A History of Science, Volume 2
by
Henry Smith Williams
Part 2 out of 5
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,
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