CLASSICS OF
MODERN SCIENCE
THERE is no grander nor more intellectually elevating spectacle than
that of the utterances of the fundamental investigators in their
gigantic power. Possessed as yet of no methods--for these were first
created by their labors and are only rendered comprehensible to us by
their performances--they grapple with and subjugate the object of their
inquiry and imprint upon it the forms of conceptual thought.
--ERNST MACH
CLASSICS
OF
MODERN SCIENCE
(COPERNICUS TO PASTEUR)
EDITED BY
WILLIAM S. KNICKERBOCKER, PH.D.
PROFESSOR OF ENGLISH IN THE UNIVERSITY
OF THE SOUTH · EDITOR, THE
SEWANEE REVIEW
ALFRED · A · KNOPF · NEW YORK
MCMXXVII
COPYRIGHT 1927, BY ALFRED · A · KNOPF, INC.
SET UP, ELECTROTYPED, PRINTED AND BOUND BY
THE VAIL-BALLOU PRESS, BINGHAMTON, N. Y.
PAPER FURNISHED BY W. F. ETHERINGTON & CO.,
NEW YORK
MANUFACTURED
IN THE UNITED STATES OF AMERICA
TO MY FORMER ASSOCIATES OF THE FACULTY,
AND THE STUDENTS OF THE NEW YORK
STATE COLLEGE OF FORESTRY AT SYRACUSE
UNIVERSITY.
PREFACE
“The history of science,” wrote Du Bois-Reymond, “is the real history
of mankind.” Gradually we are coming to realize the significance of
that statement, and the sooner we realize it on a grand scale the more
shall we hasten the happiness of man.
Fortunately for education, science no longer has to fight for its
inclusion among the courses offered for study in colleges and
universities. As scientific knowledge increases and the technique
of teaching science improves, the exact knowledge of the few more
rapidly becomes the accepted knowledge of the many. More than that,
the scientific attitude of mind produces many of the virtues which in
old-fashioned courses in ethics were taught as objectively as a problem
in geometry. Patience, endurance, humility, teachableness, honesty,
accuracy--without these it is impossible for a scientist properly to
work. And the history of science is as inspiring in its human values as
are the legends of the saints. Contemplate the heroism of a Galileo,
the patience of a Darwin, the humility of a Pasteur; a modern eleventh
chapter of _Hebrews_ might be written listing the names of all
those men of faith who by quiet work, unremitting in their zeal, one by
one discovered facts which have made man’s lot easier and happier in
what was otherwise to him a hostile and unhappy universe.
Little by little, accretion upon accretion, man’s knowledge of
the physical forces of his universe has been increased, but his
progress has often been retarded by those who, with good intentions,
superstitiously feared the power of the gods who, as in the story of
Brunhilde, encircled their mysteries with a ring of fire. Periodically
superstition re-arises, but it does not permanently halt the advance
deploy of armed skirmishers, however much it may temporarily retard
the advancement of knowledge. Since the seventeenth century, however,
so remarkable has been the progress of science, so evident have been
its beneficent achievements, that regardless of the present assault
upon one phase of science, western civilization is committed to this
way of discovery. But it is no easy way! “The rapid increase of
natural knowledge,” wrote Thomas Henry Huxley, “which is the chief
characteristic of our age, is affected in various ways. The main army
of science moves to the conquest of the new worlds slowly and surely,
nor ever cedes an inch of the territory gained. But the advance is
covered and facilitated by the ceaseless activity of clouds of light
troops provided with a weapon--always efficient, if not always an
arm of precision--the scientific imagination. It is the business of
these _enfants perdus_ of science to make raids into the realms
of ignorance wherever they see, or think they see, a chance; and
cheerfully to accept defeat, or it may be annihilation, as the reward
of error. Unfortunately the public, which watches the progress of the
campaign, too often mistakes a dashing incursion ... for a forward
movement of the main body; fondly imagining that the strategic movement
to the rear, which occasionally follows, indicates a battle lost by
science.”
It is regrettable that Huxley was compelled to use the metaphor of
a battle in describing the general advance of scientific knowledge;
how much better it would have been if he could have used a scientific
word like _enzyme_ or _catalyst_ in referring to those courageous men
of the laboratory and the field who went forth alone with instruments
to discover things as they really are and changed fields of knowledge
through their discoveries. But if he had employed these scientific
terms, no one, apart from the select company of scientists themselves
who have had to evolve a special language of their own to express
new matters and new meanings, would understand him. People who use
strange tongues are always suspect to the populace. If science is to
be “understanded” by the people, the people’s language must be used.
Fortunately, for the sake of science, scientists themselves are now
keenly aware of the necessity of presenting their findings in language
which may be understood by the ordinary man. Huxley himself made the
_liaison_ in his age, an age in which battles were highly idealised.
His grandson, however, speaking to our age, rephrases the idea in a
mode more acceptable to us: “Each science or branch of science seems
roughly to go through three main phases in its development. There is
first a preliminary phase in which miscellaneous sporadic knowledge
is amassed and is dated; theories are pursued, often to be proved
valueless. There then comes a classic or heroic age, in which a general
principle of firmly interrelated principles is gradually laid down,
upon which in its turn a coherent architecture of theory can be built,
and finally this passes over into a period of maturity, in which the
position is consolidated, the scope of the principles widened, their
bases more finally tested, and their consequences worked out in fullest
detail. Naturally, each stage lasts for a considerable time, and in
many cases a science which thought itself securely embarked upon the
third phase is reminded by some fundamental discovery that it is still
only in the second.”[1]
These movements of science have produced a copious literature which
has not enjoyed the same attention and reading as imaginative books,
because, once the ideas are known and incorporated into the existing
body of scientific knowledge, these scientific writings tend to acquire
chiefly an historical interest. Yet they are monuments of the advance
of civilization, and deserve a better fate. Many of them are still
interesting to read as human documents because they illustrate how
painfully and slowly man’s exact knowledge of verifiable phenomena has
been accumulated. No one outside of the small company of highly trained
scientists can read all of them through, yet most of them have sections
which are as readable and as exciting as any modern novel. It is the
purpose of this book to present to the young college student and to the
general reader some of the more representative of these classics in the
literature of science, bringing together in this convenient form at
least some reminders of a vast field of reading where one may browse
for a lifetime with interest and profit. If it be used in conjunction
with a history of science it will readily supply a vivid sense of
the movement of the mind of western civilization, increasing in us a
respect for the effort of our ancestors, and inspire us to encourage
and to forward the work of contemporary scientists, and restrain us at
least from hindering them in their efforts.
Although the selections may be used as a textbook in courses like
Introduction to Modern Civilization, Philosophy, and The History of
Science now given in the more progressive colleges and universities,
it may also profitably be used as a text for freshman or sophomore
readings in English courses given in colleges predominantly technical
or scientific, like Engineering, Agricultural, and Forestry Colleges.
In those English courses where emphasis upon ideas is made to provide
the inspiration for writing, these selections will be found, as I
found them in my own work, to stir up considerable discussion and
to provide opportunities for reading modern scientific literature.
Moreover, the literary style of science at its best will be found to be
excellently illustrated in these straightforward, coherent sentences
written by some of the world’s clearest thinkers. They illustrate
concretely what Tyndall remarked in his closing words of the famous
_Belfast Address_: “It has been said that science divorces itself
from literature. The statement, like so many others, arises from
lack of knowledge. A glance at the less technical writings of its
leaders--of its Helmholtz, its Huxley, and its Du Bois-Reymond--would
show what breadth of literary culture they command. Where among
modern writers can you find their superiors in clearness and vigor
of literary style? Science desires no isolation, but freely combines
with every effort toward the bettering of man’s estate. Single-handed
and supported not with outward sympathy, but by inward force, it has
built at least one great wing of the many-mansioned home which man in
his totality demands.... The world embraces not only a Newton, but a
Shakespeare; not only a Boyle, but a Raphael; not only a Kant, but a
Beethoven; not only a Darwin, but a Carlyle. Not in each of these, but
in all, is human nature whole. They are not opposed, but supplementary;
not mutually exclusive, but reconcilable.”
WILLIAM S. KNICKERBOCKER
UNIVERSITY OF THE SOUTH
SEWANEE, TENN.
_April 5, 1927_
FOOTNOTES:
[Footnote 1: Julian Huxley, in _Harper’s Magazine_ for April,
1926.]
CONTENTS
I FRANCIS BACON (1561-1626) 1
THE METHOD OF INDUCTIVE SCIENCE
ON THE INTERPRETATION OF NATURE, OR THE
REIGN OF MAN
II NICOLAUS COPERNICUS (1473-1543) 20
THE NEW IDEA OF THE UNIVERSE
III JOHANN KEPLER (1671-1630) 29
ON THE PRINCIPLES OF ASTRONOMY
IV GALILEO GALILEI (1564-1642) 36
THE COPERNICAN VERSUS THE PTOLEMAIC ASTRONOMIES
V WILLIAM HARVEY (1578-1667) 46
THE CIRCULATION OF BLOOD IN ANIMALS
VI ROBERT BOYLE (1627-1691) 49
THE DISCOVERY OF THE LAW OF THE COMPRESSIBILITY
OF GASSES
VII CHRISTIAN HUYGHENS (1629-1695) 52
THE WAVE THEORY OF LIGHT
VIII ANTHONY VON LEEUWENHOECK (1632-1723) 62
OBSERVATIONS ON ANIMALCULÆ
IX SIR ISAAC NEWTON (1642-1727) 67
THE THEORY OF GRAVITATION
X BENJAMIN FRANKLIN (1706-1790) 72
THE IDENTITY OF LIGHTNING AND ELECTRICITY
XI LINNAEUS (1707-1778) 76
THE SEX OF PLANTS
XII JOSEPH BLACK (1728-1799) 89
THE DISCOVERY OF CARBONIC ACID GAS
XIII JOSEPH PRIESTLEY (1733-1804) 96
THE DISCOVERY OF OXYGEN
XIV HENRY CAVENDISH (1731-1810) 102
THE COMBINATION OF HYDROGEN AND OXYGEN
INTO WATER
XV SIR WILLIAM HERSCHEL (1738-1822) 109
THE DISCOVERY OF URANUS
ON THE NAME OF THE NEW PLANET
ON NEBULOUS STARS
XVI KARL WILHELM SCHEELE (1742-1786) 122
THE CONSTITUENTS OF AIR
XVII ANTOINE LAURENT LAVOISIER (1743-1794) 129
THE NATURE OF COMBUSTION
XVIII ALESSANDRO VOLTA (1745-1827) 135
NEW GALVANIC INSTRUMENT
XIX PIERRE SIMON LAPLACE (1749-1827) 138
THE NEBULAR HYPOTHESIS
XX EDWARD JENNER (1749-1823) 148
THE THEORY OF VACCINATION
XXI COUNT RUMFORD (1753-1814) 157
THE NATURE OF HEAT
XXII JOHN DALTON (1766-1844) 166
THE ATOMIC THEORY
XXIII MARIE FRANÇOIS XAVIER BICHAT (1771-1802) 168
THE DOCTRINE OF TISSUES
XXIV AMADEO AVOGADRO (1776-1856) 177
THE MOLECULES IN GASES PROPORTIONAL TO
THE VOLUMES
XXV SIR HUMPHREY DAVY (1778-1829) 183
ON SOME NEW PHENOMENA OF CHEMICAL
CHANGES PRODUCED BY ELECTRICITY
XXVI MICHAEL FARADAY (1791-1867) 190
ON FLUID CHLORINE
ELECTRICITY FROM MAGNETISM
XXVII JOSEPH HENRY (1797-1878) 198
ON THE PRODUCTION OF CURRENTS AND SPARKS
OF ELECTRICITY FROM MAGNETISM
XXVIII SIR CHARLES LYELL (1797-1875) 206
UNIFORMITY IN THE SERIES OF PAST CHANGES
IN THE ANIMATE AND INANIMATE WORLD
XXIX CHARLES DARWIN (1809-1882) 226
NATURAL SELECTION
XXX THEODOR SCHWANN (1810-1882) 245
CELL THEORY
XXXI HERMANN VON HELMHOLTZ (1821-1894) 273
THE CONSERVATION OF ENERGY
XXXII LOUIS PASTEUR (1822-1895) 304
INOCULATION FOR HYDROPHOBIA
XXXIII JAMES CLERK MAXWELL (1831-1879) 320
THE MAXWELL AND HERZ THEORY OF ELECTRICITY
AND LIGHT
XXXIV AUGUST WEISMANN (1834-1914) 334
THE CONTINUITY OF THE GERM-PLASM AS THE
FOUNDATION OF A THEORY OF HEREDITY
XXXV SIR NORMAN LOCKYER (1836-1920) 360
THE CHEMISTRY OF THE STARS
XXXVI ROBERT KOCH (1843-1910) 374
THEORY OF BACTERIA
CLASSICS OF
MODERN SCIENCE
I
FRANCIS BACON
1561-1626
_Francis Bacon, Lord Verulam, is distinguished in the history of
science for his criticism of the methods of knowledge of his day.
In his great writings, “The Advancement of Learning” (1605), “Novum
Organum” (1620), and “De Augmentis Scientiarum” (1623), he cumulatively
outlined a new method, named after him, whereby all knowledge was
referred to experience and corrected by experiment. His inductive
method was epoch-making in that it established the technique underlying
all modern science._
_He was born in London, January 22, 1561, the son of Sir Nicholas
Bacon, Lord Keeper of the Seals. In 1573, at the age of twelve, he
matriculated in Trinity College, Cambridge. After his father’s death,
in 1579, he led a precarious life, accumulated many debts, and ended
by accusing his intimate friend, Lord Essex, of treason. In 1607 King
James appointed him Solicitor. In 1613 he became Attorney General,
and in 1618 was made Lord Chancellor and knighted Baron Verulam. The
following year he was impeached for bribery, and imprisoned four days
for the offense. Thereafter, until his death on April 9, 1626, he gave
himself wholly to the development of his new scientific method._
THE METHOD OF INDUCTIVE SCIENCE[2]
They who have presumed to dogmatize on nature, as on some well
investigated subject, either from self-conceit or arrogance, and in the
professorial style, have inflicted the greatest injury on philosophy
and learning. For they have tended to stifle and interrupt inquiry
exactly in proportion as they have prevailed in bringing others to
their opinion; and their own activity has not counterbalanced the
mischief they have occasioned by corrupting and destroying that of
others. They again who have entered upon a contrary course, and
asserted that nothing whatever can be known, whether they have fallen
into this opinion from their hatred of the ancient sophists, or from
the hesitation of their minds, or from an exuberance of learning, have
certainly adduced reasons for it which are by no means contemptible.
They have not, however, derived their opinion from true sources,
and, hurried on by their zeal and some affectation, have certainly
exceeded due moderation. But the more ancient Greeks (whose writings
have perished), held a more prudent mean, between the arrogance of
dogmatism, and the despair of scepticism; and though too frequently
intermingling complaints and indignation at the difficulty of inquiry,
and the obscurity of things, and champing, as it were, the bit, have
still persisted in pressing their point, and pursuing their intercourse
with nature; thinking, as it seems, that the better method was not to
dispute upon the very point of the possibility of anything being known,
but to put it to the test of experience. Yet they themselves, by only
employing the power of the understanding, have not adopted a fixed
rule, but have laid their whole stress upon intense meditation, and a
continual exercise and perpetual agitation of the mind.
Our method, though difficult in its operation, is easily explained.
It consists in determining the degrees of certainty, whilst we, as it
were, restore the senses to their former rank, but generally reject
that operation of the mind which follows close upon the senses, and
open and establish a new and certain course for the mind from the first
actual perceptions of the senses themselves. This, no doubt, was the
view taken by those who have assigned so much to logic; showing clearly
thereby that they sought some support for the mind, and suspected its
natural and spontaneous mode of action. But this is now employed too
late as a remedy, when all is clearly lost, and after the mind, by
the daily habit and intercourse of life, has come prepossessed with
corrupted doctrines, and filled with the vainest idols. The art of
logic, therefore, being (as we have mentioned) too late a precaution,
and in no way remedying the matter, has tended more to confirm errors,
than to disclose truth. Our only remaining hope and salvation is to
begin the whole labor of the mind again; not leaving it to itself,
but directing it perpetually from the very first, and attaining our
end as it were by mechanical aid. If men, for instance, had attempted
mechanical labors with their hands alone, and without the power and aid
of instruments, as they have not hesitated to carry on the labors of
their understanding with the unaided efforts of their mind, they would
have been able to move and overcome but little, though they had exerted
their utmost and united powers. And just to pause awhile on this
comparison, and look into it as a mirror; let us ask, if any obelisk of
a remarkable size were perchance required to be moved, for the purpose
of gracing a triumph or any similar pageant, and men were to attempt it
with their bare hands, would not any sober spectator avow it to be an
act of the greatest madness? And if they should increase the number of
workmen, and imagine that they could thus succeed, would he not think
so still more? But if they chose to make a selection, and to remove
the weak, and only employ the strong and vigorous, thinking by this
means, at any rate, to achieve their object, would he not say that they
were more fondly deranged? Nay, if not content with this, they were
to determine on consulting the athletic art, and were to give orders
for all to appear with their hands, arms, and muscles regularly oiled
and prepared, would he not exclaim that they were taking pains to rave
by method and design? Yet men are hurried on with the same senseless
energy and useless combination in intellectual matters, as long as
they expect great results either from the number and agreement, or the
excellence and acuteness of their wits; or even strengthen their minds
with logic, which may be considered as an athletic preparation, but yet
do not desist (if we rightly consider the matter) from applying their
own understandings merely with all this zeal and effort. Whilst nothing
is more clear, than that in every great work executed by the hand of
man without machines or implements, it is impossible for the strength
of individuals to be increased, or that of the multitude to combine.
Having premised so much, we lay down two points on which we would
admonish mankind lest they should fail to see or to observe them. The
first of these is, that it is our good fortune (as we consider it), for
the sake of extinguishing and removing contradiction and irritation of
mind, to leave the honor and reverence due to the ancients untouched
and undiminished, so that we can perform our intended work, and yet
enjoy the benefit of our respectful moderation. For if we profess
to offer something better than the ancients, and yet should pursue
the same course as they have done, we could never, by any artifice,
contrive to avoid the imputation of having engaged in a contest or
rivalry as to our respective wits, excellencies, or talents; which,
though neither inadmissible nor new (for why should we not blame and
point out anything that is imperfectly discovered or laid down by
them, of our own right, a right common to all), yet however just and
allowable, would perhaps be scarcely an equal match, on account of
the disproportion of our strength. But since our present plan leads
us to open an entirely different course to the understanding, and one
unattempted and unknown to them, the case is altered. There is an end
to party zeal, and we only take upon ourselves the character of a
guide, which requires a moderate share of authority and good fortune,
rather than talents and excellence. The first admonition relates to
persons, the next to things.
We make no attempt to disturb the system of philosophy that now
prevails, or any other which may or will exist, either more correct or
more complete. For we deny not that the received system of philosophy,
and others of a similar nature, encourage discussion, embellish
harangues, are employed, and are of service in the duties of the
professor, and the affairs of civil life. Nay, we openly express and
declare that the philosophy we offer will not be very useful in such
respects. It is not obvious, or to be understood in a cursory view,
nor does it flatter the mind in its preconceived notions, nor will
it descend to the level of the generality of mankind unless by its
advantages and effects.
Let there exist, then (and may it be of advantage to both), two
sources, and two distributions of learning, and in like manner
two tribes, and as it were kindred families of contemplators or
philosophers, without any hostility or alienation between them; but
rather allied and united by mutual assistance. Let there be, in short,
one method of cultivating the sciences, and another in discovering
them. And as for those who prefer and more readily receive the former,
on account of their haste or from motives arising from their ordinary
life, or because they are unable from weakness of mind to comprehend
and embrace the other (which must necessarily be the case with by
far the greater number), let us wish that they may prosper as they
desire in their undertaking, and attain what they pursue. But if any
individual desire, and is anxious not merely to adhere to, and make
use of present discoveries, but to penetrate still further, and not
to overcome his adversaries in disputes, but nature by labor, not in
short to give elegant and specious opinions, but to know to a certainty
and demonstration, let him, as a true son of science (if such be his
wish), join with us; that when he has left the antechambers of nature
trodden by the multitude, an entrance may at last be discovered to her
inner apartments. And in order to be better understood, and to render
our meaning more familiar by assigning determinate names, we have
accustomed ourselves to call the one method the anticipation of the
mind, and the other the interpretation of nature.
We have still one request left. We have at least reflected and taken
pains, in order to render our propositions not only true, but of easy
and familiar access to men’s minds, however wonderfully prepossessed
and limited. Yet it is but just that we should obtain this favor from
mankind (especially in so great a restoration of learning and the
sciences), that whosoever may be desirous of forming any determination
upon an opinion of this our work either from his own perceptions,
or the crowd of authorities, or the forms of demonstrations, he
will not expect to be able to do so in a cursory manner, and whilst
attending to other matters; but in order to have a thorough knowledge
of the subject, will himself, by degrees, attempt the course which we
describe and maintain; will be accustomed to the subtlety of things
which is manifested by experience; and will correct the depraved and
deeply-rooted habits of his mind by a seasonable, and, as it were, just
hesitation: and then, finally (if he will), use his judgment when he
has begun to be master of himself.
ON THE INTERPRETATION OF NATURE, OR THE REIGN OF MAN[3]
Man acts, then, upon natural bodies (besides merely bringing them
together or removing them) by seven principal methods: I. By the
exclusion of all that impedes and disturbs; II. by compression,
extension, agitation, and the like; III. by heat and cold; IV. by
detention in a suitable place; V. by checking or directing motion; VI.
by peculiar harmonies; VII. by a seasonable and proper alternation,
series, and succession of all these, or, at least, of some of them.
I. With regard to the first--common air, which is always at hand, and
forces its admission, as also the rays of the heavenly bodies, create
much disturbance. Whatever, therefore, tends to exclude them may
well be considered as generally useful. The substance and thickness
of vessels in which bodies are placed when prepared for operations
may be referred to this head. So also may the accurate methods of
closing vessels by consolidation, or the _lutum sapientiæ_ as
the chemists call it. The exclusion of air by means of liquids at
the extremity is also very useful, as when they pour oil on wine,
or the juices of herbs, which by spreading itself upon the top like
a cover, preserves them uninjured from the air. Powders, also, are
serviceable, for although they contain air mixed up in them, yet they
ward off the power of the mass of circumambient air, which is seen in
the preservation of grapes and other fruits in sand or flour. Wax,
honey, pitch, and other resinous bodies, are well used in order to
make the exclusion more perfect, and to remove the air and celestial
influence. We have sometimes made an experiment by placing a vessel or
other bodies in quicksilver, the most dense of all substances capable
of being poured round others. Grottoes and subterraneous caves are of
great use in keeping off the effects of the sun, and the predatory
action of air, and in the north of Germany are used for granaries.
The depositing of bodies at the bottom of water may be also mentioned
here; and I remember having heard of some bottles of wine being let
down into a deep well in order to cool them, but left there by chance,
carelessness, and forgetfulness, for several years, and then taken
out; by which means the wine not only escaped becoming flat or dead,
but was much more excellent in flavor, arising (as it appears) from
a more complete mixture of its parts. But if the case require that
bodies should be sunk to the bottom of water, as in rivers or the sea,
and yet should not touch the water, nor be enclosed in sealed vessels,
but surrounded only by air, it would be right to use that vessel which
has been sometimes employed under water above ships that have sunk, in
order to enable the divers to remain below and breathe occasionally
by turns. It was of the following nature:--A hollow tub of metal was
formed, and sunk so as to have its bottom parallel with the surface of
the water; it thus carried down with it to the bottom of the sea all
the air contained in the tub. It stood upon three feet (like a tripod),
being of rather less height than a man, so that, when the diver was
in want of breath, he could put his head into the hollow of the tub,
breathe, and then continue his work. We hear that some sort of boat or
vessel has now been invented, capable of carrying men some distance
under water. Any bodies, however, can easily be suspended under some
such vessel as we have mentioned, which has occasioned our remarks upon
the experiment.
Another advantage of the careful and hermetical closing of bodies is
this--not only the admission of external air is prevented (of which we
have treated), but the spirit of bodies also is prevented from making
its escape, which is an internal operation. For anyone operating on
natural bodies must be certain as to their quantity, and that nothing
has evaporated or escaped, since profound alterations take place in
bodies, when art prevents the loss or escape of any portion, whilst
nature prevents their annihilation. With regard to this circumstance,
a false idea has prevailed (which if true would make us despair of
preserving quantity without diminution), namely, that the spirit of
bodies, and air when rarefied by a great degree of heat, cannot be so
kept in by being enclosed in any vessel as not to escape by the small
pores. Men are led into this idea by the common experiments of a cup
inverted over water, with a candle or piece of lighted paper in it,
by which the water is drawn up, and of those cups which, when heated,
draw up the flesh. For they think that in each experiment the rarefied
air escapes, and that its quantity is therefore diminished, by which
means the water or flesh rises by the motion of connection. This is,
however, most incorrect. For the air is not diminished in quantity,
but contracted in dimensions, nor does this motion of the rising of
the water begin till the flame is extinguished, or the air cooled, so
that physicians place cold sponges, moistened with water, on the cups,
in order to increase their attraction. There is, therefore, no reason
why men should fear much from the ready escape of air: for although it
be true that the most solid bodies have their pores, yet neither air,
nor spirit, readily suffers itself to be rarefied to such an extreme
degree; just as water will not escape by a small chink.
II. With regard to the second of the seven above-mentioned methods, we
must especially observe, that compression and similar violence have a
most powerful effect either in producing locomotion, and other motions
of the same nature, as may be observed in engines and projectiles, or
in destroying the organic body, and those qualities, which consist
entirely in motion (for all life, and every description of flame and
ignition are destroyed by compression, which also injures and deranges
every machine); or in destroying those qualities which consist in
position and a coarse difference of parts, as in colors; for the color
of a flower when whole, differs from that it presents when bruised, and
the same may be observed of whole and powdered amber; or in tastes,
for the taste of a pear before it is ripe, and of the same pear when
bruised and softened, is different, since it becomes perceptibly
more sweet. But such violence is of little avail in the more noble
transformations and changes of homogeneous bodies, for they do not,
by such means, acquire any constantly and permanently new state, but
one that is transitory, and always struggling to return to its former
habit and freedom. It would not, however, be useless to make some more
diligent experiments with regard to this; whether, for instance, the
condensation of a perfectly homogeneous body (such as air, water, oil,
and the like) or their rarefaction, when effected by violence, can
become permanent, fixed, and, as it were, so changed, as to become
a nature. This might at first be tried by simple perseverance, and
then by means of helps and harmonies. It might readily have been
attempted (if we had but thought of it), when we condensed water (as
was mentioned above), by hammering and compression, until it burst out.
For we ought to have left the flattened globe untouched for some days,
and then to have drawn off the water, in order to try whether it would
have immediately occupied the same dimensions as it did before the
condensation. If it had not been done so, either immediately, or soon
afterwards, the condensation would have appeared to have been rendered
constant; if not, it would have appeared that a restitution took place,
and that the condensation had been transitory. Something of the same
kind might have been tried with the glass eggs; the egg should have
been sealed up suddenly and firmly, after a complete exhaustion of
the air, and should have been allowed to remain so for some days, and
it might then have been tried whether, on opening the aperture, the
air would be drawn in with a hissing noise, or whether as much water
would be drawn into it when immersed, as would have been drawn into it
at first, if it had not continued sealed. For it is probable (or, at
least, worth making the experiment) that this might have happened, or
might happen, because perseverance has a similar effect upon bodies
which are a little less homogeneous. A stick bent together for some
time does not rebound, which is not owing to any loss of quantity in
the wood during the time, for the same would occur (after a larger
time) in a plate of steel, which does not evaporate. If the experiment
of simple perseverance should fail, the matter should not be given up,
but other means should be employed. For it would be no small advantage,
if bodies could be endued with fixed and constant natures by violence.
Air could then be converted into water by condensation, with other
similar effects; for man is more the master of violent motions than of
any other means.
III. The third of our seven methods is referred to that great practical
engine of nature as well as of art, cold and heat. Here, man’s power
limps, as it were, with one leg. For we possess the heat of fire, which
is infinitely more powerful and intense than that of the sun (as it
reaches us), and that of animals. But we want cold, except such as we
can obtain in winter, in caverns, or by surrounding objects with snow
and ice, which, perhaps, may be compared in degree with the noontide
heat of the sun in tropical countries, increased by the reflection of
mountains and walls. For this degree of heat and cold can be borne
for a short period only by animals, yet it is nothing compared with
the heat of a burning furnace, or the corresponding degree of cold.
Everything with us has a tendency to become rarefied, dry, and wasted,
and nothing to become condensed or soft, except by mixtures, and,
as it were, spurious methods. Instances of cold, therefore, should
be searched for most diligently, such as may be found by exposing
bodies upon buildings in a hard frost, in subterraneous caverns, by
surrounding bodies with snow and ice in deep places excavated for
that purpose, by letting bodies down into wells, by burying bodies in
quicksilver and metals, by immersing them in streams which petrify
wood, by burying them in the earth (which the Chinese are reported to
do with their china, masses of which, made for that purpose, are said
to remain in the ground for forty or fifty years, and to be transmitted
to their heirs as a sort of artificial mine), and the like. The
condensations which take place in nature, by means of cold, should also
be investigated, that by learning their causes, they may be introduced
into the arts; such as are observed in the exudation of marble and
stones, in the dew upon the panes of glass in a room towards morning
after a frosty night, in the formation and the gathering of vapors
under the earth into water, whence spring fountains, and the like.
Besides the substances which are cold to the touch, there are others
which have also the effect of cold, and condense; they appear, however,
to act only upon the bodies of animals, and scarcely any further. Of
these we have many instances, in medicines and plasters. Some condense
the flesh and tangible parts, such as astringent and inspissating
medicines, others the spirits, such as soporifics. There are two modes
of condensing the spirits, by soporifics or provocatives to sleep;
the one by calming the motion, the other by expelling the spirit. The
violet, dried roses, lettuces, and other benign or mild remedies,
by their friendly and gently cooling vapors, invite the spirits to
unite, and restrain their violent and perturbed motion. Rosewater, for
instance, applied to the nostrils in fainting fits, causes the resolved
and relaxed spirits to recover themselves, and, as it were, cherishes
them. But opiates, and the like, banish the spirits by their malignant
and hostile quality. If they be applied, therefore, externally, the
spirits immediately quit the part and no longer readily flow into it;
but if they be taken internally, their vapor, mounting to the head,
expels, in all directions, the spirits contained in the ventricles of
the brain, and since these spirits retreat, but cannot escape, they
consequently meet and are condensed, and are sometimes completely
extinguished and suffocated; although the same opiates, when taken in
moderation, by a secondary accident (the condensation which succeeds
their union), strengthen the spirits, render them more robust, and
check their useless and inflammatory motion, by which means they
contribute not a little to the cure of diseases, and the prolongation
of life.
The preparations of bodies, also, for the reception of cold should not
be omitted, such as that water a little warmed is more easily frozen
than that which is quite cold, and the like.
Moreover, since nature supplies cold so sparingly, we must act like
the apothecaries, who, when they cannot obtain any simple ingredient,
take a succedaneum, or quid pro quo, as they term it, such as aloes for
xylobalsamum, cassia for cinnamon. In the same manner we should look
diligently about us, to ascertain whether there may be any substitutes
for cold, that is to say, in what other manner condensation can be
effected, which is the peculiar operation of cold. Such condensations
appear hitherto to be of four kinds only. 1. By simple compression,
which is of little avail towards permanent condensation, on account
of the elasticity of substances, but may still however be of some
assistance. 2. By the contraction of the coarser, after the escape
or departure of the finer parts of a given body; as is exemplified
in induration by fire, and the repeated heating and extinguishing of
metals, and the like. 3. By the cohesion of the most solid homogeneous
parts of a given body, which were previously separated, and mixed with
others less solid, as in the return of sublimated mercury to its simple
state, in which it occupies much less space than it did in powder, and
the same may be observed of the cleansing of all metals from their
dross. 4. By harmony or the application of substances which condense by
some latent power. These harmonies are as yet but rarely observed, at
which we cannot be surprised, since there is little to hope for from
their investigation, unless the discovery of forms and conformation
be attained. With regard to animal bodies, it is not to be questioned
that there are many internal and external medicines which condense
by harmony, as we have before observed, but this action is rare in
inanimate bodies. Written accounts, as well as report, have certainly
spoken of a tree in one of the Tercera or Canary Islands (for I do not
exactly recollect which) that drips perpetually, so as to supply the
inhabitants, in some degree, with water; and Paracelsus says that the
herb called _ros solis_ is filled with dew at noon, whilst the sun
gives out its greatest heat, and all other herbs around it are dry. We
treat both these accounts as fables; they would, however, if true, be
of the most important service, and most worthy of examination. As to
the honey-dew, resembling manna, which is found in May on the leaves
of the oak, we are of opinion that it is not condensed by any harmony
or peculiarity of the oak-leaf, but that whilst it falls equally upon
other leaves it is retained and continues on those of the oak, because
their texture is closer, and not so porous as that of most of the other
leaves.
With regard to heat, man possesses abundant means and power; but his
observation and inquiry are defective in some respects, and those of
the greatest importance, notwithstanding the boasting of quacks. For
the effects of intense heat are examined and observed, whilst those of
a more gentle degree of heat, being of the most frequent occurrence
in the paths of nature, are, on that very account, least known. We
see, therefore, the furnaces, which are most esteemed, employed in
increasing the spirits of bodies to a great extent, as in the strong
acids, and some chemical oils; whilst the tangible parts are hardened,
and, when the volatile part has escaped, become sometimes fixed; the
homogeneous parts are separated, and the heterogeneous incorporated and
agglomerated in a coarse lump; and (what is chiefly worthy of remark)
the junction of compound bodies, and the more delicate conformations
are destroyed and confounded. But the operation of a less violent heat
should be tried and investigated, by which more delicate mixtures, and
regular conformations may be produced and elicited, according to the
example of nature, and in imitation of the effect of the sun, which we
have alluded to in the aphorism on the instances of alliance. For the
works of nature are carried on in much smaller portions, and in more
delicate and varied positions than those of fire, as we now employ
it. But man will then appear to have really augmented his power, when
the works of nature can be imitated in species, perfected in power,
and varied in quantity; to which should be added the acceleration in
point of time. Rust, for instance, is the result of a long process,
but _crocus martis_ is obtained immediately; and the same may be
observed of natural verdigris and ceruse. Crystal is formed slowly,
whilst glass is blown immediately: stones increase slowly, whilst
bricks are baked immediately, etc. In the mean time (with regard to
our present subject) every different species of heat should, with its
peculiar effects, be diligently collected and inquired into; that
of the heavenly bodies, whether their rays be direct, reflected, or
refracted, or condensed by a burning-glass; that of lightning, flame,
and ignited charcoal; that of fire of different materials, either open
or confined, straitened or overflowing, qualified by the different
forms of the furnaces, excited by the bellows, or quiescent, removed to
a greater or less distance, or passing through different media; moist
heats, such as the _balneum Mariæ_, and the dunghill; the external
and internal heat of animals; dry heats, such as the heat of ashes,
lime, warm sand; in short, the nature of every kind of heat, and its
degrees.
We should, however, particularly attend to the investigation and
discovery of the effects and operations of heat, when made to approach
and retire by degrees, regularly, periodically, and by proper intervals
of space and time. For this systematical inequality is in truth the
daughter of heaven and mother of generation, nor can any great result
be expected from a vehement, precipitate, or desultory heat. For this
is not only most evident in vegetables, but in the wombs of animals
also there arises a great inequality of heat, from the motion, sleep,
food, and passions of the female. The same inequality prevails in
those subterraneous beds where metals and fossils are perpetually
forming, which renders yet more remarkable the ignorance of some of the
reformed alchemists, who imagined they could attain their object by the
equable heat of lamps, or the like, burning uniformly. Let this suffice
concerning the operation and effects of heat; nor is it time for us
to investigate them thoroughly before the forms and conformations
of bodies have been further examined and brought to light. When we
have determined upon our models, we may seek, apply, and arrange our
instruments.
IV. The fourth mode of action is by continuance, the very steward and
almoner, as it were, of nature. We apply the term continuance to the
abandonment of a body to itself for an observable time, guarded and
protected in the mean while from all external force. For the internal
motion then commences to betray and exert itself when the external and
adventitious is removed. The effects of time, however, are far more
delicate than those of fire. Wine, for instance, cannot be clarified
by fire as it is by continuance. Nor are the ashes produced by
combustion so fine as the particles dissolved or wasted by the lapse
of ages. The incorporations and mixtures, which are hurried by fire,
are very inferior to those obtained by continuance; and the various
conformations assumed by bodies left to themselves, such as mouldiness,
etc., are put a stop to by fire or a strong heat. It is not, in the
mean time, unimportant to remark that there is a certain degree of
violence in the motion of bodies entirely confined; for the confinement
impedes the proper motion of the body. Continuance in an open vessel,
therefore, is useful for separations, and in one hermetically sealed
for mixtures, that in a vessel partly closed, but admitting the
air, for putrefaction. But instances of the operation and effect of
continuance must be collected diligently from every quarter.
V. The direction of motion (which is the fifth method of action) is
of no small use. We adopt this term, when speaking of a body which,
meeting with another, either arrests, repels, allows, or directs
its original motion. This is the case principally in the figure and
position of vessels. An upright cone, for instance, promotes the
condensation of vapor in alembics, but when reversed, as in inverted
vessels, it assists the refining of sugar. Sometimes a curved form,
or one alternately contracted and dilated, is required. Strainers may
be ranged under this head, where the opposed body opens a way for
one portion of another substance and impedes the rest. Nor is this
process or any other direction of motion carried on externally only,
but sometimes by one body within another. Thus, pebbles are thrown
into water to collect the muddy particles, and syrups are refined by
the white of an egg, which glues the grosser particles together so as
to facilitate their removal. Telesius, indeed, rashly and ignorantly
enough attributes the formation of animals to this cause, by means of
the channels and folds of the womb. He ought to have observed a similar
formation of the young in eggs which have no wrinkles or inequalities.
One may observe a real result of this direction of motion in casting
and modelling.
VI. The effects produced by harmony and aversion (which is the
sixth method) are frequently buried in obscurity; for these occult
and specific properties (as they are termed), the sympathies and
antipathies, are for the most part but a corruption of philosophy. Nor
can we form any great expectation of the discovery of the harmony which
exists between natural objects, before that of their forms and simple
conformations, for it is nothing more than the symmetry between these
forms and conformations.
The greater and more universal species of harmony are not, however,
so wholly obscure, and with them, therefore, we must commence. The
first and principal distinction between them is this; that some bodies
differ considerably in the abundance and rarity of their substance, but
correspond in their conformation; others, on the contrary, correspond
in the former and differ in the latter. Thus the chemists have well
observed, that in their trial of first principles sulphur and mercury,
as it were, pervade the universe; their reasoning about salt, however,
is absurd, and merely introduced to compromise earthy dry fixed bodies.
In the other two, indeed, one of the most universal species of natural
harmony manifests itself. Thus there is a correspondence between
sulphur, oil, greasy exhalations, flame, and, perhaps, the substance of
the stars. On the other hand, there is a like correspondence between
mercury, water, aqueous vapor, air, and perhaps pure inter-sidereal
ether. Yet do these two quarternions, or great natural tribes (each
within its own limits), differ immensely in quantity and density of
substance, whilst they generally agree in conformation, as is manifest
in many instances. On the other hand, the metals agree in such quantity
and density (especially when compared with vegetables, etc.), but
differ in many respects in conformation. Animals and vegetables, in
like manner, vary in their almost infinite modes of conformation, but
range within very limited degrees of quantity and density of substance.
The next most general correspondence is that between individual bodies
and those which supply them by way of menstruum or support. Inquiry,
therefore, must be made as to the climate, soil, and depth at which
each metal is generated, and the same of gems, whether produced in
rocks or mines, also as to the soil in which particular trees, shrubs,
and herbs, mostly grow and, as it were, delight; and as to the best
species of manure, whether dung, chalk, sea sand, or ashes, etc., and
their different propriety and advantage according to the variety of
soils. So also the grafting and setting of trees and plants (as regards
the readiness of grafting one particular species on another) depends
very much upon harmony, and it would be amusing to try an experiment
I have lately heard of, in grafting forest trees (garden trees alone
having hitherto been adopted), by which means the leaves and fruit
are enlarged, and the trees produce more shade. The specific food of
animals again should be observed, as well as that which cannot be used.
Thus the carnivorous cannot be fed on herbs, for which reason the order
of _feuilletans_, the experiment having been made, has nearly
vanished; human nature being incapable of supporting their regimen,
although the human will has more power over the bodily frame than
that of other animals. The different kinds of putrefaction from which
animals are generated should be noted.
The harmony of principal bodies with those subordinate to them (such
indeed may be deemed those we have alluded to above) are sufficiently
manifest, to which may be added those that exist between different
bodies and their objects, and, since these latter are more apparent,
they may throw great light when well observed and diligently examined
upon those which are more latent.
The more internal harmony and aversion, or friendship and enmity
(for superstition and folly have rendered the terms of sympathy and
antipathy almost disgusting) have been either falsely assigned, or
mixed with fable, or most rarely discovered from neglect. For if
one were to allege that there is an enmity between the vine and the
cabbage, because they will not come up well sown together, there is
a sufficient reason for it in the succulent and absorbent nature of
each plant, so that the one defrauds the other. Again, if one were
to say that there is a harmony and friendship between the corn and
the corn-flower, or the wild poppy, because the latter seldom grow
anywhere but in cultivated soils, he ought rather to say, there is an
enmity between them, for the poppy and the corn-flower are produced and
created by those juices which the corn has left and rejected, so that
the sowing of the corn prepares the ground for their production. And
there are a vast number of similar false assertions. As for fables,
they must be totally exterminated. There remains, then, but a scanty
supply of such species of harmony as has borne the test of experiment,
such as that between the magnet and iron, gold and quicksilver, and
the like. In chemical experiments on metals, however, there are some
others worthy of notice, but the greatest abundance (where the whole
are so few in numbers) is discovered in certain medicines, which,
from their occult and specific qualities (as they are termed), affect
particular limbs, humors, diseases, or constitutions. Nor should we
omit the harmony between the motion and phenomena of the moon, and
their effects on lower bodies, which may be brought together by an
accurate and honest selection from the experiments of agriculture,
navigation, and medicine, or of other sciences. By as much as these
general instances, however, of more latent harmony, are rare, with
so much the more diligence are they to be inquired after, through
tradition, and faithful and honest reports, but without rashness and
credulity, with an anxious and, as it were, hesitating degree of
reliance. There remains one species of harmony which, though simple
in its mode of action, is yet most valuable in its use, and must
by no means be omitted, but rather diligently investigated. It is
the ready or difficult coition or union of bodies in composition, or
simple juxtaposition. For some bodies readily and willingly mix, and
are incorporated, others tardily and perversely; thus powders mix best
with water, chalk, and ashes with oils, and the like. Nor are these
instances of readiness and aversion to mixture to be alone collected,
but others, also, of the collocation, distribution, and digestion of
the parts when mingled, and the predominance after the mixture is
complete.
VII. Lastly, there remains the seventh, and last of the seven, modes
of action; namely that by the alternation and interchange of the
other six; but of this, it will not be the right time to offer any
examples, until some deeper investigation shall have taken place of
each of the others. The series, or chain of this alternation, in its
mode of application to separate effects, is no less powerful in its
operation, than difficult to be traced. But men are possessed with the
most extreme impatience, both of such inquiries, and their practical
application, although it be the clue of the labyrinth in all greater
works.
But it must be noted, that in this our organ, we treat of logic, and
not of philosophy. Seeing, however, that our logic instructs and
informs the understanding, in order that it may not, with the small
hooks, as it were, of the mind, catch at, and grasp mere abstractions,
but rather actually penetrate nature, and discover the properties and
effects of bodies, and the determinate laws of their substance (so that
this science of ours springs from the nature of things, as well as
from that of the mind); it is not to be wondered at, if it have been
continually interspersed and illustrated with natural observations and
experiments, as instances of our method. The prerogative instances are,
as appears from what has preceded, twenty-seven in number, and are
termed: solitary instances, migrating instances, conspicuous instances,
clandestine instances, constitutive, instances, similar instances,
singular instances, deviating instances, bordering instances,
instances of power, accompanying and hostile instances, subjunctive
instances, instances of alliance, instances of the cross, instances
of divorce, instances of the gate, citing instances, instances of the
road, supplementary instances, lancing instances, instances of the
rod, instances of the course, doses of nature, wrestling instances,
suggesting instances, generally useful instances, and magical
instances. The advantage, by which these instances excel the more
ordinary, regards specifically either theory or practice, or both. With
regard to theory, they assist either the senses or the understanding;
the senses, as in the five instances of the lamp; the understanding,
either by expediting the exclusive mode of arriving at the form, as in
solitary instances, or by confining, and more immediately indicating
the affirmative, as in the migrating, conspicuous, accompanying, and
subjunctive instances; or by elevating the understanding, and leading
it to general and common natures, and that either immediately, as in
the clandestine and singular instances, and those of alliance; or very
nearly so, as in the constitutive; or still less so, as in the similar
instances; or by correcting the understanding of its habits, as in
the deviating instances; or by leading to the grand form or fabric of
the universe, as in the bordering instances; or by guarding it from
false forms and causes, as in those of the cross and of divorce. With
regard to practice, they either point it out, or measure, or elevate
it. They point it out, either by showing where we must commence in
order not to repeat the labors of others, as in the instances of power;
or by inducing us to aspire to that which may be possible, as in the
suggesting instances; the four mathematical instances measure it. The
generally useful and the magical elevate it.
Again, out of these twenty-seven instances, some must be collected
immediately, without waiting for a particular investigation of
properties. Such are the similar, singular, deviating, and bordering
instances, those of power, and of the gate, and suggesting, generally
useful, and magical instances; for these either assist and cure
the understanding and senses, or furnish our general practice. The
remainder are to be collected when we furnish our synoptical tables
for the work of the interpreter, upon any particular nature; for these
instances, honored and gifted with such prerogatives, are like the
soul amid the vulgar crowd of instances, and (as we from the first
observed) a few of them are worth a multitude of the others. When,
therefore, we are forming our tables they must be searched out with the
greatest zeal, and placed in the table. And, since mention must be made
of them in what follows, a treatise upon their nature has necessarily
been prefixed. We must next, however, proceed to the supports and
corrections of induction, and thence to concretes, the latent process,
and latent conformations, and the other matters, which we have
enumerated in their order in the twenty-first aphorism, in order that,
like good and faithful guardians, we may yield up their fortune to
mankind upon the emancipation and majority of their understanding; from
which must necessarily follow an improvement of their estate, and an
increase of their power over nature. For man, by the fall, lost at once
his state of innocence, and his empire over creation, both of which can
be partially recovered even in this life, the first by religion and
faith, the second by the arts and sciences. For creation did not become
entirely and utterly rebellious by the curse, but in consequence of the
Divine decree, “in the sweat of thy brow shalt thou eat bread,” she
is compelled by our labors (not assuredly by our disputes or magical
ceremonies), at length, to afford mankind in some degree his bread,
that is to say, to supply man’s daily wants.
FOOTNOTES:
[Footnote 2: Selection from the Preface to the _Novum Organum_.]
[Footnote 3: Part II, Conclusion of the _Novum Organum_.]
II
NICOLAUS COPERNICUS
1473-1543
_One of the first and most striking contributions to modern science
was the substitution of the Copernican for the Ptolemaic conception of
the universe._
_Nicolaus Copernicus was born in the Prussian village of Thorn,
located on the Vistula River, February 19, 1473. Although destined for
the Church, he became interested in medicine, which he studied at the
University of Cracow. Later, he turned to mathematics and continued
his studies at the Universities of Vienna, Bologna, Padua, Ferrara,
and Rome. Although he settled down as canon at Frauenberg, Poland, and
gratuitously practised medicine in conjunction with his ecclesiastical
duties, he found considerable time for other intellectual pursuits.
Reading widely in the Greek philosophers, he came across a statement
that the earth moved in its own orbit. This idea deeply appealed to
him. “Occasioned by this,” he wrote, “I also began to think of a
motion of the earth, and although the idea seemed absurd, still, as
others before me had been permitted to assume certain circles in order
to explain the motions of the stars, I believed it would be readily
permitted me to try whether on the assumption of some motion of the
earth better explanations of the revolutions of the heavenly bodies
might not be found. And thus I have, assuming the motions which I in
the following work attribute to the earth, after long and careful
investigation, finally found that when the motions of the other planets
are referred to the circulation of the earth and are computed for the
revolution of each star, not only do the phenomena necessarily follow
therefrom, but the order and magnitude of the stars and all their orbs
and the heaven itself are so connected that in no part can anything be
transposed without confusion to the rest and to the whole universe.”_
_In 1530 he issue a “Commentariolus” which outlined his theory, but
his prudence prompted him to withhold the publication of his great
work, “De Orbium Caelestium Revolutionibus,” until 1543. In May of that
year the first printed copy was laid on his death-bed._
THE NEW IDEA OF THE UNIVERSE[4]
I can well believe, most holy father, that certain people, when they
hear of my attributing motion to the earth in these books of mine, will
at once declare that such an opinion ought to be rejected. Now, my own
theories do not please me so much as not to consider what others may
judge of them. Accordingly, when I began to reflect upon what those
persons who accept the stability of the earth, as confirmed by the
opinion of many centuries, would say when I claimed that the earth
moves, I hesitated for a long time as to whether I should publish that
which I have written to demonstrate its motion, or whether it would
not be better to follow the example of the Pythagoreans, who used to
hand down the secrets of philosophy to their relatives and friends only
in oral form. As I well considered all this, I was almost impelled to
put the finished work wholly aside, through the scorn I had reason to
anticipate on account of the newness and apparent contrariness of my
theory to reason.
My friends, however, dissuaded me from such a course and admonished
me that I ought to publish my book, which had lain concealed in my
possession not only nine years, but already into four times the ninth
year. Not a few other distinguished and very learned men asked me to do
the same thing, and told me that I ought not, on account of my anxiety,
to delay any longer in consecrating my work to the general service of
mathematicians.
But your holiness will perhaps not so much wonder that I have dared to
bring the results of my night labors to the light of day, after having
taken so much care in elaborating them, but is waiting instead to
hear how it entered my mind to imagine that the earth moved, contrary
to the accepted opinion of mathematicians--nay, almost contrary to
ordinary human understanding. Therefore I will not conceal from your
holiness that what moved me to consider another way of reckoning the
motions of the heavenly bodies was nothing else than the fact that the
mathematicians do not agree with one another in their investigations.
In the first place, they are so uncertain about the motions of the sun
and moon that they cannot find out the length of a full year. In the
second place, they apply neither the same laws of cause and effect, in
determining the motions of the sun and moon and of the five planets,
nor the same proofs. Some employ only concentric circles, others use
eccentric and epicyclic ones, with which, however, they do not fully
attain the desired end. They could not even discover nor compute the
main thing--namely, the form of the universe and the symmetry of its
parts. It was with them as if some should, from different places, take
hands, feet, head, and other parts of the body, which, although very
beautiful, were not drawn in their proper relations, and, without
making them in any way correspond, should construct a monster instead
of a human being.
Accordingly, when I had long reflected, on this uncertainty of
mathematical tradition, I took the trouble to read again the books of
all the philosophers I could get hold of, to see if some one of them
had not once believed that there were other motions of the heavenly
bodies. First I found in Cicero that Niceties had believed in the
motion of the earth. Afterwards I found in Plutarch, likewise, that
some others had held the same opinion. This induced me also to begin to
consider the movability of the earth, and, although the theory appeared
contrary to reason, I did so because I knew that others before me had
been allowed to assume rotary movements at will, in order to explain
the phenomena of these celestial bodies. I was of the opinion that I,
too, might be permitted to see whether, by presupposing motion in the
earth, more reliable conclusions than hitherto reached could not be
discovered for the rotary motions of the spheres. And thus, acting on
the hypothesis of the motion which, in the following book, I ascribe
to the earth, and by long and continued observations, I have finally
discovered that if the motion of the other planets be carried over to
the relation of the earth and this is made the basis for the rotation
of every star, not only will the phenomena of the planets be explained
thereby, but also the laws and the size of the stars; all their spheres
and the heavens themselves will appear so harmoniously connected that
nothing could be changed in any part of them without confusion in the
remaining parts and in the whole universe.
THAT THE UNIVERSE IS SPHERICAL
First we must remark that the universe is spherical in form, partly
because this form being a perfect whole requiring no joints, is the
most complete of all, partly because it makes the most capacious
form, which is best suited to contain and preserve everything; or
again because all the constituent parts of the universe, that is the
sun, moon, and the planets appear in this form; or because everything
strives to attain this form, as appears in the case of drops of water
and other fluid bodies if they attempt to define themselves. So no one
will doubt that this form belongs to the heavenly bodies.
THAT THE EARTH IS ALSO SPHERICAL
That the earth is also spherical is therefore beyond question, because
it presses from all sides upon its center. Although by reason of
the elevations of the mountains and the depressions of the valleys
a perfect circle cannot be understood, yet this does not affect the
general spherical nature of the earth. This appears in the following
manner. To those who journey towards the North the north pole of the
daily revolution of the heavenly sphere seems gradually to rise, while
the opposite seems to sink. Most of the stars in the region of the Bear
seem not to set, while some of the southern stars seem not to rise at
all. So Italy does not see Canopes which is visible to the Egyptians.
And Italy sees the outermost star of the Stream, which our region of a
colder zone does not know. On the other hand to those who go towards
the South the others seem to rise and those to sink which are high in
our region. Moreover, the inclination of the Poles to the diameter
of the earth bears always the same relation, which could happen only
in the case of a sphere. So it is evident that the earth is included
between the two poles, and is therefore spherical in form. Let us add
that the inhabitants of the East do not observe the eclipse of the sun
or of the moon which occurs in the evening, and the inhabitants of the
West those which occur in the morning, while those who dwell between
see those later and these earlier. That the water also has the same
form can be observed from ships, in that the land which cannot be seen
from the deck, is visible from the mast-tree. And conversely if a light
be placed at the mast-head it seems to those who remain on the shores
gradually to sink and at last still sinking to disappear. It is clear
that the water also according to its nature continually presses like
the earth downward, and does not rise above its banks higher than its
convexity permits. So the land extends above the ocean as much as the
land happens to be higher.
WHETHER THE EARTH HAS A CIRCULAR MOTION, AND CONCERNING THE LOCATION OF
THE EARTH
As it has been already shown that the earth has the form of a sphere,
we must consider whether a movement also coincides with this form, and
what place the earth holds in the universe. Without this there will be
no secure results to be obtained in regard to the heavenly phenomena.
The great majority of authors of course agree that the earth stands
still in the center of the universe, and consider it inconceivable and
ridiculous to suppose the opposite. But if the matter is carefully
weighed it will be seen that the question is not yet settled and
therefore by no means to be regarded lightly. Every change of place
which is observed is due, namely, to a movement of the observed object
or of the observer, or to movements of both, naturally in different
directions, for if the observed object and the observer move in the
same manner and in the same direction no movement will be seen. Now it
is from the earth that the revolution of the heavens is observed and it
is produced for our eyes. Therefore if the earth undergoes no movement
this movement must take place in everything outside of the earth, but
in the opposite direction than if everything on the earth moved, and
of this kind is the daily revolution. So this appears to affect the
whole universe, that is, everything outside the earth with the single
exception of the earth itself. If, however, one should admit that this
movement was not peculiar to the heavens, but that the earth revolved
from west to east, and if this was carefully considered in regard to
the apparent rising and setting of the sun, the moon and the stars,
it would be discovered that this was the real situation. Since the
sky, which contains and shelters all things, is the common seat of all
things, it is not easy to understand why motion should not be ascribed
rather to the thing contained than to the containing, to the located
rather than to the location. From this supposition follows another
question of no less importance, concerning the place of the earth,
although it has been accepted and believed by almost all, that the
earth occupies the middle of the universe. But if one should suppose
that the earth is not at the center of the universe, that, however,
the distance between the two is not great enough to be measured on the
orbits of the fixed stars, but would be noticeable and perceptible on
the orbit of the sun or of the planets: and if one was further of the
opinion that the movements of the planets appeared to be irregular
as if they were governed by a center other than the earth, then such
an one could perhaps have given the true reasons for the apparently
irregular movement. For since the planets appear now nearer and now
farther from the earth, this shows necessarily that the center of their
revolutions is not the center of the earth: although it does not settle
whether the earth increases and decreases the distance from them or
they their distance from the earth.
REFUTATION OF THE ARGUMENT OF THE ANCIENTS THAT THE EARTH REMAINS STILL
IN THE MIDDLE OF THE UNIVERSE, AS IF IT WERE ITS CENTER
From this and similar reasons it is supposed that the earth rests at
the center of the universe and that there is no doubt of the fact.
But if one believed that the earth revolved, he would certainly be
of the opinion that this movement was natural and not arbitrary. For
whatever is in accord with nature produces results which are the
opposite of those produced by force. Things upon which force or an
outside power has acted, must be injured and cannot long endure: what
happens by nature, however, preserves itself well and exists in the
best condition. So Ptolemy feared without good reason that the earth
and all earthly objects subject to the revolution would be destroyed
by the act of nature, since this latter is opposed to artificial acts,
or to what is produced by the human spirit. But why did not he fear
the same, and in a much higher degree, of the universe, whose motion
must be as much more rapid as the heavens are greater than the earth?
Or has the heaven become so immense because it has been driven outward
from the center by the inconceivable power of the revolution; while if
it stood still, on the contrary, it would collapse and fall together?
But surely if this is the case the extent of the heavens would increase
infinitely. For the more it is driven higher by the outward force of
the movement, so much the more rapid will the movement become, because
of the ever increasing circle which must be traversed in 24 hours; and
conversely if the movement grows the immensity of the heavens grows. So
the velocity would increase the size and the size would increase the
velocity unendingly. According to the physical law that the endless
cannot wear away nor in any way move, the heavens must necessarily
stand still.
But it is said that beyond the sky no body, no place, no vacant space,
in fact nothing at all exists; then it is strange that some thing
should be enclosed by nothing. But if the heaven is endless and is
bounded only by the inner hollow, perhaps this establishes all the more
clearly the fact that there is nothing outside the heavens, because
everything is within it, but the heaven must then remain unmoved.
The highest proof on which one supports the finite character of the
universe is its movement. But whether the universe is endless or
limited we will leave to the physiologues; this remains sure for us
that the earth enclosed between the poles, is bounded by a spherical
surface. Why therefore should we not take the position of ascribing
to a movement conformable to its nature and corresponding to its
form, rather than suppose that the whole universe whose limits are
not and cannot be known moves? and why will we not recognize that
the appearance of a daily revolution belongs to the heavens, but the
actuality to the earth; and that the relation is similar to that of
which one says: “We run out of the harbor, the lands and cities retreat
from us.” Because if a ship sails along quietly, everything outside
of it appears to those on board as if it moved with the motion of
the boat, and the boatman thinks that the boat with all on board is
standing still, this same thing may hold without doubt of the motion
of the earth, and it may seem as if the whole universe revolved. What
shall we say, however, of the clouds and other things floating, falling
or raising in the air--except that not only does the earth move with
the watery elements belonging with it, but also a large part of the
atmosphere, and whatever else is in any way connected with the earth;
whether it is because the air immediately touching the earth has the
same nature as the earth, or that the motion has become imparted to the
atmosphere. A like astonishment must be felt if that highest region
of the air be supposed to follow the heavenly motion, as shown by
those suddenly appearing stars which the Greeks call comets or bearded
stars, which belong to that region and which rise and set like other
stars. We may suppose that part of the atmosphere, because of its great
distance from the earth, has become free from the earthly motion. So
the atmosphere which lies close to the earth and all things floating in
it would appear to remain still, unless driven here and there by the
wind or some other outside force, which chance may bring into play;
for how is the wind in the air different from the current in the sea?
We must admit that the motion of things rising and falling in the air
is in relation to the universe a double one, being always made up of a
rectilinear and a circular movement. Since that which seeks of its own
weight to fall is essentially earthy, so there is no doubt that these
follow the same natural law as their whole; and it results from the
same principle that those things which pertain to fire are forcibly
driven on high. Earthly fire is nourished with earthly stuff, and it
is said that the flame is only burning smoke. But the peculiarity of
the fire consists in this that it expands whatever it seizes upon,
and it carries this out so consistently that it can in no way and
by no machinery be prevented from breaking its bonds and completing
its work. The expanding motion, however, is directed from the center
outward; therefore if any earthly material is ignited it moves upward.
So to each single body belongs a single motion, and this is evinced
preferably in a circular direction as long as the single body remains
in its natural place and its entirety. In this position the movement
is the circular movement which as far as the body itself is concerned
is as if it did not occur. The rectilinear motion, however, seizes
upon those bodies which have wandered or have been driven from their
natural position or have been in any way disturbed. Nothing is so much
opposed to the order and form of the world as the displacement of one
of its parts. Rectilinear motion takes place only when objects are
not properly related, and are not complete according to their nature
because they have separated from their whole and have lost their unity.
Moreover, objects which have been driven outward or away, leaving out
of consideration the circular motion, do not obey a single, simple
and regular motion, since they cannot be controlled simply by their
lightness or by the force of their weight, and if in falling they have
at first a slow movement the rapidity of the motion increases as they
fall, while in the case of earthly fire which is forced upwards--and
we have no means of knowing any other kind of fire--we will see that
its motion is slow as if its earthly origin thereby showed itself.
The circular motion, on the other hand, is always regular, because it
is not subject to an intermittent cause. Those other objects, however,
would cease to be either light or heavy in respect to their natural
movement if they reached their own place, and thus they would fit into
that movement. Therefore if the circular movement is to be ascribed
to the universe as a whole and the rectilinear to the parts, we might
say that the revolution is to the straight line as the natural state
is to sickness. That Aristotle divided motion into three sorts, that
from the center out, that inward toward the center, and that around
about the center, appears to be merely a logical convenience, just
as we distinguish point, line and surface, although one cannot exist
without the others, and none of them are found apart from bodies. This
fact is also to be considered, that the condition of immovability is
held to be nobler and more divine than that of change and inconstancy,
which latter therefore should be ascribed rather to the earth than
to the universe, and I would add also that it seems inconsistent to
attribute motion to the containing and locating element rather than to
the contained and located object, which the earth is. Finally since the
planets plainly are at one time nearer and at another time farther from
the earth, it would follow, on the theory that the universe revolves,
that the movement of the one and same body which is known to take place
about a center, that is the center of the earth, must also be directed
toward the center from without and from the center outward. The
movement about the center must therefore be made more general, and it
suffices if that single movement be about its own center. So it appears
from all these considerations that the movement of the earth is more
probable than its fixity, especially in regard to the daily revolution,
which is most peculiar to the earth.
FOOTNOTES:
[Footnote 4: Selections from the Introduction to _De Orbium
Caelestium Revolutionibus_.]
III
JOHANN KEPLER
1571-1630
_Tycho Brahe (1546-1601), nobleman of Denmark, studied law at
the University of Copenhagen and became attracted to astronomical
studies by the occurrence of a predicted eclipse. Constructing his
own instruments, he made observations of the stars at Augsburg
and Wittenberg, and in 1576 established the first observatory at
Huen, where he continued his work for twenty years. Banished from
Germany, he was invited by Emperor Rudolph to Prague, where he began
his compilation of the Rudolphin Tables which listed many of his
observations on the locations of the planets. Hearing of Kepler’s
interest in astronomy, he secured the young German’s assistance and
assigned to him the study of the planet Mars, which study Kepler
continued after Tycho Brahe’s death in 1601._
_Johann Kepler, the son of an innkeeper, was born December 27, 1571,
in Württemberg and sent to a local school, from which he was removed
when he was nine years old because of his father’s impoverishment.
After three years of work in the tavern, he was sent to a monastic
school and thence to the University of Tübingen. Although he was very
frail in physique, he was a good student and attained high scholarly
standing. Becoming interested in the Copernican theory, in 1599 he was
invited by Tycho Brahe to become his assistant at Prague._
_Kepler found his master’s tables sufficiently accurate in his
efforts to discover some recognizable motion of the planet Mars which
would account for its apparent positions. In the course of this work
he corrected some of the Ptolemaic ideas which Copernicus had not
completely abandoned. The latter retained the epicycle motion of the
planets within their larger revolutions in cycles. In comparing this
theory with his tables, Kepler found that it would not satisfactorily
account for the positions of Mars; and he was therefore led to the
long studies and mathematical computations which finally resulted
in his discovery of the orbit of Mars, and to the establishment of
the first two of his three famous laws: “1. the planet describes an
ellipse, the sun being in one focus; 2. the straight line joining the
planet to the sun sweeps out equal areas in equal intervals of time.”
(Sedgwick and Tyler, pp. 211-213). He published these laws in 1609 in
his “Commentaries on the Motions of Mars.”_
_In 1611, when his patron, Emperor Rudolph, was compelled to
abdicate, Kepler was left penniless, but he moved to Linz where he was
appointed to a professorship. In 1619 he published his “Harmony of
the World,” which contained his third law: “The squares of the times
of revolution of any two planets (including the earth) about the sun
are proportional to the cubes of their mean distances from the sun.”
(Sedgwick and Tyler, p. 213). This was the triumph about which he wrote
in the year of its discovery, 1618: “What I prophesied twenty-two years
ago, as soon as I found the heavenly orbits were of the same number
as the five (regular) solids, what I fully believed long before I
had seen Ptolemy’s Harmonies, what I promised my friends in the name
of this book, which I christened before I was sixteen years old, I
urged as an end to be sought, that for which I joined Tycho Brahe, for
which I settled at Prague, for which I have spent most of my life at
astronomical calculations--at last I have brought to light, and seen to
be true beyond my fondest hopes. It is not eighteen months since I saw
the first ray of light, three months since the unclouded sun-glorious
sight! burst upon me. Let nothing confine me: I will indulge my sacred
ecstasy. I will triumph over mankind by the honest confession that I
have stolen the golden vases of the Egyptians to raise a tabernacle for
my God far away from the lands of Egypt. If you forgive me, I rejoice;
if you are angry, I cannot help it. The book is written; the die is
cast. Let it be read now or by posterity, I care not which. It may well
wait a century for a reader, as God had waited six thousand years for
an observer.” Kepler died at Ratisbon, November 15, 1630._
ON THE PRINCIPLES OF ASTRONOMY[5]
What is _astronomy_? It is the science of treating of the causes
of those celestial appearances which we who live on the earth observe
and which mark the changes of times and seasons; by the studying of
which we are able to predict for the future the face of the heavens,
that is, the stellar phenomena, and to assign fixed dates for those
which have occurred in the past.
_Why is it called astronomy?_ From the law (νουος) or governance
of the stars (ἀστρα), that is, of the motions in which the stars move,
just as economy is named from the law of domestic affairs (οἰκονουία)
and paedonomy (παιδονουία) from the ruling of youths.
_What is the relation of this science to the other sciences?_ 1)
It is a branch of physics because it investigates the causes of natural
objects and events, and because among its subjects are the motions of
the heavenly bodies, and because it has the same end as physics, to
inquire into the conformation of the world and its parts.
2) Astronomy is the soul of geography and hydrography, for the various
appearances of the sky in various districts and regions of the earth
and sea are known only by astronomy.
3) Chronology is dependent upon it, because the movements of the
heavenly bodies prescribe seasons and years and date the histories.
4) Meteorology is also its subordinate, for the stars move and
influence this sublunary nature and even men themselves.
5) It includes a large part of optics, because it has a subject in
common with that; that is, the light of the heavenly bodies, and
because it corrects many errors of sight in regard to the character of
the earth and its motions.
6) It is, however, subordinate to the general subject of mathematics
and uses arithmetic and geometry as its two wings, studying the extent
and form of the bodies and motions of the universe and computing the
periods, by these means expediting its demonstrations and reducing them
to use and practical value.
_How many, then, are the branches of astronomical study?_ The
departments of the study of astronomy are five; historical, in the
matter of observations, optical as to the hypothesis, physical as
to the causes of the hypotheses, arithmetical as to the tables and
calculations, mechanical as to its instruments.
* * * * *
_Since we must begin with appearances, explain how the world seems to
be made up._ The world is commonly thought, accepting the testimony
of the eyes, to be an immense structure consisting of two parts, the
earth and the sky.
_What do men imagine concerning the figure of the earth?_ The
earth seems to be a broad plane extending in a circle in every
direction around the spectator. And from this appearance of a plane
bounded by a great circle the appellation, _orbis terrarum_,
the circle of the earth, has arisen, and has been taken over by the
Scripture and among other nations.
_What do men imagine to be the center of the earth?_ Each nation,
unless it has become familiar with the notion of the circle, thinks by
the instinct of nature and the error of vision that its country is in
the center or middle of this plane circle. So the common people among
the Jews believe still that Jerusalem, the earliest home of their race,
is situated at the center of the world.
_What do men think about the waters?_ Since men proceeding as far
as possible in any direction finally came upon the ocean, some have
thought that the earth is like a disc swimming in the waters, and that
the waters are held up by the lower part of the sky, whence poets have
called the ocean, the father of all things. Others believe that a strip
of land surrounds the ocean which keeps the water from flowing away,
and these suppose there is land under the water, saying that the water
is held up by the earth. Besides these there are still others who,
since the ocean seems higher than the land if it is looked at from the
edge of the shore, believe that the earth is, as it were, sunk in the
waters and supernaturally guarded by the omnipotence of God lest the
waters rushing in from the deep should overwhelm it.
_What do men imagine to be under both the land and the waters?_
There has been great discussion among men marveling concerning the
foundation which could bear up the great mass of the earth so that
it should remain for so many centuries firm and immovable and should
not sink; and Heraclitus among the early philosophers, and Lactantius
among the ecclesiastics said that it reached down to the lowest root of
things.
_How about the other part of the world, the sky and its extent?_
Men have thought that the sky was not much larger than the earth, and
indeed was connected with the earth and the ocean at the circumference
of the circle, so that it bounded the earth; and that anyone going
that far, if it could be done, would run up against the sky, blocking
further progress. With this idea of men the Scriptures also agreed.
So also the poets said that Mt. Atlas, a lofty mountain on the
farthest shore of Africa, bore up the sky on his shoulders, and Homer
placed the Aethiopeans at the extremities of the rising and setting
sun, thinking that because of the contiguity of the earth and sky
there, the sun was so close to them that it burned their skin.
_What form do they ascribe to the sky?_ The eyes ascribe to the
sky the shape of a tent, extending over our heads and beyond the
sun, moon and stars, or rather the shape of an arch overspanning the
terrestrial plane, with a long curve, so that the part of the sky just
over the head of the spectator is much nearer to him than the part that
touches the mountains.
_What have men conceived in regard to the motion of the sky?_
Whether the sky moves or stands still is not apparent to the sight
because the tenuity of its substance escapes the eyes, unless indeed
those things appear to stand still in which the eye can perceive no
variation. But the changing positions of the sun, moon and stars in
relation to the ends of the earth was apparent to the eyes. For the
sun seems to emerge from an opening between the sky and the immovable
mountains and ocean, as if coming out of a chamber, and having
traversed the vault of the sky seems to sink again in the opposite
region; so also the moon, and the planets, and the whole host of stars
proceed as if strictly marshalled and drawn up in line, first one and
then the other marching along, each in his order and place.
And so, since the ocean lies beyond the extreme lands, the mass of men
have thought that the sun plunges into the ocean and is extinguished,
and from the opposite region a new sun issues forth daily from the
ocean. The poets have used this figure in their creations. But,
indeed, there have been even philosophers who have declared that on
the farthest shores of Lusitania could be heard the roar of the ocean
extinguishing the flames of the sun, as Strabo recounts.
* * * * *
_I understand the forms of the sky and the earth and the atmosphere
surrounding the earth, also the place of the earth in the universe; now
I would ask what causes the stars to seem to rise daily from the one
part of the horizon and to sink in the opposite part; the motion of the
sky or of the earth?_ The astronomy of Copernicus shows that our
sight has led us astray in regard to this motion; for the stars do not
actually come up from beyond the mountains and climb toward the zenith,
but rather the mountains which surround us and which are a part of the
surface of the earth are revolved along with the whole globe about its
axis from west to east and by this revolution the immovable stars of
the east are disclosed to us one after the other, and those of the west
are obscured, so the stars are not passing over us, but the vertical
point is moving through the fixed stars.
_You say that by this marvelous hypothesis may be explained
satisfactorily all the phenomena of the first motion and the spherical
theory._ Just so, and that is the scope of this section, to
demonstrate in fact what has been suggested in words.
_How do you expect to be able to prove this absurd hypothesis,
and by what arguments?_ It is possible to demonstrate that this
first motion results from the revolution of the earth about its axis,
while the heavenly bodies are at rest (as far as this first motion is
concerned), by seven kinds of arguments: 1) from the subject of the
motion; 2) from the velocity of the motion; 3) from the equableness of
the motion; 4) from the cause of the motion, or the moving principle;
5) from the motive instruments, that is, the axis and the poles; 6)
from the object of the first motion; and 7) from the indications or
results.
_Demonstrate it then from the subject of the motion._ Nature does
not seek difficult means when she can use simple ones. Now, by the
rotation of the earth, a very small body, about its axis, toward the
east, the same thing is accomplished as by the rotation of the immense
universe about its axis toward the west. Just as it is more likely that
a man’s head turns in the auditorium than that the auditorium is turned
about his head, so it is more credible that the earth is rotating from
west to east, than that the rest of the machine of the universe is
revolved from east to west, since in both cases the same thing results.
If the first motion is in the heavenly bodies, then they are subject
to two motions, one common to the whole universe, the other particular
to each sphere; but it is much more probable that the two motions
should be distinct in regard to their subjects, so that the second set
of motions, which is multifold, should belong to each sphere, and the
first, which is single, should belong to the single body of the earth,
and to it alone.
_Why cannot the whole machinery of the universe be moved?_ The
universe is either infinite or finite. Suppose it to be the former,
according to the opinion of William Gilbert, who thinks that the
omnipotence of God is illustrated in this that the universe extends
outward infinitely, so that the infinite power of the creator would be
recognized from the infinite extent of the creation. Although this may
be refuted by metaphysical arguments, no argument on either side can be
drawn from astronomy, in which trust is placed rather in the evidence
of the senses than in abstract reasonings not dependent on observation.
But supposing this universe to be infinite, Aristotle has shown that
the whole universe should not be moved about in a revolution since it
is the whole.
But let the universe be finite; then there is nothing outside the
universe which would locate the universe but should remain quiet
itself. Where there is nothing that rests there is no motion. For 1)
motion is the separation of a movable thing from its place and its
transfer to another place: 2) the motion of a machine about an axis and
quiescent poles cannot be grasped by the mind where there is nothing in
respect to which the poles remain still.
FOOTNOTES:
[Footnote 5: From _The Epitome of Astronomy_.]
IV
GALILEO GALILEI
1564-1642
_Galileo Galilei, born at Pisa, February 15, 1564, was the son of
a mathematician who, seeing no future in that profession, had him
educated for the practice of medicine. But when Galileo was about
eighteen years of age, while observing a large lamp swinging in
the Pisa cathedral, he noticed that, regardless of the length of
the oscillation, the time did not vary. In spite of his father’s
discouragements, therefore, he became absorbed in mathematics and
abandoned the study of medicine. Applying himself to the study of
motion, he performed his famous experiment of letting bodies of
different weights fall from the leaning tower of Pisa, proving that
things of unequal weight, if heavier than the resistance of air, fall
with the same speed. The doctrine of inertia which he deduced from
this and similar experiments decisively answered the opponents of
Copernicus; for the principle stated that bodies would continue to
move in the same direction forever unless their course was disturbed
or opposed by another force, and that the motion of bodies resulted
from independent forces operating upon them. His treatise on the center
of gravity in solids earned him a lectureship at the University of
Pisa._
_Meeting malignant opposition at Pisa, he secured the chair of
mathematics at Padua (which he held from 1592 to 1610) and there
continued his observations and experiments in physics and chemistry.
He succeeded in making a crude thermometer in 1600. In 1609 he learned
that Hans Lippershey, an optician of Middleburg, had succeeded in
making a telescope. He thereupon made one of his own and improved it
until it had a power of magnifying thirty-two times, enabling him to
discover the mountainous surface of the moon, the moons of the planet
Jupiter, the fact that Venus showed different sides like the moon, and
that many small stars made up the Milky Way._
_In 1610 he left Padua for Florence, and by 1613 openly declared
his acceptance of Copernican ideas. Immediately he was opposed by
theologians, and after being given an opportunity to renounce his
adherence to the new system of astronomy, was sentenced in 1616 not to
hold, teach, or defend it. In 1623, when his friend Maffeo was made
Pope Urban VIII, he wrote his dialogues on the system of the world. He
had much difficulty in getting them published and succeeded only when
he assured the authorities that they were not heretical. It was quite
evident, however, that the dialogues were slightly concealed arguments
for the acceptance of the Copernican system and consequently in 1633
he was summoned before the Inquisition and compelled to renounce his
heresy. In 1637, a few months after he had discovered the librations
of the moon, he lost his sight. He died five years later, January 8,
1642._
THE COPERNICAN VERSUS THE PTOLEMAIC ASTRONOMIES[6]
Formerly I used frequently to visit the marvelous city of Venice
and to meet there Signore Giovan Francesco Sagredo, a man of most
distinguished ancestry and remarkable intelligence. Thither also came
from Florence, Signore Filippo Salviati, whose least claim to renown
was his noble blood and great wealth; a noble mind, that held no
enjoyment of greater price than that of study and thought. With both
of these men I often discussed these questions, in the presence of
a Peripatetic philosopher, who apparently valued the acquisition of
knowledge in no way in so high a degree, as he did the renown which his
interpretations of Aristotle had gained for him.
Now that cruel death has robbed the cities of Venice and Florence
of these two enlightened men in the bloom of their years, I have
endeavored, as far as my weak powers may permit, to perpetuate their
fame in these pages by making them the speakers in this dialogue.
The valiant Peripatetic also shall not fail to appear; because of
his over-weaning love for the commentary of Simplicius, it seemed
permissible to omit his own name and let him pass under that of his
favorite author. May the souls of these two great men accept this
public testimony of my undying love; may the recollection of their
eloquence aid me in setting down for posterity the spoken discussions.
SECOND DAY
SALVIATI: We departed yesterday so often and so far from the
direct path of our discussion, that I can scarcely return to the right
point and proceed without your help.
SAGREDO: I find it quite intelligible that you are somewhat at
a loss, since you have had your head so full of both the things already
brought forward and things still to be discussed. I, however, who as
merely a listener have in mind only the things already discussed, may
I hope set our investigation straight by a brief summary of what has
been gone over. So, if my memory fails not, the chief result of our
yesterday’s conversation was that we tested thoroughly which of the
two theories was the more probable and better grounded; that according
to which the substance of the heavenly bodies is unproducible,
indestructible, unchangeable, intangible, in brief not subject to
any variation aside from change of location, and so presents a fifth
element which is entirely distinct from our elementary, producible,
destructible, changeable bodies; or the other view, according to which
an incongruity between parts of the universe is rejected, our earth
rather enjoys the same privileges as the rest of the constituent
bodies of the universe, in a word, is a freely moving ball just as
the moon, Jupiter, Venus, or any other planet. Finally we noticed the
many similarities in particular between the earth and the moon, and of
course with the moon more than any other planet because of the closer
and more definite knowledge which we possess of it by reason of its
less distance. Since we agreed that this second opinion possessed the
greater probability, the logical consequence, it seems to me, is that
we should investigate the question whether we should hold the world
immovable, as has been formerly believed in general, or movable as some
ancient philosophers believed and as some recent ones suppose: and if
movable, how its movement could have been produced.
SALV.: Let us begin our discussion with the admission
that whatever sort of motion may be ascribed the earth, we, as its
inhabitants and therefore partakers in the movement, would be
unconscious of it, as if it did not occur, since we can only take into
consideration earthly things. Therefore it is necessary that this
movement should seem to belong to all the other bodies and visible
objects in common which, separated from the earth, have no share in its
movement. The correct method of determining whether movement is to be
attributed to the earth, and what movement, is that one should inquire
and observe whether an apparent movement can be ascribed to the bodies
outside of the earth, which belongs to all of them in the same degree.
So a movement which, for example, can be supposed of the moon, and not
of Venus or Jupiter or other stars, cannot be peculiar to the earth.
Now there is such a general movement governing all other objects,
namely that which the sun, moon, planets, fixed stars, in a word the
whole universe with the single exception of the earth, seems to follow
from east to west within the space of twenty-four hours. This, at least
at first glance, may be just as well attributed to the earth alone, as
to the rest of the entire universe except the earth.
SAGR.: I understand clearly that your suggestion is correct.
An objection, however, forces itself upon me that I cannot solve. That
is, since Copernicus ascribes to the earth a further movement aside
from the daily one, according to the above mentioned principle this
should be apparently un-noticeable on the earth, but should be visible
in the rest of the universe. I come then to the conclusion that either
he plainly erred when he ascribed to the earth a movement to which
no counterpart is apparent in the firmament, or else such a movement
exists, and then Ptolemaus is guilty of a second error in that he did
not refute with arguments this movement as well as that daily rotation.
SALV.: Your objection is very just. If we take up this
other movement, you shall see how much superior in intelligence was
Copernicus to Ptolemaus, in that he saw what this one did not, namely
how wonderfully this second motion is reflected in the rest of the
heavenly bodies. For the present, however, we will leave this aside and
return to our first consideration. Proceeding from the most general
suppositions, I will present the arguments which seem to favor the
motion of the earth, in order then to hear the opposing arguments
of Signore Simplicio. First, then, when we consider the immense
circumference of the stellar sphere in comparison with the smallness
of the earth, which is contained in that several million times, and
therefore regard the velocity of motion which would be necessary for
an entire revolution in the course of a day and night, I am unable to
understand how any one could hold it more reasonable and credible that
it is this whole stellar sphere that moves and that the earth remains
still.
SAGR.: Even if universal phenomena which depend upon these
movements could be explained as readily by the one hypothesis as by
the other, yet by the first general impression I would regard as more
unreasonable the view that the whole universe moves; just as if any
one should climb to the top of your dome for the purpose of getting
a view of the city and its environs and then should demand that the
whole region be made to move around him to save him the trouble of
turning his head. In any event, there would have to be great advantages
connected with this theory, which were lacking in the other, in
order that such an absurdity should be balanced and outweighed and
should appear more credible than the opposite opinion. But Aristotle,
Ptolemaus, and Signore Simplicio must find such advantages in their
theory, and I should be glad if we might hear these advantages if they
exist, or if they do not, that some one would explain to me why they do
not and cannot exist.
SALV.: If, in spite of every sort of investigation, I am
able to find no such differences, I believe I have thereby discovered
that such difference does not exist. So in my opinion it is useless
to pursue this further: rather let us proceed. Motion is only so far
motion and acts as such, if it stands in relation to things which lack
motion. In relation to things that are all in the same degree affected
by it, it is as much without effect as if it did not take place. The
wares with which a ship is loaded move, when they depart from Venice
and arrive at Aleppo, passing Korfu, Candia, Cyprus etc; since Venice,
Korfu and Candia remain fixed and do not move with the ship. But in
respect to the bales, chests, and other pieces of baggage which are
on the ship as cargo or ballast, the movement of the ship itself from
Venice to Syria is as good as non-existent, since their position in
relation to one another does not change; and this is due to the fact
that the movement is a common one in which they all take part. If of
the wares on the ship one bale moves only an inch away from the chest,
this is for it a greater movement in relation to the chest, than the
whole journey of 2,000 miles which they undergo in common.
Therefore, since plainly the motion which many movable bodies undergo
in common is without effect and, with regard to their mutual position
toward one another, it is as if it did not exist, for there is no
change among them; and since it only affects the relative position
of such bodies as do not share in the movement, for in this case the
mutual relation is changed; since we have divided the universe into
two parts, of which one must be movable and the other immovable; then
for all purposes this movement will be of the same effect whether it
is ascribed to the earth alone or to all the rest of the universe. For
the working of such a motion is on nothing but the relative position in
which the earth and the heavenly bodies stand to one another, and aside
from this relative position nothing changes. If now it is indifferent
for accomplishing this result whether the earth alone moves and the
whole universe rests, or the earth rests and the whole universe is
subject to one common movement, who can believe that Nature--who by
common agreement does not employ great means when she can obtain the
same result by smaller ones--would have undertaken to set in motion
an immeasurable number of mighty bodies, and that with incredible
velocity, to accomplish what could be obtained by the moderate motion
of one single body around the center?
SIMPL.: I do not agree that that mighty movement would be as
if it did not happen in regard to the sun, the moon, the innumerable
host of fixed stars. Do you call it nothing that the sun goes from
one meridian to another, rises from one horizon, sinks under another,
brings now day, now night; that the moon goes through similar changes
and likewise the other planets, as well as the fixed stars?
SALV.: All the changes mentioned by you are such only with
respect to the earth. To demonstrate this, only imagine yourself away
from the earth; there is then no rising or setting of the sun, no
horizons, no meridians, no day, no night; in a word, by the movement
mentioned no change in the relation of the moon to the sun or to any
other star is evoked. All these changes have reference to the earth;
they are supposed only because the sun is first visible in China, then
Egypt, Greece, France, Spain, America, and so on, and so also for the
moon and the other heavenly bodies. The same process would occur in
the same way, if, without disturbing so vast a part of the universe,
the earth alone should be revolved.
The difficulty is however doubled since a second very important one is
added. That is, if one attributes to the firmament this mighty motion,
one must regard it as necessarily opposed to the particular movements
of all the planets, all of which indisputably have their own movements
from west to east, and in comparison very moderate movements at that.
One is then forced to the conclusion that they depart from that
rapid daily motion, namely from east to west, to go in the opposite
direction. But, if we suppose that the earth moves, the opposition of
motions disappears and the single movement from west to east fits in
with all the facts and explains them most satisfactorily.
SIMPL.: As far as this opposition of motions is concerned that
has little importance, since Aristotle proves that the circular motions
are not opposed to one another and that the apparent opposition cannot
actually be called so.
SALV.: Does Aristotle prove that or merely suppose it,
because it aids him for a certain purpose? If, according to his own
declaration, those things are opposed which mutually destroy one
another I do not see how two moving bodies which meet one another in a
circular motion should do one another less harm than if they meet on a
straight line.
SAGR.: Wait a moment, I pray. Tell me, Signore Simplicio, if
two knights run into one another with leveled lances on the open field,
if two squadrons or two streams on their way to the sea break through
and unite with one another, would you call such collisions opposed
movements?
SIMPL.: Of course we would call them opposed.
SAGR.: How then is there no opposition in circular motions?
For the movements mentioned take place upon the surface of the earth
or water, both of which are recognized to be circular in form and so
the motions must be circular. Do you understand, Signore Simplicio,
what circular motions are not opposed to one another? Two circles which
touch each other on the outside and of which the revolution of one is
in a reverse direction from that of the other. If, however, one circle
is within the other, then motions in different directions must be
opposed to one another.
SALV.: Whether opposed or not opposed is merely a strife of
words. I know that in fact it is simpler and more natural to accomplish
everything with one motion than to call in two. If you do not wish to
call them opposite, then call them reverse. Moreover, I mention this
introduction of a double movement not as something impossible, and in
no way propose to deduce from it a strong proof for the motion of the
earth, but merely a high degree of probability for it.
The improbability of the movement of the universe about the earth is
tripled, however, by the complete upsetting of that arrangement which
governs all the heavenly bodies whose circular motion is accepted not
doubtfully but with full assurance. That is, that in such cases the
larger the orbit the longer the time required for its completion,
and the smaller, the shorter. Saturn, whose course surpasses all the
planets in extent, completes it in thirty years. Jupiter revolves in a
smaller circle in twelve years. Mars in two, the moon in a month. We
see clearly in the case of the Medicean stars [the moons of Jupiter]
that the one nearest Jupiter goes through its orbit in a very short
time, namely, forty-two hours, the next nearest in three and a half
days, the third in seven days, and the farthest removed in sixteen
days. This thoroughly constant rule remains unchanged if we ascribe
the twenty-four hour movement to the revolution of the earth, but if
we suppose the earth to remain unmoved, we must proceed from the short
period of the moon to increasingly greater periods, to the two year
period of Mars, the twelve year period of Jupiter, the thirty year
period of Saturn, and then abruptly to a disproportionately larger
orbit, to which must also be ascribed the revolution in twenty-four
hours. And these suppositions entail the smallest part of the
disturbance of the otherwise constant law. For when one passes from
the orbit of Saturn to those of the fixed stars and attributes to them
even greater orbits, which correspond to the period of revolution
of many thousands of years, one must pass from this by a much more
disproportionate transition to that other movement and ascribe to them
a period of revolution about the earth of twenty-four hours. But if
the movement of the earth is supposed, the regularity of the period is
accounted for in the best possible way; from the slow period of Saturn
we arrive at the immovable fixed star.
A fourth difficulty also is encountered which must be added if
we suppose the motion of the smaller sphere. I mean the great
dissimilarity in movements of these stars, some of which must revolve
at a tremendous rate in immense circles, others slowly in smaller
circles, according as they are placed at greater or smaller distances
from the pole. And not only the size of the different circles and so
the velocity of movement varies greatly in different fixed stars, but
also the same stars change their courses and their velocity; herein
is the fifth difficulty. That is, those stars which 2,000 years ago
stood on the equator of the stellar sphere and thereafter moved in
the greatest circles, must now, since to-day they have moved several
degrees from it, move more slowly and in smaller circles. Within a
conceivable time it will happen that one of those which have been
continually moving will eventually reach the pole and cease to revolve,
then later, after a period of rest, begin to move again. The other
stars, however, which undoubtedly move, all have, as has been said, as
orbit an immense circle and move in it without change.
The improbability is increased (and this may be called a sixth
difficulty) for him who investigates basic principles, by the fact that
one cannot imagine the firmness which that immense sphere must possess,
in whose depths so many stars are so solidly fixed that in spite of
such varieties of motions they are held together in the revolution
without in any way changing their relative positions. But if according
to the most probable view the heavens are fluid, so that each star may
describe its own orbit, by what law and according to what principles
are their orbits governed, so that seen from the earth they appear as
if held in one sphere? To accomplish this it seems to me it would be
easier and more convenient to make them stationary instead of movable,
just as the paving stones in the market place are kept in order more
easily than the troops of children who race over them.
Finally the seventh objection; if we ascribe the daily revolution to
the highest heavens we must suppose this to be of such power and force
that it bears along the innumerable crowd of fixed stars, every one a
body of immense mass and much larger than the earth, further, all the
planets, although these by their nature move in an opposite direction.
Moreover, we must suppose that the element of fire and the greater
portion of the air is also borne along; therefore, singly and alone the
little earth ball withstands stubbornly and independently this mighty
force: a supposition that seems to me to have much against it. I cannot
explain how the earth, a body freely suspended and balanced on its
axis, inclined by nature as much toward motion as the rest, surrounded
by a fluid medium, is not seized on by this general revolution. We do
not encounter this difficulty, however, if we suppose the earth to
move, a body so small, so inconsiderable in comparison with the whole
universe that it could have no effect at all upon this.
FOOTNOTES:
[Footnote 6: Translated from the _Dialogo dei due Massima Systemi del
Mondo_ (1632).]
V
WILLIAM HARVEY
1578-1657
_In 1615 William Harvey stated his theory of the circulation of the
blood, which he derived from patient observations, in his lectures
on anatomy. The theory was epoch-making in the history of physiology
because it initiated the study of the chemical constituency of the
blood and of its function in nutrition._
_Harvey, born April 1, 1578, in the south of England, attended the
University of Cambridge, and took his degree in 1597. The following
four years he studied at Padua under Fabricius. In 1602, when he
returned to England, he began the practice of medicine, and in 1609
became connected with St. Bartholomew’s Hospital. He published his
“Excercitatio” in 1628, served for several years as physician to
Charles I, and retired in 1646 to private life. He died June 3,
1657._
_He described the process of his discovery as follows: “I frequently
and seriously bethought me, and long revolved in my mind, what might be
the quantity of blood which was transmitted, in how short a time its
passage might be effected, and the like; and not finding it possible
that this could be supplied by the juices of the ingested aliment
without the veins on the one hand being drained, and the arteries on
the other hand becoming ruptured through the excessive charge of blood,
unless the blood should somehow find its way from the arteries into
the veins, and so return to the right side of the heart; I began to
think whether there might not be a motion, as it were, in a circle. Now
this I afterwards found to be true; and I finally saw that the blood,
forced by the action of the left ventricle into the arteries, was
distributed to the body at large, and its several parts, in the same
manner as it is sent through the lungs, impelled by the right ventricle
into the pulmonary artery, and that it then passed through the veins
and along the vena cava, and so round to the left ventricle in the
manner already indicated,--which motion we may be allowed to call
circular._”
THE CIRCULATION OF BLOOD IN ANIMALS[7]
Thus far I have spoken of the passages of the blood from the veins
into the arteries, and of the manner in which it is transmitted and
distributed by the action of the heart; points to which some, moved
either by the authority of Galen or Columbus, or the reasonings of
others, will give in their adhesion. But what remains to be said upon
the quantity and source of the blood which thus passes, is of so novel
and unheard-of character, that I not only fear injury to myself from
the envy of the few, but I tremble lest I have mankind at large for my
enemies, so much doth wont and custom, that become as another nature,
and doctrine once sown and that hath struck deep root, and respect
for antiquity influence all men: Still the die is cast, and my trust
is in my love of truth, and the candour that inheres in cultivated
minds. And sooth to say, when I surveyed my mass of evidence, whether
derived from vivisections, and my various reflections on them, or from
the ventricles of the heart and the vessels that enter into and issue
from them, the symmetry and size of these conduits,--for nature doing
nothing in vain, would never have given them so large a relative size
without a purpose,--or from the arrangement and intimate structure
of the valves in particular, and of the other parts of the heart in
general, with many other things besides, I frequently and seriously
bethought me, and long revolved in my mind, what might be the quantity
of blood that was transmitted, in how short a time its passage might
be effected, and the like; and not finding it possible that this could
be supplied by the juices of the ingested aliment without the veins on
the one hand becoming drained, and the arteries on the other getting
ruptured, through the excessive charge of blood, unless the blood
should somehow find its way from the arteries into the veins, and so
return to the right side of the heart; I began to think whether there
might not be _A Motion, As It Were, In A Circle_. Now this I
afterward found to be true; and I finally saw that the blood, forced
by the action of the left ventricle into the arteries, was distributed
to the body at large, and its several parts, in the same manner as it
is sent through the lungs, impelled by the right ventricle into the
pulmonary artery, and that it then passes through the veins and along
the vena cava, and so round to the left ventricle in the manner already
indicated. Which motions we may be allowed to call circular, in the
same way as Aristotle says that the air and rain emulate the circular
motion of the superior bodies; for the moist earth, warmed by the sun,
evaporates; the vapours drawn upwards are condensed, and descending
in the form of rain, moisten the earth again; and by this arrangement
are generations of living things produced; and in like manner too are
tempests and meteors engendered by the circular motion, and by the
approach and recession of the sun.
And so, in all likelihood, does it come to pass in the body, through
the motion of the blood; the various parts are nourished, cherished,
quickened by the warmer, more perfect, vaporous, spiritous, and, as
I may say, alimentive blood; which, on the contrary, in contact with
these parts becomes cooled, coagulated, and, so to speak, effete;
whence it returns to its sovereign the heart, as if to its source,
or to the inmost home of the body, there to recover its state of
excellence, or perfection.
Here it resumes its due fluidity and receives an infusion of natural
heat--powerful, fervid, a kind of treasury of life, and is impregnated
with spirits, and it might be said with balsam; and thence it is again
dispersed; and all this depends on the motion and action of the heart.
The heart, consequently, is the beginning of life; the sun of the
microcosm, even as the sun in his turn might well be designated the
heart of the world; for it is the heart by whose virtue and pulse
the blood is moved, perfected, made apt to nourish, and is preserved
from corruption and coagulation; it is the household divinity which,
discharging its function, nourishes, cherishes, quickens the whole
body, and is indeed the foundation of life, the source of all action.
FOOTNOTES:
[Footnote 7: From _An Anatomical Disquisition on the Motion of the
Heart-Blood in Animals_.]
VI
ROBERT BOYLE
1627-1691
_Robert Boyle, fourteenth child of the Earl of Cork, was born
January 25, 1627, in Munster, Ireland. He went to Eton, studied under
the rector of Stalbridge, and later traveled on the Continent under
private tutors. On the death of his father in 1644, he inherited the
manor at Stalbridge. At the age of eighteen he became associated with
the English scientific investigators at Oxford who later founded
the Royal Society, and engaged actively in physical experiments and
researches. The greatest of his achievements was his discovery of the
law of the compressibility of gases. He died December 30, 1691._
THE DISCOVERY OF THE LAW OF THE COMPRESSIBILITY OF GASES[8]
We took a long glass tube, which, by a dexterous hand and the help of a
lamp, was in such a manner crooked at the bottom, that the part turned
up was almost parallel to the rest of the tube, and the orifice of
this shorter leg of the syphon (if I may so call the whole instrument)
being hermetically sealed, the length of it was divided into inches
(each of which was subdivided into eight parts) by a straight list of
paper, which, containing those divisions, was carefully pasted all
along it. Then putting in as much quicksilver as served to fill the
arch or bended part of the syphon, that the mercury standing in a level
might reach in one leg to the bottom of the divided paper, and just
to the same height or horizontal line in the other, we took care, by
frequently inclining the tube, so that the air might freely pass from
one leg into the other by the sides of the mercury (we took, I say,
care), that the air at last included in the shorter cylinder should be
the same laxity with the rest of the air about it. This done, we began
to pour quicksilver into the longer leg of the syphon, which, by its
weight pressing up that in the shorter leg, did by degrees straighten
the included air; and continuing this pouring in of quicksilver till
the air in the shorter leg was by condensation reduced to take up but
half the space it possessed (I say possessed, not filled) before, we
cast our eyes upon the longer leg of the glass, upon which we likewise
pasted a slip of paper carefully divided into inches and parts, and we
observed, not without delight and satisfaction, that the quicksilver
in that longer part of the tube was 29 inches higher than the other.
Now that this observation does both very well agree with and confirm
our hypothesis, will be easily discerned by him that takes notice what
we teach: and Monsieur Pascal and our English friend’s [Mr. Townley’s]
experiments prove, that the greater the weight is that leans upon the
air, the more forcible is its endeavor of dilation, and consequently
its power of resistance (as other springs are stronger when bent by
greater weights). For this being considered, it will appear to agree
rarely well with the hypothesis, that as according to it the air in
that degree of density, and correspondent measure of resistance, to
which the weight of the incumbent atmosphere had brought it, was unable
to counterbalance and resist the pressure of a mercurial cylinder of
about 29 inches, as we are taught by the Torricellian experiment; so
here the same air being brought to a degree of density about twice
as great as that it had before, obtains a spring twice as strong as
formerly. As may appear by its being able to sustain or resist a
cylinder of 29 inches in the longer tube, together with the weight of
the atmospherical cylinder that leaned upon those 29 inches of mercury;
and, as we just now inferred from the Torricellian experiment, was
equivalent to them.
(_The tube broke at this point and, unable to proceed after several
similar efforts, Boyle tried the converse experiment--to determine the
spring of rarefied air. A tube, about 6 feet in length, and sealed at
one end, was nearly filled with mercury, and into it was placed_)--
A slender glass pipe of about the bigness of a swan’s quill, and open
at both ends; all along of which was pasted a narrow list of paper,
divided into inches and half-quarters. This slender pipe being thrust
down into the greater tube almost filled with quicksilver, the glass
helped to make it swell to the top of the tube; and the quicksilver
getting in at the lower orifice of the pipe filled it up till the
mercury included in that was near about a level with the surface of
the surrounding mercury in the tube. There being, as near as we could
guess, little more than an inch of the slender pipe left above the
surface of the restagnant mercury, and consequently unfilled therewith,
the prominent orifice was carefully closed with sealing-wax melted;
after which the pipe was let alone for a while that the air, dilated a
little by the heat of the wax, might, upon refrigeration, be reduced
to its wonted density. And then we observed, by the help of the
above-mentioned list of paper, whether we had not included somewhat
more or somewhat less than an inch of air; and in either case we were
fain to rectify the error by a small hole made (with a heated pin) in
the wax, and afterward closed up again. Having thus included a just
inch of air, we lifted up the slender pipe by degrees, till the air
was dilated to an inch, an inch and a half, two inches, etc., and
observed in inches and eighths the length of the mercurial cylinder,
which, at each degree of the air’s expansion, was impelled above the
surface of the restagnant mercury in the tube. The observations being
ended, we presently made the Torricellian experiment with the above
mentioned great tube of 6 feet long, that we might know the height of
the mercurial cylinder for that particular day and hour, which height
we found to be 29-3/4 inches.
FOOTNOTES:
[Footnote 8: From Thorpe, _Essays on Historical Chemistry_.]
VII
CHRISTIAN HUYGHENS
1629-1695
_Christian Huyghens was born at The Hague, April 14, 1629. He
studied law in Breda, but becoming attracted to the study of
mathematics he neglected his legal practice for it. In 1655 he
improved the method of grinding telescopic lenses, and, assisted
by his brother, discovered the sixth satellite of Saturn and the
fact that it was belted with rings. In 1657 he presented to the
States-General the first pendulum clock. In 1678 he evolved his wave
theory of light, and published it at Leyden in 1690. He died at The
Hague, June 8, 1695._
THE WAVE THEORY OF LIGHT[9]
Proofs in optics, as in every science in which mathematics is applied
to matter, are founded upon facts from experience--as for example,
that light moves in straight lines, that the angles of incidence and
reflection are equal, and that light rays are refracted in accordance
with the law of sines [i. e., that the ratio between the sines of the
incident and refracted ray is constant for the same substance.] For
this last law is now as generally and surely known as either of the
others.
Most writers in optics have been content to assume these facts, but
others more curious have attempted to discover the source and reason of
these phenomena, looking upon them as being in themselves interesting
data. Yet although they have propounded some ingenious theories,
intelligent readers still require a fuller explanation before being
entirely satisfied. Therefore I herein offer some considerations on the
matter with the hope of making clearer this branch of physics which has
not improperly gained the reputation of being very obscure.
I feel myself particularly indebted to those that first began to study
these profound subjects, and to lead us to hope them capable of orderly
explanation. Yet I have been surprised to find these very investigators
accepting arguments far from clear as if proof conclusive. No one has
yet offered even a probable explanation of the first two remarkable
phenomena of light,--why it moves in straight lines, and why rays from
any and all directions can cross one another without interference.
I shall attempt in this treatise to submit clearer and more probable
reasons, along the lines of modern philosophy, first for the
transmission of light, and, second, for its reflection when it meets
certain bodies.
Further, I shall explain the fact of rays said to undergo refraction in
passing through various transparent bodies. Here I shall consider also,
the refractions due to the differing densities of the atmosphere. Later
I shall investigate the remarkable refraction occurring in Icelandic
crystals. Finally, I shall study the different shapes necessary in
transparent and reflecting bodies in order to bring together rays upon
a single point or to deflect them in different ways. Here we shall see
how easy it is by our new theory to determine not alone the ellipses,
hyperbolas, and other curves which M. Descartes has so shrewdly
constructed for this end, but as well the curve that one surface of a
lens must have when the other surface is known, as spherical, plane, or
any other figure.
We cannot but believe that light is the motion of a certain material.
Thus when we reflect on its production, we discover that here on
the earth it is usually emitted from fire and flame, and that these
unquestionably contain bodies in rapid motion, since they can soften
and melt many other more solid substances. If we note its effects, we
see that when light is brought to a point, as, for example, by concave
mirrors, it can cause combustion the same as fire: that is, it can
force bodies apart, a power that certainly argues motion, at least in
that true science where one believes all natural phenomena to result
from mechanical causes. Moreover, in my mind we must either admit this
or give up all hope of ever understanding anything in natural science.
Since, according to this philosophy, it is believed certain that the
sensation of sight is produced only by the impulse of some form of
matter against the nerves at the base of the eye, we have yet another
reason for believing light to be a motion in the substance lying
between us and the body producing the light.
As soon as we consider, moreover, the enormous speed with which light
travels in every direction, and the fact that when rays come from
different directions, even from those exactly opposite, they cross
without interference, it must be plain that we do not see luminous
objects by means of particles transmitted from the objects to us, as a
shot or an arrow moves through the air. For surely this would not allow
for the two qualities of light just mentioned, particularly the latter
(that of speed). Light, then, is transmitted in some other way, a
comprehension of which we may get from our knowledge of how sound moves
through the air.
We know that sound is sent out in all directions through the medium of
the air, a substance invisible and impalpable, by means of a motion
that is communicated successively from one part of the air to the next;
and as this movement has the same speed in all directions, it must form
spherical surfaces that keep enlarging until at last they strike the
ear. Now there can be no doubt that light likewise reaches us from a
luminous substance through some motion caused in the matter lying in
the intervening space,--for we have seen above that this cannot take
place through transmission of matter from one place to another.
If, moreover, light requires time for its passage--a matter we shall
discuss in a moment--it will then follow that this movement is caused
in the substance gradually, and therefore is transmitted, like sound,
by surfaces and spherical waves. I call these _waves_ because of
their likeness to those formed when one throws a pebble into water,
which are examples of gradual propagation in circles, although from a
different cause and on a plane surface.
In regard to the question of light requiring time for its transmission,
let us consider whether there is any experimental evidence against it.
What experiments we can make here on the earth with sources of light
placed at great distances (although indicating that it does not take a
sensible time for light to pass over these distances) are subject to
the objection that these distances are yet too small, and that we can
only argue that the movement of light is enormously fast. M. Descartes
thought it to be instantaneous and based his opinion upon much better
reasons taken from the eclipse of the moon. Yet as I shall make clear,
even this evidence is not decisive. I shall state the matter in a
somewhat different way from his in order more easily to exhibit all the
consequences.
Suppose S to be the position of the sun, E A part of the orbit of the
earth, S E M a straight line intersecting in M, the orbit of the moon,
represented by the circle A M.
Now if light requires time--say an hour--to move the distance between
the earth and the moon, then [at the time of an eclipse] it follows
that when the earth has come to E its shadow, or the stoppage of the
light of the sun, will not yet have reached M [the moon], and will
not for an hour. Counting from the instant the earth reaches E, it
will be an hour before it will reach M if it is to be obscured there.
This eclipse will not be seen from the earth for yet another hour.
Suppose that during these two hours the earth has moved to X, the moon
appearing eclipsed at M, the sun still being seen at S. For I assume as
does Copernicus that the sun is fixed and since light moves in straight
lines, is always seen in its true position.
But as a matter of fact, we are assured that the eclipsed moon always
appears directly opposite the sun; while on the above supposition [that
light takes an hour in passing between the moon and the earth], its
position ought to be back of the straight line by the angle Y X M, the
supplement of the angle S X M. But this is not the case, for this angle
Y X M would be very easily noticed, it being about 33 degrees. For by
our analysis (found in the essay on the causes of the phenomena of
Saturn), the distance from the sun to the earth, S E, is about 12,000
times the diameter of the earth, and hence 400 times the distance of
the moon, which is 30 diameters. The angle X M E then will be nearly
400 times as great as E S X, which is 5 minutes, i. e., the angular
distance travelled by the earth in two hours [the earth traversing
almost a degree in a day]. Thus the angle E M X is almost 33 degrees,
and likewise the angle M X Y, being 5 minutes greater [than E M X].
Now it must be remembered that in this computation it is assumed that
the speed of light is such as to consume an hour in passing from here
to the moon. But if we assume it to take only a minute of time, then
the angle Y X M would amount to only 33 minutes, and if it only takes
ten seconds, this angle will be less than six minutes. Now so small
an angle is not observable in a lunar eclipse and hence it is not
permissible to argue that light is absolutely instantaneous.
It is rather unusual, we admit, to take for granted a speed 100,000
times as great as that of sound, which (following my experiments)
travels about 180 toises [about 1150 feet] in a second, or during a
pulse-beat. Yet this supposition is not at all impossible, for it is
not necessary to carry a body at such speed but only for motion to
traverse successively from one point to another.
Hence I do not hesitate in this matter to assume that the passage
of light takes time, for on this assumption all phenomena can be
explained, while on the contrary supposition none of them can be
explained. In fact, it seems to me and to many others as well, that
M. Descartes, whose purpose has been to discuss all physical matters
clearly, and who has certainly succeeded in this better than any one
before him, has written nothing on light and its qualities that is not
either hard to understand or even incomprehensible.
Moreover, this idea that I have propounded as an hypothesis has lately
been made a well nigh established fact by that keen calculation of
Roemer, whose method I will here take occasion to describe, on the
expectation that he will himself in the future fully confirm this
theory.
His method, the same as the one we have just discussed, is
astronomical. He shows not only that light takes time for its passage,
but calculates also its speed and that this must be at least six times
as much as the rate I have just given as an estimate.
In his demonstration he uses the eclipses of the small satellites that
revolve around Jupiter, and very frequently pass into his shadow.
Roemer’s reasoning is this:
Let S be the sun, B C D E the yearly orbit of the earth, J Jupiter and
G H the orbit of his nearest satellite, for this one because of its
short period is better suited to this investigation than any one of the
other three. Suppose G to be the point where the satellite enters, and
H where it leaves, Jupiter’s shadow.
Suppose that when the earth is at B, the satellite is seen to emerge
[at G], at some time before the last quarter. Were the earth to remain
stationary there, 42-1/2 hours would elapse before the next emergence
would take place, for this much time is taken by the satellite in
making one revolution in its orbit and returning to opposition to the
sun. For example, if the earth remained at B during 30 revolutions,
then after 30 times 42-1/2 hours, the satellite would again be seen
to emerge. If in the meantime the earth has moved to C, farther from
Jupiter, it is clear that if light requires time for its passage, the
emergence of the satellite will be seen later when the earth is at C
than when at B. For we must add to the 30 times 42-1/2 hours, the time
occupied by light in passing over the difference between the distances
[of the earth from Jupiter] G B and G C, i. e., M C. So in the other
quarter, when the earth travels from D to E, approaching Jupiter, the
eclipses will occur earlier when the earth is at E than when at D.
Now by many observations of these eclipses throughout ten years, it is
shown that these inequalities are actually of some moment, amounting to
as much as ten minutes or more: whence it is argued that in traversing
the whole diameter of the earth’s orbit, K L, double the distance from
the earth to the sun, light takes about 22 minutes.
The motion of Jupiter in its orbit while the earth passes from B
to C or from D to E has been taken into consideration in Roemer’s
calculation, where it is also proved that these inequalities cannot
be caused by any irregularity or eccentricity in the movement of the
satellite.
Now if we consider the enormous size of this diameter K L [the earth’s
orbit] which I have estimated to be about 24,000 times that of the
earth, we get some comprehension of the extraordinary speed of light.
Even if K L were only 22,000 diameters of the earth, a speed traversing
this distance in 22 minutes would be equal to the rate of a thousand
diameters a minute, i. e., 16 2-3 diameters a second (or a pulse-beat)
which makes more than 1,100 times 100,000 toises, since one diameter of
the earth equals 2,865 leagues, of which there are 25 to the degree,
and since in accordance with the very precise calculation made by M.
Picard in 1609 under orders from the king, each league contains 2,282
toises.
As I stated before sound moves only 180 toises per second. Hence
the speed of light is over 600,000 times as great as that of sound,
which, however, is very different from being instantaneous,--it is the
difference between any finite number and infinity. The theory that
light movements are propagated from point to point in time being thus
demonstrated, it follows that light moves in spherical waves, as does
sound.
But if they are alike in this regard, they are unlike in others, as
in the original cause of the motion that transmits them, the medium
through which they move, and the manner in which they are transmitted
in it.
We know that sound is caused by the rapid vibration of some body
(either as a whole or in part), this vibration setting in motion the
adjoining air. But light movements must arise at every point of the
luminous body, otherwise all the various parts of the body would not be
visible. This fact will be clearer from what follows.
In my judgment, this movement of light-giving bodies cannot be more
satisfactorily explained than by supposing that those that are fluid,
e. g., a flame, and probably the sun and stars, consist of particles
that float about in a much rarer medium, that sets them in violent
motion, causing them to strike against the still more minute particles
of the surrounding ether. In the case of light-giving solids such as
red-hot metal or carbon we may suppose this movement to be caused by
the rapid motions of the metal or wood, the particles on the surface
exciting the ether. Hence the vibration producing light must be much
shorter and faster than that causing sound, since we do not find that
sound disturbances give rise to light any more than the wave of the
hand through the air causes sound.
The next question is in regard to the nature of the medium through
which the vibration produced by light-giving bodies moves. I have
named it _ether_, but it plainly differs from the medium through
which sound moves. The latter is simply the air we feel and breathe,
and when it is removed from any space, the medium which carries light
still remains. This is shown by surrounding the sounding body in a
glass vessel, and exhausting the air by means of the air-pump that Mr.
Boyle has devised, and with which he has performed so many striking
experiments. In trying this experiment, however, it is best to set the
sounder on cotton or feathers so that it cannot communicate vibrations
to the glass receiver or the air-pump, a point hitherto neglected.
Then, when all the air has been exhausted, one catches no sound from
the metal when it is struck.
Hence we conclude not only that our atmosphere which cannot penetrate
glass is the medium through which sound acts, but that the medium
carrying light-vibrations is something different: for after the vessel
is exhausted of air, light passes through it as easily as before.
The last point is proven even more conclusively by the famous
experiment of Torricelli. [Fill a long closed glass tube with mercury,
then invert it.] The top of the glass tube not filled by the mercury
contains a high vacuum, but transmits light as well as when filled
with air. This demonstrates that there is within the tube some form
of matter different from air, and which penetrates either glass or
mercury, or both, though both are impenetrable to air. And if a like
experiment is tried with a little water on top of the mercury, it
becomes equally clear that the substance in question traverses either
glass or water or both.
In regard to the different methods of transmission of sound and light,
in the case of sound it is easy to see what happens when one remembers
that air can be compressed and reduced to a much smaller volume than
usual, and that it tends with the same force to expand to its original
volume. This quality, considered along with its penetrability retained
in spite of such condensation seems to show that it consists of small
particles that float about in rapid vibration in an ether consisting
of still more minute particles. Sound, then, is caused by the struggle
of these particles to escape when at any point in the course of a wave
they are more crowded together than at some other point.
Now the wonderful speed of light considered with its other qualities,
does not permit us to believe it to be transmitted in the same manner.
Therefore I shall try to explain the way in which I think it must
take place. I must first, however, describe that quality of hard
substances through which they transmit motion one to another. If one
take a number of balls of the same size of any hard substance, and
place them touching one another in one line, he will find that on
letting a ball of the same size strike against one end of the line,
the motion is transmitted in an instant to the other end of the line.
The last ball is driven from the line while the others are apparently
undisturbed, the ball that struck the line coming to a dead stop.
This is an illustration of a transmission of motion at great speed,
varying directly as the hardness of the balls. Yet it is certain that
this transmission is not instantaneous, but requires time. For if the
movement, or if you wish, the tendency to move, did not pass from one
ball to another in succession, they would all be set in motion at the
same instant and would all move forward at the same time. Now this is
so far from the case that only the last one leaves the row, and it has
the speed of the ball that first struck the line.
There are other experiments, also demonstrating that all bodies, even
those thought hardest, such as steel, glass and agate, are really
elastic, and bend a little, no matter whether they are in rods, balls,
or bodies of any other shape,--that is, they give slightly at the
point where struck, and at once regain their former shape. Thus I have
discovered that in letting a glass or agate ball strike on a large,
thick, flat piece of the same substance the surface of which has been
roughened by the breath, the place where it strikes is shown by a
circular indentation that varies in size directly as the force of the
blow. This indicates that the materials give when struck and then fly
back,--an event that necessarily takes time.
Now to apply such a motion to the explanation of light, there is
nothing in the way of our imagining the particles of ether to have
an almost complete hardness, and an elasticity as perfect as we need
wish. We need not here discuss the cause of either this hardness or
elasticity, as this would lead us too far from the question at issue.
I will remark, however, by the way, that these particles of ether,
in spite of their minuteness, are also composed of parts and that
their elasticity depends on a very rapid motion of a subtle substance
traversing them in all directions and making them take a structure
that offers a ready passage to this fluid. This agrees with the idea
of M. Descartes, except that I would not, like him, give the pores the
shape of round, hollow canals. This is so far from being at all absurd
or incomprehensible that it is easily credible that nature uses an
infinite series of different-sized molecules in order to produce her
marvelous effects.
Moreover, although we do not know the cause of elasticity, we cannot
have failed to notice that most bodies possess this characteristic;
hence it is not unreasonable to suppose that it is a quality of the
minute, invisible particles of the ether. And it is a fact that if one
looks for some other method of accounting for the gradual transmission
of light, he will have a hard time finding any supposition better
suited than elasticity to explain the fact of uniform speed. This
[uniform speed] seems to be a necessary assumption, for if the motion
slowed down when distributed over a great mass of matter at a far
distance from its source, then this great speed would at last be lost.
On the other hand, we suppose ether to have the property of elasticity
so that its particles regain their shape with equal activity whether
struck a hard or gentle blow. Thus the rate at which light would move
would remain constant.
FOOTNOTES:
[Footnote 9: Translated from _Traité de la Lumière_.]
VIII
ANTHONY VAN LEEUWENHOECK
1632-1723
_Born in Delft, Holland, October 24, 1632, Anthony Van Leeuwenhoeck,
a lens-maker for microscopes, made several important biological
discoveries. In 1673 he noticed the red globules in the blood; in
1675 he discovered animalculæ in water; in 1677 he described the
spermatozoa; in 1690 he traced the passage of blood from the arteries
into the veins. Among his other achievements were his investigations
of the tubules of teeth, the solidity of hair, the structure of the
epidermis, and his descriptions of insect anatomies. He announced most
of his findings to the Royal Society of London. Against the generally
accepted idea of spontaneous generation, he held that all things
generated their kind. He died at Delft, August 26, 1723._
OBSERVATIONS ON ANIMALCULÆ[10]
In the year 1675, I discovered very small living creatures in rain
water, which had stood but few days in a new earthen pot glazed blue
within. This invited me to view this water with great attention,
especially those little animals appearing to me ten thousand times less
than those represented by M. Swammerdam, and by him called water-fleas,
or water-lice, which may be perceived in the water with the naked eye.
The first sort I several times observed to consist of 5, 6, 7, or 8
clear globules without being able to discern any film that held them
together, or contained them. When these animalcula or living atoms
moved, they put forth two little horns, continually moving. The space
between these two horns was flat, though the rest of the body was
roundish, sharpening a little towards the end, where they had a tail,
near four times the length of the whole body, of the thickness, by my
microscope, of a spider’s web; at the end of which appeared a globule
of the size of one of those which made up the body. These little
creatures, if they chanced to light on the least filament or string,
or other particle, were entangled therein, extending their body in a
long round, and endeavoring to disentangle their tail. Their motion of
extension and contraction continued a while; and I have seen several
thousands of these poor little creatures, within the space of a grain
of gross sand, lie fast clustered together in a few filaments.
I also discovered a second sort, of an oval figure; and I imagined
their head to stand on a sharp end. These were a little longer than
the former. The inferior part of their body is flat, furnished with
several extremely thin feet, which moved very nimbly. The upper part of
the body was round, and had within 8, 10, or 12 globules, where they
were very clear. These little animals sometimes changed their figure
into a perfect round, especially when they came to lie on a dry place.
Their body was also very flexible; for as soon as they struck against
the smallest fibre or string, their body was bent in, which bending
presently jerked out again. When I put any of them on a dry place, I
observed that, changing themselves into a round, their body was raised
pyramidal-wise, with an extant point in the middle; and having laid
thus a little while, with a motion of their feet, they burst asunder,
and the globules were presently diffused and dissipated, so that I
could not discern the least thing of any film, in which the globules
had doubtless been enclosed; and at this time of their bursting
asunder, I was able to discover more globules than when they were alive.
I observed a third sort of little animals, that were twice as long as
broad, and to my eye eight times smaller than the first. Yet I thought
I discerned little feet, whereby they moved very briskly, both in round
and straight line.
There was a fourth sort, which were so small that I was not able to
give them any figure at all. These were a thousand times smaller than
the eye of a large louse. These exceeded all the former in celerity. I
have often observed them to stand still as it were on a point, and then
turn themselves about with that swiftness, as we see a top turn round,
the circumference they made being no larger than that of a grain of
small sand, and then extending themselves straight forward, and by and
by lying in a bending posture. I discovered also several other sorts
of animals; these were generally made up of such soft parts, as the
former, that they burst asunder as soon as they came to want water.
May 26, it rained hard; the rain growing less, I caused some of that
rain-water running down from the house top, to be gathered in a clean
glass, after it had been washed two or three times with water. And in
this I observed some few very small living creatures, and seeing them,
I thought they might have been produced in the leaded gutters in some
water that had remained there before.
I perceived in pure water, after some days, more of those animals, as
also some that were somewhat larger. And I imagine, that many thousands
of these little creatures do not equal an ordinary grain of sand in
bulk; and comparing them with a cheese-mite, which may be seen to
move with the naked eye, I make the proportion of one of these small
water-creatures to a cheese-mite to be like that of a bee to a horse;
for, the circumference of one of these little animals in water is not
so large as the thickness of a hair in a cheese-mite.
In another quantity of rain-water, exposed for some days to the air,
I observed some thousands of them in a drop of water, which were of
the smallest sort that I had seen hitherto. And in some time after I
observed, besides the animals already noted, a sort of creatures that
were eight times as large, of almost a round figure; and as those very
small animalcula swam gently among each other, moving as gnats do in
the air, so did these larger ones move far more swiftly, tumbling round
as it were, and then making a sudden downfall.
In the waters of the river Maese I saw very small creatures of
different kinds and colours, and so small, that I could very hardly
discern their figures; but the number of them was far less than those
found in rain-water. In the water of a very cold well in the autumn, I
discovered a very great number of living animals very small, that were
exceedingly clear, and a little larger than the smallest I ever saw.
In sea-water I observed at first, a little blackish animal, looking as
if it had been made up of two globules. This creature had a peculiar
motion, resembling the skipping of a flea on white paper, so that it
might very well be called a water-flea; but it was far less than the
eye of that little animal, which Dr. Swammerdam calls the water-flea. I
also discovered little creatures therein that were clear, of the same
size with the former animal, but of an oval figure, having a serpentine
motion. I further noticed a third sort, which were very slow in their
motion; their body was of a mouse colour, clear toward the oval point;
and before the head and behind the body there stood out a sharp little
point angle-wise. This sort was a little larger. But there was yet a
fourth somewhat longer than oval. Yet of all these sorts there were
but a few of each. Some days after viewing this water, I saw 100 where
before I had seen but one; but these were of another figure, and not
only less, but they were also very clear, and of an oblong oval figure,
only with this difference, that their heads ended sharper; and although
they were a thousand times smaller than a small grain of sand, yet when
they lay out of the water in a dry place, they burst in pieces and
spread into three or four very little globules, and into some aqueous
matter, without any other parts appearing in them.
Having put about one-third of an ounce of whole pepper in water, and
it having lain about three weeks in the water, to which I had twice
added some snow-water, the other water being in great part exhaled;
I discerned in it with great surprise an incredible number of little
animals, of divers kinds, and among the rest, some that were three
or four times as long as broad; but their whole thickness did not
much exceed the hair of a louse. They had a very pretty motion, often
tumbling about and sideways; and when the water was let to run off from
them, they turned round like a top; at first their body changed into an
oval, and afterwards, when the circular motion ceased, they returned to
their former length. The second sort of creatures discovered in this
water, were of a perfect oval figure, and they had no less pleasing or
nimble a motion than the former; and these were in far greater numbers.
There was a third sort, which exceeded the two former in number, and
these had tails like those I had formerly observed in rain-water.
The fourth sort, which moved through the three former sorts, were
incredibly small, so that I judged, that if 100 of them lay one by
another, they would not equal the length of a grain of coarse sand;
and according to this estimate, 1,000,000 of them could not equal the
dimensions of a grain of such coarse sand. There was discovered a fifth
sort, which had near the thickness of the former, but almost twice the
length.
In snow-water, which had been about three years in a glass bottle
well stopped, I could discover no living creatures; and having poured
some of it into a porcelain tea-cup, and put therein half an ounce of
whole pepper, after some days I observed some animalcula, and those
exceedingly small ones, whose body seemed to me twice as long as broad,
but they moved very slowly, and often circularly. I observed also a
vast multitude of oval-figured animalcula, to the number of 8,000 in a
single drop.
FOOTNOTES:
[Footnote 10: From the _Transactions of the Royal Society of
London_.]
IX
SIR ISAAC NEWTON
1642-1727
_Sir Isaac Newton, whose researches in light, gravitation, and
mathematics are outstanding in the history of modern science, was born
in Woolsthorpe, Lincolnshire, December 25, 1642. He was the son of an
English farmer who died before Newton was born. His early education
was interrupted by his mother’s poverty, but his ingenuity in making
mechanical toys soon provided a means whereby he was enabled to return
to school. He entered Cambridge University in 1661 and took his degree
in 1665; two years later he was made a fellow of the university, and
in 1669 became professor of mathematics._
_In 1665 he discovered his method of fluxions, not greatly unlike
Leibnitz’s Differential Calculus. In 1672 he was elected a fellow of
the Royal Society and shortly afterwards sent them a paper describing
how he had broken up light by means of a prism, demonstrating by that
means the compound nature of the sun’s rays._
_In 1687 elaborated his theory of gravitation in “Philosophiæ
Naturalis Principia Mathematica.” This was the result of his
reflections and researches dating from 1666, when he attempted to
explain the moon’s motion by the hypothesis of the assumed influence
of gravitation. In the meantime, through the use of telescopic
instruments, French geographers had tested the spherical shape of the
earth and had made a new and more accurate triangulation. Using the
data which they supplied, Newton perceived that these data agreed
with his theory that the force varied inversely as the square of the
distance. Overcome with the emotion incident to the solution of a
great problem, he begged a friend to complete his calculations, with
the result that the new astronomy begun by Copernicus, and continued
by Brahe, Kepler, and Galileo, was formulated and mathematically
interpreted by a single mechanical principle._
_Although he later made some chemical investigations, his papers
were accidentally destroyed, and it is said that he never recovered
from the shock of losing them. In 1695 he was made warden, and in 1699
promoted to the mastership of the mint, which office he retained at a
munificent salary until his death on March 20, 1727._
THE THEORY OF GRAVITATION[11]
BOOK III. PROPOSITION V. THEOREM V. SCHOLIUM
The force which retains the celestial bodies in their orbits has been
hitherto called centripetal force; but it being now made plain that it
can be no other than a gravitating force, we shall hereafter call it
gravity. For the cause of that centripetal force which retains the moon
in its orbit will extend itself to all the planets.