"I have found that all bodies (metallic, soft, or fluid ones
excepted)," he says, "may be made electric by first heating them
more or less and then rubbing them on any sort of cloth. So that
all kinds of stones, as well precious as common, all kinds of
wood, and, in general, everything that I have made trial of,
became electric by beating and rubbing, except such bodies as
grow soft by beat, as the gums, which dissolve in water, glue,
and such like substances. 'Tis also to be remarked that the
hardest stones or marbles require more chafing or heating than
others, and that the same rule obtains with regard to the woods;
so that box, lignum vitae, and such others must be chafed almost
to the degree of browning, whereas fir, lime-tree, and cork
require but a moderate heat.

"Having read in one of Mr. Gray's letters that water may be made
electrical by holding the excited glass tube near it (a dish of
water being fixed to a stand and that set on a plate of glass, or
on the brim of a drinking-glass, previously chafed, or otherwise
warmed), I have found, upon trial, that the same thing happened
to all bodies without exception, whether solid or fluid, and that
for that purpose 'twas sufficient to set them on a glass stand
slightly warmed, or only dried, and then by bringing the tube
near them they immediately became electrical. I made this
experiment with ice, with a lighted wood-coal, and with
everything that came into my mind; and I constantly remarked that
such bodies of themselves as were least electrical had the
greatest degree of electricity communicated to them at the
approval of the glass tube."

His next important discovery was that colors had nothing to do
with the conduction of electricity. "Mr. Gray says, towards the
end of one of his letters," he writes, "that bodies attract more
or less according to their colors. This led me to make several
very singular experiments. I took nine silk ribbons of equal
size, one white, one black, and the other seven of the seven
primitive colors, and having hung them all in order in the same
line, and then bringing the tube near them, the black one was
first attracted, the white one next, and others in order
successively to the red one, which was attracted least, and the
last of them all. I afterwards cut out nine square pieces of
gauze of the same colors with the ribbons, and having put them
one after another on a hoop of wood, with leaf-gold under them,
the leaf-gold was attracted through all the colored pieces of
gauze, but not through the white or black. This inclined me first
to think that colors contribute much to electricity, but three
experiments convinced me to the contrary. The first, that by
warming the pieces of gauze neither the black nor white pieces
obstructed the action of the electrical tube more than those of
the other colors. In like manner, the ribbons being warmed, the
black and white are not more strongly attracted than the rest.
The second is, the gauzes and ribbons being wetted, the ribbons
are all attracted equally, and all the pieces of gauze equally
intercept the action of electric bodies. The third is, that the
colors of a prism being thrown on a white gauze, there appear no
differences of attraction. Whence it proceeds that this
difference proceeds, not from the color, as a color, but from the
substances that are employed in the dyeing. For when I colored
ribbons by rubbing them with charcoal, carmine, and such other
substances, the differences no longer proved the same."

In connection with his experiments with his thread suspended on
glass poles, Dufay noted that a certain amount of the current is
lost, being given off to the surrounding air. He recommended,
therefore, that the cords experimented with be wrapped with some
non-conductor--that it should be "insulated" ("isolee"), as he
said, first making use of this term.


DUFAY DISCOVERS VITREOUS AND RESINOUS ELECTRICITY

It has been shown in an earlier chapter how Von Guericke
discovered that light substances like feathers, after being
attracted to the sulphur-ball electric-machine, were repelled by
it until they touched some object. Von Guericke noted this, but
failed to explain it satisfactorily. Dufay, repeating Von
Guericke's experiments, found that if, while the excited tube or
sulphur ball is driving the repelled feather before it, the ball
be touched or rubbed anew, the feather comes to it again, and is
repelled alternately, as, the hand touches the ball, or is
withdrawn. From this he concluded that electrified bodies first
attract bodies not electrified, "charge" them with electricity,
and then repel them, the body so charged not being attracted
again until it has discharged its electricity by touching
something.

"On making the experiment related by Otto von Guericke," he says,
"which consists in making a ball of sulphur rendered electrical
to repel a down feather, I perceived that the same effects were
produced not only by the tube, but by all electric bodies
whatsoever, and I discovered that which accounts for a great part
of the irregularities and, if I may use the term, of the caprices
that seem to accompany most of the experiments on electricity.
This principle is that electric bodies attract all that are not
so, and repel them as soon as they are become electric by the
vicinity or contact of the electric body. Thus gold-leaf is first
attracted by the tube, and acquires an electricity by approaching
it, and of consequence is immediately repelled by it. Nor is it
reattracted while it retains its electric quality. But if while
it is thus sustained in the air it chance to light on some other
body, it straightway loses its electricity, and in consequence is
reattracted by the tube, which, after having given it a new
electricity, repels it a second time, which continues as long as
the tube keeps its electricity. Upon applying this principle to
the various experiments of electricity, one will be surprised at
the number of obscure and puzzling facts that it clears up. For
Mr. Hauksbee's famous experiment of the glass globe, in which
silk threads are put, is a necessary consequence of it. When
these threads are arranged in the form of rays by the electricity
of the sides of the globe, if the finger be put near the outside
of the globe the silk threads within fly from it, as is well
known, which happens only because the finger or any other body
applied near the glass globe is thereby rendered electrical, and
consequently repels the silk threads which are endowed with the
same quality. With a little reflection we may in the same manner
account for most of the other phenomena, and which seem
inexplicable without attending to this principle.

"Chance has thrown in my way another principle, more universal
and remarkable than the preceding one, and which throws a new
light on the subject of electricity. This principle is that there
are two distinct electricities, very different from each other,
one of which I call vitreous electricity and the other resinous
electricity. The first is that of glass, rock-crystal, precious
stones, hair of animals, wool, and many other bodies. The second
is that of amber, copal, gumsack, silk thread, paper, and a
number of other substances. The characteristic of these two
electricities is that a body of the vitreous electricity, for
example, repels all such as are of the same electricity, and on
the contrary attracts all those of the resinous electricity; so
that the tube, made electrical, will repel glass, crystal, hair
of animals, etc., when rendered electric, and will attract silk
thread, paper, etc., though rendered electrical likewise. Amber,
on the contrary, will attract electric glass and other substances
of the same class, and will repel gum-sack, copal, silk thread,
etc. Two silk ribbons rendered electrical will repel each other;
two woollen threads will do the like; but a woollen thread and a
silken thread will mutually attract each other. This principle
very naturally explains why the ends of threads of silk or wool
recede from each other, in the form of pencil or broom, when they
have acquired an electric quality. From this principle one may
with the same ease deduce the explanation of a great number of
other phenomena; and it is probable that this truth will lead us
to the further discovery of many other things.

"In order to know immediately to which of the two classes of
electrics belongs any body whatsoever, one need only render
electric a silk thread, which is known to be of the resinuous
electricity, and see whether that body, rendered electrical,
attracts or repels it. If it attracts it, it is certainly of the
kind of electricity which I call VITREOUS; if, on the contrary,
it repels it, it is of the same kind of electricity with the
silk--that is, of the RESINOUS. I have likewise observed that
communicated electricity retains the same properties; for if a
ball of ivory or wood be set on a glass stand, and this ball be
rendered electric by the tube, it will repel such substances as
the tube repels; but if it be rendered electric by applying a
cylinder of gum-sack near it, it will produce quite contrary
effects--namely, precisely the same as gum-sack would produce. In
order to succeed in these experiments, it is requisite that the
two bodies which are put near each other, to find out the nature
of their electricity, be rendered as electrical as possible, for
if one of them was not at all or but weakly electrical, it would
be attracted by the other, though it be of that sort that should
naturally be repelled by it. But the experiment will always
succeed perfectly well if both bodies are sufficiently
electrical."[1]

As we now know, Dufay was wrong in supposing that there were two
different kinds of electricity, vitreous and resinous. A little
later the matter was explained by calling one "positive"
electricity and the other "negative," and it was believed that
certain substances produced only the one kind peculiar to that
particular substance. We shall see presently, however, that some
twenty years later an English scientist dispelled this illusion
by producing both positive (or vitreous) and negative (or
resinous) electricity on the same tube of glass at the same time.

After the death of Dufay his work was continued by his
fellow-countryman Dr. Joseph Desaguliers, who was the first
experimenter to electrify running water, and who was probably the
first to suggest that clouds might be electrified bodies. But
about, this time--that is, just before the middle of the
eighteenth century--the field of greatest experimental activity
was transferred to Germany, although both England and France were
still active. The two German philosophers who accomplished most
at this time were Christian August Hansen and George Matthias
Bose, both professors in Leipsic. Both seem to have conceived the
idea, simultaneously and independently, of generating electricity
by revolving globes run by belt and wheel in much the same manner
as the apparatus of Hauksbee.

With such machines it was possible to generate a much greater
amount of electricity than Dufay had been able to do with the
rubbed tube, and so equipped, the two German professors were able
to generate electric sparks and jets of fire in a most startling
manner. Bose in particular had a love for the spectacular, which
he turned to account with his new electrical machine upon many
occasions. On one of these occasions he prepared an elaborate
dinner, to which a large number of distinguished guests were
invited. Before the arrival of the company, however, Bose
insulated the great banquet-table on cakes of pitch, and then
connected it with a huge electrical machine concealed in another
room. All being ready, and the guests in their places about to be
seated, Bose gave a secret signal for starting this machine,
when, to the astonishment of the party, flames of fire shot from
flowers, dishes, and viands, giving a most startling but
beautiful display.

To add still further to the astonishment of his guests, Bose then
presented a beautiful young lady, to whom each of the young men
of the party was introduced. In some mysterious manner she was
insulated and connected with the concealed electrical machine, so
that as each gallant touched her fingertips he received an
electric shock that "made him reel." Not content with this, the
host invited the young men to kiss the beautiful maid. But those
who were bold enough to attempt it received an electric shock
that nearly "knocked their teeth out," as the professor tells it.


LUDOLFF'S EXPERIMENT WITH THE ELECTRIC SPARK

But Bose was only one of several German scientists who were
making elaborate experiments. While Bose was constructing and
experimenting with his huge machine, another German, Christian
Friedrich Ludolff, demonstrated that electric sparks are actual
fire--a fact long suspected but hitherto unproved. Ludolff's
discovery, as it chanced, was made in the lecture-hall of the
reorganized Academy of Sciences at Berlin, before an audience of
scientists and great personages, at the opening lecture in 1744.

In the course of this lecture on electricity, during which some
of the well-known manifestations of electricity were being shown,
it occurred to Ludolff to attempt to ignite some inflammable
fluid by projecting an electric spark upon its surface with a
glass rod. This idea was suggested to him while performing the
familiar experiment of producing a spark on the surface of a bowl
of water by touching it with a charged glass rod. He announced to
his audience the experiment he was about to attempt, and having
warmed a spoonful of sulphuric ether, he touched its surface with
the glass rod, causing it to burst into flame. This experiment
left no room for doubt that the electric spark was actual fire.

As soon as this experiment of Ludolff's was made known to Bose,
he immediately claimed that he had previously made similar
demonstrations on various inflammable substances, both liquid and
solid; and it seems highly probable that he had done so, as he
was constantly experimenting with the sparks, and must almost
certainly have set certain substances ablaze by accident, if not
by intent. At all events, he carried on a series of experiments
along this line to good purpose, finally succeeding in exploding
gun-powder, and so making the first forerunner of the electric
fuses now so universally used in blasting, firing cannon, and
other similar purposes. It was Bose also who, observing some of
the peculiar manifestations in electrified tubes, and noticing
their resemblance to "northern lights," was one of the first, if
not the first, to suggest that the aurora borealis is of electric
origin.

These spectacular demonstrations had the effect of calling public
attention to the fact that electricity is a most wonderful and
mysterious thing, to say the least, and kept both scientists and
laymen agog with expectancy. Bose himself was aflame with
excitement, and so determined in his efforts to produce still
stronger electric currents, that he sacrificed the tube of his
twenty-foot telescope for the construction of a mammoth
electrical machine. With this great machine a discharge of
electricity was generated powerful enough to wound the skin when
it happened to strike it.

Until this time electricity had been little more than a plaything
of the scientists--or, at least, no practical use had been made
of it. As it was a practising physician, Gilbert, who first laid
the foundation for experimenting with the new substance, so again
it was a medical man who first attempted to put it to practical
use, and that in the field of his profession. Gottlieb Kruger, a
professor of medicine at Halle in 1743, suggested that
electricity might be of use in some branches of medicine; and the
year following Christian Gottlieb Kratzenstein made a first
experiment to determine the effects of electricity upon the body.
He found that "the action of the heart was accelerated, the
circulation increased, and that muscles were made to contract by
the discharge": and he began at once administering electricity in
the treatment of certain diseases. He found that it acted
beneficially in rheumatic affections, and that it was
particularly useful in certain nervous diseases, such as palsies.
This was over a century ago, and to-day about the most important
use made of the particular kind of electricity with which he
experimented (the static, or frictional) is for the treatment of
diseases affecting the nervous system.

By the middle of the century a perfect mania for making
electrical machines had spread over Europe, and the whirling,
hand-rubbed globes were gradually replaced by great cylinders
rubbed by woollen cloths or pads, and generating an "enormous
power of electricity." These cylinders were run by belts and
foot-treadles, and gave a more powerful, constant, and
satisfactory current than known heretofore. While making
experiments with one of these machines, Johann Heinrichs Winkler
attempted to measure the speed at which electricity travels. To
do this he extended a cord suspended on silk threads, with the
end attached to the machine and the end which was to attract the
bits of gold-leaf near enough together so that the operator could
watch and measure the interval of time that elapsed between the
starting of the current along the cord and its attracting the
gold-leaf. The length of the cord used in this experiment was
only a little over a hundred feet, and this was, of course,
entirely inadequate, the current travelling that space apparently
instantaneously.

The improved method of generating electricity that had come into
general use made several of the scientists again turn their
attention more particularly to attempt putting it to some
practical account. They were stimulated to these efforts by the
constant reproaches that were beginning to be heard on all sides
that electricity was merely a "philosopher's plaything." One of
the first to succeed in inventing something that approached a
practical mechanical contrivance was Andrew Gordon, a Scotch
Benedictine monk. He invented an electric bell which would ring
automatically, and a little "motor," if it may be so called. And
while neither of these inventions were of any practical
importance in themselves, they were attempts in the right
direction, and were the first ancestors of modern electric bells
and motors, although the principle upon which they worked was
entirely different from modern electrical machines. The motor was
simply a wheel with several protruding metal points around its
rim. These points were arranged to receive an electrical
discharge from a frictional machine, the discharge causing the
wheel to rotate. There was very little force given to this
rotation, however, not enough, in fact, to make it possible to
more than barely turn the wheel itself. Two more great
discoveries, galvanism and electro-magnetic induction, were
necessary before the practical motor became possible.

The sober Gordon had a taste for the spectacular almost equal to
that of Bose. It was he who ignited a bowl of alcohol by turning
a stream of electrified water upon it, thus presenting the
seeming paradox of fire produced by a stream of water. Gordon
also demonstrated the power of the electrical discharge by
killing small birds and animals at a distance of two hundred
ells, the electricity being conveyed that distance through small
wires.


THE LEYDEN JAR DISCOVERED

As yet no one had discovered that electricity could be stored, or
generated in any way other than by some friction device. But very
soon two experimenters, Dean von Kleist, of Camin, Pomerania, and
Pieter van Musschenbroek, the famous teacher of Leyden,
apparently independently, made the discovery of what has been
known ever since as the Leyden jar. And although Musschenbroek is
sometimes credited with being the discoverer, there can be no
doubt that Von Kleist's discovery antedated his by a few months
at least.

Von Kleist found that by a device made of a narrow-necked bottle
containing alcohol or mercury, into which an iron nail was
inserted, be was able to retain the charge of electricity, after
electrifying this apparatus with the frictional machine. He made
also a similar device, more closely resembling the modern Leyden
jar, from a thermometer tube partly filled with water and a wire
tipped with a ball of lead. With these devices he found that he
could retain the charge of electricity for several hours, and
could produce the usual electrical manifestations, even to
igniting spirits, quite as well as with the frictional machine.
These experiments were first made in October, 1745, and after a
month of further experimenting, Von Kleist sent the following
account of them to several of the leading scientists, among
others, Dr. Lieberkuhn, in Berlin, and Dr. Kruger, of Halle.

"When a nail, or a piece of thick brass wire, is put into a small
apothecary's phial and electrified, remarkable effects follow;
but the phial must be very dry, or warm. I commonly rub it over
beforehand with a finger on which I put some pounded chalk. If a
little mercury or a few drops of spirit of wine be put into it,
the experiment succeeds better. As soon as this phial and nail
are removed from the electrifying-glass, or the prime conductor,
to which it has been exposed, is taken away, it throws out a
pencil of flame so long that, with this burning machine in my
hand, I have taken above sixty steps in walking about my room.
When it is electrified strongly, I can take it into another room
and there fire spirits of wine with it. If while it is
electrifying I put my finger, or a piece of gold which I hold in
my hand, to the nail, I receive a shock which stuns my arms and
shoulders.

"A tin tube, or a man, placed upon electrics, is electrified much
stronger by this means than in the common way. When I present
this phial and nail to a tin tube, which I have, fifteen feet
long, nothing but experience can make a person believe how
strongly it is electrified. I am persuaded," he adds, "that in
this manner Mr. Bose would not have taken a second electrical
kiss. Two thin glasses have been broken by the shock of it. It
appears to me very extraordinary, that when this phial and nail
are in contact with either conducting or non-conducting matter,
the strong shock does not follow. I have cemented it to wood,
metal, glass, sealing-wax, etc., when I have electrified without
any great effect. The human body, therefore, must contribute
something to it. This opinion is confirmed by my observing that
unless I hold the phial in my hand I cannot fire spirits of wine
with it."[2]

But it seems that none of the men who saw this account were able
to repeat the experiment and produce the effects claimed by Von
Kleist, and probably for this reason the discovery of the obscure
Pomeranian was for a time lost sight of.

Musschenbroek's discovery was made within a short time after Von
Kleist's--in fact, only a matter of about two months later. But
the difference in the reputations of the two discoverers insured
a very different reception for their discoveries. Musschenbroek
was one of the foremost teachers of Europe, and so widely known
that the great universities vied with each other, and kings were
bidding, for his services. Naturally, any discovery made by such
a famous person would soon be heralded from one end of Europe to
the other. And so when this professor of Leyden made his
discovery, the apparatus came to be called the "Leyden jar," for
want of a better name. There can be little doubt that
Musschenbroek made his discovery entirely independently of any
knowledge of Von Kleist's, or, for that matter, without ever
having heard of the Pomeranian, and his actions in the matter are
entirely honorable.

His discovery was the result of an accident. While experimenting
to determine the strength of electricity he suspended a
gun-barrel, which he charged with electricity from a revolving
glass globe. From the end of the gun-barrel opposite the globe
was a brass wire, which extended into a glass jar partly filled
with water. Musschenbroek held in one hand this jar, while with
the other he attempted to draw sparks from the barrel. Suddenly
he received a shock in the hand holding the jar, that "shook him
like a stroke of lightning," and for a moment made him believe
that "he was done for." Continuing his experiments, nevertheless,
he found that if the jar were placed on a piece of metal on the
table, a shock would be received by touching this piece of metal
with one hand and touching the wire with the other--that is, a
path was made for the electrical discharge through the body. This
was practically the same experiment as made by Von Kleist with
his bottle and nail, but carried one step farther, as it showed
that the "jar" need not necessarily be held in the hand, as
believed by Von Kleist. Further experiments, continued by many
philosophers at the time, revealed what Von Kleist had already
pointed out, that the electrified jar remained charged for some
time.

Soon after this Daniel Gralath, wishing to obtain stronger
discharges than could be had from a single Leyden jar, conceived
the idea of combining several jars, thus for the first time
grouping the generators in a "battery" which produced a discharge
strong enough to kill birds and small animals. He also attempted
to measure the strength of the discharges, but soon gave it up in
despair, and the solution of this problem was left for late
nineteenth-century scientists.

The advent of the Leyden jar, which made it possible to produce
strong electrical discharges from a small and comparatively
simple device, was followed by more spectacular demonstrations of
various kinds all over Europe. These exhibitions aroused the
interest of the kings and noblemen, so that electricity no longer
remained a "plaything of the philosophers" alone, but of kings as
well. A favorite demonstration was that of sending the electrical
discharge through long lines of soldiers linked together by
pieces of wire, the discharge causing them to "spring into the
air simultaneously" in a most astonishing manner. A certain monk
in Paris prepared a most elaborate series of demonstrations for
the amusement of the king, among other things linking together an
entire regiment of nine hundred men, causing them to perform
simultaneous springs and contortions in a manner most amusing to
the royal guests. But not all the experiments being made were of
a purely spectacular character, although most of them
accomplished little except in a negative way. The famous Abbe
Nollet, for example, combined useful experiments with spectacular
demonstrations, thus keeping up popular interest while aiding the
cause of scientific electricity.


WILLIAM WATSON

Naturally, the new discoveries made necessary a new nomenclature,
new words and electrical terms being constantly employed by the
various writers of that day. Among these writers was the English
scientist William Watson, who was not only a most prolific writer
but a tireless investigator. Many of the words coined by him are
now obsolete, but one at least, "circuit," still remains in use.

In 1746, a French scientist, Louis Guillaume le Monnier, bad made
a circuit including metal and water by laying a chain half-way
around the edge of a pond, a man at either end holding it. One of
these men dipped his free hand in the water, the other presenting
a Leyden jar to a rod suspended on a cork float on the water,
both men receiving a shock simultaneously. Watson, a year later,
attempted the same experiment on a larger scale. He laid a wire
about twelve hundred feet long across Westminster Bridge over the
Thames, bringing the ends to the water's edge on the opposite
banks, a man at one end holding the wire and touching the water.
A second man on the opposite side held the wire and a Leyden jar;
and a third touched the jar with one hand, while with the other
he grasped a wire that extended into the river. In this way they
not only received the shock, but fired alcohol as readily across
the stream as could be done in the laboratory. In this experiment
Watson discovered the superiority of wire over chain as a
conductor, rightly ascribing this superiority to the continuity
of the metal.

Watson continued making similar experiments over longer
watercourses, some of them as long as eight thousand feet, and
while engaged in making one of these he made the discovery so
essential to later inventions, that the earth could be used as
part of the circuit in the same manner as bodies of water.
Lengthening his wires he continued his experiments until a
circuit of four miles was made, and still the electricity seemed
to traverse the course instantaneously, and with apparently
undiminished force, if the insulation was perfect.


BENJAMIN FRANKLIN

Watson's writings now carried the field of active discovery
across the Atlantic, and for the first time an American scientist
appeared--a scientist who not only rivalled, but excelled, his
European contemporaries. Benjamin Franklin, of Philadelphia,
coming into possession of some of Watson's books, became so
interested in the experiments described in them that he began at
once experimenting with electricity. In Watson's book were given
directions for making various experiments, and these assisted
Franklin in repeating the old experiments, and eventually adding
new ones. Associated with Franklin, and equally interested and
enthusiastic, if not equally successful in making discoveries,
were three other men, Thomas Hopkinson, Philip Sing, and Ebenezer
Kinnersley. These men worked together constantly, although it
appears to have been Franklin who made independently the
important discoveries, and formulated the famous Franklinian
theory.

Working steadily, and keeping constantly in touch with the
progress of the European investigators, Franklin soon made some
experiments which he thought demonstrated some hitherto unknown
phases of electrical manifestation. This was the effect of
pointed bodies "in DRAWING OFF and THROWING OFF the electrical
fire." In his description of this phenomenon, Franklin writes:

"Place an iron shot of three or four inches diameter on the mouth
of a clean, dry, glass bottle. By a fine silken thread from the
ceiling right over the mouth of the bottle, suspend a small cork
ball, about the bigness of a marble; the thread of such a length
that the cork ball may rest against the side of the shot.
Electrify the shot, and the ball will be repelled to the distance
of four or five inches, more or less, according to the quantity
of electricity. When in this state, if you present to the shot
the point of a long, slender shaft-bodkin, at six or eight inches
distance, the repellency is instantly destroyed, and the cork
flies to the shot. A blunt body must be brought within an inch,
and draw a spark, to produce the same effect.

"To prove that the electrical fire is DRAWN OFF by the point, if
you take the blade of the bodkin out of the wooden handle and fix
it in a stick of sealing-wax, and then present it at the distance
aforesaid, or if you bring it very near, no such effect follows;
but sliding one finger along the wax till you touch the blade,
and the ball flies to the shot immediately. If you present the
point in the dark you will see, sometimes at a foot distance, and
more, a light gather upon it like that of a fire-fly or
glow-worm; the less sharp the point, the nearer you must bring it
to observe the light; and at whatever distance you see the light,
you may draw off the electrical fire and destroy the repellency.
If a cork ball so suspended be repelled by the tube, and a point
be presented quick to it, though at a considerable distance, 'tis
surprising to see how suddenly it flies back to the tube. Points
of wood will do as well as those of iron, provided the wood is
not dry; for perfectly dry wood will no more conduct electricity
than sealing-wax.

"To show that points will THROW OFF as well as DRAW OFF the
electrical fire, lay a long, sharp needle upon the shot, and you
cannot electrify the shot so as to make it repel the cork ball.
Or fix a needle to the end of a suspended gun-barrel or iron rod,
so as to point beyond it like a little bayonet, and while it
remains there, the gun-barrel or rod cannot, by applying the tube
to the other end, be electrified so as to give a spark, the fire
continually running out silently at the point. In the dark you
may see it make the same appearance as it does in the case before
mentioned."[3]

Von Guericke, Hauksbee, and Gray had noticed that pointed bodies
attracted electricity in a peculiar manner, but this
demonstration of the "drawing off" of "electrical fire" was
original with Franklin. Original also was the theory that he now
suggested, which had at least the merit of being thinkable even
by non-philosophical minds. It assumes that electricity is like a
fluid, that will flow along conductors and accumulate in proper
receptacles, very much as ordinary fluids do. This conception is
probably entirely incorrect, but nevertheless it is likely to
remain a popular one, at least outside of scientific circles, or
until something equally tangible is substituted.


FRANKLIN'S THEORY OF ELECTRICITY

According to Franklin's theory, electricity exists in all bodies
as a "common stock," and tends to seek and remain in a state of
equilibrium, just as fluids naturally tend to seek a level. But
it may, nevertheless, be raised or lowered, and this equilibrium
be thus disturbed. If a body has more electricity than its normal
amount it is said to be POSITIVELY electrified; but if it has
less, it is NEGATIVELY electrified. An over-electrified or "plus"
body tends to give its surplus stock to a body containing the
normal amount; while the "minus" or under-electrified body will
draw electricity from one containing the normal amount.

Working along lines suggested by this theory, Franklin attempted
to show that electricity is not created by friction, but simply
collected from its diversified state, the rubbed glass globe
attracting a certain quantity of "electrical fire," but ever
ready to give it up to any body that has less. He explained the
charged Leyden jar by showing that the inner coating of tin-foil
received more than the ordinary quantity of electricity, and in
consequence is POSITIVELY electrified, while the outer coating,
having the ordinary quantity of electricity diminished, is
electrified NEGATIVELY.

These studies of the Leyden jar, and the studies of pieces of
glass coated with sheet metal, led Franklin to invent his
battery, constructed of eleven large glass plates coated with
sheets of lead. With this machine, after overcoming some defects,
he was able to produce electrical manifestations of great
force--a force that "knew no bounds," as he declared ("except in
the matter of expense and of labor"), and which could be made to
exceed "the greatest know effects of common lightning."

This reference to lightning would seem to show Franklin's belief,
even at that time, that lightning is electricity. Many eminent
observers, such as Hauksbee, Wall, Gray, and Nollet, had noticed
the resemblance between electric sparks and lightning, but none
of these had more than surmised that the two might be identical.
In 1746, the surgeon, John Freke, also asserted his belief in
this identity. Winkler, shortly after this time, expressed the
same belief, and, assuming that they were the same, declared that
"there is no proof that they are of different natures"; and still
he did not prove that they were the same nature.


FRANKLIN INVENTS THE LIGHTNING-ROD

Even before Franklin proved conclusively the nature of lightning,
his experiments in drawing off the electric charge with points
led to some practical suggestions which resulted in the invention
of the lightning-rod. In the letter of July, 1750, which he wrote
on the subject, he gave careful instructions as to the way in
which these rods might be constructed. In part Franklin wrote:
"May not the knowledge of this power of points be of use to
mankind in preserving houses, churches, ships, etc., from the
stroke of lightning by directing us to fix on the highest parts
of the edifices upright rods of iron made sharp as a needle, and
gilt to prevent rusting, and from the foot of these rods a wire
down the outside of the building into the grounds, or down round
one of the shrouds of a ship and down her side till it reaches
the water? Would not these pointed rods probably draw the
electrical fire silently out of a cloud before it came nigh
enough to strike, and thereby secure us from that most sudden and
terrible mischief?

"To determine this question, whether the clouds that contain the
lightning are electrified or not, I propose an experiment to be
tried where it may be done conveniently. On the top of some high
tower or steeple, place a kind of sentry-box, big enough to
contain a man and an electrical stand. From the middle of the
stand let an iron rod rise and pass, bending out of the door, and
then upright twenty or thirty feet, pointed very sharp at the
end. If the electrical stand be kept clean and dry, a man
standing on it when such clouds are passing low might be
electrified and afford sparks, the rod drawing fire to him from a
cloud. If any danger to the man be apprehended (though I think
there would be none), let him stand on the floor of his box and
now and then bring near to the rod the loop of a wire that has
one end fastened to the leads, he holding it by a wax handle; so
the sparks, if the rod is electrified, will strike from the rod
to the wire and not effect him."[4]

Not satisfied with all the evidence that he had collected
pointing to the identity of lightning and electricity, he adds
one more striking and very suggestive piece of evidence.
Lightning was known sometimes to strike persons blind without
killing them. In experimenting on pigeons and pullets with his
electrical machine, Franklin found that a fowl, when not killed
outright, was sometimes rendered blind. The report of these
experiments were incorporated in this famous letter of the
Philadelphia philosopher.

The attitude of the Royal Society towards this clearly stated
letter, with its useful suggestions, must always remain as a blot
on the record of this usually very receptive and liberal-minded
body. Far from publishing it or receiving it at all, they derided
the whole matter as too visionary for discussion by the society.
How was it possible that any great scientific discovery could be
made by a self-educated colonial newspaper editor, who knew
nothing of European science except by hearsay, when all the great
scientific minds of Europe had failed to make the discovery? How
indeed! And yet it would seem that if any of the influential
members of the learned society had taken the trouble to read over
Franklin's clearly stated letter, they could hardly have failed
to see that his suggestions were worthy of consideration. But at
all events, whether they did or did not matters little. The fact
remains that they refused to consider the paper seriously at the
time; and later on, when its true value became known, were
obliged to acknowledge their error by a tardy report on the
already well-known document.

But if English scientists were cold in their reception of
Franklin's theory and suggestions, the French scientists were
not. Buffon, perceiving at once the importance of some of
Franklin's experiments, took steps to have the famous letter
translated into French, and soon not only the savants, but
members of the court and the king himself were intensely
interested. Two scientists, De Lor and D'Alibard, undertook to
test the truth of Franklin's suggestions as to pointed rods
"drawing off lightning." In a garden near Paris, the latter
erected a pointed iron rod fifty feet high and an inch in
diameter. As no thunder-clouds appeared for several days, a guard
was stationed, armed with an insulated brass wire, who was
directed to test the iron rods with it in case a storm came on
during D'Alibard's absence. The storm did come on, and the guard,
not waiting for his employer's arrival, seized the wire and
touched the rod. Instantly there was a report. Sparks flew and
the guard received such a shock that he thought his time had
come. Believing from his outcry that he was mortally hurt, his
friends rushed for a spiritual adviser, who came running through
rain and hail to administer the last rites; but when he found the
guard still alive and uninjured, he turned his visit to account
by testing the rod himself several times, and later writing a
report of his experiments to M. d'Alibard. This scientist at once
reported the affair to the French Academy, remarking that
"Franklin's idea was no longer a conjecture, but a reality."


FRANKLIN PROVES THAT LIGHTNING IS ELECTRICITY

Europe, hitherto somewhat sceptical of Franklin's views, was by
this time convinced of the identity of lightning and electricity.
It was now Franklin's turn to be sceptical. To him the fact that
a rod, one hundred feet high, became electrified during a storm
did not necessarily prove that the storm-clouds were electrified.
A rod of that length was not really projected into the cloud, for
even a very low thunder-cloud was more than a hundred feet above
the ground. Irrefutable proof could only be had, as he saw it, by
"extracting" the lightning with something actually sent up into
the storm-cloud; and to accomplish this Franklin made his silk
kite, with which he finally demonstrated to his own and the
world's satisfaction that his theory was correct.

Taking his kite out into an open common on the approach of a
thunder-storm, he flew it well up into the threatening clouds,
and then, touching, the suspended key with his knuckle, received
the electric spark; and a little later he charged a Leyden jar
from the electricity drawn from the clouds with his kite.

In a brief but direct letter, he sent an account of his kite and
his experiment to England:

"Make a small cross of two light strips of cedar," he wrote, "the
arms so long as to reach to the four corners of a large, thin,
silk handkerchief when extended; tie the corners of the
handkerchief to the extremities of the cross so you have the body
of a kite; which being properly accommodated with a tail, loop,
and string, will rise in the air like those made of paper; but
this being of silk is fitter to bear the wind and wet of a
thunder-gust without tearing. To the top of the upright stick of
the cross is to be fixed a very sharp-pointed wire, rising a foot
or more above the wood. To the end of the twine, next the hand,
is to be tied a silk ribbon; where the silk and twine join a key
may be fastened. This kite is to be raised when a thunder-gust
appears to be coming on, and the person who holds the string must
stand within a door or window or under some cover, so that the
silk ribbon may not be wet; and care must be taken that the twine
does not touch the frame of the door or window. As soon as any of
the thunder-clouds come over the kite, the pointed wire will draw
the electric fire from them, and the kite, with all the twine,
will be electrified and the loose filaments will stand out
everywhere and be attracted by the approaching finger, and when
the rain has wet the kite and twine so that it can conduct the
electric fire freely, you will find it stream out plentifully
from the key on the approach of your knuckle, and with this key
the phial may be charged; and from electric fire thus obtained
spirits may be kindled and all other electric experiments
performed which are usually done by the help of a rubbed glass
globe or tube, and thereby the sameness of the electric matter
with that of lightning completely demonstrated."[5]

In experimenting with lightning and Franklin's pointed rods in
Europe, several scientists received severe shocks, in one case
with a fatal result. Professor Richman, of St. Petersburg, while
experimenting during a thunder-storm, with an iron rod which he
had erected on his house, received a shock that killed him
instantly.

About 1733, as we have seen, Dufay had demonstrated that there
were two apparently different kinds of electricity; one called
VITREOUS because produced by rubbing glass, and the other
RESINOUS because produced by rubbed resinous bodies. Dufay
supposed that these two apparently different electricities could
only be produced by their respective substances; but twenty years
later, John Canton (1715-1772), an Englishman, demonstrated that
under certain conditions both might be produced by rubbing the
same substance. Canton's experiment, made upon a glass tube with
a roughened surface, proved that if the surface of the tube were
rubbed with oiled silk, vitreous or positive electricity was
produced, but if rubbed with flannel, resinous electricity was
produced. He discovered still further that both kinds could be
excited on the same tube simultaneously with a single rubber. To
demonstrate this he used a tube, one-half of which had a
roughened the other a glazed surface. With a single stroke of the
rubber he was able to excite both kinds of electricity on this
tube. He found also that certain substances, such as glass and
amber, were electrified positively when taken out of mercury, and
this led to his important discovery that an amalgam of mercury
and tin, when used on the surface of the rubber, was very
effective in exciting glass.



XV. NATURAL HISTORY TO THE TIME OF LINNAeUS

Modern systematic botany and zoology are usually held to have
their beginnings with Linnaeus. But there were certain precursors
of the famous Swedish naturalist, some of them antedating him by
more than a century, whose work must not be altogether
ignored--such men as Konrad Gesner (1516-1565), Andreas
Caesalpinus (1579-1603), Francisco Redi (1618-1676), Giovanni
Alfonso Borelli (1608-1679), John Ray (1628-1705), Robert Hooke
(1635-1703), John Swammerdam (1637-1680), Marcello Malpighi
(1628-1694), Nehemiah Grew (1628-1711), Joseph Tournefort
(1656-1708), Rudolf Jacob Camerarius (1665-1721), and Stephen
Hales (1677-1761). The last named of these was, to be sure, a
contemporary of Linnaeus himself, but Gesner and Caesalpinus
belong, it will be observed, to so remote an epoch as that of
Copernicus.

Reference has been made in an earlier chapter to the microscopic
investigations of Marcello Malpighi, who, as there related, was
the first observer who actually saw blood corpuscles pass through
the capillaries. Another feat of this earliest of great
microscopists was to dissect muscular tissue, and thus become the
father of microscopic anatomy. But Malpighi did not confine his
observations to animal tissues. He dissected plants as well, and
he is almost as fully entitled to be called the father of
vegetable anatomy, though here his honors are shared by the
Englishman Grew. In 1681, while Malpighi's work, Anatomia
plantarum, was on its way to the Royal Society for publication,
Grew's Anatomy of Vegetables was in the hands of the publishers,
making its appearance a few months earlier than the work of the
great Italian. Grew's book was epoch-marking in pointing out the
sex-differences in plants.

Robert Hooke developed the microscope, and took the first steps
towards studying vegetable anatomy, publishing in 1667, among
other results, the discovery of the cellular structure of cork.
Hooke applied the name "cell" for the first time in this
connection. These discoveries of Hooke, Malpighi, and Grew, and
the discovery of the circulation of the blood by William Harvey
shortly before, had called attention to the similarity of animal
and vegetable structures. Hales made a series of investigations
upon animals to determine the force of the blood pressure; and
similarly he made numerous statical experiments to determine the
pressure of the flow of sap in vegetables. His Vegetable Statics,
published in 1727, was the first important work on the subject of
vegetable physiology, and for this reason Hales has been called
the father of this branch of science.

In botany, as well as in zoology, the classifications of Linnaeus
of course supplanted all preceding classifications, for the
obvious reason that they were much more satisfactory; but his
work was a culmination of many similar and more or less
satisfactory attempts of his predecessors. About the year 1670
Dr. Robert Morison (1620-1683), of Aberdeen, published a
classification of plants, his system taking into account the
woody or herbaceous structure, as well as the flowers and fruit.
This classification was supplanted twelve years later by the
classification of Ray, who arranged all known vegetables into
thirty-three classes, the basis of this classification being the
fruit. A few years later Rivinus, a professor of botany in the
University of Leipzig, made still another classification,
determining the distinguishing character chiefly from the flower,
and Camerarius and Tournefort also made elaborate
classifications. On the Continent Tournefort's classification was
the most popular until the time of Linnaeus, his systematic
arrangement including about eight thousand species of plants,
arranged chiefly according to the form of the corolla.

Most of these early workers gave attention to both vegetable and
animal kingdoms. They were called naturalists, and the field of
their investigations was spoken of as "natural history." The
specialization of knowledge had not reached that later stage in
which botanist, zoologist, and physiologist felt their labors to
be sharply divided. Such a division was becoming more and more
necessary as the field of knowledge extended; but it did not
become imperative until long after the time of Linnaeus. That
naturalist himself, as we shall see, was equally distinguished as
botanist and as zoologist. His great task of organizing knowledge
was applied to the entire range of living things.

Carolus Linnaeus was born in the town of Rashult, in Sweden, on
May 13, 1707. As a child he showed great aptitude in learning
botanical names, and remembering facts about various plants as
told him by his father. His eagerness for knowledge did not
extend to the ordinary primary studies, however, and, aside from
the single exception of the study of physiology, he proved
himself an indifferent pupil. His backwardness was a sore trial
to his father, who was desirous that his son should enter the
ministry; but as the young Linnaeus showed no liking for that
calling, and as he had acquitted himself well in his study of
physiology, his father at last decided to allow him to take up
the study of medicine. Here at last was a field more to the
liking of the boy, who soon vied with the best of his
fellow-students for first honors. Meanwhile he kept steadily at
work in his study of natural history, acquiring considerable
knowledge of ornithology, entomology, and botany, and adding
continually to his collection of botanical specimens. In 1729 his
botanical knowledge was brought to the attention of Olaf Rudbeck,
professor of botany in the University of Upsala, by a short paper
on the sexes of plants which Linnaeus had prepared. Rudbeck was
so impressed by some of the ideas expressed in this paper that he
appointed the author as his assistant the following year.

This was the beginning of Linnaes's career as a botanist. The
academic gardens were thus thrown open to him, and he found time
at his disposal for pursuing his studies between lecture hours
and in the evenings. It was at this time that he began the
preparation of his work the Systema naturae, the first of his
great works, containing a comprehensive sketch of the whole field
of natural history. When this work was published, the clearness
of the views expressed and the systematic arrangement of the
various classifications excited great astonishment and
admiration, and placed Linaeus at once in the foremost rank of
naturalists. This work was followed shortly by other
publications, mostly on botanical subjects, in which, among other
things, he worked out in detail his famous "system."

This system is founded on the sexes of plants, and is usually
referred to as an "artificial method" of classification because
it takes into account only a few marked characters of plants,
without uniting them by more general natural affinities. At the
present time it is considered only as a stepping-stone to the
"natural" system; but at the time of its promulgation it was
epoch-marking in its directness and simplicity, and therefore
superiority, over any existing systems.

One of the great reforms effected by Linnaeus was in the matter
of scientific terminology. Technical terms are absolutely
necessary to scientific progress, and particularly so in botany,
where obscurity, ambiguity, or prolixity in descriptions are
fatally misleading. Linnaeus's work contains something like a
thousand terms, whose meanings and uses are carefully explained.
Such an array seems at first glance arbitrary and unnecessary,
but the fact that it has remained in use for something like two
centuries is indisputable evidence of its practicality. The
descriptive language of botany, as employed by Linnaeus, still
stands as a model for all other subjects.

Closely allied to botanical terminology is the subject of
botanical nomenclature. The old method of using a number of Latin
words to describe each different plant is obviously too
cumbersome, and several attempts had been made prior to the time
of Linnaeus to substitute simpler methods. Linnaeus himself made
several unsatisfactory attempts before he finally hit upon his
system of "trivial names," which was developed in his Species
plantarum, and which, with some, minor alterations, remains in
use to this day. The essence of the system is the introduction of
binomial nomenclature--that is to say, the use of two names and
no more to designate any single species of animal or plant. The
principle is quite the same as that according to which in modern
society a man has two names, let us say, John Doe, the one
designating his family, the other being individual. Similarly
each species of animal or plant, according to the Linnaeean
system, received a specific or "trivial" name; while various
species, associated according to their seeming natural affinities
into groups called genera, were given the same generic name. Thus
the generic name given all members of the cat tribe being Felis,
the name Felis leo designates the lion; Felis pardus, the
leopard; Felis domestica, the house cat, and so on. This seems
perfectly simple and natural now, but to understand how great a
reform the binomial nomenclature introduced we have but to
consult the work of Linnaeus's predecessors. A single
illustration will suffice. There is, for example, a kind of
grass, in referring to which the naturalist anterior to Linnaeus,
if he would be absolutely unambiguous, was obliged to use the
following descriptive formula: Gramen Xerampelino, Miliacea,
praetenuis ramosaque sparsa panicula, sive Xerampelino congener,
arvense, aestivum; gramen minutissimo semine. Linnaeus gave to
this plant the name Poa bulbosa--a name that sufficed, according
to the new system, to distinguish this from every other species
of vegetable. It does not require any special knowledge to
appreciate the advantage of such a simplification.

While visiting Paris in 1738 Linnaeus met and botanized with the
two botanists whose "natural method" of classification was later
to supplant his own "artificial system." These were Bernard and
Antoine Laurent de Jussieu. The efforts of these two scientists
were directed towards obtaining a system which should aim at
clearness, simplicity, and precision, and at the same time be
governed by the natural affinities of plants. The natural system,
as finally propounded by them, is based on the number of
cotyledons, the structure of the seed, and the insertion of the
stamens. Succeeding writers on botany have made various
modifications of this system, but nevertheless it stands as the
foundation-stone of modern botanical classification.



APPENDIX

REFERENCE LIST

CHAPTER I

SCIENCE IN THE DARK AGE

[1] (p. 4). James Harvey Robinson, An Introduction to the History
of Western Europe, New York, 1898, p. 330.

[2] (p. 6). Henry Smith Williams, A Prefatory Characterization of
The History of Italy, in vol. IX. of The Historians' History of
the World, 25 vols., London and New York, 1904.


CHAPTER III

MEDIAeVAL SCIENCE IN THE WEST

[1] (p. 47). Etigene Muntz, Leonardo do Vinci, Artist, Thinker,
and Man of Science, 2 vols., New York, 1892. Vol. II., p. 73.


CHAPTER IV

THE NEW COSMOLOGY--COPERNICUS TO KEPLER AND GALILEO

[1] (p. 62). Copernicus, uber die Kreisbewegungen der Welfkorper,
trans. from Dannemann's Geschichle du Naturwissenschaften, 2
vols., Leipzig, 1896.

[2] (p. 90). Galileo, Dialogo dei due Massimi Systemi del Mondo,
trans. from Dannemann, op. cit.

CHAPTER V

GALILEO AND THE NEW PHYSICS [1] (p. 101). Rothmann, History of
Astronomy (in the Library of Useful Knowledge), London, 1834.

[2] (p. 102). William Whewell, History of the Inductive Sciences,
3 Vols, London, 1847-Vol. II., p. 48.

[3] (p. 111). The Lives of Eminent Persons, by Biot, Jardine,
Bethune, etc., London, 1833.

[4] (p. 113). William Gilbert, De Magnete, translated by P.
Fleury Motteley, London, 1893. In the biographical memoir, p.
xvi.

[5] (p. 114). Gilbert, op. cit., p. x1vii.

[6] (p. 114). Gilbert, op. cit., p. 24.


CHAPTER VI

TWO PSEUDO-SCIENCES--ALCHEMY AND ASTROLOGY

[1] (p. 125). Exodus xxxii, 20.

[2] (p. 126). Charles Mackay, Popular Delusions, 3 vols., London,
1850. Vol. II., p. 280.

[3] (p. 140). Mackay, op. cit., Vol. 11., p. 289.

[4] (P. 145). John B. Schmalz, Astrology Vindicated, New York,
1898.

[5] (p. 146). William Lilly, The Starry Messenger, London, 1645,
p. 63.

[6] (p. 149). Lilly, op. cit., p. 70.

[7] (p. 152). George Wharton, An Astrological jugement upon His
Majesty's Present March begun from Oxford, May 7, 1645, pp. 7-10.

[8] (p. 154). C. W. Roback, The Mysteries of Astrology, Boston,
1854, p. 29.


CHAPTER VII

FROM PARACELSUS TO HARVEY

[1] (p. 159). A. E. Waite, The Hermetic and Alchemical Writings
of Paracelsus, 2 vols., London, 1894. Vol. I., p. 21.

[2] (p. 167). E. T. Withington, Medical History from the Earliest
Times, London, 1894, p. 278.

[3] (p. 173). John Dalton, Doctrines of the Circulation,
Philadelphia, 1884, p. 179.

[4] (p. 174). William Harvey, De Motu Cordis et Sanguinis,
London, 1803, chap. X.

[5] (p. 178). The Works of William Harvey, translated by Robert
Willis, London, 1847, p. 56.


CHAPTER VIII

MEDICINE IN THE SIXTEENTH AND SEVENTEENTH CENTURIES

[1] (p. 189). Hermann Baas, History of Medicine, translated by H.
E. Henderson, New York, 1894, p. 504.

[2] (p. 189). E. T. Withington, Medical History from the Earliest
Times, London, 1894, p. 320.


CHAPTER IX

PHILOSOPHER-SCIENTISTS AND NEW INSTITUTIONS OF LEARNING

[1] (p. 193). George L. Craik, Bacon and His Writings and
Philosophy, 2 vols., London, 1846. Vol. II., p. 121.

[2] (p. 193). From Huxley's address On Descartes's Discourse
Touching the Method of Using One's Reason Rightly and of Seeking
Scientific Truth.

[3] (p. 195). Rene Descartes, Traite de l'Homme (Cousins's
edition. in ii vols.), Paris, 1824. Vol, VI., p. 347.


CHAPTER X

THE SUCCESSORS OF GALILEO IN PHYSICAL SCIENCE

[1] (p. 205). See The Phlogiston Theory, Vol, IV.

[2] (p. 205). Robert Boyle, Philosophical Works, 3 vols., London,
1738. Vol. III., p. 41.

[3] (p. 206). Ibid., Vol. III., p. 47.

[4] (p. 206). Ibid., Vol. II., p. 92.

[5] (p. 207). Ibid., Vol. II., p. 2.

[6] (p. 209). Ibid., Vol. I., p. 8.

[7] (p. 209). Ibid., vol. III., p. 508.

[8] (p. 210). Ibid., Vol. III.) p. 361.

[9] (p. 213). Otto von Guericke, in the Philosophical
Transactions of the Royal Society of London, No. 88, for 1672, p.
5103.

[10] (p. 222). Von Guericke, Phil. Trans. for 1669, Vol I., pp.
173, 174.

CHAPTER XI

NEWTON AND THE COMPOSITION OF LIGHT

[1] (p. 233). Phil. Trans. of Royal Soc. of London, No. 80, 1672,
pp. 3076-3079. [2] (p 234). Ibid., pp. 3084, 3085.

[3] (p. 235). Voltaire, Letters Concerning the English Nation,
London, 1811.

CHAPTER XII

NEWTON AND THE LAW OF GRAVITATION

[1] (p. 242). Sir Isaac Newton, Principia, translated by Andrew
Motte, New York, 1848, pp. 391, 392.

[2] (p. 250). Newton op. cit., pp. 506, 507.

CHAPTER XIV

PROGRESS IN ELECTRICITY FROM GILBERT AND VON GUERICKE TO FRANKLIN

[1] (p. 274). A letter from M. Dufay, F.R.S. and of the Royal
Academy of Sciences at Paris, etc., in the Phil. Trans. of the
Royal Soc., vol. XXXVIII., pp. 258-265.

[2] (p. 282). Dean von Kleist, in the Danzick Memoirs, Vol. I.,
p. 407. From Joseph Priestley's History of Electricity, London,
1775, pp. 83, 84.

[3] (p. 288). Benjamin Franklin, New Experiments and Observations
on Electricity, London, 1760, pp. 107, 108.

[4] (p. 291). Franklin, op. cit., pp. 62, 63.

[5] (p. 295). Franklin, op. cit., pp. 107, 108.

[For notes and bibliography to vol. II. see vol. V.]