BARON ALEXANDER VON HUMBOLDT
From the painting by Professor Julius Schrader, Ksq. , at the American Museum ol
Natural History, owned by Morris K. Jesup
THE STORY OF
NINETEENTH-CENTURY
SCIENCE
BY
HENRY SMITH WILLIAMS, M.D.
ILLUSTRATED
HARPER 5- BROTHERS PUBLISHERS
NEW YORK AND LONDON
I9OI
Copyright, 1900, by HENKY SMITH WILLIAMS.
AU rights reservrj.
CONTENTS
I. SCIENCE AT THE BEGINNING OF THE CENTURY ... 1
II. THE CENTURY'S PROGRESS IN ASTRONOMY 44
III THE CENTURY'S PROGRESS IN PALEONTOLOGY .... 88
IV. THE CENTURY'S PROGRESS IN GEOLOGY 123
V. THE CENTURY'S PROGRESS IN METEOROLOGY .... 157
VI. THS CENTURY'S PROGRESS IN PHYSICS. THE "IMPON-
DERABLES" 192
VII. THE ETHEII AND PONDERABLE MATTER 230
VIII. THE CENTURY'S PROGRESS IN CHEMISTRY 252
IX. THE CENTURY'S PROGRESS IN BIOLOGY. THEORIES OP
ORGANIC EVOLUTION 288
X. THE CENTURY'S PROGRESS IN ANATOMY AND PHYSI-
OLOGY ... 321
XL THE CENTURY'S PROGRESS IN SCIENTIFIC MKDICINE . 354
XII. THE CENTURY'S PROGRESS IN EXPERIMENTAL PSYCHOL-
OGY 395
XIII. SOME UNSOLVED SCIENTIFIC PROBLEMS 433
i. SOLAR AND TELLURIC PROBLEMS 435
n. PHYSICAL PROBLEMS 443
m. LIFE PROBLEMS 449
INDEX ...... ,459
ILLUSTKATIONS
PAGE
BARON ALEXANDER VON IITJMBOLDT Frontispiece
HUMPHRY DAVY 3
JOSIAH WEDGWOOD 6
HERSCHEL AND HIS SISTER AT THE TELESCOPE 9
JAMES LOUIS LAGRANGE 14
JAMES HUTTON 18
BENJAMIN THOMPSON — COUNT RUMFORD 25
JOSKPH PRIESTLY 30
LAVOISIER IN HIS LABORATORY . ' 37
EDWARD JENNER . 41
FUIEDRICH WILHELM BESSEL 45
HEINKICH WILHELM MATTHIAS OLBERS 55
SIR JOHN HERSCHEL 61
THE GREAT REFRACTOR OF THE NATIONAL OBSERVATORY AT
WASHINGTON 67
A TYPICAL STAR CLUSTER — CENTAURI 71
SPECTRA OF STARS IN CARINA 73
STAR SPECTRA 75
LORD ROSSE'S TELESCOPE 77
NO. 1 — SIDEREAL TIME, 15 HOURS, 50 MINUTES )
NO. 2— SIDEREAL TIME, 17 HOURS, 50 MINUTES I
THE OXFORD HELIOMETER 85
GEORGES CUVIER 92
THE WARREN MASTODON, FOUND NEAR NEWBURG, ON THE
HUDSON 94
V
ILLUSTRATIONS
PAGE
THE SKULL, LACKING THE LOWER JAW, OF EOBASILEUS COR-
NUTUS, COPE 96
METAMYNODON, OR SWIMMING RHINOCEROS, FROM SOUTH DA-
KOTA '. 101
HYRACHYUS, OR RUNNING RHINOCEROS, FROM SOUTHERN WYO-
MING 103
PROFESSOR B. D. COPE 106
PROTOROHIPPUS, THE ANCESTRAL FOUR-TOED HORSE .... 110
PROFESSOR O. C. MARSH 112
THE EVOLUTION OF A HORSE'S FOOT AND OF A HORSE'S HEAD 115
FOOTPRINTS OF REPTILES FOUND IN CONNECTICUT SAND-
STONE 118
TITANOTHERE FROM SOUTH DAKOTA 120
THE RESULTS OF EROSION BY RUNNING WATER 127
THE RESULTS OF EROSION BY WIND 131
A MOUNTAIN CARVED FROM HORIZONTAL STRATA 133
LOUIS JEAN RODOLPH AGASSIZ . . . . )
135
ADAM SEDGWICK, F.R.8 )
JAMES DWIGHT DANA )
> Io7
SIR RODERICK IMPEY MURCHISON . )
WILLIAM SMITH, LL.D 139
GEORGE POULETTE SCROPE, F.R.S . )
> 141
SIR CHARLES LYELL, BART., F.R 8 )
A LANDSCAPE AND MAMMAL OF THE TERTIARY AGE .... 143
A LANDSCAPE AND TERRESTRIAL REPTILE OF THE MICSOZOIC
TIME 147
MANHATTAN ISLAND IN THE QUATERNARY AGE — THE MASTO-
DON 151
SIR RICHARD OWEN 155
A METEORIC STONE 159
CIRRUS CLOUDS 163
CUMULUS CLOUDS 165
STRATUS CLOUDS 168
JEAN BAPTISTE BIOT 1 73
LIEUTENANT MATTHEW FONTAINE MAURY 179
A WHIRLWIND IN A DUSTY ROAD 183
WATERSPOUTS IN MID-ATLANTIC ,,,... 185
vi
ILLUSTRATIONS
PAGE
A SAND-STORM ON THE MOJAVE DESEHT 1£7
THOMAS YOUNG 195
HANS CHRISTIAN OERSTED -|
DOMINIQUE FRANCOIS ARAGO
J- 201
AUGUSTIN JEAN FRESNEL
JAMES CLERK MAXWELL ,
MICHAEL FARADAY 211
JAMES PRESCOTT JOULE ^
WILLIAM THOMSON (LORD KELVIN)
1" 219
JULIUS ROBERT MAYER
JOHN TYNDALL
HERMANN LUDVVIG FERDINAND HELMHOLTZ 237
JOHN DALTON 254
JOSEPH LOUIS GAY-LUSSAC 257
JOHAN JAKOIJ BEKZELIUS 261
JUSTUS TON LIEBIG . . ~. 267
ROBERT WILLIAM BUNSEN 277
GUSTAV ROBERT KIIICHHOFF 279
LOUIS JACQUES MANDE DAGUERRE 281
JOHN W. DRAPER 285
ERASMUS DARWIN 290
JEAN BAPTISTE DE LAMARCK 294
ETIENNE GEOFFROY SAINT-HILAIHE 299
CHARLES ROBERT DARWIN 304
ALFRED RUSSELL WALLACE 308
THOMAS HENRY HUXLEY 311
ASA GRAY 314
ERNEST HAECKEL 319
MARIE FRANCOIS XAVIER BICHAT 323
WILLIAM HYDE WOLLASTON 326
MATTHIAS JAKOB SCHLEIDEN 330
KARL ERNST VON BAER 333
JOHANNES MULLER 337
WILLIAM BENJAMIN CARPENTER 339
MAX SCHULTZE 341
HUGO VON MOTH- 344
JEAN BAPTISTE DUMAS 346
vii
ILLUSTRATIONS
PAGE
CLAUDE BERNARD 351
LAENNEC, INVENTOR OF THE STETHOSCOPE, AT THE NECKER
HOSPITAL, PARIS 357
RUDOLF ArIRCHOW 364
WILLIAM T. G. MORTON 367
CRAWFORD W. LONG 371
THEODOR SCHWANN 377
SIR JOSEPH LISTER 383
LOUIS PASTEUR 391
PINEL AT LA SALPETRIERE, IN 1795, RELEASING THE INSANE
FROM THEIR MANACLES 397
SIR CHARLES BELL 402
FRANCOIS MAGENDIE 403
EMIL. DU BOIS-REYMOND 408
GUSTAV THEODOR FECHNER 413
JEAN MARTIN CHARCOT 416
PAUL BROCA , 421
THE STORY OF NINETEENTH-
CENTURY SCIENCE
THE STORY OF NINETEENTH-
CENTURY SCIENCE
NOT many months ago word came out of Germany of
a scientific discovery that startled the world. It came
first as a rumor, little credited; then as a pronounced
report; at last as a demonstration. It told of a new
manifestation of energy, in virtue of which the interior
of opaque objects is made visible to human eyes. One
had only to look into a tube containing a screen of a cer-
tain composition, and directed towards a peculiar electri-
cal apparatus, to acquire clairvoyant vision more won-
derful than the discredited second sight of the medium.
Coins within a purse, nails driven into wood, spectacles
within a leather case, became clearly visible when sub-
jected to the influence of this magic tube; and when a
human hand was held before the tube, its bones stood re-
vealed in weird simplicity, as if the living, palpitating flesh
about them were but the shadowy substance of a ghost.
Not only could the human eye see these astounding
revelations, but the impartial evidence of inanimate
THE STORY OF NINETEENTH-CENTURY SCIENCE
chemicals could be brought forward to prove that the
mind harbored no illusion. The photographic film re-
corded the things that the eye might see, and ghostty
pictures galore soon gave a quietus to the doubts of the
most sceptical. Within a month of the announcement
of Professor Rontgen's experiments comment upon the
" X ray " and the " new photography " had become a
part of the current gossip of all Christendom.
It was but natural that thoughtful minds should have
associated this discovery of our boasted latter-day epoch
with another discovery that was made in the earliest in-
fancy of our century. In the year 1801 Mr. Thomas
Wedgwood, of the world-renowned family of potters,
and Humphry Davy, the youthful but already famous
chemist, made experiments which showed that it was
possible to secure the imprint of a translucent body
upon a chemically prepared plate by exposure to sunlight.
In this way translucent pictures were copied, and skele.
tal imprints were secured of such objects as leaves and
the wings of insects — imprints strikingly similar to the
"shadowgraphs" of more opaque objects which we se-
cure by means of the " new photography" to-day. But
these experimenters little dreamed of the real signifi-
cance of their observations. It was forty years before
practical photography, which these observations fore-
shadowed, was developed and made of any use outside
the laboratory.
It seems strange enough now that imaginative men—
and Davy surely was such a man — should have paused
on the very brink of so great a discovery. But to harbor
that thought is to misjudge the nature of the human
mind. Things that have once been done seem easy;
things that have not been done are difficult, though they
2
HUMPHRY DAVY
From the painting by H. Howard
SCIENCE AT THE BEGINNING OF THE CENTURY
lie but a hair's-breadth off the beaten track. Who can
to-day foretell what revelations may be made, what use-
ful arts developed, forty years hence through the agency
of what we now call the new photography ?
It is no part of my purpose, however, to attempt the
impossible feat of casting a horoscope for the new pho-
tography. My present theme is reminiscent, not pro-
phetic. I wish to recall what knowledge of the sciences
men had in the days when that discovery of Wedgwood
and Davy was made, almost a hundred years ago ; to
inquire what was the scientific horizon of a person
standing at the threshold of our own century. Let us
glance briefly at each main department of the science of
that time, that we may know whither men's minds were
trending in those closing days of the eighteenth century,
and what were the chief scientific legacies of that cen-
tury to its successor.
ii
In the field of astronomy the central figure during
this closing epoch of the eighteenth century is William
Herschel, the Hanoverian, whom England has made
hers by adoption. He is a man with a positive genius
for sidereal discovery. At first a mere amateur in as-
tronomy, he snatches time from his duties as music-
teacher to grind him a telescopic mirror, and begins gaz-
ing at the stars. Not content with his first telescope,
he makes another, and another, and he has such genius
for the work that he soon possesses a better instrument
than was ever made before. His patience in grinding
the curved reflective surface is monumental. Some-
times for sixteen hours together he must walk steadily
about the mirror, polishing it, without once removing
5
THE STORY OF NINETEENTH-CENTURY SCIENCE
JOSIAH WEDGWOOD
From a painting by Sir Joshua Reynolds
his hands. Meantime his sister, always his chief lieuten-
ant, cheers him with her presence, and from time to time,
puts food into his mouth. The telescope completed, the
astronomer turns night into da\r, and from sunset to sun-
rise, year in and year out, sweeps the heavens unceas-
6
SCIENCE AT THE BEGINNING OF THE CENTURY
ingly, unless prevented by clouds or the brightness of
the moon. His sister sits always at his side, recording
his observations. They are in the open air, perched
high at the mouth of the reflector, and sometimes it is
O '
so cold that the ink freezes in the bottle in Caroline
HerschePs hand ; but the two enthusiasts hardly notice
a thing so commonplace as terrestrial weather. They
are living in distant worlds.
The results ? What could they be ? Such enthusiasm
would move mountains. But, after all, the moving of
mountains seems a Liliputian task compared with what
Herschel really does with those wonderful telescopes.
lie moves worlds, stars, a universe — even, if you please,
a galaxy of universes ; at least he proves that they
move, which seems scarcely less wonderful ; and he
expands the cosmos, as man conceives it, to thousands
of times the dimensions it had before. As a mere be-
ginning, he doubles the diameter of the solar system
by observing the great outlying planet which we now
call Uranus, but which he christens Georgium Sidus,
in honor of his sovereign, and which his French con-
temporaries, not relishing that name, prefer to call
Herschel.
This discovery is but a trifle compared with what Her-
schel does later on, but it gives him world-wide reputa-
tion none the less. Comets and moons aside, this is the
first addition to the solar system that has been made
within historic times, and it creates a veritable furor of
popular interest and enthusiasm. Incidentally King
George is flattered at having a Avorld named after him,
and he smiles on the astronomer, and comes with his
court to have a look at his namesake. The inspection
is highly satisfactory ; and presently the royal favor
7
THE STORY OF NINETEENTH-CENTURY SCIENCE
enables the astronomer to escape the thraldom of teach-
ing music, and to devote his entire time to the more con-
genial task of star-gazing.
Thus relieved from the burden of mundane embarrass-
ments, he turns with fresh enthusiasm to the skies, and
his discoveries follow one another in bewildering profu-
sion. He finds various hitherto unseen moons of our
sister planets ; he makes special studies of Saturn, and
proves that this planet, with its rings, revolves on its
axis ; he scans the spots on the sun, and suggests that
they influence the weather of our earth ; in short, he
extends the entire field of solar astronomy. But very
soon this field becomes too small for him, and his most
important researches carry him out into the regions of
space compared with which the span of our solar system
is a mere point. With his perfected telescopes he enters
abysmal vistas which no human e}'e ever penetrated be-
fore, which no human eye had hitherto more than vague-
ly imagined. He tells us that his forty-foot reflector
will bring him light from a distance of " at least eleven
and three-fourths millions of millions of millions of
miles" — light which left its source two million years
ago. The smallest stars visible to the unaided eye are
those of the sixth magnitude ; this telescope, he thinks,
has power to reveal stars of the 1342d magnitude.
But what does Herschel learn regarding these awful
depths of space and the stars that people them ? That
is what the world wishes to know. Copernicus, Galileo,
Kepler, have given us a solar system, but the stars have
been a mystery. What says the great reflector — are the
stars points of light, as the ancients taught, and as more
than one philosopher of the eighteenth century has still
contended, or are the}' suns, as others hold I HerscheJ
HERSCHEL AND HIS SISTER AT THE TELESCOPE
SCIENCE AT THE BEGINNING OF THE CENTURY
answers, they are suns, each and every one of all the
millions — suns, many of them, larger than the one that
is the centre of our tiny system. Not only so, but they
are moving suns. Instead of being fixed in space, as has
been thought, they are whirling in gigantic orbits about
some common centre. Is our sun that centre ? Far from
it. Our sun is only a star, like all the rest, circling on
with its attendant satellites — our giant sun a star, no
different from myriad other stars, not even so large as
some ; a mere insignificant spark of matter in an infinite
shower of sparks.
Nor is this all. Looking beyond the few thousand
stars that are visible to the naked eye, Herschel sees
series after series of more distant stars, marshalled in
galaxies of millions ; but at last he reaches a distance
beyond which the galaxies no longer increase. And yet
—so he thinks— he has not reached the limits of his vi-
sion. "What then? He has come to the bounds of the
sidereal system ; seen to the confines of the universe.
He believes that he can outline this system, this universe,
and prove that it has the shape of an irregular globe,
oblately flattened to almost disklike proportions, and di-
vided at one edge — a bifurcation that is revealed even to
the naked eye in the forking of the Milky Way.
This, then, is our universe as Herschel conceives it — a
vast galaxy of suns, held to one centre, revolving, poised
in space. But even here those marvellous telescopes do
not pause. Far, far out beyond the confines of our uni-
verse, so far that the awful span of our own system
might serve as a unit of measure, are revealed other sys-
tems, other universes, like our own, each composed, as
he thinks, of myriads of suns, clustered like our galaxy
into an isolated system — mere islands of matter in an
11
THE STORY OF NINETEENTH-CENTURY SCIENCE
infinite ocean of space. So distant from our universe
are these ne\v universes of Herschel's discovery that
their light reaches us only as a dim nebulous glow, in
most cases invisible to the unaided eye. About a hundred
of these nebulae were known when Herschel began his
studies. Before the close of the century he has discov-
ered about two thousand more of them, and many of these
had been resolved by his largest telescopes into clusters
of stars. He believes that the farthest of these nebulae
that he can see is at least 300,000 times as distant from
us as the nearest fixed star. Yet that nearest star is so
remote that its light, travelling 180,000 miles a second,
requires three and one-half years to reach our planet.
As if to give the finishing -touches to this novel
scheme of cosmology, Herschel, though in the main
very little given to unsustained theorizing, allows him-
self the privilege of one belief that he cannot call upon
his telescopes to substantiate. He thinks that all the
myriad suns of his numberless systems are instinct with
life in the human sense. Giordano Bruno and a long
line of his followers had held that some of our sister
planets may be inhabited, but Herschel extends the
thought to include the moon, the sun, the stars — all the
heavenly bodies. He believes that he can demonstrate
the habitability of our own sun, and reasoning from
analogy, he is firmly convinced that all the suns of all
the systems are " well supplied with inhabitants." In
this, as in some other inferences, Herschel is misled by
the faulty physics of his time. Future generations, work-
ing with perfected instruments, may not sustain him
all along the line of his observations even, let alone his
inferences. But how one's egotism shrivels and shrinks
as one grasps the import of his sweeping thoughts !
12
SCIENCE AT THE BEGINNING OF THE CENTURY
Continuing his observations ol the innumerable nebu-
lae, Herschel is led presently to another curious specula-
tive inference. He notes that some star groups are much
more thickly clustered than others, and he is led to in-
fer that such varied clustering tells of varying ages of
the different nebula?. He thinks that at first all space
may have been evenly sprinkled with the stars, and that
the grouping has resulted from the action of gravita-
tion. Looking forward, it appears that the time must
come when all the suns of a system will be drawn to-
gether and destroyed by impact at a common centre.
Already, it seems to him, the thickest clusters have
" outlived their usefulness," and are verging towards
their doom.
But again, other nebulae present an appearance sug-
gestive of an opposite condition. They are not resolva-
able into stars, but present an almost uniform appear-
ance throughout, and are hence believed to be composed
of a shining fluid, which in some instances is seen to be
condensed at the centre into a glowing mass. In such
a nebula Herschel thinks he sees a sun in process of
formation.
Taken together, these two conceptions outline a ma-
jestic cycle of world formation and world destruction —
a broad scheme of cosmogony, such as had been vaguely
adumbrated two centuries before by Kepler, and in
more recent times by Wright and Kant and Sweden-
borg. This so - called " nebular hypothesis " assumes
that in the beginning all space was uniformly filled
with cosmic matter in a state of nebular or " fire-mist "
diffusion, " formless and void." It pictures the con-
densation— coagulation, if you wilA — of portions of this
mass to form segregated masses, a.ul the ultimate devel-
13
THE STORY OF NINETEENTH-CENTURY SCIENCE
opment out of these masses of the sidereal bodies which
we see. Thus far the mind follows readily ; but now
come difficulties. How happens it, for example, that
JAMES LOUIS LAGRANGE
the cosmic mass from which was born our solar system
was divided into several planetary bodies instead of re-
maining a single mass? Were the planets struck off
from the sun by the chance impact of comets, as Buffon
14
SCIENCE AT THE BEGINNING OF THE CENTURY
has suggested ? or thrown out by explosive volcanic ac-
tion, in accordance with the theory of Dr. Darwin ? or
do they owe their origin to some unknown law ? In
any event, how chanced it that all were projected in
nearly the same plane as we now find them ?
It remained for a mathematical astronomer to solve
these puzzles. The man of all others competent to take
the subject in hand was the French astronomer Laplace.
For a quarter of a century he had devoted his transcen-
dent mathematical abilities to the solution of problems
of motion of the heavenly bodies. Working in friendly
rivalry with his countryman Lagrange, his only peer
among the mathematicians of the age, he had taken up
and solved one by one the problems that Newton left
obscure. Largely through the efforts of these two men
the last lingering doubts as to the solidarity of the New-
tonian hypothesis of universal gravitation had been re-
moved. The share of Lagrange was hardly less than
that of his co-worker ; but Lagrange will longer be re-
membered, because he ultimately brought his completed
labors into a system, and incorporating with them the
labors of his contemporaries, produced in the Mecanique
Celeste the undisputed mathematical monument of the
century, a fitting complement to the Prindpia of New-
ton, which it supplements and in a sense completes.
In the closing years of the century Laplace takes up
the nebular hypothesis of cosmogony, to which we have
just referred, and gives it definitive proportions; in fact,
makes it so thoroughly his own that posterity will al-
ways link it with his name. Discarding the crude no-
tions of cometary impact and volcanic eruption, Laplace
fills up the gaps in the hypothesis with the aid only of
well-known laws of gravitation and motion. He assumes
15
THE STORY OF NINETEENTH-CENTURY SCIENCE
that the primitive mass of cosmic matter which was
destined to form our solar system was revolving on its
axis even at a time when it was still nebular in charac-
ter, and filled all space to a distance far beyond the
present limits of the system. As this vaporous mass
contracted through loss of heat, it revolved more and
more swiftly, and from time to time, through balance
of forces at its periphery, rings of its substance were
whirled off and left revolving there, to subsequently
become condensed into planets, and in their turn whirl
off minor rings that became moons. The main body of
the original mass remains in the present as the still con-
tracting and rotating body which we call the sun.
The nebular hypothesis thus given detailed comple-
tion by Laplace is a worthy complement of the grand
cosmologic scheme of Herschel. Whether true or false,
the two conceptions stand as the final contributions of
the eighteenth century to the history of man's ceaseless
efforts to solve the mysteries of cosmic origin and cosmic
structure. The world listens eagerly and without preju-
dice to the new doctrines ; and that attitude tells of a
marvellous intellectual growth of our race. Mark the
transition. In the year 1600, Bruno was burned at the
stake for teaching that our earth is not the centre of the
universe. In 1700, Newton was pronounced "impious
and heretical" by a large school of philosophers for
declaring that the force which holds the planets in their
orbits is universal gravitation. In 1800, Laplace and
Herschel are honored for teaching that gravitation
built up the system which it still controls; that our
universe is but a minor nebula, our sun but a minor star,
our earth a mere atom of matter, our race only one of
myriad races peopling an infinity of worlds. Doctrines
16
SCIENCE AT THE BEGINNING OF THE CENTURY
which but the span of two human lives before would
have brought their enunciators to the stake were now
pronounced not impious, but sublime.
in
One might naturally suppose that the science of the
earth, which lies at man's feet, would at least have kept
pace with the science of distant stars. But perhaps the
very obviousness of the phenomena delayed the study
of the crust of the earth. It is the unattainable that
allures and mystifies and enchants the developing mind.
The proverbial child spurns its toys and cries for the
moon.
So in those closing days of the eighteenth centurj7",
when astronomers had gone so far towards explaining
the mysteries of the distant portions of the universe,
we find a chaos of opinion regarding the structure and
formation of the earth. Guesses were not wanting to
explain the formation of the world, it is true, but, with
one or two exceptions, these are bizarre indeed. One
theory supposed the earth to have been at first a solid
mass of ice, which became animated only after a comet
had dashed against it. Other theories conceived the
original globe as a mass of water, over which floated
vapors containing the solid elements, which in due time
were precipitated as a crust upon the waters. In a
word, the various schemes supposed the original mass to
have been ice, or water, or a conglomerate of water and
solids, according to the random fancies of the theorists;
and the final separation into land and water was con-
ceived to have taken place in all the ways which fancy,
quite unchecked by any tenable data, could invent.
B 17
THE STORY OF NINETEENTH-CENTURY SCIEN'CE
JAMES HUTTON
Whatever important changes in the general character
of the surface of the globe were conceived to have taken
place since its creation were generally associated with
the Mosaic deluge, and the theories which attempted to
explain this catastrophe were quite on a par with those
which dealt with a remoter period of the earth's history.
18
SCIENCE AT THE BEGINNING OF THE CEVLTKY
Some speculators, holding that the interior of the globe
is a great abyss of waters, conceived that the crust had
dropped into this chasm and had thus been inundated.
Others held that the earth had originally revolved on
a vertical axis, and that the sudden change to its pres-
ent position had caused the catastrophic shifting of
its oceans. But perhaps the favorite theory was that
which supposed a comet to have wandered near the
earth, and in whirling about it to have carried the wa-
ters, through gravitation, in a vast tide over the conti-
nents.
Thus blindly groped the majority of eighteenth-cen-
tury philosophers in their attempts to study what we
now term geology. Deluded by the old deductive
methods, they founded not a science, but the ghost of a
science, as immaterial and as unlike anything in nature
as any other phantom that could be conjured from the
depths of the speculative imagination. And all the while
the beckoning earth lay beneath the feet of these vision-
aries; but their eyes were fixed in air.
At last, however, there came a man who had the
penetration to see that the phantom science of geology
needed before all else a body corporeal, and who took to
himself the task of supplying it. This was Dr. James
Hutton, of Edinburgh, physician, farmer, and manufact-
uring chemist; patient, enthusiastic, level-headed devotee
of science. Inspired by his love of chemistry to study
the character of rocks and soils, Ilutton had not gone far
before the earth stood revealed to him in a new light.
He saw, what generations of predecessors had blindly
refused to see, that the face of nature everywhere,
instead of being rigid and immutable, is perennially
plastic, and year by year is undergoing metamorphic
19
THE STORY OF NINETEENTH-CENTURY SCIENCE
changes. The solidest rocks are day by day disinte-
grated, slowly, but none the less surely, by wind and
rain and frost, by mechanical attrition and chemical
decomposition, to form the pulverized earth and clay.
This soil is being swept away by perennial showers, and
carried off to the oceans. The oceans themselves beat
on their shores, and eat insidiously into the structure of
sands and rocks. Everywhere, slowly but surely, the
surface of the land is being worn away; its substance is
being carried to burial in the seas.
Should this denudation continue long enough, thinks
Hutton, the entire surface of the continents must be
worn away. Should it be continued long enough! And
with that thought there flashes on his mind an inspiring
conception — the idea that solar time is long, indefinitely
long. That seems a simple enough thought — almost a
truism — to the nineteenth-centur}7 mind ; but it required
genius to conceive it in the eighteenth. Hutton pon-
dered it, grasped its full import, and made it the basis of
his hypothesis, his " theory of the earth."
The hypothesis is this — that the observed changes
of the surface the earth, continued through indefinite
lapses of time, must result in conveying all the land at
last to the sea ; in wearing continents away till the
oceans overflow them. What then ? Why, as the con-
tinents wear down, the oceans are filling up. Along
their bottoms the detritus of wasted continents is de-
posited in strata, together with the bodies of marine
animals and vegetables. Why might not this debris
solidify to form layers of rocks — the basis of new con-
tinents? Why not, indeed?
But have we any proof that such formation of rocks
in an ocean-bed has, in fact, occurred? To be sure we
20
SCIENCE AT THE BEGINNING OF THE CENTURY
have. It is furnished by every bed of limestone, every
outcropping fragment of fossil-bearing rock, every strati-
fied cliff. Ho\v else than through such formation in an
ocean-bed came these rocks to be stratified i How else
came they to contain the shells of once living organisms
embedded in their depths? The ancients, finding fossil
shells embedded in the rocks, explained them as mere
freaks of " nature and the stars." Less superstitious
generations had repudiated this explanation, but had
failed to give a tenable solution of the mystery. To
Hutton it is a mystery no longer. To him it seems
clear that the basis of the present continents was laid in
ancient sea-beds, formed of the detritus of continents
yet more ancient.
But two links are still wanting to complete the chain
of Button's hypothesis. Through what agency has the
ooze of the ocean-bed been transformed into solid rock ?
And through what agency has this rock been lifted
above the surface of the water, to form new continents?
Hutton looks about him for a clew, and soon he finds
it. Everywhere about us there are outcropping rocks
that are not stratified, but which give evidence to the
observant eye of having once been in a molten state.
Different minerals are mixed together; pebbles are
scattered through masses of rock like plums in a pud-
ding; irregular crevices in otherwise solid masses of
rock — so-called veinings — are seen to be filled with
equally solid granite of a different variety, which can
have gotten there in no conceivable way, so Hutton
thinks, but by running in while molten, as liquid metal
is run into the moulds of the founder. Even the strati-
fied rocks, though they seemingly have not been melted,
give evidence in some instances of having been sub-
21
THE STORY OF NINETEENTH-CENTURY SCIENCE
jected to the action of heat. Marble, for example, is
clearly nothing but calcined limestone.
With such evidence before him, Hutton is at no loss
to complete his hypothesis. The agency which has solid-
ified the ocean-beds, he says, is subterranean heat. The
same agency, acting excessively, has produced volcanic
cataclysms, upheaving ocean-beds to form continents.
The rugged and uneven surfaces of mountains, the tilted
and broken character of stratified rocks everywhere, are
the standing witnesses of these gigantic upheavals.
And with this the imagined cycle is complete. The
continents, worn away and carried to the sea by the action
of the elements, have been made over into rocks again
in the ocean-beds, and then raised once more into conti-
nents. And this massive cycle, in Button's scheme, is
supposed to have occurred not once only, but over and
over again, times without number. In this unique view
ours is indeed a world without beginning and without
end ; its continents have been making and unmaking in
endless series since time began.
Hutton formulated his hypothesis while yet a young
man, not long after the middle of the century. He
first gave it publicity in 1781, in a paper before the
Royal Society of Edinburgh, a paper which at the mo-
ment neither friend nor foe deigned to notice. It was
not published in book form till the last decade of the
century, when Hutton had lived with and worked over
his theory for almost fifty years. Then it caught the
eye of the world. A school of followers expounded the
Huttonian doctrines; a rival school, under Werner, in
Germany, opposed some details of the hypothesis ; and
the educated world as a whole viewed disputants
askance. The very novelty of the new views forbade their
22
SCIENCE AT THE BEGINNING OF THE CENTURY
immediate acceptance. Bitter attacks were made upon
the " heresies," and that was meant to be a soberly tem-
pered judgment which in 1800 pronounced Hutton's
theories " not only hostile to sacred history, but equally
hostile to the principles of probability, to the results of
the ablest observations on the mineral kingdom, and to
the dictates of rational philosophy." And all this be-
cause Hutton's theory presupposed the earth to have
been in existence more than six thousand years.
Thus it appears that though the thoughts of men had
widened, in these closing days of the eighteenth cen-
tury, to include the stars, they had not as yet expanded
to receive the most patent records that are written
everywhere on the surface of the earth. Before Hut-
ton's views could be accepted, his pivotal conception
that time is long must be established by convincing
proofs. The evidence was being gathered by William
Smith, Cuvier, and other devotees of the budding science
of paleontology in the last days of the century, but the
record of their completed labors belongs to another
epoch.
IV
The eighteenth - century philosopher made great
strides in his studies of the physical properties of mat-
ter, and the application of these properties in mechan-
ics, as the steam-engine, the balloon, the optic telegraph,
the spinning-jenny, the cotton-gin, the chronometer, the
perfected compass, the Leyden jar, the lightning-rod,
and a host of minor inventions testify. In a speculative
way he had thought out more or less tenable concep-
tions as to the ultimate nature of matter, as witness the
theories of Leibnitz and Boscovich and Davy, to which
23
THE STORY OF NINETEEXTII-CRNTURY SCIENCE
we may recur. But he had not as yet conceived the
notion of a distinction between matter and energy,
which is so fundamental to the physics of a later epoch.
He did not speak of heat, light, electricity, as forms of
energy or "force"; he conceived them as subtile forms
of matter — as highly attenuated yet tangible fluids, sub-
ject to gravitation and chemical attraction ; though he
had learned to measure none of them but heat with ac-
curacy, and this one he could test only within narrow
limits until late in the century, when Josiah Wedgwood,
the famous potter, taught him to gauge the highest tem-
peratures with the clay pyrometer.
He spoke of the matter of heat as being the most uni-
versally distributed fluid in nature; as entering in some
degree into the composition of nearly all other sub-
stances ; as being sometimes liquid, sometimes con-
densed or solid, and as having weight that could be de-
tected with the balance. Following Newton, he spoke
of light as a " corpuscular emanation " or fluid, composed
of shining particles which possibly are transmutable
into particles of heat, and which enter into chemical
combination with the particles of other forms of matter.
Electricity he considered a still more subtile kind of mat-
ter— perhaps an attenuated form of light. Magnetism,
" vital fluid," and by some even a " gravic fluid," and a
fluid of sound, were placed in the same scale ; and taken
together, all these supposed subtile forms of matter were
classed as " imponderables."
This view of the nature of the " imponderables '' was
in some measure a retrogression, for many seventeenth-
century philosophers, notably Hooke and Iluygens and
Boyle, had held more correct views; but the materi-
alistic conception accorded so well with the eighteen th-
24
SCIENCE AT THE BEGINNING OF THE CENTURY
century tendencies of thought that only here and there
a philosopher, like Euler, called it in question, until well
on towards the close of the century. Current speech re-
ferred to the materiality of the "imponderables" un-
Iquestioningly. Students of meteorology — a science that
was just dawning — explained atmospheric phenomena
BENJAMIN THOMPSON— COUNT RUMFORD
THE STORY OF NINETEENTH-CENTURY SCIENCE
on the supposition that heat, the heaviest imponderable,
predominated in the lower atmosphere, and that light,
electricity, and magnetism prevailed in successively
higher strata. And Lavoisier, the most philosophical
chemist of the century, retained heat and light on a par
with oxygen, hydrogen, iron, and the rest, in his list of
elementary substances.
But just at the close of the century the confidence in
the status of the imponderables was rudely shaken in
the minds of philosophers by the revival of the old idea
of Fra Paolo and Bacon and Boyle, that heat, at any
rate, is not a material fluid, but merely a mode of mo-
tion or vibration among the particles of " ponderable "
matter. The new champion of the old doctrine as to
the nature of heat was a very distinguished philosopher
and diplomatist of the time, who, it may be worth re-
calling, was an American. He was a sadly expatriated
American, it is true, as his name, given all the official
appendages, will amply testify ; but he had been born
and reared in a Massachusetts village none the less, and
he seems always to have retained a kindly interest in
the land of his nativity, even though he lived abroad in
the service of other powers during all the later years of
his life, and was knighted by England, ennobled by Ba-
varia, and honored by the most distinguished scientific
bodies of Europe. The American, then, who cham-
pioned the vibratory theory of heat, in opposition to all
current opinion, in this closing era of the eighteenth
century, was Lieutenant-General Sir Benjamin Thomp-
son, Count Rumford, F. R. S.
Rumford showed that heat may be produced in in-
definite quantities by friction of bodies that do not
themselves lose any appreciable matter in the process,
26
SCIENCE AT THE BEGINNING OF THE CENTURY
and claimed that this proves the immateriality of heat.
Later on he added force to the argument by proving, in
refutation of the experiments of Bowditch, that no body
either gains or loses weight in virtue of being heated
or cooled. He thought it proved that heat is only a
mode of motion.
But contemporary judgment, while it listened respect-
fully to Rumford, was little minded to accept his ver-
dict. The cherished beliefs of a generation are not to
be put down with a single blow. Where many minds
have a similar drift, however, the first blow may precip-
itate a general conflict ; and so it was here. Young
Humphry Davy had duplicated Rumford's experiments,
and reached similar conclusions; and soon others fell
into line. Then, in 1800, Dr. Thomas Young—" Phe-
nomenon Young" they called him at Cambridge, because
he was reputed to know everything — took up the cud-
gels for the vibratory theory of light, and it began to
be clear that the two " imponderables," heat and light,
must stand or fall together ; but no one as yet made a
claim against the fluidity of electricity.
But before this speculative controversy over the nat-
ure of the "imponderables" had made more than a fair
beginning, in the last year of the century, a discovery
was announced which gave a new impetus to physical
science, and for the moment turned the current of spec-
ulation into another channel. The inventor was the
Italian scientist Volta ; his invention, the apparatus to
be known in future as the voltaic pile — the basis of the
galvanic battery. Ten years earlier Galvani had discov-
ered that metals placed in contact have the power to
excite contraction in the muscles of animals apparently
dead. Working along lines suggested by this discovery,
27
THE STORY OF NINETEENTH-CENTURY SCIENCE
Volta developed an apparatus composed of two metals
joined together and acted on by chemicals, which ap-
peared to accumulate or store up the galvanic influence,
whatever it might be. The effect could be accentuated
by linking together several such " piles " into a " bat-
tery."
This invention took the world by storm. Nothing
like the enthusiasm it created in the philosophic world
had been known since the invention of the Leyden jar,
more than half a century before. Within a few weeks
after Yolta's announcement, batteries made according
to his plan were being experimented with in every im-
portant laboratory in Europe. The discovery was made
in March. Early in May two Englishmen, Messrs.
Nicholson and Carlyle, practising with the first battery
made in their country, accidentally discovered the de-
composition of water by the action of the pile. And
thus in its earliest infancy the new science of " galvan-
ism " had opened the way to another new science — elec-
tro-chemistry.
As the century closed, half the philosophic world was
speculating as to whether "galvanic influence" were a
new imponderable or only a form of electricity ; and the
other half was eagerly seeking to discover what new
marvels the battery might reveal. The least imagina-
tive man could see that here was an invention that
would be epoch-making, but the most visionary dreamer
could not" even vaguely adumbrate the real measure of
its importance. Hitherto electricity had been only a
laboratory aid or a toy of science, with no suggestion of
practical utility beyond its doubtful application in medi-
cine ; in future, largely as the outgrowth of Yolta's dis-
covery, it • was destined to become a great economic
28
SCIENCE AT THE BEGINNING OF THE CENTURY
agency, whose limitations not even the enlarged vision
of our later century can pretend to outline.
Of all the contests that were waging in the various
fields of science in this iconoclastic epoch, perhaps the
fiercest and most turbulent was that which fell within
the field of chemistry. Indeed, this was one of the
most memorable warfares in the history of polemics. It
was a battle veritably Napoleonic in its inception, scope,
and incisiveness. As was fitting, it was a contest of
France against the world ; but the Napoleonic parallel
fails before the end, for in this case France won not
only speedily and uncompromisingly, but for all time.
The main point at issue concerned the central doc-
trine of the old chemistry — the doctrine of Becher and
Stahl, that the only combustible substance in nature is
a kind of matter called phlogiston, which enters into
the composition of other bodies in varying degree, thus
determining their inflammability. This theory seems
crude enough now, since we know that phlogiston was a
purely fictitious element, }7et it served an excellent pur-
pose when it was propounded and it held its place as
the central doctrine of chemical philosophy for almost a
century.
At the time when this theory was put forward, it
must be recalled, the old Aristotelian idea that the four
primal elements are earth, air, fire, and water still held
sway as the working foundation of all chemical philoso-
phies. Air and water were accepted as simple bodies.
Only a few acids and alkalies were known, and these
but imperfectly ; and the existence of gases as we now
29
THE STORY OF NINETEENTH-CENTURY SCIENCE
know them, other than air, was hardly so much as sus-
pected. All the known facts of chemistry seemed then
JOSEPH PRIESTLY
to harmonize with the phlogiston hypothesis; and so.
later on, did the new phenomena which were discovered
30
SCIENCE AT THE BEGINNING OF THE CENTURY
in such profusion during the third quarter of the eigh-
teenth century — the epoch of pneumatic chemistry.
Hydrogen gas, discovered by Cavendish in 1776, and
called inflammable air, was thought by some chemists
to be the very principle of phlogiston itself. Other
" airs " were adjudged " dephlogisticated " or " phlogis-
ticated." in proportion as they supported or failed to
support combustion. The familiar fact of a candle
flame going out when kept in a confined space of or-
dinary air was said to be due to the saturation of this
air with phlogiston. And all this seemed to tally beau-
tifully with the prevailing theory.
But presently the new facts began, as new facts al-
ways will, to develop an iconoclastic tendency. The
phlogiston theory had dethroned fire from its primacy
as an element by alleging that flame is due to a union
of the element heat with the element phlogiston. Now
earths were decomposed, air and water were shown to
be compound bodies, and at last the existence of phlo-
giston itself was to be called in question. The structure
of the old chemical philosophy had been completely rid-
dled ; it was now to be overthrown. The culminating
observation which brought matters to a crisis was the
discovery of oxygen, which was made by Priestley in
England and Scheelein Sweden, working independently,
in the year 1 77i. Priestley called the new element " de-
phlogisticated air"; Scheele called it "empyreal air."
But neither Priestley nor Scheele realized the full im-
port of this discovery ; nor, for that matter, did any
one else at the moment. Yery soon, however, one man
at least had an inkling of it. This was the great French
chemist Antoine Laurent Lavoisier. It has sometimes
been claimed that he himself discovered oxygen inde-
31
THE STORY OF NINETEENTH-CENTURY SCIENCE
pendently of Priestley and Scheele. At all events, he at
once began experimenting with it, and very soon it
dawned upon him that this remarkable substance might
furnish a key to the explanation of many of the puzzles
of chemistry. He found that oxygen is consumed or
transformed during the combustion of any substance in
air. He- reviewed the phenomena of combustion in the
light of this new knowledge. It seemed to him that
the new element explained them all without aid of the
supposititious element phlogiston. What proof, then,
have we that phlogiston exists ? Very soon he is able
to answer that there is no proof, no reason to believe
that it exists. Then why not denounce phlogiston as a
myth, and discard it from the realm of chemistry ?
Precisely this is what Lavoisier purposes to do. He
associates with him three other famous French chemists,
Berthollet, Guy ton de Morveau, and Fourcroy, and sets
to work to develop a complete system of chemistry based
on the new conception. In 1788 the work is completed
and given to the world. It is not merely an epoch-mak-
ing book; it is revolutionar}7. It discards phlogiston
altogether, alleging that the elements really concerned
in combustion are oxygen and heat. It claims that
acids are compounds of oxygen with a base, instead of
mixtures of " earth " and water ; that metals are simple
elements, not compounds of " earth " and " phlogiston " ;
and that water itself, like air, is a compound of oxygen
with another element.
In applying these ideas the new system proposes an
altogether new nomenclature for chemical substances.
Hitherto the terminology of the science has been a mat-
ter of whim and caprice. Such names as " liver of sul-
phur," " mercury of life," " horned moon," " the double
32 .
SCIENCE AT THE BEGINNING OF THE CENTURY
secret," " the salt of many virtues," and the like,
have been accepted without protest by the chemical
world. With such a terminology continued progress
wras as impossible as human progress without speech.
The new chemistry of Lavoisier and his confreres, fol-
lowing the model set by zoology half a century earlier,
designates each substance by a name instead of a phrase,
applies these names according to fixed rules, and? in
short, classifies the chemical knowledge of the time and
brings it into a system, lacking which no body of knowl-
edge has full title to the name of science.
Though Lavoisier was not alone in developing this
revolutionary scheme, posterity remembers him as its
originator. His dazzling and comprehensive genius ob-
scured the feebler lights of his confreres. Perhaps, too,
his tragic fate was not without influence in augmenting
his posthumous fame. In 179i he fell by the guillotine,
guiltless of any crime but patriotism — a victim of the
" Keign of Terror." " The Republic has no need of
savants" remarked the functionary who signed the
death-warrant of the most famous chemist of the cen-
tury.
The leader of the reform movement in chemistry
thus died at the hands of bigotry and fanaticism — •
rather, let us say, as the victim of a national frenzy —
while the cause he championed was young, yet not too
soon to see the victory as good as won. The main body
of French chemists had accepted the new doctrines al-
most from the first, and elsewhere the opposition had
been of that fierce, eager type which soon exhausts itself
in the effort. At Berlin they began by burning Lovoi-
sier in effigy, but they ended speedily by accepting the
new theories. In England the fight was more stubborn,
c 33
THE STORY OF NINETEENTH-CENTURY SCIENCE
but equally decisive. At first the new chemistry was
opposed by such great men as Black, of " latent heat "
fame ; Rutherford, the discoverer of nitrogen ; and Cav-
endish, the inventor of the pneumatic trough and the
discoverer of the composition of water, not to mention
a coterie of lesser lights ; but one by one they wavered
and went over to the enemy. Oddly enough, the
doughtiest and most uncompromising of all the cham-
pions of the old " phlogistic "' ideas was Dr. Priestley,
the very man whose discovery of oxygen had paved the
way for the " antiphlogistic " movement — a fact which
gave rise to Cuvier's remark that Priestley was undoubt-
edly one of the fathers of modern chemistry, but a
father who never wished to recognize his daughter.
A most extraordinary man was this Dr. Priestley.
Davy said of him, a generation later, that no other per-
son ever discovered so many new and curious substances
as he ; yet to the last he was only an amateur in science,
his profession being the ministry. There is hardly an-
other case in history of a man not a specialist in science
accomplishing so much in original research as did Joseph
Priestley, the chemist, physiologist, electrician ; the
mathematician, logician, and moralist ; the theolo-
gian, mental philosopher, and political economist. He
took all knowledge for his field ; but how he found time
for his numberless researches and multifarious writings,
along with his every-day duties, must ever remain a
mystery to ordinary mortals.
That this marvellously receptive, flexible mind should
have refused acceptance to the clearly logical doctrines
of the new chemistry seems equally inexplicable. But
so it was. To the very last, after all his friends had
capitulated, Priestley kept up the fight. From America,
34
SCIENCE AT THE BEGINNING OF THE CENTURY
whither he had gone to live in 1794, he sent out the last
defy to the enemy in 1800, in a brochure entitled " The
Doctrine of Phlogiston Upheld," etc. In the mind of
its author this was little less than a paean of victory ;
but all the world besides knew that it was the swan-
song of the doctrine of phlogiston. Despite the defiance
of this single warrior the battle was really lost and won,
and as the century closed, "antiphlogistic" chemistry had
practical possession of the field.
VI
Several causes conspired to make exploration all the
fashion during the closing epoch of the eighteenth cen-
tury. New aid to the navigator had been furnished by
the perfected compass and quadrant, and by the invention
of the chronometer; medical science had banished scurvy,
which hitherto had been a perpetual menace to the voy-
ager; and, above all, the restless spirit of the age im-
pelled the venturesome to seek novelty in fields alto-
gether new. Some started for the pole, others tried for
a northeast or northwest passage to India, yet others
sought the great fictitious antarctic continent told of by
tradition. All these of course failed of their immediate
purpose, but they added much to the world's store of
knowledge and its fund of travellers' tales.
Among all these tales none was more remarkable
than those which told of strange living creatures found
in antipodal lands. And here, as did not happen in
every field, the narratives were often substantiated by
the exhibition of specimens that admitted no question.
Many a company of explorers returned more or less
laden with such trophies from the animal and vegetable
35
THE STORY OF NINETEENTH-CENTURY SCIENCE
kingdoms, to the mingled astonishment, delight, and be-
wilderment of the closet naturalists. The followers of
Linnaeus in. the " golden age of natural history," a few
decades before, had increased the number of known spe-
cies of fishes to about 400, of birds to 1000, of insects to
3000, and of plants to 10,000. But now these sudden
accessions from new territories doubled the figure for
plants, tripled it for fish and birds, and brought the
number of described insects above 20,000.
Naturally enough, this wealth of new material was
sorely puzzling to the classifiers. The more discerning
began to see that the artificial system of Linnaeus, won-
derful and useful as it bad been, must be advanced upon
before the new material could be satisfactorily disposed
of. The way to a more natural system, based on less
arbitrary signs, had been pointed out by Jussieu in
botany, but the zoologists were not prepared to make
headway towards such a system until they should gain a
wider understanding of the organisms with which they
had to deal through comprehensive studies of anatomy.
Such studies of individual forms in their relations to the
entire scale of organic beings were pursued in these last
decades of the century, but though two or three most
important generalizations were achieved (notably Kaspar
"Wolff's conception of the cell as the basis of organic life,
and Goethe's all-important doctrine of metamorphosis
of parts), yet, as a whole, the work of the anatomists of
the period was germinative rather than fruit-bearing.
Bichat's volumes, telling of the recognition of the fun-
damental tissues of the body, did not begin to appear
till the last year of the century. The announcement by
Cuvier of the doctrine of correlation of parts bears the
same date, but in general the studies of this great nat-
86
LAVOISIEH IN HIS LABORATORY
SCIEXCE AT THE BEGINNING OF THE CENTURY
uralist, which in due time were to stamp him as the
successor of Linnaeus, were as yet only fairly begun.
In the field of physiology, on the other hand, two
most important works were fairly consummated in this
epoch — the long-standing problems of digestion and
respiration were solved, almost coincidently. Two very
distinguished physiologists share the main honors of dis-
covery in regard to the function of digestion — the Abbe
Spallanzani, of the University of Pavia, Italy, and John
Hunter, of England. Working independently, these inves-
tigators showed at about the same time that digestion is
primarily a chemical rather than a mechanical process.
It is a curious commentary on the crude notions of me-
chanics of previous generations that it should have been
necessary to prove by experiment that the thin, almost
membranous stomach of a mammal has not the power to
pulverize, by mere attrition, the foods that are taken into
it. However, the proof was now for the first time forth-
coming, and the question of the general character of the
function of digestion was forever set at rest.
To clear up the mysteries of respiration was a task that
fell to the lot of chemistry. The solution of the problem
followed almost as a matter of course upon the advances
of that science in the latter part of the century. Hitherto
no one since Mayow, of the previous century, whose flash
of insight had been strangely overlooked and forgotten,
had even vaguely surmised the true function of the lungs.
The great Boerhaave had supposed that respiration is
chiefly important as an aid to the circulation of the
blood ; his great pupil, Haller, had believed to the day of
his death in 1777 that the main purpose of the function
is to form the voice. No genius could hope to fathom
the mystery of the lungs so long as air was supposed to
89
THE STORY OF NINETEENTH-CENTURY SCIENCE
be a simple element, serving a mere mechanical purpose
in the economy of the earth.
But the discovery of oxygen gave the clew, and very
soon all the chemists were testing the air that came
from the lungs — Dr. Priestley, as usual, being in the
van. His initial experiments were made in 1777, and
from the outset the problem was as good as solved.
Other experimenters confirmed his results in all their
essentials — notably Scheeleand Lavoisier and Spallanzani
and Davy. It was clearly established that there is chem-
ical action in the contact of the air with the tissue of the
lungs ; that some of the oxygen of the air disappears,
and that carbonic acid gas is added to the inspired air.
It was shown, too, that the blood, having come in con-
tact with the air, is changed from black to red in color.
These essentials were not in dispute from the first. But
as to just what chemical changes caused these results
was the subject of controversy. "Whether, for example,
oxygen is actually absorbed into the blood, or whether
it merely unites with carbon given off from the blood,
was long in dispute.
Each of the main disputants was biassed by his own
particular views as to the moot points of chemistry^
Lavoisier, for example, believed oxygen gas to be com-
posed of a metal oxygen combined with the alleged ele-
ment heat; Dr. Priestley thought it a compound of pos-
itive electricity and phlogiston ; and Humphry Davy,
when he entered the lists, a little later, supposed it to be
a compound of oxygen and light. Such mistaken no-
tions naturally complicated matters, and delayed a com-
plete understanding of the chemical processes of respi-
ration. It was some time, too, before the idea gained
acceptance that the most important chemical changes
40
SCIENCE AT TIIE BEGINNING OF THE CENTURY
do not occur in the lungs themselves, but in the ultimate
tissues. Indeed, the matter \vas not clearly settled at
the close of the century. Nevertheless, the problem of
respiration had been solved in its essentials. Moreover,
the vastly important fact had been established that a
process essentially identical with respiration is necessary
to the existence not only of all creatures supplied with
lungs, but to fishes, insects, and even vegetables — in
short, to every kind of living organism.
EDWARD JENKER
From the painting by Sir Thomas Lawrence
THE STORY OF NINETEENTH-CENTURY SCIENCE
All advances in science have a bearing, near or re-
mote, on the welfare of our race ; but it remains to
credit to the closing decade of the eighteenth century a
discovery which, in its power of direct and immediate
benefit to humanity, surpasses any other discovery of
this or any previous epoch. Needless to say I refer to
Jenner's discovery of the method of preventing small-
pox by inoculation with the virus of cow-pox. It de-
tracts nothing from the merit of this discovery to say
that the preventive power of accidental inoculation had
long been rumored among the peasantry of England.
Such vague, unavailing half-knowledge is often the fore-
runner of fruitful discovery. To all intents and purposes
Jenner's discovery was original and unique. Neither,
considered as a perfected method, was it in any sense an
accident. It was a triumph of experimental science;
how great a triumph it is difficult now to understand, for
we of to-day can only vaguely realize what a ruthless and
ever-present scourge small-pox had been to all previous
generations of men since history began. Despite all
efforts to check it by medication and by direct inocula-
tion, it swept now and then over the earth as an all-
devastating pestilence, and year by year it claimed one-
tenth of all the beings in Christendom by death as its
average quota of victims. " From small-pox and love
but few remain free," ran the old saw. A pitted face
was almost as much a matter of course a hundred years
ago as a smooth one is to-day.
Little wonder, then, that the world gave eager ac-
ceptance to Jenner's discovery. The first vaccination
was made in 1796. Before the close of the century the
method was practised everywhere in Christendom. No
urging was needed to induce the majority to give it
42
SCIENCE AT THE BEGINNING OF THE CENTURY
trial; passengers on a burning ship do not hold aloof
from the life-boats. Kich and poor, high and low,
sought succor in vaccination, and blessed the name of
their deliverer. Of all the great names that were be-
fore the world in the closing days of the century,
there was perhaps no other one at once so widely
known and so uniformly reverenced as that of the Eng-
lish physician Edward Jenner. Surely there was no
other one that should be recalled with greater gratitude
by posterity.
CHAPTER II
THE CENTURY'S PROGRESS IN ASTRONOMY
THE first day of our century was fittingly signalized
by the discovery of a new world. On the evening of
Januarv 1, 1801, an Italian astronomer, Piazzi, observed
an apparent star of about the eighth magnitude (hence,
of course, quite invisible to the unaided eye), which later
on was seen to have moved, and was thus shown to be
vastly nearer the earth than any true star. He at first
supposed, as Herschel had done when he first saw
Uranus, that the unfamiliar body was a comet; but
later observation proved it a tiny planet, occupying a
position in space between Mars and Jupiter. It was
christened Ceres, after the tutelary goddess of Sicily.
Though unpremeditated, this discovery was not un-
expected, for astronomers had long surmised the exist-
ence of a planet in the wide gap between Mars and
Jupiter. Indeed, they were even preparing to make
concerted search for it, despite the protests of philoso-
phers, who argued that the planets could not possibly
exceed the magic number seven, when Piazzi forestalled
their efforts. But a surprise came with the sequel; for
the very next year Dr. Olbers, the wonderful physician-
astronomer of Bremen, while following up the course of
44
FIUEDRICII WILHELM BESSEL
T11E CENTURY'S PROGRESS IN ASTRONOMY
Ceres, happened on another tiny moving star, similarly
located, which soon revealed itself as planetary. Thus
two planets were found where only one was expected.
The existence of the supernumerary was a puzzle, but
Olbers solved it for the moment by suggesting that
Ceres and Pallas, as he called his captive, might be frag-
ments of a quondam planet, shattered by internal ex-
plosion, or by the impact of a comet. Other similar
fragments, he ventured to predict, would be found when
searched for. William Herschel sanctioned this theory,
and suggested the name asteroids for the tiny planets.
The explosion theory was supported by the discovery of
another asteroid, by Harding, of Lilienthal, in 1804, and
it seemed clinched when Olbers himself found a fourth
in 1807. The new-comers were named Juno and Vesta
respectively.
There the case rested till 1845, when a Prussian
amateur astronomer named Hencke found another aste-
roid, after long searching, and opened a new epoch of
discovery. From then on the finding of asteroids be-
came a commonplace. Latterly, with the aid of pho-
tography, the list has been extended to above four hun-
dred, and as yet there seems no dearth in the supply,
though doubtless all the larger members have been re-
vealed. Even these are but a few hundreds of miles in
diameter, while the smaller ones are too tiny for meas-
urement. The combined bulk of these minor planets is
believed to be but a fraction of that of the earth.
Olbers's explosion theory, long accepted by astrono-
mers, has been proven open to fatal objections. The
minor planets are now believed to represent a ring of
cosmical matter, cast off from the solar nebula like the
rings that went to form the major planets, but prevented
47
THE STOEY OF NINETEENTH-CENTURY SCIENCE
from becoming aggregated into a single body by the
perturbing mass of Jupiter.
As we have seen, the discovery of the first asteroid
confirmed a conjecture ; the other important planetary
discovery of our century fulfilled a prediction. Nep-
tune was found through scientific prophecy. No one
suspected the existence of a trans-Uranian planet till
Uranus itself, by hair-breadth departures from its pre-
dicted orbit, gave out the secret. No one saw the dis-
turbing planet till the pencil of the mathematician, with
almost occult divination, had pointed out its place in
the heavens. The general predication of a trans-
Uranian planet was made by Bessel, the great Konigs-
berg astronomer, in 184-0; the analysis that revealed its
exact location was undertaken, half a decade later, by
two independent workers — John Couch Adams, just
graduated senior wrangler at Cambridge, England, and
U. J. J. Leverrier, the leading French mathematician of
his generation.
Adams's calculation .was first begun and first com-
pleted. But it had one radical defect — it was the work
of a young and untried man. So it found lodgment in a
pigeon-hole of the desk of England's Astronomer Royal,
and an opportunity was lost which English astronomers
have never ceased to mourn. Had the search been
made, an actual planet would have been seen shining
there, close to the spot where the pencil of the mathe-
matician had placed its hypothetical counterpart. But
the search was not made, and while the prophecy of
Adams gathered dust in that regrettable pigeon-hole,
Leverrier's calculation was coming on, his tentative
results meeting full encouragement from Arago and
other French savants. At last the laborious calculations
48
THE CENTURY'S PROGRESS IX ASTRONOMY
proved satisfactory, and, confident of the result, Leverrier
sent to the Berlin observatory, requesting that search be
made for the disturber of Uranus in a particular spot of
the heavens. Dr. Galle received the request September
23, 1846. That very night he turned his telescope to the
indicated region, and there, within a single degree of
the suggested spot, he saw a seeming star, invisible to
the unaided eye, which proved to be the long-sought
planet, henceforth to be known as Neptune. To the
average mind, which finds something altogether mysti-
fying about abstract mathematics, this was a feat
savoring of the miraculous.
Stimulated by this success, Leverrier calculated an
orbit for an interior planet from perturbations of Mer-
cury, but though prematurely christened Vulcan, this
hypothetical nurseling of the sun still haunts the realm
of the undiscovered, along with certain equally hypo-
thetical trans-N"eptunian planets whose existence has
been suggested by "residual perturbations" of Uranus,
and by the movements of comets. No other veritable
additions to the sun's planetary family have been made
in our century, beyond the finding of seven small moons,
which chiefly attest the advance in telescopic powers.
Of these, the tiny attendants of our Martian neighbor,
discovered by Professor Hall with the great Washington
refractor, are of greatest interest, because of their small
size and extremely rapid flight. One of them is poised
only 6000 miles from Mars, and whirls about him almost
four times as fast as he revolves, seeming thus, as viewed
by the Martian, to rise in the west and set in the east, and
making the month only one-fourth as long as the day.
The discovery of the inner or crape ring of Saturn,
made simultaneously in 1850 by William C. Bond, at
D 49
THE STORY OF NINETEENTH-CENTURY SCIENCE
the Harvard observatory, in America, and the Rev.
W. R. Dawes in England, was another interesting op-
tical achievement ; but our most important advances
in knowledge of Saturn's unique system are due to the
mathematician. Laplace, like his predecessors, supposed
these rings to be solid, and explained their stability as
due to certain irregularities of contour which Herschel
had pointed out. But about 1851 Professor Peirce of
Harvard showed the untenability of this conclusion,
proving that were the rings such as Laplace thought
them, they must fall of their own weight. Then Pro-
fessor J. Clerk Maxwell of Cambridge took the matter
in hand, and his analysis reduced the puzzling rings to a
cloud of meteoric particles — a " shower of brickbats "-
each fragment of which circulates exactly as if it were
an independent planet, though of course perturbed and
jostled more or less by its fellows. Mutual perturbations,
and the disturbing pulls of Saturn's orthodox satellites,
as investigated by Max-well, explain nearly all the phe-
nomena of the rings in a manner highly satisfactory.
But perhaps the most interesting accomplishments of
mathematical astronomy — from a mundane stand-point,
at any rate — are those that refer to the earth's own
satellite. That seemingly staid body was long ago
discovered to have a propensit}r to gain a little on the
earth, appearing at eclipses an infinitesimal moment
ahead of time. Astronomers were sorely puzzled by
this act of insubordination ; but at last Laplace and
Lagrange explained it as due to an oscillatory change in
the earth's orbit, thus fully exonerating the moon, and
seeming to demonstrate the absolute stability and per-
manence of our planetary system, which the moon's
misbehavior had appeared to threaten.
50
THE CENTURY'S PROGRESS IN ASTRONOMY
This highly satisfactory conclusion was an orthodox
belief of celestial mechanics until 1853, when Professor
Adams of Xeptunian fame, with whom complex analyses
were a pastime, reviewed Laplace's calculation, and dis-
covered an error, which, when corrected, left about half
the moon's acceleration unaccounted for. This was a
momentous discrepancy, which at first no one could
explain. But presently Professor Helmholtz, the great
German physicist, suggested that a key might be found
in tidal friction, which, acting as a perpetual brake on
the earth's rotation, and affecting not merely the waters
but the entire substance of our planet, must in the long
sweep of time have changed its rate of rotation. Thus
the seeming acceleration of the moon might be account-
ed for as actual retardation of the earth's rotation — a
lengthening of the day instead of a shortening of the
month.
Again the earth was shown to be at fault, but this
time the moon could not be exonerated, while the esti-
mated stability of our system, instead of being re-estab-
lished, was quite upset. For the tidal retardation is not
an oscillatory change which will presently correct itself,
like the orbital wobble, but a perpetual change, acting
always in one direction. Unless fully counteracted by
some opposing reaction, therefore (as it seems not to be),
the effect must be cumulative, the ultimate consequences
disastrous. The exact character of these consequences
was first estimated by Professor G. H. Darwin, in 1879.
He showed that tidal friction in retarding the earth
must also push the moon out from the parent planet on
a spiral orbit. Plainly, then, the moon must formerly
have been nearer the earth than at present. At some
very remote period it must have actually touched the
51
THE STORY OF NINETEENTH-CENTURY SCIENCE
earth ; must, in other words, have been thrown off from
the then plastic mass of the earth, as a polyp buds out
from its parent polyp. At that time the earth was spin-
ning about in a day of from two to four hours.
Now the day has been lengthened to twenty-four
hours, and the moon has been thrust out to a distance
of a quarter-million miles; but the end is not yet. The
same progress of events must continue, till, at some re-
mote period in the future, the day has come to equal
the month, lunar tidal action has ceased, and one face of
the earth looks out always at the moon, with that same
fixed stare which even now the moon has been brought
to assume towards her parent orb. Should we choose to
take even greater liberties with the future, it may be
made to appear (though some astronomers dissent from
this prediction) that, as solar tidal action still continues,
the day must finally exceed the month, and lengthen
out little by little towards coincidence with the year;
and that the moon meantime must pause in its outward
flight, and come swinging back on a descending spiral,
until finally, after the lapse of untold a5ons, it ploughs
and ricochets along the surface of the earth, and plunges
to catastrophic destruction.
But even though imagination pause far short of this
direful culmination, it still is clear that modern calcula-
tions, based on inexorable tidal friction, suffice to revo-
lutionize the views formerly current as to the stability
of the planetary system. The eighteenth-century math-
ematician looked upon this system as a vast celestial
machine which had been in existence about six thousand
years, and which was destined to run on forever. The
analyst of to-day computes both the past and the future
of this system in millions instead of thousands of years,
52
THE CENTURY'S PROGRESS IN ASTRONOMY
yet feels well assured that the solar system offers no
contradiction to those laws of growth and decay which
seem everywhere to represent the immutable order of
nature.
ii
Until the mathematician ferreted out the secret, it
surely never could have been suspected by any one that
the earth's serene attendant,
"That orbed maiden, with white fire laden,
Whom mortals call the moon,"
could be plotting injury to her parent orb. But there
is another inhabitant of the skies whose purposes have
not been similarly free from popular suspicion. Needless
to say I refer to the black sheep of the sidereal family,
'that " celestial vagabond " the comet.
Time out of mind these wanderers have been sup-
posed to presage war, famine, pestilence, perhaps the
destruction of the world. And little wonder. Here is
a body which comes flashing out of boundless space into
our system, shooting out a pyrotechnic tail some hun-
dreds of millions of miles in length ; whirling perhaps
through the very atmosphere of the sun at a speed of
three or four hundred miles a second ; then darting off
on a hyperbolic orbit that forbids it ever to return, or
an elliptical one that cannot be closed for hundreds or
thousands of years ; the tail meantime pointing always
away from the sun, and fading to nothingness as the
weird voyager recedes into the spacial void whence it
came. Not many times need the advent of such an ap-
parition coincide with the outbreak of a pestilence, or
the death of a Caesar, to stamp the race of comets as an
53
THE STORY OF NINETEENTH-CENTURY SCIENCE
ominous clan in the minds of all snperstitious genera-
tions.
It is true a hard blow was struck at the prestige of
these alleged supernatural agents when Newton proved
that the great comet of 1680 obeyed Kepler's laws in its
flight about the sun ; and an even harder one when the
same visitant came back in 1758, obedient to Halley's
prediction, after its three-quarters of a century of voy-
aging out in the abyss of space. Proved thus to bow to
natural law, the celestial messenger could no longer
fully sustain its role. But long-standing notoriety can-
not be lived down in a day, and the comet, though
proved a " natural " object, was still regarded as a very
menacing one for another hundred years or so. It re-
mained for our own century to completely unmask the
pretender, and show how egregiously our forebears had
been deceived.
The unmasking began early in the century, when Dr.
Olbers, then the highest authority on the subject, ex-
pressed the opinion that the spectacular tail, which had
all along been the comet's chief stock in trade as an
earth - threatener, is in reality composed of the most
filmy of vapors, repelled from the cometary body by the
sun, presumably through electrical action, with a veloc-
ity comparable to that of light. This luminous sug-
gestion was held more or less in abeyance for half a cen-
tury. Then it was elaborated by Zollner, and particu-
larly by Bredichin, of the Moscow observatory, into
what has since been regarded as the most plausible of
cometary theories. It is held that comets and the sun
are similarly electrified, and hence mutually repulsive.
Gravitation vastly outmatches this repulsion in the
body of the comet, but yields to it in the case of gases,
54
HEIMUCII \VILIIELM MATTHIAS
THE CENTURY'S PROGRESS IN ASTRONOMY
because electrical force varies with the surface, while
gravitation varies only with the mass. From study of
atomic weights, and estimates of the velocity of thrust
of cometary tails, Bredichin concluded that the chief
components of the various kinds of tails are hydrogen,
hydrocarbons, and the vapor of iron ; and spectroscopic
analysis goes far towards sustaining these assumptions.
But, theories aside, the unsubstantialness of the corn-
et's tail has been put to a conclusive test. Twice during
our century the earth has actually plunged directly
through one of these threatening appendages, in 1819,
and again in 1861, once being immersed to a depth of
some 300,000 miles in its substance. Yet nothing dread-
ful happened to us. There was a peculiar glow in the
atmosphere, so the more imaginative observers thought,
and that was all. After such fiascoes, the coraetary
train could never again pose as a world-destroyer.
But the full measure of the comet's humiliation is not
yet told. The pyrotechnic tail, composed as it is of por-
tions of the comet's actual substance, is tribute paid the
sun, and can never be recovered. Should the obeisance to
the sun be many times repeated, the train-forming mate-
rial will be exhausted, and the comet's chiefest glory will
have departed. Such a fate has actually befallen a mul-
titude of comets, which Jupiter and the other outlying
planets have dragged into our system, and helped the
sun to hold captive here. Many of these tailless comets
were known to the eighteenth-century astronomers, but
no one at that time suspected the true meaning of their
condition. It was not even known how closely some of
them are enchained, until the German astronomer Encke,
in 1822, showed that one which he had rediscovered, and
which has since borne his name, was moving in an orbit
57
THE STORY OF NINETEENTH-CENTURY SCIENCE
so contracted that it must complete its circuit in about
three and a half years. Shortly afterwards another
comet, revolving in a period of about six years, was dis-
covered by Biela, and given his name. Only two more
of these short-period comets were discovered during our
first half -century, but latterly they have been shown to
be a numerous family. Nearly twenty are known which
the giant Jupiter holds so close that the utmost reach of
their elliptical tether does not let them go beyond the
orbit of Saturn. These aforetime wanderers have adapt-
ed themselves wonderfully to planetary customs, for all
of them revolve in the same direction with the planets,
and in planes not wide of the ecliptic.
Checked in their proud hyperbolic sweep, made cap-
tive in a planetary net, deprived of their trains, these
quondam free lances of the heavens are now mere
shadows of their former selves. Considered as to mere
bulk, they are very substantial shadows, their extent be-
ing measured in hundreds of thousands of miles ; but
their actual mass is so slight that they are quite at the
mercy of the gravitation pulls of their captors. And
worse is in store for them. So persistently do sun and
planets tug at them that they are doomed presently to
be torn into shreds.
Such a fate has already overtaken one of them, under
the very eyes of the astronomers, within the relatively
short period during which these ill-fated comets have
been observed. In 1832 Biela's comet passed quite near
the earth, as astronomers measure distance, and in doing
so created a panic on our planet. It did no greater harm
than that, of course, and passed on its way as usual.
The very next time it came within telescopic hail it was
seen to have broken into two fragments. Six years later
58
THE CENTURY'S PROGRESS IN ASTRONOMY
these fragments were separated by many millions of
miles ; and in 1852, when the comet was due again, as'
tronomers looked for it in vain. It had been completely
shattered.
What had become of the fragments ? At that time
no one positively knew. But the question was to be
answered presently. It chanced that just at this period
astronomers were paying much attention to a class of
bodies which they had hitherto somewhat neglected, the
familiar shooting-stars or meteors. The studies of Pro-
fessor Newton of Yale and Professor Adams of Cam-
bridge with particular reference to the great meteor-
shower of November, 1866, which Professor Newton
had predicted, and shown to be recurrent at intervals of
thirty-three years, showed that meteors are not mere
sporadic swarms of matter flying at random, but exist
in isolated swarms, and sweep about the sun in regular
elliptical orbits.
Presently it was shown by the Italian astronomer
Schiaparelli that one of these meteor swarms moves
in the orbit of a previously observed comet, and other
coincidences of the kind were soon forthcoming. The
conviction grew that meteor swarms are really the
debris of comets ; and this conviction became a prac-
tical certainty when, in November, 1872, the earth
crossed the orbit of the ill-starred Biela, and a shower
of meteors came whizzing into our atmosphere in lieu of
the lost comet.
And so at last the full secret was out. The awe-inspir-
ing comet, instead of being the planetary body it had all
along been regarded, is really nothing more nor less
than a great aggregation of meteoric particles, which
have become clustered together out in space somewhere,
59
THE STORY OF NINETEENTH-CENTURY SCIENCE
and which by jostling one another or through electrical
action become luminous. So widely are the individual
particles separated that the cometary body as a whole
has been estimated to be thousands of times less dense
than the earth's atmosphere at sea-level. Hence the
ease with which the comet may be dismembered and its
particles strung out into streaming swarms.
So thickly is the space we traverse strewn with this
cometary dust that the earth sweeps up, according to
Professor Newcomb's estimate, a million tons of it each
day. Each individual particle, perhaps no larger than
a millet seed, becomes a shooting-star or meteor as it
burns to vapor in the earth's upper atmosphere. And
if one tiny planet sweeps up such masses of this cosmic
matter, the amount of it in the entire stretch of our sys-
tem must be beyond all estimate. What a story it tells
of the myriads of cometary victims that have fallen prey
to the sun since first he stretched his planetary net across
the heavens.
in
When Biela's comet gave the inhabitants of the earth
such a fright in 1832, it really did not come within
fifty millions of miles of us. Even the great comet
through whose filmy tail the earth passed in 1861 was
itself fourteen millions of miles away. The ordi-
nary mind, schooled to measure space by the tiny
stretches of a pygmy planet, cannot grasp the import of
such distances ; yet these are mere units of measure
compared with the vast stretches of sidereal space.
Were the comet which hurtles past us at a speed of,
say, a hundred miles a second to continue its mad flight
unchecked straight out into the void of space, it must fly
60
SIR JOHN HERSCHEL
From the painting by II. W. Pickersgill, R. A., in St. John's College, Cambridge
THE CENTURY'S PROGRESS IN ASTRONOMY
on its frigid way eight thousand years before it could
reach the very nearest of our neighbor stars ; and even
•t Cj 7
then it would have penetrated but a mere arm's-length
into the vistas where lie the dozen or so of sidereal resi-
dents that are next beyond. Even to the trained mind
such distances are only vaguely imaginable. Yet the
astronomer of our century has reached out across this
unthinkable void and brought back many a secret
which our predecessors thought forever beyond human
grasp.
A tentative assault upon this stronghold of the stars
was being made by Herschel at the beginning of the
century. In 1802 that greatest of observing astrono-
mers announced to the Eoyal Society his discovery that
certain double stars had changed their relative positions
towards one another since he first carefully charted
them twenty years before. Hitherto it had been sup-
posed that double stars were mere optical effects. Now
it became clear that some of them, at any rate, are true
" binary systems," linked together presumably by gravi-
tation, and revolving about one another. Halley had
shown, three-quarters of a century before, that the stars
have an actual or "proper" motion in space; Herschel
himself had proved that the sun shares this motion with
the other stars. Here was another shift of place, hith-
erto quite unsuspected, to be reckoned with by the as-
tronomer in fathoming sidereal secrets.
When John Herschel, the only son and the worthy
successor of the great astronomer, began star-gazing in
earnest, after graduating senior wrangler at Cambridge,
and making two or three tentative professional starts in
other directions to which his versatile genius impelled
him, his first extended work was the observation of his
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THE STORY OF NINETEENTH-CENTURY SCIENCE
father's double stars. His studies, in which at first he had
the collaboration of Mr. James South, brought to light
scores of hitherto unrecognized pairs, and gave fresh
data for the calculation of the orbits of those longer
O
known. So also did the independent researches of F.
G. W. Struve, the enthusiastic observer of the famous
Russian observatory at the university of Dorpat, and
subsequently at Pulkowa. Utilizing data gathered by
these observers, M. Savary of Paris showed in 1827 that
the observed elliptical orbits of the double stars are ex-
plicable by the ordinary laws of gravitation, thus con-
firming the assumption that Newton's laws applv- to
these sidereal bodies. Henceforth there could be no
reason to doubt that the same force which holds terres-
trial objects on our globe pulls at each and every par-
ticle of matter throughout the visible universe.
The pioneer explorers of the double stars early found
that the systems into which the stars are linked are by
no means confined to single pairs. Often three or four
stars are found thus closely connected into gravitation
systems ; indeed, there are all gradations between bi-
nary systems and great clusters containing hundreds or
even thousands of members. It is known, for example,
that the familiar cluster of the Pleiades is not merely
an optical grouping, as was formerly supposed, but an
actual federation of associated stars, some 2500 in num-
ber, only a few of which are visible to the unaided eye.
And the more carefully the motions ot the stars are
studied, the more evident it becomes that wideh7 sepa-
rated stars are linked together into infinitely complex
systems, as yet but little understood. At the same time
all instrumental advances tend to resolve more and more
seemingly single stars into close pairs and minor clus-
64
THE CENTURY'S PROGRESS IN ASTRONOMY
ters. The two Herschels between them discovered
some thousands of these close multiple systems ; Struve
and others increased the list to above ten thousand ;
and Mr. S. "W. Burn ham, of late years the most enthusi-
astic and successful of double -star pursuers, added a
thousand new discoveries while he was still an amateur
in astronomy, and by profession the stenographer of a
Chicago court. Clearly the actual number of multiple
stars is beyond all present estimate.
The elder Herschel's early studies of double stars
were undertaken in the hope that these objects might
aid him in ascertaining the actual distance of a star,
through measurement of its annual parallax ; that is to
say, of the angle which the diameter of the earth's orbit
would subtend as seen from the star. The expectation
was not fulfilled. The apparent shift of position of a
star as viewed from opposite sides of the earth's orbit,
from which the parallax might be estimated, is so ex-
tremely minute that it proved utterly inappreciable,
even to the almost preternaturally acute vision of Her-
schel, with the aid of any instrumental means then at
command. So the problem of star distance allured and
eluded him to the end, and he died in 1822 without see-
ing it even in prospect of solution. His estimate of the
minimum distance of the nearest star, based though it
was on the fallacious test of apparent brilliancy, was a
singularly sagacious one, but it was at best a scientific
guess, not a scientific measurement.
Just about this time, however, a great optician came
to the aid of the astronomers. Joseph Fraunhofer per-
fected the refracting telescope, as Herschel had perfected
the reflector, and invented a wonderfully accurate " he-
liometer," or sun-measurer. With the aid of these in-
E 65
THE STORY OF NINETEENTH-CENTURY SCIENCE
struments the old and almost infinitely difficult problem
of star distance was solved. In 1838 Bessel announced
from the Konigsberg observatory that he had succeeded,
after months of effort, in detecting and measuring the
parallax of a star. Similar claims had been made often
enough before, always to prove fallacious when put to
further test; but this time the announcement carried
the authority of one of the greatest astronomers of the
age, and scepticism was silenced.
Nor did Bessel's achievement long await corrobora-
tion. Indeed, as so often happens in fields of discov-
ery, two other workers had almost simultaneously
solved the same problem — Struve at Pulkowa, where
the great Russian observatory, which so long held the
palm over all others, had now been established ; and
Thomas Henderson, then working at the Cape of Good
Hope, but afterwards the Astronomer Royal of Scotland.
Henderson's observations had actual precedence in point
of time, but Bessel's measurements were so much more
numerous and authoritative that he has been uniformly
considered as deserving the chief credit of the discovery,
which priority of publication secured him.
By an odd chance, the star on which Henderson's ob-
servations were made, and consequently the first star the
parallax of which was ever measured, is our nearest
neighbor in sidereal space, being, indeed, some ten bill-
ions of miles nearer than the one next beyond. Yet
even this nearest star is more than 200,000 times as re-
mote from us as the sun. The sun's light flashes to the
earth in eight minutes, and to Neptune in about three
and a half hours, but it requires three and a half years
to signal Alpha Centauri. And as for the great major-
ity of the stars, had they been blotted out of existence
66
THE GREAT REFRACTOR OF THE NATIONAL OBSERVATORY
AT WASHINGTON
THE CENTURY'S PROGRESS IN ASTRONOMY
before the Christian era, we of to-day should still re-
ceive their light and seem to see them just as we do.
When we look up to the sky, we study ancient history ;
we do not see the stars as they are, but as they were
years, centuries, even millennia ago.
The information derived from the parallax of a star
by no means halts with the disclosure of the distance of
that body. Distance known, the proper motion of the
star, hitherto only to be reckoned as so many seconds of
arc, may readily be translated into actual speed of prog-
ress ; relative brightness. becomes absolute lustre, as com-
pared with the sun * and in the case of the double stars
the absolute mass of the components may be computed
from the laws of gravitation. It is found that stars
differ enormously among themselves in all these regards.
As to speed, some, like our sun, barely creep through
space — compassing ten or twenty miles a second, it is
true, yet even at that rate only passing through the
equivalent of their own diameter in a day. At the
other extreme, among measured stars, is one that
moves two hundred miles a second ; yet even this "fly-
ing star," as seen from the earth, seems to change its
place by only about three and a half lunar diameters
in a thousand years. In brightness, some stars yield to
the sun, while others surpass him as the arc-light sur-
passes a candle. Arcturus, the brightest measured star,
shines like two hundred suns ; and even this giant orb
is dim beside those other stars which are so distant that
their parallax cannot be measured, yet which greet our
eyes at first magnitude. As to actual bulk, of which
apparent lustre furnishes no adequate test, some stars
are smaller than the sun, while others exceed him hun-
dreds or perhaps thousands of times. Yet one and all,
THE STORY OF NINETEENTH-CENTURY SCIENCE
so distant are they, remain mere diskless points of light
before the utmost powers of the modern telescope.
All this seems wonderful enough, but even greater
things were in store. In 1859 the spectroscope came
upon the scene, perfected by Kirchhoff and Bunsen,
along lines pointed out by Fraunhofer almost half a
century before. That marvellous instrument, by reveal-
ing the telltale lines sprinkled across a prismatic spec-
trum, discloses the chemical nature and physical condi-
tion of any substance whose light is submitted to it,
telling its story equally well, provided the light be
strong enough, whether the luminous substance be near
or far — in the same room or at the confines of space.
Clearly such an instrument must prove a veritable magic
wand in the hands of the astronomer.
Yery soon eager astronomers all over the world were
putting the spectroscope to the test. Kirchhoff himself
led the way, and Donati and Father Secchi in Italy,
Huggins and Miller in England, and Rutherfurd in
America, were the chief of his immediate followers.
The results exceeded the dreams of the most visionary.
At the very outset, in 1860, it was shown that such
common terrestrial substances as sodium, iron, calcium,
magnesium, nickel, barium, copper, and zinc exist in the
form of glowing vapors in the sun, and very soon the
stars gave up a corresponding secret. Since then the
work of solar and sidereal analysis has gone on steadily
in the hands of a multitude of workers (prominent
among whom, in this country, are Professor Young of
Princeton, Professor Langley of Washington, and Pro-
fessor Pickering of Harvard), and more than half the
known terrestrial elements have been definitely located
in the sun, while fresh discoveries are in prospect.
70
THE CENTURY'S PROGRESS IN ASTRONOMY
It is true the sun also contains some seeming elements
that are unknown on the earth, but this is no matter for
surprise. The modern chemist makes no claim for his
-
A TYPICAL STAR CLUSTER— CEKTAURI
Clements except that they have thus far resisted all
human efforts to dissociate them ; it would be nothing
strange if some of them, when subjected to the crucible
71
THE STORY OF NINETEENTH-CENTURY SCIENCE
of the sun, which is seen to vaporize iron, nickel, silicon,
should fail to withstand the test. But again, chemistry
has by no means exhausted the resources of the earth's
supply of raw material, and the substance which sends
its message from a star may exist undiscovered in the
dust we tread or in the air we breathe. Only last year
t\vo new terrestrial elements were discovered ; but one
of these had for years been known to the astronomer as
a solar and suspected as a stellar element, and named
helium because of its abundance in tho sun. The spec-
troscope had reached out millions of miles into space
and brought back this new element, and it took the
chemist a score of years to discover that he had all
along had samples of the same substance unrecognized
in his sublunary laboratory. There is hardly a more
picturesque fact than that in the entire history of
science.
But the identity in substance of earth and sun and
stars was not more clearly shown than the diversity of
their existing physical conditions. It was seen that sun
and stars, far from being the cool, earthlike, habitable
bodies that Herschel thought them (surrounded by
glowing clouds, and protected from undue heat by other
clouds), are in truth seething caldrons of fiery liquid, or
gas made viscid by condensation, with lurid envelopes
of belching flames. It was soon made clear, also, par-
ticularly by the studies of Rutherfurd and of Secchi,
that stars differ among themselves in exact constitution
or condition. There are white or Sirian stars, whose
spectrum revels in the lines of hydrogen ; yellow or
solar stars (our sun being the type), showing various
metallic vapors; and sundry red stars, with banded
spectra indicative of carbon compounds; besides, the
72
THE CENTURY'S PROGRESS IN ASTRONOMY
purely gaseous stars of more recent discovery, which
Professor Pickering had specially studied. Zollner's
famous interpretation of these diversities, as indicative
iVM ', f i
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Si
'1"'".'*V' '"
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i "' • IV, '"',
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I
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SPECTRA OF STARS IX CARINA
of varying stages of cooling, has been called in question
as to the exact sequence it postulates, but the general
proposition that stars exist under widely varying condi-
tions of temperature is hardly in dispute.
73
THE STORY OF NINETEENTH-CENTURY SCIENCE
The assumption that different star types mark vary-
ing stages of cooling has the further support of modern
physics, which has been unable to demonstrate any way
in which the sun's radiated energy may be restored, or
otherwise made perpetual, since meteoric impact has
been shown to be — under existing conditions at any
rate — inadequate. In accordance with the theory of
Helmholtz, the chief supply of solar energy is held to
be contraction of the solar mass itself, and plainly this
must have its limits. Therefore, unless some means as
yet unrecognized is restoring the lost energy to the
stellar bodies, each of them must gradually lose its lus-
tre, and come to a condition of solidification, seeming
sterility, and frigid darkness. In the case of our own
particular star, according to the estimate of Lord Kel-
vin, such a culmination appears likely to occur within a
period of five or six million years.
But by far the strongest support of such a forecast as
this is furnished by those stellar bodies which even now
appear to have cooled to the final stage of star develop-
ment and ceased to shine. Of this class examples in
miniature are furnished by the earth and the smaller of
its companion planets. But there are larger bodies of
the same type out in stellar space — veritable "dark
stars " — invisible, of course, yet nowadays clearly recog-
nized.
The opening up of this " astronomy of the invisible "
is another of the great achievements of our century, and
again it is Bessel to whom the honor of discovery is due.
"While testing his stars for parallax, that astute observer
was led to infer, from certain unexplained aberrations of
motion, that various stars, Sirius himself among the
number, are accompanied by invisible companions, and
74
THE CENTURY'S PROGRESS IN ASTRONOMY
in 1840 he definitely predicated the existence of such
"dark stars." The correctness of the inference was
shown twenty years later, when Alvan Clark, Jun., the
American optician, while testing a new lens, discovered
STAlt SPECTRA
the companion of Sirius, which proved thus to be faintly
luminous. Since then the existence of other and quite
invisible star companions has been proved incontestably,
75
THE STORY OF NINETEENTH-CENTURY SCIENCE
not merely by renewed telescopic observations, but by
the curious testimony of the ubiquitous spectroscope.
One of the most surprising accomplishments of that
instrument is the power to record the flight of a luminous
object directly in the line of vision. If the luminous
body approaches swiftly, its Fraunhofer lines are shifted
from their normal position towards the violet end of the
spectrum; if it recedes, the lines shift in the opposite
direction. The actual motion of stars whose distance is
unknown may be measured in this way. But in certain
cases the light lines are seen to oscillate on the spectrum
at regular intervals. Obviously the star sending such
light is alternately approaching and receding, and the
inference that it is revolving about a companion is una-
voidable. From this extraordinary test the orbital dis-
tance, relative mass, and actual speed of revolution of
the absolutely invisible body may be determined. Thus
the spectroscope, which deals only with light, makes
paradoxical excursions into the realm of the invisible.
What secrets may the stars hope to conceal when ques-
tioned by an instrument of such necromantic power?
IV
But the spectroscope is not alone in this audacious
assault upon the strongholds of nature. It has a worthy
companion and assistant in the photographic film, whose
efficient aid has been invoked by the astronomer even
more recently. Pioneer work in celestial photography
was, indeed, done by Arago in France and by the elder
Draper in America in 1839, but the results then achieved
were only tentative, and it was not till forty years later
that the method assumed really important proportions.
76
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I
THE CENTURY'S PROGRESS IN ASTRONOMY
In 1880 Dr. Henry Draper, at Hastings-on-the-Hudson,
made the first successful photograph of a nebula. Soon
after, Dr. David Gill, at the Cape observatory, made fine
photographs of a comet, and the flecks of starlight on
his plates first suggested the possibilities of this method
in charting the heavens.
Since then star-charting with the film has come to
virtually supersede the old method. A concerted effort is
being made by astronomers in various parts of the world
to make a complete chart of the heavens, and before
the close of our century this work will be accomplished,
some fifty or sixty millions of visible stars being placed
on record with a degree of accuracy hitherto unapproach-
able. Moreover, other millions of stars are brought to
* O
light by the negative which are too distant or dim to be
visible with any telescopic powers yet attained — a fact
which wholly discredits all previous inferences as to the
limits of our sidereal system. Hence, notwithstanding
the wonderful instrumental advances of our century,
knowledge of the exact form and extent of our universe
seems more unattainable than it seemed a century ago.
Yet the new instruments, while leaving so much
untold, have revealed some vastly important secrets of
cosmic structure. In particular, they have set at rest
the long-standing doubts as to the real structure and
position of the mysterious nebula — those hazy masses,
only two or three of them visible to the unaided eye,
which the telescope reveals in almost limitless abundance,
scattered everywhere among the stars, but grouped in
particular about the poles of the stellar stream or disk
which we call the Milky Way.
Herschel's later view, which held that some at least
of the nebulae are composed of a " shining fluid," in
79
THE STORY OF NINETEENTH-CENTURY SCIENCE
process of condensation to form stars, was generally
accepted for almost half a century. But in 1844, when
Lord Rosse's great six-foot reflector — the largest tele-
scope ever yet constructed — was turned on the nebulae,
it made this hypothesis seem very doubtful. Just as
Galileo's first lens had resolved the Milky Way into
stars, just as Herschel had resolved nebulae that resisted
all instruments but his own, so Lord Rosse's even greater
reflector resolved others that would not yield to Her-
schel's largest mirror. It seemed a fair inference that
with sufficient power, perhaps some day to be attained,
all nebulae would yield, hence that all are in reality
what Herschel had at first thought them — vastly distant
" island universes," composed of aggregations of stars,
comparable to our own galactic system.
But the inference was wrong; for when the spectro-
scope was first applied to a nebula in 1864, by Dr. Hug-
gins, it clearly showed the spectrum not of discrete stars,
but of a great mass of glowing gases, hydrogen among
others. More extended studies showed, it is true, that
some nebulae give the continuous spectrum of solids or
liquids, but the different types intermingle and grade
into one another. Also, the closest affinity is shown be-
tween nebulae and stars. Some nebulae are found to
contain stars, singly or in groups, in their actual midst;
certain condensed "planetary" nebulas are scarcely to
be distinguished from stars of the gaseous type; and re-
cently the photographic film has shown the presence of
nebulous matter about stars that to telescopic vision dif-
fer in no respect from the generality of their fellows in
the galaxy. The familiar stars of the Pleiades cluster,
for example, appear on the negative immersed in a hazy
blur of light. All in all, the accumulated impressions of
80
I 2
33
THE CENTURY'S PROGRESS IN ASTRONOMY
the photographic film reveal a prodigality of nebulous
matter in. the stellar system not hitherto even con-
jectured.
And so, of course, all question of "island universes"
vanishes, and the nebulae are relegated to their true po-
sition as component parts of the one stellar system — the
one universe — that is open to present human inspection.
And these vast clouds of world-stuff have been found
by Professor Keeler, of the Lick Observatory, to be
floating through space at the starlike speed of from ten
to thirty-eight miles per second.
The linking of nebula3 with stars, so clearly evi-
denced by all these modern observations, is, after all,
only the scientific corroboration of what the elder Her-
schel's later theories affirmed. But the nebulae have
other affinities not until recently suspected ; for the
spectra of some of them are practically identical with
the spectra of certain comets. The conclusion seems
warranted that comets are in point of fact minor nebu-
lae that are drawn into our system ; or, putting it other-
wise, that the telescopic nebulae are simply gigantic dis-
tant comets.
Following up the suprising clews thus suggested, Mr.
J. Norman Lockyer, of London, has in recent years
elaborated what is perphaps the most comprehensive
cosmogonic guess that has ever been attempted. His
theory, known as the " meteoric hypothesis," probably
bears the same relation to the speculative thought of
our time that the nebular hypothesis of Laplace bore to
that of the eighteenth century. Outlined in a few
words, it is an attempt to explain all the major phe-
nomena of the universe as due, directly or indirectly, to
the gravitational impact of such meteoric particles, or
THE STORY OF NINETEENTH-CENTURY SCIENCE
specks of cosmic dust, as comets are composed of. Neb-
ulae are vast cometary clouds, with particles more or
less widely separated, giving off gases through meteoric
collisions, internal or external, and perhaps glowing also
with electrical or phosphorescent light. Gravity eventu-
ally brings the nebular particles into closer aggregations,
and increased collisions finally vaporize the entire mass,
forming planetary nebulas and gaseous stars. Contin-
ued condensation may make the stellar mass hotter and
more luminous for a time, but eventually leads to its
liquefaction, and ultimate consolidation — the aforetime
nebulae becoming in the end a dark or planetary star.
The exact correlation which Mr. Lockyer attempts to
point out between successive stages of meteoric con-
densation and the various types of observed stellar bod-
ies does not meet with unanimous acceptance. Mr.
Kanyard, for example, suggests that the visible nebulae
may not be nascent stars, but emanations from stars,
and that the true pre-stellar nebulae are invisible until
condensed to stellar proportions. But such details aside,
the broad general hypothesis that all the bodies of the
universe^ are, so to speak, of a single species — that neb-
ulae (including comets), stars of all types, and planets,
are but varying stages in the life history of a single
race or type of cosmic organisms— is accepted by the
dominant thought of our time as having the highest war-
rant of scientific probability.
All this, clearly, is but an amplification of that nebu-
lar hypothesis which, long before the spectroscope gave
us warrant to accurately judge our sidereal neighbors,
had boldly imagined the development of stars out of
nebular and of planets out of stars. But Mr. Lockyer's
hypothesis does not stop with this. Having traced the
84
THE CENTURY'S PROGRESS IN ASTRONOMY
developmental process from the nebula to the dark star,
it sees no cause to abandon this dark star to its fate by
assuming, as the original speculation assumed, that this
is a culminating and final stage of cosmic existence.
For the dark star, though its molecular activities have
come to relative stability and impotence, still retains the
enormous potentialities of molar motion; and clearly,
THE OXFORD HELIOMETER
THE STORY OF NINETEENTH-CENTURY SCIENCK
where motion is, stasis is not. Sooner or later, in its
ceaseless flight through space, the dark star must col-
lide with some other stellar body, as Dr. Croll imagines
of the dark bodies which his " pre-nebular theory " pos-
tulates. Such collision may be long delayed ; the dark
star may be drawn in-cometlike circuit about thousands
of other stellar masses, and be hurtled on thousands of
diverse parabolic or elliptical orbits, before it chances to
collide — but that matters not : " billions are the units
in the arithmetic of eternity," and sooner or later, we
can hardly doubt, a collision must occur. Then without
question the mutual impact must shatter both colliding
bodies into vapor, or vapor combined with meteoric
fragments ; in short, into a veritable nebula, the matrix
of future worlds. Thus the dark star, which is the last
term of one series of cosmic changes, becomes the first
term of another series — at once a post-nebular and a pre-
nebular condition ; and the nebular hypothesis, thus am-
plified, ceases to be a mere linear scale, and is rounded
out to connote an unending series of cosmic cycles, more
nearly satisfying the imagination.
In this extended view, nebulae and luminous stars are
but the infantile and adolescent 'stages of the life his-
tory of the cosmic individual; the dark star, its adult
stage, or time of true virility. Or we may think of the
shrunken dark star as the germ-cell, the pollen-grain, of
the cosmic organism. Reduced in size, as becomes a
germ-cell, to a mere fraction of the nebular body from
which it sprang, it yet retains within its seemingly non-
vital body all the potentialities of the original organism,
and requires only to blend with a fellow-cell to bring a
new generation into being. Thus may the cosmic race,
whose aggregate census makes up the stellar universe,
86
THE CENTURY'S PROGRESS IN ASTRONOMY
be perpetuated — individual solar systems, such as ours,
being born, and growing old, and dying to live again in
their descendants, while the universe as a whole main-
tains its unified integrity throughout all these internal
mutations — passing on, it may be, by infinitesimal stages,
to a culmination hopelessly beyond human compre-
hension.
CHAPTEE ni
THE CENTURY'S PROGRESS IN PALEONTOLOGY
EVER since Leonardo da Vinci first recognized the
true character of fossils, there had been here and there
a man who realized that the earth's rocky crust is one
gigantic mausoleum. Here and there a dilettante had
filled his cabinets with relics from this monster crypt ;
here and there a philosopher had pondered over them—
questioning whether perchance they had once been alive,
or whether they were not mere abortive souvenirs of
that time when the fertile matrix of the earth was sup-
posed to have
"teemed at a birth
Innumerous living creatures, perfect forms,
Limbed and full-grown."
Some few of these philosophers — as Robert Hooke and
Steno in the seventeenth century, and Moro, Leibnitz,
Buffon, Whitehurst, Werner, Hutton. and others in the
eighteenth — had vaguely conceived the importance of
fossils as records of the earth's ancient history, but the
wisest of them no more suspected the full import of the
story written in the rocks than the average stroller in a
modern museum suspects the meaning of the hieroglyphs
on the case of a mummy.
88
THE CENTURY'S PROGRESS IN PALEONTOLOGY
It was not that the rudiments of this story are so very
hard to decipher — though in truth they are hard enough
—but rather that the men who made the attempt had all
along viewed the subject through an atmosphere of pre-
conception, which gave a distorted image. Before this
image could be corrected it was necessary that a man
should appear who could see without prejudice, and
apply sound common-sense to what he saw. And such
a man did appear towards the close of the century in the
person of William Smith, the English surveyor. He
was a self-taught man, and perhaps the more indepen-
dent for that, and he had the gift, besides his sharp eyes
and receptive mind, of a most tenacious memory. By
exercising these faculties, rare as they are homely, he
led the way to a science which was destined, in its
later developments, to shake the structure of established
thought to its foundations.
Little enough did William Smith suspect, however,
that any such dire consequences were to come of his act
when he first began noticing the fossil shells that here
and there are to be found in the stratified rocks and soils
of the regions over which his surveyor's duties led him.
Nor, indeed, was there anything of such apparent revo-
lutionary character in the facts which he unearthed ;
yet in their implications these facts were the most dis-
concerting of any that had been revealed since the day
of Copernicus and Galileo. In its bald essence Smith's
discovery was simply this: that the fossils in the rocks,
instead of being scattered haphazard, are arranged in
regular systems, so that any given stratum of rock is
labelled by its fossil population ; and that the order of
succession of such groups of fossils is always the same in
any vertical series of strata in which they occur. That
THE STORY OF NINETEENTH-CENTURY SCIENCE
is to say, if fossil A underlies fossil B in any given region,
it never overlies it in any other series; though a kind of
fossils found in one set of strata may be quite omitted
in another. Moreover, a fossil once having disappeared
never reappears in any later stratum.
From these novel facts Smith drew the common-sense
inference that the earth had had successive populations
of creatures, each of which in its turn had become extinct.
He partially verified this inference by comparing the
fossil shells with existing species of similar orders, and
found that such as occur in older strata of the rocks had
no counterparts among living species. But on the whole,
being eminently a practical man, Smith troubled himself
but little about the inferences that might be drawn from
his facts. He was chiefly concerned in using the key he
had discovered as an aid to the construction of the first
geological map of England ever attempted, and he left
to others the untangling of any snarls of thought that
might seem to arise from his discovery of the succession
of varying forms of life on the globe.
He disseminated his views far and wide, however, in
the course of his journeyings — quite disregarding the
fact that peripatetics went out of fashion when the
printing-press came in — and by the beginning of our
century he had begun to have a following among the
geologists of England. It must not for a moment be
supposed, however, that his contention regarding the
succession of strata met with immediate or general ac-
ceptance. On the contrary, it was most bitterly an-
tagonized. For a long generation after the discovery
was made, the generality of men, prone as always to
strain at gnats and swallow camels, preferred to believe
that the fossils, instead of being deposited in successive
90
THE CENTURY'S PROGRESS IN PALEONTOLOGY
ages, had been swept all at once into their present posi-
tions by the current of a mighty flood — and that flood,
needless to say, the Noachian deluge. Just how the
numberless successive strata could have been laid down
in orderly sequence to the depth of several miles in one
such fell cataclysm was indeed puzzling, especially after
it came to be admitted that the heaviest fossils were not
found always at the bottom ; but to doubt that this had
been done in some way was rank heresy in the early
days of our century.
ii
But once discovered, William Smith's unique facts as
to the succession of forms in the rocks would not down.
There was one most vital point, however, regarding
which the inferences that seem to follow from these
facts needed verification — the question, namely, whether
the disappearance of a fauna from the register in the
rocks really implies the extinction of that fauna. Every-
thing really depended upon the answer to that question,
and none but an accomplished naturalist could answer it
with authority. Fortunately the most authoritative nat-
uralist of the time, Georges Cuvier, took the question in
hand — not, indeed, with the idea of verifying any sug-
gestion of Smith's, but in the course of his own original
studies — at the very beginning of the century, when
Smith's views were attracting general attention.
Cuvier and Smith were exact contemporaries, both
men having been born in 1769, that "fertile year"
which gave the world also Chateaubriand, Yon Hum-
boldt, Wellington, and Napoleon. But the French nat-
uralist was of very different antecedents from the Eng-
91
THE STORY OF NINETEENTH-CENTURY SCIENCE
GEORGES CUVIEB
lish surveyor. He was brilliantly educated, had early
gained recognition as a scientist, and while yet a young
man had come to be known as the foremost comparative
anatomist of his time. It was the anatomical studies
that led him into the realm of fossils. Some bones dug
out of the rocks by workmen in a quarry were brought
to his notice, and at once his trained eye told him that
they were different from anything he had seen before.
92
THE CENTURY'S PROGRESS IN PALEONTOLOGY
Hitherto such bones, when not entirely ignored, had
been for the most part ascribed to giants of former days,
or even to fallen angels. Cuvier soon showed that
neither giants nor angels were in question, but ele-
phants of an unrecognized species. Continuing his
studies, particularly with material gathered from g}rp-
sum beds near Paris, he had accumulated, by the begin-
ning of our century, bones of about twenty-five species
of anima-ls that he believed to be different from any now
living on the globe.
The fame of these studies went abroad, and presently
fossil bones poured in from all sides, and Cuvier's con-
victions that extinct forms of animals are represented
among the fossils was sustained by the evidence of many
strange and anomalous forms, some of them of gigantic
size. In 1816 the famous Ossemenls Fossiles, describing
these novel objects, was published, and vertebrate paleon-
tology became a science. Among other things of great
popular interest the book contained the first authorita-
tive description of the hairy elephant, named by Cuvier
the mammoth, the remains of which had been found
embedded in a mass of ice in Siberia in 1802, so wonder-
fully preserved that the dogs of the Tungusian fisher-
men actually ate its flesh. Bones of the same species
had been found in Siberia several years before by the
naturalist Pallas, who had also found the carcass of a
rhinoceros there, frozen in a mud bank ; but no one then
suspected that these were members of an extinct popula-
tion—they were supposed to be merely transported relics
of the flood.
Cuvier, on the other hand, asserted that these and the
other creatures he described had lived and died in the
region where their remains were found, and that most
93
THE STORY OF NINETEENTH-CENTURY SCIENCE
of them have no living representatives upon the globe.
This, to be sure, was nothing more than William Smith
had tried all along to establish regarding lower forms of
life ; but great monsters appeal to the imagination in a
THE WAKUEN MASTODON, FOUND NEAU NEWBUUO,
ON THE HUDSON
way quite beyond the power of mere shells ; so the an-
nouncement of Cuvier's discoveries aroused the interest
of the entire world, and the Ossements Fossiles was
accorded a popular reception seldom given a work of
technical science — a reception in which the enthusiastic
approval of progressive geologists was mingled with the
bitter protests of the conservatives.
94
THE CENTURY'S PROGRESS IN PALEONTOLOGY
In England the interest thus aroused was sent to fever-
heat in 1821 by the discovery of abundant beds of fossil
bones in the stalagmite-covered floor of a cave at Kirk-
dale, Yorkshire, which went to show that England too
had once had her share of gigantic beasts. Dr. Buck-
land, the incumbent of the recently established chair of
geology at Oxford, and the most authoritative English
geologist of the day, took these finds in hand and showed
that the bones belonged to a number of species, including
such alien forms as elephants, rhinoceroses, hippopotami,
and hyenas. He maintained that all of these creatures
had actually lived in Britain, and that the caves in which
their bones were found had been the dens of hyenas.
The claim was hotly disputed as a matter of course.
As late as 1827 books were published denouncing Buck-
land, Doctor of Divinity though he was, as one who had
joined in an " unhallowed cause," and reiterating the old
cry that the fossils were only remains of tropical species
washed thither by the' deluge. That they were found
in solid rocks or in caves offered no difficulty, at least
not to the fertile imagination of Granville Penn, the
leader of the conservatives, who clung to the old idea
of Woodward and Cattcut that the deluged ha dissolved
the entire crust of the earth to a paste, into which the
relics now called fossils had settled. The caves, said
Mr. Penn, are merely the result of gases given off by
the carcasses during decomposition — great air-bubbles,
so to speak, in the pasty mass becoming caverns when
the waters receded and the paste hardened to rocky
consistency.
But these and such like fanciful views were doomed
even in the day of their utterance. Already in 1823 other
gigantic creatures, christened ichthyosaurus and plesio-
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THE STORY OF NINETEENTH-CENTURY SCIENCE
saurus by Conybeare, had been found in deeper strata of
British rocks; and these, as well as other monsters whose
remains were unearthed in various parts of the world,
bore such strange forms that even the most sceptical
could scarcely hope to find their counterparts among
living creatures. Cuvier's contention that all the larger
SKULL, LACKING JAW, OP EOBASILEUS COHNUTUS, COPE
vertebrates of the existing age are known to naturalists
was borne out by recent explorations, and there seemed
no refuge from the conclusion that the fossil records
tell of populations actually extinct. But if this were
'96
THE CENTURY'S PROGRESS IN PALEONTOLOGY
admitted, then Smith's view that there have been suc-
cessive rotations of population could no longer be denied.
Nor could it be in doubt that the successive faunas, whose
individual remains have been preserved in myriads, rep-
resentino- extinct species by thousands and tens of thou-
sands, must have required vast periods of time for the
production and growth of their countless generations.
As these facts came to be generally known, and as it
came to be understood in addition that the very matrix
of the rock in which fossils are embedded is in many
cases itself one gigantic fossil, composed of the remains
of microscopic forms of life, common-sense, which, after
all, is the final tribunal, came to the aid of belabored
science. It was conceded that the only tenable inter-
pretation of the record in the rocks is that numerous
populations of creatures, distinct from one another and
from present forms, have risen and passed away; and
that the geologic ages in which these creatures lived
were of inconceivable length. The rank and file came
thus, with the aid of fossil records, to realize the import
of an idea which James Hutton, and here and there
another thinker, had conceived with the swift intuition
of genius long before the science of paleontology came
into existence. The Huttonian proposition that time is
long had been abundantly established, and by about the
close of the first third of our century geologists had
begun to speak of "ages" and "untold »ons of time"
with a familiarity which their predecessors had reserved
for days and decades.
in
And now a new question pressed for solution. If the
earth has been inhabited by successive populations of
o 97
THE STORY OF NINETEENTH-CENTURY SCIENCE
beings now extinct, how have all these creatures been
destroyed ? That question, however, seemed to present
no difficulties. It was answered out of hand by the
application of an old idea. All down the centuries,
whatever their varying phases of cosmogonic thought,
there had been ever present the idea that past times
were not as recent times; that in remote epochs the
earth had been the scene of awful catastrophes that
have no parallel in "these degenerate days." Naturally
enough this thought, embalmed in every cosmogonic
speculation of whatever origin, was appealed to in
explanation of the destruction of these hitherto un im-
agined hosts, which now, thanks to science, rose from
their abysmal slumber as incontestable, but also as silent
and as thought -provocative as Sphinx or pyramid.
These ancient hosts, it was said, have been exterminated
at intervals of odd millions of years by the recurrence
of catastrophes of which the Mosaic deluge is the latest,
but perhaps not the last.
This explanation had fullest warrant of scientific au-
thority. Cuvier had prefaced his classical work with a
speculative disquisition whose very title (Discours sur les
devolutions du Globe) is ominous of catastrophism, and
whose text fully sustains the augury. And Buckland,
Cuvier's foremost follower across the Channel, had gone
even beyond the master, naming the work in which he
described the Kirkdale fossils, Reliquiae Diluviance, or
Proofs of a Universal Deluge.
Both these authorities supposed the creatures whose
remains they studied to have perished suddenly in the
mighty flood whose awful current, as they supposed,
gouged out the modern valleys, and hurled great blocks
of granite broadcast over the land. And they invoked
THE CENTURY'S PROGRESS IN PALEONTOLOGY
similar floods for the extermination of previous popula-
tions.
It is true these scientific citations had met with only
qualified approval at the time of their utterance, because
then the conservative majority of mankind did not con-
cede that there had been a plurality of populations or
revolutions; but now that the belief in past geologic
ages had ceased to be a heresy, the recurring catastro-
phes of the great paleontologists were accepted with
acclaim. For the moment science and tradition were at
one, and there was a truce to controversy, except indeed
in those outlying skirmish-lines of thought whither news
from headquarters does not permeate till it has become
ancient history at its source.
The truce, however, was not for long. Hardly had
contemporary thought begun to adjust itself to the
conception of past ages of incomprehensible extent,
each terminated by a catastrophe of the Noachian
type, when a man appeared who made the utterly be-
wildering assertion that the geological record, instead
of proving numerous catastrophic revolutions in the
earth's past history, gives no warrant to the preten-
sions of any universal catastrophe whatever, near or
remote.
This iconoclast was Charles Lyell, the Scotchman, who
was soon to be famous as the greatest geologist of his
time. As a voiing man he had become imbued with the
•-
force of the Huttonian proposition, that present causes
are one with those that produced the past changes of
the globe, and he carried that idea to what he conceived
to be its logical conclusion. To his mind this excluded
O
the thought of catastrophic changes in either inorganic
or organic worlds.
99
THE STORY OF NINETEENTH-CENTURY SCIENCE
But to deny catastrophism was to suggest a revolu-
tion in current thought. Needless to say such revolu-
tion could not be effected without a long contest. For
a score of years the matter was argued pro and con,
often with most unscientific ardor. A mere outline of
the controversy would fill a volume ; yet the essential
facts with which Lyell at last established his proposi-
tion, in its bearings on the organic world, may be epito-
mized in few words. The evidence which seems to tell
of past revolutions is the apparently sudden change of
fossils from one stratum to another of the rocks. But
Lyell showed that this change is not always com-
plete. Some species live on from one alleged epoch
into the next. By no means all the contemporaries
of the mammoth are extinct, and numerous marine
forms vastly more ancient still have living represent-
atives.
Moreover, the blanks between strata in any particular
vertical series are amply filled in with records in the
form of thick strata in some geographically distant
series. For example, in some regions Silurian rocks are
directly overlaid by the coal measures ; but elsewhere
this sudden break is tilled in with the Devonian rocks
that tell of a great " age of fishes." So commonly are
breaks in the strata in one region filled up in another,
that we are forced to conclude that the record shown
by any single vertical series is of but local significance —
telling, perhaps, of a time when that particular sea-bed
oscillated above the water-line, and so ceased to receive
sediment until some future age when it had oscillated
back again. But if this be the real significance of the
seemingly sudden change from stratum to stratum, then
the whole case for catastrophism is hopelessly lost ; for
100
THE CENTURY'S PROGRESS IN PALEONTOLOGY
such breaks in the strata furnish the only suggestion
•/ oo
geology can offer of sudden and catastrophic changes of
wide extent.
When evidence from widely separated regions is
gathered, said Lyell, it becomes clear that the number-
less species that have been exterminated in the past
METAMYNODON, OR SWIMMING RHINOCEROS, FROM SOUTH DAKOTA
have died out one by one, just as individuals of a species
die, not in vast shoals ; if whole populations have passed
away, it has been not by instantaneous extermination,
but by the elimination of a species now here, now there,
much as one generation succeeds another in the life his-
tory of any single species. The causes which have
brought about such gradual exterminations, and in the
long lapse of ages have resulted in rotations of popula-
tion, are the same natural causes that are still in opera-
tion. Species have died out in the past as they are
dying out in the present, under influence of changed
101
THE STORY OF NINETEENTH-CENTURY SCIENCE
surroundings, such as altered climate, or the migration
into their territory of more masterful species. Past and
present causes are one — natural law is changeless and
eternal.
Such was the essence of the Huttonian doctrine, which
Lyell adopted and extended, and with which his name
will always be associated. Largely through his efforts,
.though of course not without the aid of many other
workers after a time, this idea — the doctrine of uniform-
itarianism, it came to be called — became the accepted
dogma of the geologic world not long after the middle
of our century. The catastrophists, after clinging madly
to their phantom for a generation, at last capitulated
without terms: the old heresy became the new ortho-
doxy, and the way was paved for a fresh controversy.
IV
The fresh controversy followed quite as a matter of
course. For the idea of catastrophism had not con-
cerned the destruction of species merely, "but their intro-
duction as well. If whole faunas had been extirpated
suddenly, new faunas had presumably been introduced
with equal suddenness by special creation ; but if species
die out gradually, the introduction of new species may
be presumed to be correspondingly gradual. Then may
not the new species of a later geological epoch be the
modified lineal descendants of the extinct population of
an earlier epoch ?.
The idea that such might be the case was not new.
It had been suggested when fossils first began to attract
conspicuous attention; and such sagacious thinkers as
Buffon and Kant and Goethe and Erasmus Darwin had
103
THE CENTURY'S PROGRESS IN PALEONTOLOGY
been disposed to accept it in the closing days of the
eighteenth century. Then, in 1809, it had been con-
tended for by one of the early workers in systematic
paleontology, Jean Baptiste Lamarck, who had studied
the fossil shells about Paris while Cuvier studied the
vertebrates, and who had been led by these studies to
conclude that there had been not merely a rotation but
a progression of life on the globe. He found the fossil
shells — the fossils of invertebrates, as he himself had
christened them — in deeper strata than Cuvier's verte-
brates; and he believed that there had been long ages
HYRACHYUS, OR RUNNING RHINOCEROS, PROM SOUTHERN WYOMING
when no higher forms than these were in existence, and
that in successive ages fishes, and then reptiles, had been
the highest of animate creatures, before mammals, in-
cluding man, appeared. Looking beyond the pale of his
bare facts, as genius sometimes will, he had insisted that
these progressive populations had developed one from
103
THE STORY OF NINETEENTH-CENTURY SCIENCE
another, under influence of changed surroundings, in
unbroken series.
Of course such a thought as this was hopelessly mis-
placed in a generation that doubted the existence of ex-
tinct species, and hardly less so in the generation that
accepted catastrophism ; but it had been kept alive by
here and there an advocate like Geoffrey St.-Hilaire,
and now the banishment of catastrophism opened the
way for its more respectful consideration. Respectful
consideration was given it by Lyell in each recurring
edition of his Principles, but such consideration led to
its unqualified rejection. In its place Lyell put forward
a modified hypothesis of special creation. He assumed
that from time to time, as the extirpation of a species
had left room, so to speak, for a new species, such new
species had been created de novo ; and he supposed that
such intermittent, spasmodic impulses of creation mani-
fest themselves nowadays quite as frequently as at any
time in the past. He did not say in so many words
that no one need be surprised to-day were he to see a
new species of deer, for example, come up out of the
ground before him, "pawing to get free," like Milton's
lion, but his theory implied as much. And that theory,
let it be noted, was not the theory of Lyell alone, but
of nearly all his associates in the geologic world. There
is perhaps no other fact that will bring home to one so
vividly the advance in thought of our own generation
as the recollection that so crude, so almost unthinkable a
conception could have been the current doctrine of sci-
ence less than half a century ago.
This theory of special creation, moreover, excluded
the current doctrine of uniformitarianism as night ex-
cludes day, though most thinkers of the time did not
104
THE CENTURY'S PROGRESS IN PALEONTOLOGY
seem to be aware of the incompatibility of the two
ideas. It may be doubted whether even Lyell himself
fully realized it. If he did, he saw no escape from the
dilemma, for it seemed to him that the record in the
rocks clearly disproved the alternative Lamarckian hy-
pothesis. And almost with one accord the paleontolo-
gists of the time sustained the verdict. Owen, Agassiz,
Falconer, Barrande, Pictet, Forbes, repudiated the idea
as unqualifiedly as their great predecessor Cuvier had
done in the earlier generation. Some of them did, in-
deed, come to believe that there is evidence of a pro-
gressive development of life in the successive ages, but
no such graded series of fossils had been discovered as
would give countenance to the idea that one species had
ever been transformed into another. And to nearly
every one this objection seemed insuperable.
But now in 1859 appeared a book which, though not
dealing primarily with paleontology, yet contained a
chapter that revealed the geological record in an alto-
gether new light. The book was Charles Darwin's Ori-
gin of Species, the chapter that wonderful citation of
the " Imperfections of the Geological Kecord." In this
epoch-making chapter Darwin shows what conditions
must prevail in any given place in order that fossils
shall be formed, how unusual such conditions are, and
how probable it is that fossils once embedded in sedi-
ment of a sea-bed will be destroyed by metamorphosis
of the rocks, or by denudation when the strata are
raised above the water-level. Add to this the fact that
only small territories of the earth have been explored
geologically, he says, and it becomes clear that the
paleontological record as we now possess it shows but a
mere fragment of the past history of organisms on the
105
THE STORY OF NINETEENTH-CENTURY SCIENCE
earth. It is a history " imperfectly kept and written in
a changing dialect. Of this history we possess the last
volume alone, relating only to two or three countries.
Of this volume only here and there a short chapter has
PROFESSOR E. D. COPE
been preserved, and of each page only here and there a
few lines." For a paleontologist to dogmatize from
such a record would be as rash, he thinks, as " for a nat-
uralist to land for five minutes on a barren point of
106
THE CENTURY'S PROGRESS IN PALEONTOLOGY
Australia and then discuss the number and range of its
productions."
This citation of observations, which when once point-
ed out seemed almost self-evident, came as a revelation
to the geological world. In the clarified view now pos-
sible old facts took on a new meaning. It was recalled
that Cuvier had been obliged to establish a new order
for some of the first fossil creatures he examined, and
that Buckland had noted that the nondescript forms were
intermediate in structure between allied existing orders.
More recently such intermediate forms had been discov-
ered over and over; so that, to name but one example,
Owen had been able, with the aid of extinct species^to
"dissolve by gradations the apparently wide interval
between the pig and the camel." Owen, moreover, had
been led to speak repeatedly of the " generalized forms ''
of extinct animals, and Agassiz had called them " syn-
thetic or prophetic types," these terms clearly implying
"that such forms are in fact intermediate or connecting
links." Darwin himself had shown some years before
that the fossil animals of any continent are closely re-
lated to the existing animals of that continent — eden-
tates predominating, for example, in South America,
and marsupials in Australia. Many observers had noted
that recent strata everywhere show a fossil fauna more
nearly like the existing one than do more ancient strata;
and that fossils from any two consecutive strata are far
more closely related to each other than are the fossils
of two remote formations, the fauna of each geological
formation being, indeed, in a wide view, intermediate
between preceding and succeeding faunas.
So suggestive were all these observations that Lyell,
the admitted leader of the geological world, after read-
107
THE STORY OF NINETEENTH-CENTURY SCIENCE
ing Darwin's citations, felt able to drop his own crass
explanation of the introduction of species, and adopt
the transmutation hypothesis, thus rounding out the
doctrine of uniformitarianism to the full proportions in
which Lamarck had conceived it half a century before.
Not all paleontologists could follow him at once, of
course ; the proof was not yet sufficiently demonstative
for that ; but all were shaken in the seeming security
of their former position, which is always a necessary
stage in the progress of thought. And popular inter-
est in the matter was raised to white heat in a twin-
kling.
So, for the third time in this first century of its ex-
istence, paleontology was called upon to play a leading
role in a controversy whose interest extended far be-
yond the bounds of staid truth-seeking science. And
the controversy waged over the age of the earth had
not been more bitter, that over catastrophism not more
acrimonious, than that which now raged over the ques-
tion of the transmutation of species. The question had
implications far beyond the bounds of paleontology, of
course. The main evidence yet presented had been
drawn from quite other fields, but by common consent
the record in the rocks might furnish a crucial test of
the truth or falsity of the hypothesis. " He who rejects
this view of the imperfections of the geological rec-
ord," said Darwin, " will rightly reject the whole
theory."
With something more than mere scientific zeal, there-
fore, paleontologists turned anew to the records in the
rocks, to inquire what evidence in proof or refutation
might be found in unread pages of the " great stone
book." And as might have been expected, many minds
JOS
THE CENTURY'S PROGRESS IN PALEONTOLOGY
being thus prepared to receive new evidence, such evi-
dence was not long withheld.
Indeed, at the moment of Darwin's writing a new
and very instructive chapter of the geologic record was
being presented to the public — a chapter which for the
first time brought man into the story. In 1859 Dr.
Falconer, the distinguished British paleontologist, made
a visit to Abbeville, in the valley of the Somme, incited
by reports that for a decade before had been sent out
from there by M. Boucher des Perthes. These reports
had to do with the alleged finding of flint implements,
clearly the work of man, in undisturbed gravel beds, in
the midst of fossil remains of the mammoth and other
extinct animals. Dr. Falconer was so much impressed
with what he saw that he urged his countrymen Pro-
fessor Prestwich to go to Abbeville and thoroughly in-
vestigate the subject. Professor Prestwich complied,
with the collaboration of Mr. John Evans, and the re-
port which these paleontologists made of their investi-
gation brought the subject of the very significant human
fossils at Abbeville prominently before the public;
whereas the publications of the original discoverer,
Boucher des Perthes, bearing date of 1847, had been al-
together ignored. A new aspect was thus given to the
current controversy.
As Dr. Falconer remarked, geology was now passing
through the same ordeal that astronomy passed in the
age of Galileo. But the times were changed since the
day when the author of the Dialogues was humbled be-
fore the Congregation of the Index, and now no Index
109
THE STORY OF NINETEENTH-CENTURY SCIENCE
Prohibitorum could avail to hide from eager human
eyes such pages of the geologic story as Nature herself
had spared. Eager searchers were turning the leaves
with renewed zeal everywhere, and with no small meas-
ure of success. In particular, interest attached just at
this time to a human skull which Dr. Fuhlrott had dis-
PROTOROHTPPUS, THE ANCESTRAL FOUR-TOED HORSE
Height at shoulder, 16 inches. From the Big Horn Mountains
covered in a cave at Neanderthal two or three years be-
fore— a cranium which has ever since been famous as
the Neanderthal skull, the type specimen of what mod-
ern zoologists are disposed to regard as a distinct spe-
cies of man, Homo neanderthalensis. Like others of the
same type since discovered at Spy, it is singularly Simian
in character — low-arched, with receding forehead and
enormous protuberant eyebrows. When it was first ex-
hibited to the scientists at Berlin by Dr. Fuhlrott, in
1857, its human character was doubted by some of the
witnesses \ of that, however, there is no present question.
110
THE CENTURY'S PROGRESS IN PALEONTOLOGY
This interesting find served to recall with fresh sio-nifi-
O O
cance some observations that had been made in France
and Belgium a long generation earlier, but whose bear-
ings had hitherto been ignored. In 1826 MM. Tournal
and Christol had made independent discoveries of what
they believed to be human fossils in the caves of the
south of France ; and in 1827 Dr. Schmerling had
found in the cave of Engis,' in Westphalia, fossil bones
',of even greater significance. Schmerling's explorations
had been made with the utmost care anil patience. At
Engis he had found human bones, including skulls, in-
termingled with those of extinct mammals of the mam-
moth period in a way that left no doubt in his mind
that all dated from the same geological epoch. He had
published a full account of his discoveries in an elaborate
monograph issued in 1833.
But at that time, as it chanced, human fossils were un-
der a ban as effectual as any ever pronounced by canonical
index, though of far different origin. The oracular voice
of Cuvier had declared against the authenticity of all hu-
man fossils. Some of the bones brought him for exam-
ination the great anatomist had pettishly pitched out of
the window, declaring them fit only for a cemetery, and
that had settled the matter for a generation : the evi-
dence gathered by lesser workers could avail nothing
against the decision rendered at the Delphi of Science.
But no ban, scientific or canonical, can long resist the
germinative power of a fact, and so now, after three
decades of suppression, the truth which Cuvier had
buried beneath the weight of his ridicule burst its
bonds, and fossil man stood revealed, if not as a flesh
and blood, at least as a skeletal entity.
The reception now accorded our prehistoric ancestor
ill
THE STORY OF NINETEENTH-CENTURY SCIENCE
by the progressive portion of the scientific world amount-
ed to an ovation ; but the unscientific masses, on the other
hand, notwithstanding their usual fondness for tracing
remote genealogies, still gave the men of Engis and
PROFESSOR O. C. MARSH
Neanderthal the cold shoulder. Nor were all of the geol-
ogists quite agreed that the contemporaneity of these hu-
man fossils with the animals whose remains had been
mingled with them had been fully established. The
bare possibility that the bones of man and of animals
112
THE CENTURY'S PROGRESS IN PALEONTOLOGY
that long preceded him had been swept together into
the caves in successive ages, and in some mysterious
way intermingled there, was clung to by the conserva-
tives as a last refuge. But even this small measure of
security was soon to be denied them, for in 1865 two as-
sociated workers, M. Edouarcl Lartet and Mr. Henry
Christy, in exploring the caves of Dordogne, unearthed
a bit of evidence against which no such objection could
be urged. This momentous exhibit was a bit of ivory,
a fragment of the tusk of a mammoth, on which was
scratched a rude but unmistakable outline portrait of
the mammoth itself. If all the evidence as to man's
antiquity before presented was suggestive merely, here
at last was demonstration ; for the cave-dwelling man
could not well have drawn the picture of the mammoth
unless he had seen that animal, and to admit that man
and the mammoth had been contemporaries was to con-
cede the entire case. So soon, therefore, as the full im-
port of this most instructive work of art came to be
realized, scepticism as to man's antiquity was silenced
for all time to come.
In the generation that has elapsed since the first draw-
ing of the cave-dweller artist was discovered, evidences
of the wide-spread existence of man in an early epoch
have multiplied indefinitely, and to-day the paleontolo-
gist traces the history of our race back beyond the iron
and bronze ages, through a neolithic or polished-stone
age, to a paleolithic or rough-stone age, with confidence
born of unequivocal knowledge. And he looks confi-
dently to the future explorer of the earth's fossil records
to extend the history back into vastly more remote
epochs, for it is little doubted that paleolithic man, the
most ancient of our recognized progenitors, is a modern
H 113
THE STORY OF NINETEENTH-CENTURY SCIENCE
compared to those generations that represented the real
childhood of our race.
VI
Coincidently with the discovery of these highly sug-
gestive pages of the geologic story, other still more in-
structive chapters were being brought to light in Amer-
ica. It was found that in the Rocky Mountain region,
in strata found in ancient lake beds, records of the
tertiary period, or age of mammals, had been made and
preserved with fulness not approached in any other
region hitherto geologically explored. These records
were made known mainly by Professors Joseph Leidy,
O. C. Marsh, and E. D. Cope, working independently,
and more recently by numerous younger paleontolo-
gists.
The profusion of vertebrate remains thus brought to
light quite beggars all previous exhibits in point of mere
numbers. Professor Marsh, for example, who was first
in the field, found 300 new tertiary species between the
y ears 1870 and 1876. Meanwhile, in cretaceous strata,
he unearthed remains of about 200 birds with teeth, 600
pterodactyls, or flying dragons, some with a spread of
wings of twenty-five feet, and 1500 mosasaurs of the
sea-serpent type, some of them sixty feet or more in
length. In a single bed of Jurassic rock, not larger
than a good-sized lecture-room, he found the remains
of 160 individuals of mammals, representing twenty
species and nine genera ; while beds of the same age
have yielded 300 reptiles, varying from the size of a
rabbit to sixty or eighty feet in length.
But the chief interest of these fossils from the West is
114
§2
ll
35"
THE CENTURY'S PROGRESS IN PALEONTOLOGY
not their number but their nature ; for among them are
numerous illustrations of just such intermediate types of
organisms as must have existed in the past if the suc-
cession of life on the globe has been an unbroken lineal
succession. Here are reptiles with bat-like wings, and
others with bird-like pelves and legs adapted for bipedal
locomotion. Here are birds with teeth and other rep-
tilian characters. In short, what with reptilian birds
and bird-like reptiles, the gap between modern reptiles
and birds is quite bridged over. In a similar way, vari-
ous diverse mammalian forms, as the tapir, the rhinoc-
eros, and the horse, are linked together by fossil pro-
genitors. And most important of all, Professor Marsh
has discovered a series of mammalian remains, occurring
in successive geological epochs, which are held to repre-
sent beyond cavil the actual line of descent of the modern
horse; tracing the lineage of our one-toed species back
through two and three toed forms, to an ancestor in the
eocene or early tertiary that had four functional toes
and the rudiment of a fifth.
These and such like revelations have come to light in
our own time; are, indeed, still being disclosed. Need-
less to say, no Index of any sort now attempts to con-
ceal them; yet something has been accomplished towards
the same end by the publication of the discoveries in
Smithsonian bulletins, and in technical memoirs of
government surveys. Fortunately, however, the results
have been rescued from that partial oblivion by such
interpreters as Professors Huxley and Cope, so the un-
scientific public has been allowed to gain at least an
inkling of the wonderful progress of paleontology in our
generation.
The writings of Huxley in particular epitomize the
117
THE STORY OF NINETEENTH-CENTURY SCIENCE
record. In 1862 he admitted candidly that the paleon-
tological record as then known, so far as it bears on the
doctrine of progressive development, negatives that doc-
trine. In 1870 he was able to " soften somewhat the
Brutus-like severity" of his former verdict, and to assert
that the results of recent researches seem "to leave a
clear balance in favor of the doctrine of the evolution of
living forms one from another." Six years later, when
reviewing the work of Marsh in America and of Gaudry
in Pikermi, he declared that, " on the evidence of paleon-
tology, the evolution of many existing forms of animal
life from their predecessors is no longer an hypothesis,
FOOTPRINTS OF REPTILES FOUND IN CONNECTICUT SANDSTONE
In the American Museum of Natural History
but an historical fact." In 1881 he asserted that the
evidence gathered in the previous decade had been so
unequivocal that, had the transmutation hypothesis not
existed, "the paleontologist would have had to invent it."
Since then the delvers after fossils have piled proof
on proof in bewildering profusion. The fossil beds in
J18
THE CENTURY'S PROGRESS IN PALEONTOLOGY
the "bad lands" of western America seem inexhaustible.
And in the Connecticut River Valley near relatives of
the great reptiles which Professor Marsh and others
have found in such profusion in the West left their
tracks on the mud flats — since turned to sandstone; and
a few skeletons also have been found. The bodies of a
race of great reptiles that were the lords of creation of
their day have been dissipated to their elements, while
the chance indentations of their feet as they raced along
the shores, mere footprints on the sands, have been pre-
served among the most imperishable of the memory-
tablets of the world.
Of the other vertebrate fossils that have been found
in the eastern portions of America, among 'the most
abundant and interesting are the skeletons of masto-
dons. Of these one of the largest and most complete is
that which was unearthed in the bed of a drained lake
near Newburg, New York, in 1845. This specimen was
larger than the existing elephants, and had tusks eleven
feet in length. It was mounted and described by Dr.
John C. Warren, of Boston, and has been famous for
half a century as the " Warren mastodon."
But to the student of racial development as recorded
by the fossils, all these sporadic finds have but incidental
interest as compared with the rich Western fossil beds
to which we have already referred. From records here
unearthed the racial evolution of many mammals has in
the past few years been made out in greater or less
detail. Professor Cope has traced the ancestry of the
camels (which, like the rhinoceroses, hippopotami, and
sundry other forms now spoken of as " Old World,"
seem to have had their origin here) with much com-
pleteness.
119
THE STORY OF NINETEENTH-CENTURY SCIENCE
A lemuroid form of mammal, believed to be of the
type from which man has descended, has also been found
in these beds. It is thought that the descendants of this
creature, and of the other "Old -World" forms above
referred to, found their way to Asia, probably, as sug-
TITANOTHERE FROM SOUTH DAKOTA
In the American Museum of Natural History
gested by Professor Marsh, across a bridge at Bering
Strait, to continue their evolution on the other hemi-
sphere, becoming extinct in the land of their nativity.
The ape-man fossil found in the tertiary strata of the
island of Java two years ago by the Dutch surgeon Dr.
Eugene Dubois, and named Pithecanthropus erectus, may
have been a direct descendant of the American tribe of
primitive lemurs, though this is only a conjecture.
120
THE CENTURY'S PROGRESS IX PALEONTOLOGY
Not all the strange beasts which have left their re-
mains in our " bad lands " are represented by living de-
scendants. The titanotheres, or brontotheridae, for ex-
ample, a gigantic tribe, off shoots of the same stock
which produced the horse and rhinoceros, represented
the culmination of a line of descent. They developed
rapidly in a geological sense, and flourished about the
middle of the tertiary period ; then, to use Agassiz's
phrase, " time fought against them." The story of their
evolution has been worked out by Professors Leidy,
Marsh, Cope, and H. F. Osborne.
The very latest bit of paleontological evidence bear-
ing on the question of the introduction of species is that
presented by Dr. J. L. Wortman in connection with the
fossil lineage of the edentates. It was suggested by
Marsh, in 1877, that these creatures, whose modern rep-
resentatives are all South American, originated in North.
America long before the two continents had any land
connection. The stages of degeneration by which these
animals gradually lost the enamel from their teeth, com-
ing finally to the unique condition of their modern de-
scendants of the sloth tribe, are illustrated by strikingly
graded specimens now preserved in the American Mu-
seum of Natural History, as shown by Dr. Wortman.
All these and a multitude of other recent observations
that cannot be even outlined here tell the same story
With one accord paleontologists of our time regard the
question of the introduction of new species as solved.
As Professor Marsh has said, " to doubt evolution to-
day is to doubt science ; and science is only another
name for truth."
Thus the third great battle over the meaning of the
fossil records has come to a conclusion. Again there
121
THE STORY OF NINETEENTH-CENTURY SCIENCE
is a truce to controversy, and it may seem to the casual
observer that the present stand of the science of fossils
is final and impregnable. But does this really mean
that a full synopsis of the story of paleontology has
been told? Or do we only await the coming of the
twentieth-century Lamarck or Darwin, who shall attack
the fortified knowledge of to-day with the batteries of
a new generalization \
CHAPTER IV
THE CENTURY'S PROGRESS IN GEOLOGY
JAMES HUTTON'S theory that continents wear away
and are replaced by volcanic upheaval had gained com-
paratively few adherents at the beginning of our cen-
tury. Even the lucid Illustrations of the Huttonian
Theory, which Play fair, the pupil and friend of the
great Scotchman, published in 1802, did not at once
prove convincing. The world had become enamoured
of the rival theory of Hutton's famous contemporary,
Werner of Saxony — the theory which taught that "in
the beginning" all the solids of the earth's present
jrust were dissolved in the heated waters of a universal
sea. Werner affirmed that all rocks, of whatever char-
icter, had been formed by precipitation from this sea,
the waters cooled ; that even veins have originated
in this way ; and that mountains are gigantic crystals,
not upheaved masses. In a word, he practically ignored
volcanic action, and denied in toto the theory of meta-
morphosis of rocks through the agency of heat.
The followers of Werner came to be known as Nep-
tunists; the Huttonians as Plutonists. The history of
geology during our first quarter-century is mainly a re-
cital of the intemperate controversy between these op-
123
THE STORY OF NINETEENTH-CENTURY SCIENCE
posing schools ; though it should not be forgotten that,
meantime, the members of the Geological Society of
London were making an effort to hunt for facts and
avoid compromising theories. Fact and theory, how-
ever, were too closely linked to be thus divorced.
The brunt of the controversy settled about the un-
stratified rocks — granites and their allies — which the
Plutonists claimed as of igneous origin. This contention
had the theoretical support of the nebular hypothesis,
then gaining ground, which supposed the earth to be a
cooling globe. The Plutonists laid great stress, too, on
the observed fact that the temperature of the earth in-
creases at a pretty constant ratio as descent towards its
centre is made in mines. But in particular they ap-
pealed to the phenomena of volcanoes.
The evidence from this source was gathered and
elaborated by Mr. G. Poulett Scrope, secretary of the
Geological Society of England, who, in 1823, published
a classical work on volcanoes, in which he claimed that
volcanic mountains, including some of the highest
known peaks, are merely accumulated masses of lava
belched forth from a crevice in the earth's crust. The
Neptunists stoutly contended for the aqueous origin of
volcanic as of other mountains.
But the facts were with Scrope, and as time went on it
came to be admitted that not merely volcanoes, but many
" trap " formations not taking the form of craters had
been made by the obtrusion of molten rock through fis-
sures in overlying strata. Such, for example, to cite
familiar illustrations, are Mount Holyoke, in Massachu-
setts, and the well-known formation of the Palisades
along the Hudson.
But to admit the "Plutonic" origin of such wide-
124
THE CENTURY'S PROGRESS IN GEOLOGY
spread formations was practically to abandon the Nep-
tunian hypothesis. So gradually the Huttonian expla-
nation of the origin of granites and other "igneous" rocks,
whether massed or in veins, came to be accepted. Most
geologists then came to think of the earth as a molten
mass, on which the crust rests as a mere film. Some,
indeed, with Lyell, preferred to believe that the molten
areas exist only as lakes in a solid crust, heated to
melting, perhaps, by electrical or chemical action, as
Davy suggested. More recently a popular theory at-
tempts to reconcile geological facts with the claim of the
physicists, that the earth's entire mass is at least as
rigid as steel, by supposing that a molten film rests be-
tween the observed solid crust and the alleged solid
nucleus. But be that as it may, the theory that subter-
ranean heat has been instrumental in determining the
condition of "primary" rocks, and in producing many
other phenomena of the earth's crust, has never been in
dispute since the long controversy between the Neptu-
nists and the Plutonists led to its establishment.
ii
If molten matter exists beneath the crust of the earth,
it must contract an cooling, and in so doing it must dis-
turb the level of the portion of the crust already solidi-
fied. So a plausible explanation of the upheaval of
continents and mountains was supplied by the Plutonian
theory, as Hutton had from the first alleged. But
now an important difference of opinion arose as to the
exact rationale of such upheavals. Hutton himself, and
practically every one else who accepted his theory, had
supposed that there are long periods of relative repose,
125
THE STORY OF NINETEENTH-CENTURY SCIENCE
during which the level of the crust is undisturbed, fol-
lowed by short periods of active stress, when continents
are thrown up with volcanic suddenness, as by the throes
of a gigantic earthquake. But now came Charles Lyell
with his famous extension of the " uniformitarian" doc-
trine, claiming that past changes of the earth's surface
have been like present changes in degree as well as in
kind. The making of continents and mountains, he said,
is going on as rapidly to-day as at any time in the past.
There have been no gigantic cataclysmic upheavals at any
time, but all changes in level of the strata as a whole have
been gradual, by slow oscillation, or at most by repeated
earthquake shocks such as are still often experienced.
In support of this very startling contention Lyell
gathered a mass of evidence of the recent changes in
level of continental areas. He corroborated by personal
inspection the claim which had been made by Play fair
in 1802, and by von Buch in 1807, that the coast-line of
Sweden is rising at the rate of from a few inches to sev-
eral feet in a century. He cited Darwin's observations
going to prove that Patagonia is similarly rising, and
Pingel's claim that Greenland is slowly sinking. Proof
as to sudden changes of level of several feet, over large
areas, due to earthquakes, was brought forward in
abundance. Cumulative evidence left it no longer open
to question that such oscillatory changes of level, either
upward or downward, are quite the rule, and it could
not be denied that these observed changes, if continued
long enough in one direction, would produce the highest
elevations. The possibility that the making of even the
highest ranges of mountains had been accomplished
without exaggerated catastrophic action came to be
freely admitted.
126
THE RESULTS OP EROSION BY RUNNING WATER
THE CENTURY'S PROGRESS IN GEOLOGY
It became clear that the supposedly stable land sur-
faces are in reality much more variable than the surface
of the " shifting sea" ; that continental masses, seeming-
ly so fixed, are really rising and falling in billows thou-
sands of feet in height, ages instead of moments being
consumed in the sweep between crest and hollow.
These slow oscillations of land surfaces being under-
stood, many geological enigmas were made clear — such
as the alternation of marine and fresh-water formations
in a vertical series, which Cuvier and Brongniart had
observed near Paris; or the sandwiching of layers of
coal, of subaerial formation, between layers of subaque-
ous clay or sandstone, which may be observed every-
where in the coal measures. In particular, the extreme
thickness of the sedimentary strata as a whole, many'
times exceeding the depth of the deepest known sea,
was for the first time explicable when it was under-
stood that such strata had formed in slowty sinking
ocean-beds.
AH doubt as to the mode of origin of stratified rocks
being thus removed, the way was opened for a more
favorable consideration of that other Huttonian doc-
trine of the extremely slow denudation of land surfaces.
The enormous amount of land erosion will be patent to
any one who uses his eyes intelligently in a mountain
district. It will be evident in any region where the
strata are tilted — as, for example, the Alleghanies —
that great folds of strata which must once have risen
miles in height have in many cases been worn entirely
away, so that now a valley marks the location of the
former eminence. Where the strata are level, as in the
case of the mountains of Sicily, the Scotch Highlands,
and the familiar Catskills, the evidence of denudation is,
i 129
THE STORY OF NINETEENTH-CENTURY SCIEN'CE
if possible, even more marked ; for here it is clear that
elevation and valley have been carved by the elements
out of land that rose from the sea as level plateaus.
But that this herculean labor of land-sculpturing could
have been accomplished by the slow action of wind and
frost and shower was an idea few men could grasp
within the first half-century after Hutton propounded
it; nor did it begin to gain general currency until
Ly ell's crusade against catastrophism, begun about 1830,
had for a quarter of a century accustomed geologists to
the thought of slow continuous changes producing final
results of colossal proportions. And even long after
that, it was combated by such men as Murchison, Di-
rector-General of the Geological Surve\7 of Great Brit-
ain, then accounted the foremost field-geologist of his
time, who continued to believe that the existing valleys
owe their main features to subterranean forces of up-
heaval. Even Murchison, however, made some recession
from the belief of the Continental authorities, £lie de
Beaumont and Leopold von Buch, who contended that
the mountains had sprung up like veritable jacks-in-the-
box. Yon Buch, whom his friend and fellow-pupil von
Humboldt considered the foremost geologist of the time,
died in 1853, still firm in his early faith that the erratic
bowlders found high on the Jura had been hurled there,
like cannon-balls, across the valley of Geneva by the
sudden upheaval of a neighboring mountain range.
in
The bowlders whose presence on the crags of the Jura
the old German accounted for in a manner so theatrical
had long been a source of contention among geologists.
130
THE CENTURY'S PROGRESS IN GEOLOGY
They are found not merely on the Jura, but on number-
less other mountains in all north temperate latitudes,
and often far out in the open country, as many a farmer
who has broken his plough against them might testify.
The early geologists accounted for them, as for nearly
everything else, with their supposititious Deluge. Brong-
THE RESULTS OF EROSION BY WIND
niart and Cuvier and Buckland and their contemporaries
appeared to have no difficulty in conceiving that masses
of granite weighing hundreds of tons had been swept
by this current scores or hundreds of miles from their
source. But of course the uniformitarian faith permit-
ted no such explanation, nor could it countenance the
projection idea; so Lyell was bound to find some other
means of transportation for the puzzling erratics.
The only available medium was ice, but fortunately
131
THE STORY OF NINETEENTH-CENTURY SCIENCE
this one seemed quite sufficient. Icebergs, said Lyell,
are observed to carry all manner of debris, and deposit
it in the sea-bottoms. Present land surfaces have often
been submerged beneath the sea. During the latest of
these submergences icebergs deposited the bowlders now
scattered here and there over the land. Nothing could
be simpler or more clearly uniformitarian. And even
the catastrophists, though they met L\Tell amicably on
almost no other theoretical ground, were inclined to ad-
mit the plausibility of his theory of erratics. Indeed, of
all Ly ell's non-conformist doctrines, this seemed the one
most likely to meet with general acceptance.
Yet, even as this iceberg theory loomed large and
larger before the geological world, observations were
making in a different field that were destined to show
its fallacy. As early as 1815 a sharp-eyed chamois-hunt-
er of the Alps, Perraudin by name, had noted the ex-
istence of the erratics, and, unlike most of his companion
hunters, had puzzled his head as to how the bowlders
got where he saw them. lie knew nothing of sub-
merged continents or of icebergs, still less of upheaving
mountains; and though he doubtless had heard of the
Flood, he had no experience of heavy rocks floating like
corks in water. Moreover, he had never observed stones
rolling up hill and perching themselves on mountain-
tops, and he was a good enough uniformitarian (though
he would have been puzzled indeed had any one told
him so) to disbelieve that stones in past times had dis-
ported themselves differently in this regard from stones
of the present. Yet there the stones are. How did they
get there?
The mountaineer thought that he could answer that
question. He saw about him those gigantic serpent-like
132
THE CENTURY'S PROGRESS IN GEOLOGY
streams of ice called glaciers, " from their far fountains
slow rolling on," carrying with them blocks of granite
and other debris to form moraine deposits. If these
glaciers had once been much more extensive than they
no\v are, they might have carried the bowlders and left
them where we find them. On the other hand, no other
natural agency within the sphere of the chamois-hunt-
A MOUNTAIN CAKVED FROM HORIZONTAL STRATA
er's knowledge could have accomplished this, ergo the
glaciers must once have been more extensive. Perraudin
would probably have said that common-sense drove him
to this conclusion ; but be that as it may, he had con-
ceived one of the few truly original and novel ideas of
which our century can boast.
133
TUB STORY OF NINETEENTH-CENTURY SCIENCE
Perraudin announced his idea to the greatest scientist
in his little world — Jean de Charpentier, director of the
mines at Bex, a skilled geologist who had been a fellow-
pupil of von Buch and von Humboldt under Werner at
the Freiberg School of Mines. Charpentier laughed at
the mountaineer's grotesque idea, and thought no more
about it. And ten years elapsed before Perraudin could
find any one who treated his notion with greater re-
spect. Then he found a listener in M. Venetz, a civil
engineer, who read a paper on the novel glacial theory
before a local society in 1823. This brought the matter
once more to the attention of de Charpentier, who now
felt that there might be something in it worth investi-
gation.
A survey of the field in the light of the new theory
soon convinced Charpentier that the chamois-hunter had
all along been right. He became an enthusiastic sup-
porter of the idea that the Alps had once been embed-
ded in a mass of ice, and in 1836 he brought the notion
to the attention of Louis Agassiz, who was spending the
summer in the Alps. Agassiz was sceptical at first, but
soon became a convert. Then he saw that the implica-
tions of the theory extended far beyond the Alps. If
the Alps had been covered with an ice sheet, so had
many other regions of the northern hemisphere. Cast-
ing abroad for evidences of glacial action, Agassiz found
them everywhere, in the form of transported erratics,
scratched and polished outcropping rocks, and moraine-
like deposits. Presently he became convinced that the
ice sheet which covered the Alps had spread over the
whole of the higher latitudes of the northern hemi-
sphere, forming an ice cap over the globe. Thus the
common -sense induction of the chamois -hunter blos-
134
THE CENTURY'S PROGRESS IN GEOLOGY
LOUIS JEAX RODOLPH AGASSIZ
somed in the mind of Ag-
assiz into the conception
of a universal Ice Age.
In 1857 Agassiz intro-
duced his theory to the
world, in a paper read
at Neuchatel, and three
years later he published
his famous Etudes sur les
Glaciers. Never did idea
make a more profound
disturbance in the scien-
tific world. Yon Buch
treated it with alternate
ridicule, contempt, and
rage; Murchison opposed it with customary vigor; even
Lyell, whose most remarkable mental endowment was
an unfailing receptiveness to new truths, could not at
once discard his ice-
berg theory in favor of
the new claimant. Dr.
Buckland, however, af-
ter Agassiz had shown
him evidence of for-
mer glacial action in
his own Scotland, be-
came a convert — the
more readily, perhaps,
as it seemed to him to
oppose the uniformita-
rian idea. Gradually
others fell in line, and
after the usual embit-
ADAM SEDGW1CK, P.R.S.
135
THE STORY OF NINETEENTH-CENTURY SCIENCE
tered controversy and the inevitable full generation of
probation, the idea of an Ice Age took its place among
the accepted tenets of geology. All manner of moot
points still demanded attention — the cause of the Ice
Age, the exact extent of the ice sheet, the precise
manner in which it produced its effects, and the exact
nature of these effects ; and not all of these have even
yet been determined. But, details aside, the Ice Age
now has full recognition from geologists as an historical
period. There may have been many Ice Ages, as Dr.
Croll contends; there was surely one; and the concep-
tion of such a period is one of the very few ideas of our
century that no previous century had even so much as
faintly adumbrated.
IV
But, for that matter, the entire subject of historical
geology is one that had but the barest beginning before
our century. Until the paleontologist found out the
key to the earth's chronology, no one — not even Button
— could have any definite idea as to the true story of the
earth's past. The only conspicuous attempt to classify
the strata was that made by Werner, who divided the
rocks into three systems, based on their supposed order
of deposition, and called primary, transition, and sec-
ondary.
Though Werner's observations were confined to the
small province of Saxony, he did not hesitate to affirm
that all over the world the succession of strata would be
found the same as there, the concentric laj'ers, accord-
ing to this conception, being arranged about the earth
with the regularity of layers on an onion. But in this
Werner was as mistaken as in his theoretical explana-
136
THE CENTURY'S PROGRESS IN GEOLOGY
JAMKS mVlGHT DAXA
tion of the origin of the
" primary " rocks. It re-
quired but little observa-
tion to show that the ex-
act succession of strata
is never precisely the
same in any widely sep-
arated regions. Never-
theless, there was a germ
of truth in Werner's sys-
tem. It contained the
idea, however faultily in-
terpreted, of a chronolog-
ical succession of strata ;
and it furnished a work-
ing outline for the observers who were to make out the
true story of geological development. But the correct
interpretation of the observed facts could only be made
after the Huttonian view
as to the origin of strata
had gained complete ac-
ceptance.
When William Smith,
having found the true key
to this story, attempted
to apply it, the territory
with which he had to
deal chanced to be one
where the surface rocks
are of that later series
which Werner termed sec-
ondary. He made numer-
rous subdivisions within
137
SIR KDUEKICK lilPEY MUKCIIISOX
THE STORY OF NINETEENTH-CENTURY SCIENCE
this system, based mainly on the fossils. Meantime it
was found that, judged by the fossils, the strata that
Brongniart and Cuvier studied near Paris were of a still
more recent period (presumed at first to be due to the
latest deluge), which came to be spoken of as tertiary.
It was in these beds, some of which seemed to have been
formed in fresh-water lakes, that many of the strange
mammals which Cuvier first described were found.
But the " transition " rocks, underlying the " second-
ary " system that Smith studied, were still practically
unexplored when, along in the thirties, they were taken
in hand by Roderick Impey Murchison, the reformed
fox-hunter and ex-captain who had turned geologist to
such notable advantage, and Adam Sedgwick, the brill-
iant Woodwardian professor at Cambridge.
Working together, these two friends classified the
transition rocks into chronological groups, since familiar
to every one in the larger outlines as the Silurian system
(age of invertebrates) and the Devonian system (age of
fishes) — names derived respectively from the country of
the ancient Silures, in Wales, and Devonshire, England.
It was subsequently discovered that these systems of
strata, which crop out from beneath newer rocks in re-
stricted areas in Britain, are spread out into broad un-
disturbed sheets over thousands of miles in continental
Europe and in America. Later on Murchison studied
them in Russia, and described them, conjointly with
Yerneuil and von Kerserling, in a ponderous and classi-
cal work. In America they were studied by Hall, New-
berry, Whitney, Dana, Whitfield, and other pioneer
geologists, who all but anticipated their English contem-
poraries.
The rocks that are of still older formation than those
138
THE CENTURY'S PROGRESS IN GEOLOGY
studied by Murchison and Sedgwick (corresponding in
location to the " primary " rocks of Werner's concep-
tion) are the surface feature of vast areas in Canada,
and were first prominently studied there by William I.
WILLIAM SMITH, LL.D.
Logan, of the Canadian Government Survey, as early as
1846, and later on by Sir William Dawson. These rocks
— comprising theLaurentian system — were formerly sup-
posed to represent parts of the original crust of the earth,
139
THE STORY OF NINETEENTH-CENTURY SCIENCE
formed on first cooling from a molten state ; but they
are now more generally regarded as once-stratified de-
posits metamorphosed by the action of heat.
Whether " primitive " or metamorphic, however, these
Canadian rocks, and analogous ones beneath the fossil-
iferous strata of other countries, are the oldest portions
of the earth's crust of which geology has any present
knowledge. Mountains of this formation, as the Adi-
rondacks, and the Storm King range overlooking the
Hudson near "West Point, are the patriarchs of their
kind, beside which Alleghanies and Sierra Nevadas are
recent upstarts, and Rockies, Alps, and Andes are mere
parvenus of yesterday.
The Laurentian rocks were at first spoken of as repre-
senting "Azoic" time; but in 1846 Dawson found a
formation deep in their midst which was believed to be
the fossil relic of a very low form of life, and after that
it became customary to speak of the system as " Eozoic."
Still more recently the title of Dawson's supposed fossil
to rank as such has been questioned, and Dana's sug-
gestion that the early rocks be termed merely Archaean
has met with general favor. Murchison and Sedgwick's
Silurian, Devonian, and Carboniferous groups (the ages
of invertebrates, of fishes, and of coal plants respective-
ly) are together spoken of as representing Paleozoic time.
William Smith's system of strata, next above these, once
called " secondary," represents Mesozoic time, or the age
of reptiles. Still higher, or more recent, are Cuvier
and Brongniart's Tertiary rocks, representing the age of
mammals. Lastly, the most recent formations, dating
back, however, to a period far enough from recent in
any but a geological sense, are classed as Quaternary,
representing the age of man.
140
THE CENTURY'S PROGRESS IN GEOLOGY
It must not be sup-
posed, however, that
the successive "ages"
of the geologist are
shut off from one an-
other in any such ar-
bitrary way as this ver-
bal classification might
seem to suggest. In
point of fact, these
"ages" have no better
warrant for existence
than have the "cen-
turies" and the "weeks"
of e Very-day COmptlta- GEORGE POULETTE SCROPE, F.R.a
tion. They are convenient, and they may even stand
for local divisions in the strata, but they are bounded by
no actual gaps in the sweep of terrestrial events.
Moreover, it must be
understood that the
"ages" of different
continents, though de-
scribed under the same
name, are not neces-
sarily of exact contem-
poraneit}7. There is no
sure test available by
which it could be
shown that the Devo-
nian age, for instance,
as outlined in the
strata of Europe, did
not begin millions of
SIR CHARLES LYELL, BART, F.R.S.
141
THE STORY OF NINETEENTH-CENTURY SCIENCE
years earlier or later than the period whose records are
said to represent the Devonian age in America. In at-
tempting to decide such details as this, mineralogical
data fail us utterly. Even in rocks of adjoining regions
identity of structure is no proof of contemporaneous
origin ; for the veritable substance of the rock of one
age is ground up to build the rocks of subsequent ages.
Furthermore, in seas where conditions change but little
the same form of rock may be made age after age. It
is believed that chalk beds still forming in some of our
present seas may form one continuous mass dating back
to earliest geologic ages. On the other hand, rocks dif-
ferent in character may be formed at the same time in
regions not far apart — say a sandstone along shore, a
coral limestone farther seaward, and a chalk bed be-
yond. This continuous stratum, broken in the process
of upheaval, might seem the record of three different
epochs.
Paleontology, of course, supplies far better chrono-
logical tests, but even these have their limitations.
There has been no time since rocks now in existence
were formed, if ever, when the earth had a uniform
climate and a single undiversified fauna over its entire
land surface, as the early paleontologists supposed.
Speaking broadly, the same general stages have attend-
ed the evolution of organic forms everywhere, but there
is nothing to show that equal periods of time witnessed
corresponding changes in diverse regions, but quite the
contrary. To cite but a single illustration, the marsupial
order, which is the dominant mammalian type of the
living fauna of Australia to-day, existed in Europe and
died out there in the Tertiary age. Hence a future
geologist might think the Australia of to-day contempo-
142
THE CENTURY'S PROGRESS IN GEOLOGY
raneous with a period in Europe which in reality ante-
dated it by perhaps millions of year
All these puzzling features unite to render the subject
of historical geology anything but the simple matter the
fathers of the science esteemed it. No one would now
attempt to trace the exact sequence of formation of all
the mountains of the globe, as filie de Beaumont did a
half-century ago. Even within the limits of a single
continent, the geologist must proceed with much caution
in attempting to chronicle the order in which its various
parts rose from the matrix of the sea. The key to this
story is found in the identification of the strata that are
the surface feature in each territory. If Devonian rocks
are at the surface in any given region, for example, it
would appear that this region became a land surface in
the Devonian age, or just afterwards. But a moment's
consideration shows that there is an element of uncer-
tainty about this, due to the steady denudation that all
land surfaces undergo. The Devonian rocks may lie at
the surface simply because the thousands of feet of car-
boniferous strata that once lay above them have been
worn away. All that the cautious geologist dare assert,
therefore, is that the region in question did not become
permanent land surface earlier than the Devonian age.
But to know even this is much — sufficient, indeed, to
establish the chronological order of elevation, if not its
exact period, for all parts of any continent that have
been geologically explored — understanding always that
there must be no scrupling about a latitude of a few mill-
ions or perhaps tens of millions of years here and there.
K 145
THE STORY OF NINETEENTH-CENTURY SCIENCE
Kegarding our own continent, for example, we learn
through the researches of a multitude of workers that
in the early day it was a mere archipelago. Its chief
island — the backbone of the future continent — was a
great Y-shaped area surrounding what is now Hudson
Bay, an area built up, perhaps, through denudation of a
yet more ancient polar continent, whose existence is only
conjectured. To the southeast an island that is now t-he
Adirondack Mountains, and another that is now the
Jersey Highlands, rose above the waste of waters ; and
far to the south stretched probably a line of islands now
represented by the Blue Eidge Mountains. Far off to
the westward another line of islands foreshadowed our
present Pacific border. A few minor islands in the in-
terior completed the archipelago.
From this bare, skeleton the continent grew, partly by
the deposit of sediment from the denudation of the orig-
inal islands (which once towered miles, perhaps, where
now they rise thousands of feet), but largely also by the
deposit of organic remains, especially in the interior sea,
which teemed with life. In the Silurian ages, inverte-
brates— brachiopods and crinoids,and cephalopods — were
the dominant types. But very early — no one knows just
when — there came fishes of many strange forms, some
of the early ones enclosed in turtlelike shells. Later
yet, large spaces within the interior sea having risen to
the surface, great marshes or forests of strange types of
vegetation grew and deposited their remains to form
coal beds. Many times over such forests were formed,
only to be destroyed by the oscillations of the land sur-
face. All told, the strata of this Paleozoic period aggre-
gate several miles in thickness, and the time consumed
in their formation stands to all later time up to the
146
TilE CENTURY'S PROGRESS IN GEOLOGY
present, according to Professor Dana's estimate, as three
to one.
Towards the close of this Paleozoic era the Appalachian
Mountains were slowly upheaved in great convoluted
folds, some of them probably reaching three or four
miles above the sea-level, though the tooth of time has
since gnawed them down to comparatively puny limits.
The continental areas thus enlarged were peopled dur-
ing the ensuing Mesozoic time with multitudes of
strange reptiles, many of them gigantic in size. The
waters, too, still teeming with invertebrates and fishes,
had their quota of reptilian monsters ; and in the air
were flying reptiles, some of which measured twenty-five
feet from tip to tip of their bat-like wings. During this
era the Sierra Nevada Mountains rose. Near the east-
ern border of the forming continent the strata were per-
haps now too thick and stiff to bend into mountain
folds, for they were rent into great fissures, letting out
floods of molten lava, remnants of which are still in evi-
dence after ages of denudation, as the Palisades along
the Hudson, and such elevations as Mount Holyoke in
western Massachusetts.
Still there remained a vast interior sea, which, later
on, in the Tertiary age, was to be divided by the slow
uprising of the land, which only yesterday — that is to
say, a million, or three or five or ten million years ago—
became the Rocky Mountains. High and erect these
young mountains stand to this day, their sharp angles
and rocky contours vouching for their youth, in strange
contrast with the shrunken forms of the old Adiron-
dacks, Green Mountains, and Appalachians, whose low-
ered heads and rounded shoulders attest the weight of
ages. In the vast lakes which still remained on either
140
THE STORY OF NINETEENTH-CENTURY SCIENCE
side of the Rocky range, Tertiary strata were slowly
formed to the ultimate depth of two or three miles, en-
closing here and there those vertebrate remains which
were to be exposed again to view by denudation when
the land rose still higher, and then, in our own time, to
tell so wonderful a story to the paleontologist.
Finally the interior seas were filled, and the shore
lines of the continent assumed nearly their present out-
line.
Then came the long winter of the glacial epoch — per-
haps of a succession of glacial epochs. The ice sheet
extended southward to about the fortieth parallel, driv-
ing some animals before it, and destroying those that
were unable to migrate. At its fulness, the great ice
mass lay almost a mile in depth over New England, as
attested by the scratched and polished rock surfaces and
deposited erratics in the White Mountains. Such a mass
presses down with a weight of about one hundred and
twenty-five tons to the square foot, according to Dr.
CroH's estimate. It crushed and ground everything be-
neath it more or less, and in some regions planed off
hilly surfaces into prairies. Creeping slowly forward, it
carried all manner of debris with it. When it melted
away its terminal moraine built up the nucleus of the
land masses now known as Long Island and Staten Isl-
and ; other of its deposits formed the " drumlins " about
Boston famous as Bunker and Breeds hills; and it left a
long irregular line of ridges of "till" or bowlder clay
and scattered erratics clear across the country at about
the latitude of New York City.
As the ice sheet slowly receded it left minor moraines
all along its course. Sometimes its deposits dammed up
river courses or inequalities in the surface, to form the
150
THE CENTURY'S PROGRESS IN GEOLOGY
lakes which everywhere abound over Northern territo-
ries. Some glacialists even hold the view first suggested
by Kamsey, of the British Geological Survey, that the
great glacial sheet scooped out the basins of many lakes,
including the system that feeds the Saint Lawrence. At
all events, it left traces of its presence all along the line
of its retreat, and its remnants exist to this day as
mountain glaciers and the polar ice cap. Indeed, we
live on the border of the last glacial epoch, for with the
closing of this period the long geologic past merges into
the present.
VI
And the present, no less than the past, is a time of
change. That is the thought which James Button con-
ceived more than a century ago, but which his contem-
poraries and successors were so very slow to appreciate.
Now, however, it has become axiomatic — one can hardly
realize that it was ever doubted. Every new scientific
truth, says Agassiz, must pass through three stages —
first, men say it is not true ; then they declare it hostile
to religion ; finally, they assert that every one has
known it always. Button's truth that natural law is
changeless and eternal has reached this final stage. No-
where now could you find a scientist who would dispute
the truth of that text which Lyell, quoting from Play-
fair's Illustrations of the Huttonian Theory, printed on
the tkle-page of his Principles: " Amid all the revolu-
tions of the globe the economy of Nature has been uni-
form, and her laws are the only things that have resisted
the general movement. The rivers and the rocks, the
seas and the continents, have been changed in all their
parts ; but the laws which direct those changes, and the
153
THE STORY OF NINETEENTH-CENTURY SCIENCE
rules to which they are subject, have remained invaria-
bly the same."
But, on the other hand, Hutton and Playfair, and in
particular Lyell, drew inferences from this principle
which the modern physicist can by no means admit.
To them it implied that the changes on the surface of
the earth have always been the same in degree as well
as in kind, and must so continue while present forces
hold their sway. In other words, they thought of the
world as a great perpetual-motion machine. But the
modern physicist, given truer mechanical insight by the
doctrines of the conservation and the dissipation of en-
ergy, will have none of that. Lord Kelvin, in particular,
has urged that in the periods of our earth's infancy and
adolescence its developmental changes must have been,
like those of any other infant organism, vastly more
rapid and pronounced than those of a later day ; and
to every clear thinker this truth also must now seem
axiomatic.
Whoever thinks of the earth as a cooling globe can
hardly doubt that its crust, when thinner, may have
heaved under strain of the moon's tidal pull — whether
or not that body was nearer — into great billows, dailv
rising and falling, like waves of the present seas vastly
magnified.
Under stress of that same lateral pressure from con-
traction which now produces the slow depression of the
Jersey coast, the slow rise of Sweden, the occasional
belching of an insignificant volcano, the jetting of a
geyser, or the trembling of an earthquake, once large
areas were rent in twain, and vast floods of lava flowed
over thousands of square miles of the earth's surface
perhaps at a single jet ; and, for aught we know to the
154
T11E CENTURY'S PROGRESS IN GEOLOGY
contrary, gigantic mountains may have heaped up their
contorted heads in cataclysms as spasmodic as even the
most ardent catastrophist of the elder day of geology
could have imagined.
The atmosphere of that early day, filled with vast
volumes of carbon, oxygen, and other chemicals that
have since been stored in beds of coal, limestone, and
SIR RICHARD OWEN
granites, may have worn down the rocks, on the one
hand, and built up organic forms on the other, with a
rapidity that would now seem hardly conceivable.
And yet wh,ile all these anomalous things went on,
155
THE STORY OF NINETEENTH-CENTURY SCIENCE
the same laws held that now are operative ; and a. true
doctrine of uniformitarianism would make no unwonted
concession in conceding them all — though most of the
embittered geological controversies of the middle of our
century were due to the failure of both parties to realize
that simple fact.
And as of the past and present, so of the future. The
same forces will continue to operate; and under oper-
ation of these unchanging forces each day will differ
from every one that has preceded it. If it be true, as
every physicist believes, that the earth is a cooling
globe, then, whatever its present stage of refrigeration,
the time must come when its surface contour will assume
a rigidity of level not yet attained. Then, just as sure-
ly, the slow action of the elements will continue to wear
away the land surfaces, particle b}r particle, and trans-
port them to the ocean, as it does to-day, until, compen-
sation no longer being afforded by the upheaval of the
continents, the last foot of dry land will sink for the
last time beneath the water, the last mountain -peak
melting away, and our globe, lapsing like any other
organism into its second childhood, will be on the sur-
O
face — as presumably it was before the first continent
rose — one vast " waste of waters." As puny man con-
ceives time and things, an awful cycle will have lapsed ;
in the sweep of the cosmic life, a pulse-beat will have
throbbed.
CHAPTER V
THE CENTURY'S PROGRESS IN METEOROLOGY
" AN astonishing miracle has just occurred in our dis-
trict," wrote M. Marais, a worthy if undistinguished
citizen of France, from his home at L'Aigle, under date
of " the 13th Floreal, year 11 " — a date which outside
of France would be interpreted as meaning May 3,
1803. This "miracle" was the appearance of a "fire-
ball " in broad daylight — " perhaps it was wildfire,"
says the naive chronicle — which " hung over the
meadow," being seen by many people, and then ex-
ploded with a loud sound, scattering thousands of
stony fragments over the surface of a territory some
miles in extent.
Such a "miracle" could not have been announced at
a more opportune time. For some years the scientific
world had been agog over the question whether such a
form of lightning as that reported — appearing in a clear
sky, and hurling literal thunder-bolts — had real existence.
Such cases had been reported often enough, it is true.
The "thunder-bolts" themselves were exhibited as sa-
cred relics before many an altar, and those who doubted
their authenticity had been chided as having "an evil
heart of unbelief." But scientific scepticism had ques-
157
THE STORY OF NINETEENTH-CENTURY SCIENCE
tioned the evidence, and late in the eighteenth century
a consensus of opinion in the French Academy had de-
clined to admit that such stones had been " conveyed to
the earth by lightning," let alone any more miraculous
agency.
In 1802, however, Edward Howard had read a paper
before the Royal Society in which, after reviewing the
evidence recently put forward, he had reached the con-
clusion that the fall of stones from the sky, sometimes
or always accompanied by lightning, must be admitted
as an actual phenomenon, however inexplicable. So
now, when the great stone-fall at L'Aigle was an-
nounced, the French Academy made haste to send the
brilliant young physicist Jean Baptiste Biot to investi-
gate it, that the matter might, if possible, be set finally
at rest. The investigation was in all respects successful,
and Blot's report transferred the stony or metallic light-
ning-bolt— the aerolite or meteorite — from the realm of
tradition and conjecture to that of accepted science.
But how explain this strange phenomenon ? At once
speculation was rife. One theory contended that the
stony masses had not actually fallen, but had been
formed from the earth by the action of the lightning ;
but this contention was early abandoned. The chemists
were disposed to believe that the aerolites had been
formed by the combination of elements floating in the
upper atmosphere. Geologists, on the other hand,
thought them of terrestrial origin, urging that they
might have been thrown up by volcanoes. The astron-
omers, as represented by Olbers and Laplace, modified
this theory by suggesting that the stones might, indeed,
have been cast out by volcanoes, but by volcanoes sit-
uated not on the earth, but on the moon.
158
THE CENTURY'S PROGRESS IN METEOROLOGY
And one speculator of the time took a step even more
daring, urging that the aerolites were neither of telluric
norselenic origin, nor yet children of the sun, as the old
A METEOUIC STONE
Greeks had, many of them, contended, but that they
are visitants from the depths of cosmic space. This
bold speculator was the distinguished German pl^sicist
Ernst F. F. Chladni, a man of no small repute in his
day. As early as 1794 he urged his cosmical theory
of meteorites, when the very existence of meteorites
was denied by most scientists. And he did more : he
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THE STORY OF NINETEENTH-CENTURY SCIENCE
declared his belief that these falling stones were really
one in origin and kind with those flashing meteors of
the upper atmosphere which are familiar everywhere as
" shooting-stars."
Each of these coruscating meteors, he affirmed, must
tell of the ignition of a bit of cosmic matter entering
the earth's atmosphere. Such wandering bits of mat-
ter might be the fragments of shattered worlds, or, as
Chladni thought more probable, merely aggregations
of "world stuff" never hitherto connected with any
large planetary mass.
Naturally enough, so unique a view met with very
scant favor. Astronomers at that time saw little to jus-
tify it; and the non-scientific world rejected it with
fervor as being " atheistic and heretical," because its
acceptance would seem to impl}7 that the universe is not
a perfect mechanism.
Some light was thrown on the moot point presently
by the observations of Brandes and Benzenberg, which
tended to show that falling-stars travel at an actual
speed of from fifteen to ninety miles a second. This
observation tended to discredit the selenic theory, since
an object, in order to acquire such speed in falling mere-
ly from the moon, must have been projected with an in-
itial velocity not conceivably to be given by any lunar
volcanic impulse. Moreover, there was a growing con-
viction that there are no active volcanoes on the moon,
and other considerations of the same tenor led to the
complete abandonment of the selenic theory.
But the theory of telluric origin of aerolites was by
no means so easily disposed of. This was an epoch
when electrical phenomena were exciting unbounded
and universal interest, and there was a not unnatural
160
THE CENTURY'S PROGRESS IN METEOROLOGY
tendency to appeal to electricity in explanation of every
obscure phenomenon ; and in this case the seeming sim-
ilarity between a lightning-flash and the flash of an
aerolite lent color to the explanation. So we find
Thomas Forster, a meteorologist of repute, still adher-
ing to the atmospheric theory of formation of aerolites
in his book published in 1823 ; and, indeed, the prevail-
ing opinion of the time seemed divided between various
telluric theories, to the neglect of any cosmical theory
whatever.
But in 1833 occurred a phenomenon which set the
matter finally at rest. A great meteoric shower oc-
curred in November of that }Tear, and in observing it
Professor Denison Olmsted, of Yale, noted that all the
stars of the shower appeared to come from a single
centre or vanishing-point in the heavens, and that
this centre shifted its position with the stars, and hence
was not telluric. The full significance of this obser-
vation was at once recognized by astronomers ; it de-
monstrated beyond all cavil the cosmical origin of the
shooting-stars. Some conservative meteorologists kept
up the argument for the telluric origin for some decades
to come as a matter of course — such a band trails always
in the rear of progress. But even these doubters were
silenced when the great shower of shooting-stars ap-
peared again in 1866, as predicted by Olbers and New-
ton, radiating from the same point of the heavens as
before.
Since then the spectroscope has added its confirmatory
evidence as to the identity of meteorite and shooting-
star, and, moreover, has linked these atmospheric meteors
with such distant cosmic residents as comets and nebula?.
Thus it appears thatChladni's daring hypothesis of 1794
L 161
THE STORY OF NINETEENTH-CENTURY SCIENCE
has been more than verified, and that the fragments of
matter dissociated from planetary connection — which he
postulated and was declared atheistic for postulating —
have been shown to be billions of times more numerous
than any larger cosmic bodies of which we have cog-
nizance—so widely does the existing universe differ from
man's preconceived notions as to what it should be.
Thus also the " miracle " of the falling stone, against
which the scientific scepticism of yesterday presented
" an evil heart of unbelief," turns out to be the most
natural of phenomena, inasmuch as it is repeated in our
atmosphere some millions of times each day.
ii
If fire-balls were thought miraculous and portentous
in days of yore, what interpretation must needs have
been put upon that vastly more picturesque phenom-
enon, the aurora? "Through all the city," says the
Book of Maccabees, " for the space of almost forty days,
there were seen horsemen running in the air, in cloth
of gold, armed with lances, like a band of soldiers : and
troops of horsemen in array encountering and running
one against another, with shaking of shields and multi-
tude of pikes, and drawing of swords, and casting of
darts, and glittering of golden ornaments and harness."
Dire omens these; and hardly less ominous the aurora
seemed to all succeeding generations that observed it
down till well into the eighteenth century — as witness
the popular excitement in England in 1710 over the
brilliant aurora of that year, which became famous
through Halley's description.
But after 1752, when Franklin dethroned the light-
162
THE CENTURY'S PROGRESS IN METEOROLOGY
ning, all spectacular meteors came to be regarded as
natural phenomena, the aurora among the rest. Frank-
lin explained the aurora — which was seen commonly
enough in the eighteenth centuiy, though only recorded
CIRRUS CLOUDS
once in the seventeenth — as due to the accumulation of
electricity on the surface of polar snows, and its dis-
charge to the equator through the upper atmosphere.
Erasmus Darwin suggested that the luminosity might be
due to the ignition of hydrogen, which was supposed by
many philosophers to form the upper atmosphere. Dai-
ton, who first measured the height of the aurora, esti-
mating it at about one hundred miles, thought the phe-
nomenon due to magnetism acting on ferruginous
particles in the air, and his explanation was perhaps
the most popular one at the beginning of the century.
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THE STORY OF NINETEENTH-CENTURY SCIENX'E
Since then a multitude of observers have studied the
aurora, but the scientific grasp has found it as elusive in
fact as it seems to casual observation, and its exact nat-
ure is as undetermined to-day as it was a hundred years
ago. There has been no dearth of theories concerning
it, however. Biot, who studied it in the Shetland Isl-
ands in 1817, thought it due to electrified ferruginous
dust, the origin of which he ascribed to Icelandic vol-
canoes. Much more recently the idea of ferruginous
particles has been revived, their presence being ascribed
not to volcanoes, but to the meteorites constantly being
dissipated in the upper atmosphere. Ferruginous dust,
presumably of such origin, has been found on the polar
snows, as well as on the snows of mountain-tops, but
whether it could produce the phenomena of auroras is
at least an open question.
Other theorists have explained the aurora as due to
the accumulation of electricity on clouds or on spicules
of ice in the upper air. Yet others think it due merely
to the passage of electricity through rarefied air itself.
Hum bold t considered the matter settled in yet another
way when Faraday showed, in 1831, that magnetism
may produce luminous effects. But perhaps the pre-
vailing theory of to-day assumes that the aurora is due
to a current of electricity generated at the equator, and
passing through upper regions of space, to enter the
earth at the magnetic poles — simply reversing the course
which Franklin assumed.
The similarity of the auroral light to that generated
in a vacuum bulb by the passage of electricity lends
support to the long-standing supposition that the aurora
is of electrical origin, but the subject still awaits com-
plete elucidation. For once even that mystery-solver
164
THE CENTURY'S PROGRESS IN METEOROLOGY
the spectroscope has been baffled, for the line it sifts
from the aurora is not matched by that of any recog-
nized substance. A like line is found in the zodiacal
light, it is true, but this is of little aid, for the zodiacal
light, though thought by some astronomers to be due to
meteor swarms about the sun, is held to be, on
whole, as mysterious as the aurora itself.
Whatever the exact nature of the aurora, it has long
been known to be intimately associated with the phe-
nomena of terrestrial magnetism. Whenever a brilliant
CUMULUS CLOUDS
aurora is visible, the world is sure to be visited with
what Ilumboldt called a magnetic storm — a "storm"
which manifests itself to human senses in no way what-
soever except by deflecting the magnetic needle and
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THE STORY OF NINETEENTH-CENTURY SCIENCE
conjuring with the electric wire. Such magnetic storms
are curiously associated also with spots on the sun — just
how no one has explained, though the fact itself is un-
questioned. Sun-spots, too, seem directly linked with
auroras, each of these phenomena passing through peri-
ods of greatest and least frequency in corresponding
cycles of about eleven years' duration.
It was suspected a full century ago by Herschel that
the variations in the number of sun spots had a direct
effect upon terrestrial weather, and he attempted to
demonstrate it by using the price of wheat as a criterion
of climatic conditions, meantime making careful observa-
tion of the sun-spots. Nothing very definite came of his
efforts in this direction, the subject being far too complex
to be determined without long periods of observation.
Latterly, however, meteorologists, particularly in the
tropics, are disposed to think they find evidence of some
such connection between sun-spots and the weather as
Herschel suspected. Indeed, Mr. Meld rum declares that
there is a positive coincidence between periods of numer-
ous sun-spots and seasons of excessive rain in India.
That some such connection does exist seems intrinsi-
cally probable. But the modern meteorologist, learning
wisdom of the past, is extremely cautious about ascribing
casual effects to astronomical phenomena. He finds it
hard to forget that until recently all manner of climatic
conditions were associated with phases of the moon ;
that not so very long ago showers of falling-stars were
considered ''prognostic" of certain kinds of weather;
and that the "equinoctial storm" had been accepted as
a verity by every one, until the unfeeling hand of statis-
tics banished it from the earth.
Yet, on the other hand, it is easily within the possi-
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THE CENTURY'S PROGRESS IN METEOROLOGY
bilities that the science of the future may reveal associa-
tions between the weather and sun-spots, auroras, and
terrestrial magnetism that as yet are hardly dreamed of.
Until such time, however, these phenomena must feel
themselves very grudgingly admitted to the inner circle
of meteorology. More and more this science concerns
itself, in our age of concentration and specialization,
with weather and climate. Its votaries no longer con-
cern themselves with stars or planets or comets or shoot-
ing-stars— once thought the very essence of guides to
weather wisdom ; and they are even looking askance at
the moon, and asking her to show cause why she also
should not be excluded from their domain. Equally
little do they care for the interior of the earth, since
they have learned that the central emanations of heat
which Mairan imagined as a main source of aerial
warmth can claim no such distinction. Even such prob-
lems as why the magnetic pole does not coincide with
the geographical, and why the force of terrestrial mag-
netism decreases from the magnetic poles to the mag-
netic equator, as Humboldt first discovered that it does,
excite them only to lukewarm interest; for magnetism,
they say, is not known to have any connection whatever
with climate or weather.
in
There is at least one form of meteor, however, of those
that interested our forebears, whose meteorological im-
portance they did not overestimate. This is the vapor
of water. How great was the interest in this familiar
meteor at the beginning of the century is attested by the
number of theories then extant regarding it; and these
conflicting theories bear witness also to the difficulty
167
THE STORY OF NINE1EENTH-CENTURY SCIENCE
with which the familiar phenomenon of the evaporation
of water was explained.
Franklin had suggested that air dissolves water much
as water dissolves salt, and this theory was still popular,
STRATUS CLOUDS
though Deluc had disproved it by showing that water
evaporates even more rapidly in a vacuum than in air.
Deluc's own theory, borrowed from earlier chemists,
was that evaporation is the chemical union of particles
of water with particles of the supposititious element heat.
Erasmus Darwin combined the two theories, suggesting
that the air might hold a variable quantity of vapor in
mere solution, and in addition a permanent moiety in
chemical combination with caloric.
Undisturbed by these conflicting views, that strangely
original genius, John Dalton, afterwards to be known as
168
THE CENTURY'S PROGRESS IN METEOROLOGY
perhaps the greatest of theoretical chemists, took the
question in hand, and solved it by showing that water
exists in the air as an utterly independent gas. He
reached a partial insight into the matter in 1793, when
his first volume of meteorological essays was published;
but the full elucidation of the problem came to him in
1801. The merit of his studies was at once recognized,
but the tenability of his hypothesis was long and ardently
disputed.
While the nature of evaporation was in dispute, as a
matter of course the question of precipitation must be
equally undetermined. The most famous theory of the
period was that formulated by Dr. Hutton in a paper
read before the Royal Society of Edinburgh, and pub-
lished in the volume of transactions which contained
also the same author's epoch-making paper on geology.
This "theory of rain" explained precipitation as due to
the cooling of a current of saturated air by contact with
a colder current, the assumption being that the surplus-
age of moisture was precipitated in a chemical sense,
just as the excess of salt dissolved in hot water is pre-
cipitated when the water cools. The idea that the cool-
ing of the saturated air causes the precipitation of its
moisture is the germ of truth that renders this paper of
Button's important. All correct later theories build on
this foundation.
The next ambitious attempt to explain the phenomena
of aqueous meteors was made by Luke Howard, in his
remarkable paper on clouds, published in the Philosoph-
ical Magazine in 1803 — the paper in which the names
cirrus, cumulus, stratus, etc., afterwards so universally
adopted, were first proposed. In this paper Howard
acknowledges his indebtedness to Dalton for the theory
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THE STORY OF NINETEENTH-CENTURY SCIENCE
of evaporation, yet he still clings to the idea that the
vapor, though independent of the air, is combined with
particles of caloric. He holds that clouds are composed
of vapor that has previously risen from the earth, com-
bating the opinions of those who believe that they are
formed by the union of hydrogen and oxygen existing
independently in the air; though he agrees with these
theorists that electricity has entered largely into the
modus opemndi of cloud formation. He opposes the
opinion of Deluc and de Saussure that clouds are com-
posed of particles of water in the form of hollow vesicles
(miniature balloons, in short, perhaps filled with hydro-
gen), which untenable opinion was a revival of the theory
as to the formation of all vapor which Dr. Halley had
advocated early in the eighteenth century.
Of particular interest are Howard's views as to the
formation of dew, which he explains as caused by the
particles of caloric forsaking the vapor to enter the cool
body, leaving the water on the surface. This comes as
near the truth perhaps as could be expected while the
old idea as to the materiality of heat held sway. How-
ard believed, however, that dew is usually formed in
the air at some height, and that it settles to the surface,
opposing the opinion, which had gained vogue in France
and in America (where Noah Webster prominently ad-
vocated it), that dew ascends from the earth.
The complete solution of the problem of dew forma-
tion— which really involved also the entire question of
precipitation of watery vapor in any form — was made
by Dr. C. W. Wells, a man of American birth, whose life,
however, after boyhood, was spent in Scotland (where
as a young man he enjoyed the friendship of David
Hume) and in London. Inspired no doubt by the re-
170
THE CENTURY'S PROGRESS IN METEOROLOGY
i
searches of Black, Hutton, and their confreres of that
Edinburgh school, Wells made observations on evapora-
tion and precipitation as early as 1784, but other things
claimed his attention ; and though he asserts that the
subject was often in his mind, he did not take it up
again in earnest until about 1812.
Meantime the observations on heat of Rumford and
Davy and Leslie had cleared the way for a proper in-
terpretation of the facts — about the facts themselves
there had long been practical unanimity of opinion. Dr.
Black, with his latent-heat observations, had really given
the clew to all subsequent discussions of the subject of
precipitation of vapor; and from his time on it had been
known that heat is taken up when water evaporates,
and given out again when it condenses. Dr. Darwin
had shown in 1788, in a paper before the Royal Society,
that air gives off heat on contracting, and takes it up on
expanding; and Dalton in his essay of 1793 had ex-
plained this phenomenon as due to the condensation and
vaporization of the water contained in the air.
But some curious and puzzling observations which
Professor Patrick "Wilson, Professor of Astronomy in
the University of Glasgow, had communicated to the
Royal Society of Edinburgh in 1784, and some similar
ones made by Mr. Six of Canterbury a few years later,
had remained unexplained. Both these gentlemen ob-
served that the air is cooler where dew is forming than
the air a few feet higher, and they inferred that the dew
in forming had taken up heat, in apparent violation of
established physical principles.
It remained for Wells, in his memorable paper of
1816, to show that these observers had simply gotten
the cart before the horse. He made it clear that the
171
THE STORY OF NINETEENTH-CENTURY SCIENCE
air is not cooler because the dew is formed, but that the
dew is formed because the air is cooler — having become
so through radiation of heat from the solids on which
the dew forms. The dew itself, in forming, gives out
its latent heat, and so tends to equalize the temperature.
This explanation made it plain why dew forms on a
clear night, when there are no clouds to reflect the radi-
ant heat. Combined with Dalton's theory that vapor
is an independent gas, limited in quantity in any given
space by the temperature of that space, it solved the
problem of the formation of clouds, rain, snow, and
hoar-frost. Thus this paper of Weils's closed the epoch
of speculation regarding this field of meteorology, as
Button's paper of 1784 had opened it. The fact that
the volume containing Hutton's paper contained also
his epoch-making paper on Geology, finds curiously a
duplication in the fact that Weils's volume contained
also his essay on Albinism, in which the doctrine of
natural selection was for the first time formulated, as
Charles Darwin freely admitted after his own efforts
had made the doctrine famous.
IV
The very next year after Dr. Weils's paper was pub-
lished, there appeared in France the third volume of the
Memoires de Physique et de C/iimie de la Soeiete d'Ar-
cueil, and a new epoch in meteorology was inaugurated.
The society in question was numerically an inconse-
quential band, listing only a dozen members. But every
name was a famous one : Arago, Berard, Berthollet,
Biot, Chaptal, de Candolle, Dulong, Gay-Lussac, llum-
boldt, Laplace, Poisson, and Thenard — rare spirits every
172
JEAN BAPTISTE BIOT
THE CENTURY'S PROGRESS IN METEOROLOGY
one. Little danger that the memoirs of such a band
would be relegated to the dusty shelves where most
proceedings of societies belong — no milk-for-babes fare
would be served to such a company.
The particular paper which here interests us closes
this third and last volume of memoirs. It is entitled Des
lignes isotlierines et de la distribution de la chaleur sur le
globe. The author is Alexander Humboldt. Needless
to say, the topic is handled in a masterly manner. The
distribution of heat on the surface of the globe, on the
mountain-sides, in the interior of the earth ; the causes
that regulate such distribution; the climatic results —
these are the topics discussed. But what gives epochal
character to the paper is the introduction of those iso-
thermal lines, circling the earth in irregular course, join-
ing together places having the same mean annual tem-
perature, and thus laying the foundation for a science of
comparative climatology.
It is true the attempt to study climates comparatively
was not new. Mai ran had attempted it in those papers
in which he developed his bizarre ideas as to central
emanations of heat. Euler had brought his profound
mathematical genius to bear on the topic, evolving the
" extraordinary conclusion that under the equator at
midnight the cold ought to be more rigorous than at
the poles in winter." And in particular Richard Kir-
wan, the English chemist, had combined the mathemat-
ical and the empirical methods, and calculated temper-
atures for all latitudes. But Humboldt differs from all
these predecessors in that he grasps the idea that the
basis of all such computations should be not theory, but
fact. He drew his isothermal lines not where some oc-
cult calculation would locate them on an ideal globe,
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THE STORY OF NINETEENTH-CENTURY SCIENCE
but where practical tests with the thermometer locate
them on our globe as it is. London, for example, lies in
the same latitude as the southern extremity of Hudson
Bay ; but the isotherm of London, as Humboldt outlines
it, passes through Cincinnati.
Of course such deviations of climatic conditions be-
tween places in the same latitude had long been known.
As Humboldt himself observes, the earliest settlers of
America were astonished to find themselves subjected
to rigors of climate for which their European experience
had not at all prepared them. Moreover, sagacious
travellers, in particular Cook's companion on his second
voyage, young George Forster, had noted as a general
principle that the western borders of continents in tem-
perate regions are always warmer than corresponding
latitudes of their eastern borders ; and of course the
general truth of temperatures being milder in the vicin-
ity of the sea than in the interior of continents had long
been familiar. But Humboldt's isothermal lines for the
first time gave tangibility to these ideas, and made prac-
ticable a truly scientific study of comparative climatol-
ogy-
In studying these lines, particularly as elaborated by
further observations, it became clear that the}' are by
no means haphazard in arrangement, but are dependent
upon geographical conditions which in most'cases are not
difficult to determine. Humboldt himself pointed out
very clearly the main causes that tend to produce de-
viations from the average — or, as Dove later on called
it. the normal — temperature of any given latitude. For
example, the mean annual temperature of a region (re-
ferring mainly to the northern hemisphere) is raised by
the proximity of a western coast ; by a divided config-
176
THE CENTURY'S PROGRESS IN METEOROLOGY
u ration of the continent into peninsulas ; by the existence
of open seas to the north or of radiating continental
surfaces to the south ; by mountain ranges to shield
from cold winds ; by the infrequency of swamps to be-
come congealed ; by the absence of woods in a dry,
sandy soil ; and by the serenity of sky in the summer
months, and the vicinity of an ocean current bringing
water which is of a higher temperature than that of the
surrounding sea.
Conditions opposite to these tend, of course, corre-
spondingly to lower the temperature. In a word, Hum-
boldt says the climatic distribution of heat depends on
the relative distribution of land and sea, and on the
" hypsometrical configuration of the continents"; and
he urges that " great meteorological phenomena cannot
be comprehended when considered independently of
geognostic relations " — a truth which, like most other
general principles, seems simple enough once it is
pointed out.
With that broad sweep of imagination which charac-
terized him, Humboldt speaks of the atmosphere as the
" aerial ocean, in the lower strata and on the shoals of
which we live," and he studies the atmospheric phe-
nomena always in relation to those of that other ocean
of water. In each of these oceans there are vast per-
manent currents, flowing always in determinate direc-
tions, which enormously modify the climatic conditions
of every zone. The ocean of air is a vast maelstrom,
boiling up always under the influence of the sun's heat
at the equator, and flowing as an upper current towards
either pole, while an under current from the poles, which
becomes the trade-winds, flows towards the equator to
supply its place.
M 177
THE STORY OF NINETEENTH-CENTURY SCIENCE
But the superheated equatorial air, becoming chilled,
descends to the surface in temperate latitudes, and con-
tinues its poleward journey as the anti-trade-winds.
The trade-winds are deflected towards the west, because
in approaching the equator they constantly pass over
surfaces of the earth having a greater and greater veloc-
ity of rotation, and so, as it were, tend to lag behind—
an explanation which Hadley pointed out in 1735, but
which was not accepted until Dalton independently
worked it out and promulgated it in 1793. For the
opposite reason, the anti-trades are deflected towards
the east ; hence it is that the western borders of con-
tinents in temperate zones are bathed in moist sea-
breezes, while their eastern borders lack this cold-dis-
pelling influence.
In the ocean of water the main currents run as more
sharply circumscribed streams — veritable rivers in the sea.
Of these the best known and most sharply circumscribed
is the familiar Gulf Stream, which has its Griffin in an
' O
equatorial current, impelled westward by trade-winds,
which is deflected northward in the main at Cape St.
Roque, entering the Caribbean Sea ancf Gulf of Mexico,
to emerge finally through the Strait of Florida, and
journey off across the Atlantic to warm the shores of
Europe.
Such, at least, is the Gulf Stream as Humboldt under-
stood it. Since his time, however, ocean currents in
general, and this one in particular, have been the subject
of no end of controversy, it being hotly disputed whether
either causes or effects of the Gulf Stream are just what
Humboldt, in common with others of his time, con-
ceived them to be. About the middle of the century,
Lieutenant M. F. Maury, the distinguished American
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THE CENTURY'S PROGRESS IN METEOROLOGY
hydrographer and meteorologist, advocated a theory of
gravitation as the chief cause of the currents, claiming
that difference in density, due to difference in temper-
ature and saltness, would sufficiently account for the
LIEUTENANT MATTHEW FONTAINK MAURY
oceanic circulation. This theory gained great popularity
through the wide circulation of Maury's Physical Geog-
raphy of the Sea, which is said to have passed through
more editions than any other scientific book of the
179
THE STORY OF NINETEENTH-CENTURY SCIENCE
period ; but it was ably and vigorously combated by Dr.
James Croll, the Scottish geologist, in his Climate and
Time, and latterty the old theory that ocean currents
are due to the trade-winds has again come into favor.
Indeed, very recently a model has been constructed, with
the aid of which it is said to have been demonstrated
that prevailing winds in the direction of the actual trade-
winds would produce such a current as the Gulf Stream.
Meantime, however, it is by no means sure that gravi-
tation does not enter into the case to the extent of pro-
ducing an insensible general oceanic circulation, inde-
pendent of the Gulf Stream and similar marked currents,
and similar in its larger outlines to the polar-equatorial
circulation of the air. The idea of such oceanic circula-
tion was first suggested in detail by Professor Lenz of
St. Petersburg, in 1845, but it was not generally recog-
nized until Dr. Carpenter independently hit upon the
idea more than twenty years later. The plausibility of
the conception is obvious ; yet the alleged fact of such
circulation has been hotly disputed, and the question is
still sub judice.
But whether or not such general circulation of ocean
water takes place, it is beyond dispute that the recog-
nized currents carry an enormous quantity of heat from
the tropics towards the poles. Dr. Croll, who has per-
haps given more attention to the physics of the subject
than almost any other person, computes that the Gulf
Stream conveys to the North Atlantic one-fourth as
much heat as that body receives directly from the sun,
and he argues that were it not for the transportation of
heat by this and similar Pacific currents, only a narrow
tropical region of the globe would be warm enough for
habitation by the existing faunas. Dr. Croll argues that
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THE CENTURY'S PROGRESS IN METEOROLOGY
a slight change in the relative values of northern and
southern trade-winds (such as he believes has taken
place at various periods in the past) would suffice to so
alter the equatorial current which now feeds the Gulf
Stream that its main bulk would be deflected southward
instead of northward, by the angle of Cape St. Koque.
Thus the Gulf Stream would be nipped in the bud, and,
according to Dr. Croll's estimates, the results would be
disastrous for the northern hemisphere. The anti-trades,
which now are warmed by the Gulf Stream, would then
blow as cold winds across the shores of western Europe,
and in all probability a glacial epoch would supervene
throughout the northern hemisphere.
The same consequences, so far as Europe is con-
cerned at least, would apparently ensue were the Isth-
mus of Panama to settle into the sea, allowing the Ca-
ribbean current to pass into the Pacific. But the geol-
ogist tells us that this isthmus rose at a comparatively
recent geological period, though it is hinted that there
had been some time previously a temporary land con-
nection between the two continents. Are we to infer,
then, that the two Americas in their unions and dis-
unions have juggled with the climate of the other hem-
isphere ? Apparently so, if the estimates made of the
influence of the Gulf Stream be tenable. It is a far cry
from Panama to Russia. Yet it seems within the possi-
bilities that the meteorologist may learn from the geolo-
gist of Central America something that will enable him
to explain to the paleontologist of Europe how it
chanced that at one time the mammoth and rhinoceros
roamed across northern Siberia, while at another time
the reindeer and musk-ox browsed along the shores of
the Mediterranean.
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THE STORY OF NINETEENTH-CENTURY SCIENCE
Possibilities, I said, not probabilities. Yet even the
faint glimmer of so alluring a possibility brings home to
one with vividness the truth of Ilumboldt's perspicuous
observation, that meteorology can. be properly compre-
hended only when studied in connection with the com-
panion sciences. There are no isolated phenomena in
nature.
Yet, after all, it is not to be denied that the chief
concern of the meteorologist must be with that other
medium, the " ocean of air, on the shoals of which we
live." For whatever may be accomplished by water
currents in the way of conveying heat, it is the wind
currents that effect the final distribution of that heat.
As Dr. Croll has urged, the waters of the Gulf Stream
do not warm the shores of Europe by direct contact,
but by warming the anti-trade-winds, which subsequent-
ly blow across the continent. And everywhere the
heat accumulated by water becomes effectual in modi-
fying climate, not so much by direct radiation as by dif-
fusion through the medium of the air.
This very obvious importance of aerial currents led
to their practical study long before meteorology had
any title to the rank of science, and Dalton's explana-
tion of the trade-winds had laid the foundation for a
science of wind dynamics before our century began.
But no substantial further advance in this direction was
effected until about 1827, when Heinrich "W. Dove, of
Konigsberg, afterwards to be known as perhaps the fore-
most meteorologist of his generation, included the winds
among the subjects of his elaborate statistical studies in
climatology.
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THE CENTURY'S PROGRESS IN METEOROLOGY
Dove classified the winds as permanent, periodical,
and variable. His great discovery was that all winds,
of whatever character, and not merely the permanent
winds, come under the influence of the earth's rotation
in such a way as to be deflected from their course, and
hence to take on a gyratory motion — that, in short, all
A. WHIRLWIND IN A DUSTY ROAD
local winds are minor eddies in the great polar-equatori-
al whirl, and tend to reproduce in miniature the char-
acter of that vast maelstrom. For the first time, then,
temporary or variable winds were seen to lie within the
province of law.
A generation later, Professor William Ferrel, the
183
THE STORY OF NINETEENTH-CENTURY SCIENCE
American meteorologist, who had been led to take up
the subject by a perusal of Maury's discourse on ocean
winds, formulated a general mathematical law, to the
effect that any body moving in a right line along the
surface of the earth in any direction tends to have its
course deflected, owing to the earth's rotation, to the
right hand in the northern and to the left hand in the
southern hemispheres. This law had indeed been stated
as early as 1835 by the French physicist Poisson, but no
one then thought of it as other than a mathematical
curiosity ; its true significance was only understood after
Professor Ferrel had independently rediscovered it (just as
Dalton rediscovered Hadley's forgotten law of the trade-
winds) and applied it to the motion of wind currents.
Then it became clear that here is a key to the phe-
nomena of atmospheric circulation, from the great polar-
equatorial maelstrom which manifests itself in the trade-
winds, to the most circumscribed riffle which is an-
nounced as a local storm. And the more the phenom-
ena were studied, the more striking seemed the parallel
between the greater maelstrom and these lesser eddies.
Just as the entire atmospheric mass of each hemisphere
is seen, when viewed as a whole, to be carried in a great
whirl about the pole of that hemisphere, so the local dis-
turbances within this great tide are found always to
take the form of whirls about a local storm-centre —
which storm-centre, meantime, is carried along in the
major current, as one often sees a little whirlpool in the
water swept along with the main current of the stream.
Sometimes, indeed, the local eddy, caught as it were in
an ancillary current of the great polar stream, is de-
flected from its normal course and may seem to travel
against the stream; but such deviations are departures
184
THE CENTURY'S PROGRESS IN METEOROLOGY
from the rule. In the great majority of cases, for ex-
ample, in the north-temperate zone, a storm-centre (with
1
WATERSPOUTS IN MID-ATLANTIC
its attendant local whirl) travels to the northeast, along
the main current of the anti-trade-wind, of which it is a
185
THE STORY OF NINETEENTH-CENTURY SCIENCE
part ; and though exceptionally its course may be to the
southeast instead, it almost never departs so widely
from the main channel as to progress to the westward.
Thus it is that storms sweeping over the United States
can be announced, as a rule, at the seaboard in advance
of their coming by telegraphic communication from the
interior, while similar storms come to Europe off the
ocean unannounced. Hence the more practical availa-
bility of the forecasts of weather bureaus in the former
country.
But these local whirls, it must be understood, are local
only in a very general sense of the word, inasmuch as a
single one may be more than a thousand miles in diam-
eter, and a small one is two or three hundred miles
across. But quite without regard to the size of the
whirl, the air composing it conducts itself always in one
of two ways. It never whirls in concentric circles ; it
always either rushes in towards the centre in a de-
scending spiral, in which case it is called a cyclone,
or it spreads out from the centre in a widening spiral,
in which case it is called an anti-cyclone. The word
cyclone is associated in popular phraseology with a
terrific storm, but it has no such restriction in techni-
cal usage. A gentle zephyr flowing towards a " storm-
centre " is just as much a cyclone to the meteorologist
as is the whirl constituting a West- Indian hurricane.
Indeed, it is not properly the wind itself that is called
the cyclone in either case, but the entire system of
whirls — including the storm-centre itself, where there
may be no wind at all.
What, then, is this storm-centre? Merely an area of
low barometric pressure— an area where the air has be-
come lighter than the air of surrounding regions. Under
186
THE CENTURY'S PROGRESS IN METEOROLOGY
influence of gravitation the air seeks its level just as
water does; so the heavy air comes flowing in from all
sides towards the low-pressure area, which thus becomes
a ''storm-centre." But the inrushing currents never
come straight to their mark. In accordance with Fer-
rers law, they are deflected to the right, and the result,
as will readily be seen, must be a vortex current", which
whirls always in one direction — namely, from left to
right, or in the direction opposite to that of the hands
of a watch held with its face upward. The velocity of
the cyclonic currents will depend largely upon the dif-
ference in barometric pressure between the storm-centre
and the confines of the cyclone system. And the veloc-
ity of the currents will determine to some extent the
degree of deflection, and hence the exact path of the
descending spiral in which the wind approaches the
centre. But in every case and in every part of the
cyclone system it is true, as Buys Ballot's famous rule
first pointed out, that a person standing with his back
to the wind has the storm-centre at his left.
The primary cause of the low barometric pressure
which marks the storm - centre and establishes the
cyclone is expansion of the air through excess of tem-
perature. The heated air, rising into cold upper regions,
has a portion of its vapor condensed into clouds, and
now a new dynamic factor is added, for each particle of
vapor, in condensing, gives up its modicum of latent
heat. Each pound of vapor thus liberates, according to
Professor Tyndall's estimate, enough heat to melt five
pounds of cast iron ; so the amount given out where
large masses of cloud are forming must enormously add
to the convection currents of the air, and hence to the
storm -developing power of the forming cyclone. In-
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THE STORY OF NINETEENTH -CENTURY SCIENCE
deed, one school of meteorologists, of whom Professor
Espy was the leader, has held that without such added
increment of energy constantly augmenting the dynamic
effects, no storm could long continue in violent action.
And it is doubted whether any storm could ever attain,
much less continue, the terrific force of that most dread-
ed of winds of temperate zones, the tornado — a storm
which obej's all the laws of cyclones, but dffers from
ordinary cyclones in having a vortex core only a few
feet or yards in diameter — without the aid of those
great masses of condensing vapor which always accom-
pany it in the form of storm-clouds.
The anti-cyclone simply reverses the conditions of the
cyclone. Its centre is an area of high pressure, and the
air rushes out from it in all directions towards surround-
ing regions of low pressure. As before, all parts of the
current will be deflected towards the right, and the re-
sult, clearly, is a whirl opposite in direction to that of
the cyclone. But here there is a tendency to dissipa-
tion rather than to concentration of energy, hence, con-
sidered as a storm-generator, the anti-cyclone is of rela-
tive insignificance.
In particular the professional meteorologist who con-
ducts a " weather bureau" — as, for example, Sergeant
Dunn, of the United States signal-service station in New
York — is so preoccupied with the observation of this
phenomenon that cyclone-hunting might be said to be
his chief pursuit. It is for this purpose, in the main,
that government weather bureaus or signal-service de-
partments have been established all over the world.
Their chief work is to follow up cyclones, with the aid
of telegraphic reports, mapping their course, and record-
ing the attendant meteorological conditions. Their so-
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THE CENTURY'S PROGRESS IN METEOROLOGY
called predictions or forecasts are essentially predica-
tions, gaining locally the effect of predictions because
the telegraph outstrips the wind.
At only one place on the globe has it been possible as
yet for the meteorologist to make long-time forecasts
meriting the title of predictions. This is in the middle
Ganges Valley of northern India. In this country the
climatic conditions are largely dependent upon the peri-
odical winds called monsoons, which blow steadily land-
ward from April to October, and seaward from October
to April. The summer monsoons bring the all-essential
rains ; if they are delayed or restricted in extent, there
will be drought and consequent famine. And such re-
striction of the monsoon is likely to result when there
has been an unusually deep or very late snowfall on the
Himalayas, because of the lowering of spring tempera-
ture by the melting snow. Thus here it is possible, by
observing the snowfall in the mountains, to predict with
some measure of success the average rainfall of the fol-
lowing summer. The drought of 1896, with the conse-
quent famine and plague that devastated India last win-
ter, was thus predicted some months in advance.
This is the greatest present triumph of practical me-
teorology. Nothing like it is yet possible anywhere in
temperate zones. But no one can say what may not be
possible in times to come, when the data now being
gathered all over the world shall at last be co-ordinated,
classified, and made the basis of broad inductions. Me-
teorology is pre-eminently a science of the future.
CHAPTER VI
THE CENTURY'S PROGRESS IN PHYSICS
THE "IMPONDERABLES"
THERE were giants abroad in the world of science in
the early days of our century. Herschel, Lagrange,
and Laplace; Cuvier, Brongniart, and Lamarck; Hum-
boldt, Goethe, Priestley — what need to extend the list ?
—the names crowd upon us. But among them all there
was no taller intellectual figure than that of a young
Quaker who came to settle in London and practise the
profession of medicine in the year 1801. The name of
this young aspirant to medical honors and emoluments
was Thomas Young. He came fresh from professional
studies at Edinburgh and on the Continent, and he had
the theory of medicine at his tongue's end; yet his
medical knowledge, compared with the mental treasures
of his capacious intellect as a whole, was but as a drop
of water in the ocean.
For it chanced that this young Quaker physician was
one of those prodigies who come but few times in a cen-
tury, and the full list of whom in the records of history
could be told on one's thumbs and fingers. His biogra-
phers tell us things about him that read like the most
patent fairy-tales. As a mere infant in arms he had
192
THE CENTURY'S PROGRESS IN PHYSICS
been able to read fluently. Before his fourth birthday
came he had read the Bible twice through, as well as
Watts's Ift/mns—poor child ! — and wrhen seven or eight
he had shown a propensity to absorb languages much
as other children absorb nursery tattle and Mother
Goose rhymes. When he was fourteen, a young lady
visiting the household of his tutor patronized the pretty
boy by asking to see a specimen of his penmanship.
The pretty boy complied readily enough, and mildly re-
buked his interrogator by rapidly writing some sen-
tences for her in fourteen languages, including such as
Arabian, Persian, and Ethiopic.
Meantime languages had been but an incident in the
education of the lad. He seems to have entered every
available field of thought — mathematics, physics, bot-
any, literature, music, painting, languages, philosophy,
archaeology, and so on to tiresome lengths — and once he
had entered any field he seldom turned aside until he
had reached the confines of the subject as then known,
and added something new from the recesses of his own
genius. He was as versatile as Priestley, as profound
as Newton himself. He had the range of a mere dilet-
tante, but even7 where the full grasp of the master. He
took early for his motto the saying that what one man
has done, another man may do. Granting that the
other man has the brain of a Thomas Young, it is a true
motto.
Such then was the young Quaker who came to London
to follow out the humdrum life of a practitioner of medi-
cine in the year 1801. But incidentally the young physi-
cian was prevailed upon to occupy the interims of early
practice by fulfilling the duties of the chair of Natural Phi-
losophy at the Royal Institution, which Count Rumford
N 193
THE STORY OF NINETEENTH-CENTURY SCIENCE
had founded, and of which Davy was then Professor of
Chemistry — the institution whose glories have been per-
petuated by such names as Faraday and Tyndall, and
which the Briton of to-day speaks of as the " Pantheon
of Science." Here it was that Thomas Young made
those studies which have insured him a niche in the
temple of fame not far removed from that of Isaac
Newton.
As early as 1793, when he was only twentj^, Young
had begun to communicate papers to the Royal Society
of London, which were adjudged worthy to be printed
in full in the Philosophical Transactions; so it is not
strange that he should have been asked to deliver the
Bakerian lecture before that learned body the very first
year after he came to London. The lecture was deliv-
ered November 12, 1801. Its subject was " The Theory
of Light and Colors," and its reading marks an epoch in
physical science ; for here was brought forward for the
first time convincing proof of that undulatory theory of
light with which every student of modern physics is fa-
miliar— the theory which holds that light is not a cor-
poreal entity, but a mere pulsation in the substance of
an all-pervading ether, just as sound is a pulsation in the
air, or in liquids or solids.
Young had, indeed, advocated this theory at an earli-
er date, but it was not until 1801 that he hit upon the
idea which enabled him to bring it to anything ap-
proaching a demonstration. It was while pondering
over the familiar but puzzling phenomena of colored
rings into which white light is broken when reflected
from thin films — Newton's rings, so called — that an ex-
planation occurred to him which at once put the entire
undulatory theory on a new footing. "With that sagac-
194
THOMAS YOUNG
From Peacock's Life of Young, by permission of John Murray, Publisher, London
THE CENTURY'S PROGRESS IN PHYSICS
ity of insight which we call genius, he saw of a sudden
that the phenomena could be explained by supposing
that when rays of light fall on a thin glass, part of the
rays being reflected from the upper surface, other rays,
reflected from the lower surface, might be so retarded
in their course through the glass that the two sets would
interfere with one another, the forward pulsation of one
ray corresponding to the backward pulsation of another,
thus quite neutralizing the effect. Some of the com-
ponent pulsations of the light being thus effaced by
mutual interference, the remaining rays would no longer
give the optical effect of white light; hence the puz-
zling colors.
By following up this clew with mathematical preci-
sion, measuring the exact thickness of the plate and the
space between the different rings of color, Young was
able to show mathematically what must be the length
of pulsation for each of the different colors of the spec-
trum. He estimated that the undulations of red light,
at the extreme lower end of the visible spectrum, must
number about 37,640 to the inch, and pass any given
spot at a rate of 463 millions of millions of undulations
in a second, while the extreme violet numbers 59,750
undulations to the inch, or 735 millions of millions to
the second.
Young similarly examined the colors that are pro-
duced by scratches on a smooth surface, in particular*
testing the light from "Mr. Coventry's exquisite mi-
crometers," which consist of lines scratched on glass at
measured intervals. These microscopic tests brought
the same results as the other experiments. The colors
were produced at certain definite and measurable angles,
and the theory of interference of undulations explained
197
THE STORY OF NINETEENTH-CENTURY SCIENCE
them perfectly, while, as Young affirmed with confi-
dence, no other theory hitherto advanced could explain
them at all. Taking all the evidence together, Young
declared that he considered the argument he had set
forth in favor of the undulatory theory of light to be
" sufficient and decisive."
This doctrine of interference of undulations was the
absolutely novel part of Young's theory. The all-
compassing genius of Kobert Hooke had, indeed, very
nearly apprehended it more than a century before, as
Young himself points out, but no one else had so much
as vaguely conceived it ; and even with the sagacious
Hooke it was only a happy guess, never distinctly out-
lined in his own mind, and utterly ignored by all others.
Young did not know of Hooke's guess until he himself
had fully formulated the theory, but he hastened then
to give his predecessor all the credit that could possibly
be adjudged his due by the most disinterested observer.
To Hooke's contemporary, Huyghens, who was the orig-
inator of the general doctrine of undulation as the ex-
planation of light, Young renders full justice also. For
himself he claims only the merit of having demonstrated
the theory which these and a few others of his prede-
cessors had advocated without full proof.
The following year Dr. Young detailed before the
Royal Society other experiments, which threw addi-
tional light on the doctrine of interference; and in 1803
he cited still others, which, he affirmed, brought the
doctrine to complete demonstration. In applying this
demonstration to the general theory of light, he made
the striking suggestion that " the luminiferous ether
pervades the substance of all material bodies with little
or no resistance, as freely, perhaps, as the wind passes
198
THE CENTURY'S PROGRESS IN PHYSICS
through a grove of trees." He asserted his belief also
that the chemical rays which Hitter had discovered
beyond the violet end of the visible spectrum are but
still more rapid undulations of the same character as
those which produce light. In his earlier lecture he
had affirmed a like affinity between the light rays and
the rays of radiant heat which Herschel detected below
the red end of the spectrum, suggesting that " light
differs from heat only in the frequency of its undu-
lations or vibrations — those undulations which are
within certain limits with respect to frequency affect-
ing the optic nerve and constituting light, and those
which are slower and probably stronger constituting
heat only." From the very outset he had recognized
the affinity between sound and light.; indeed, it had
been this affinity that led him on to an appreciation
of the undulatory theory of light.
But wrhile all these affinities seemed so clear to the
great co-ordinating brain of Young, they made no such
impression on the minds of his contemporaries. The
immateriality of light had been substantially demon-
strated, but practically no one save its author accepted
;the demonstration. Newton's doctrine of the emission
of corpuscles was too firmly rooted to be readily dis-
lodged, and Dr. Young had too many other interests to
continue the assault unceasingly. He occasionally wrote
something touching on his theory, mostly papers con-
tributed to the Quarterly Review and similar period-
icals, anonymously or under a pseudonym, for he had
conceived the notion that too great conspicuousness in
fields outside of medicine would injure his practice as a
physician. His views regarding light (including the
original papers from the Philosophical Transactions of
199
THE STORY OF NINETEENTH-CENTURY SCIENCE
the Royal Society] were again given publicity in full in
his celebrated volume on natural philosophy, consisting
in part of his lectures before the Royal Institution, pub-
lished in 1807; but even then they failed to bring con-
viction to the philosophic world. Indeed, they did not
even arouse a controversial spirit, as his first papers had
done.
So it chanced that when, in 1815, a young French
military engineer, named Augustin Jean Fresnel, re-
turning from the Napoleonic wars, became interested in
the phenomena of light, and made some experiments
concerning diffraction, which seemed to him to contro-
vert the accepted notions of the materiality of light, he
was quite unaware that his experiments had been an-
ticipated 03' a philosopher across the Channel. He
communicated his experiments and results to the French
Institute, supposing them to be absolutely novel. That
body referred them to a committee, of which, as good
fortune would have it, the dominating member was
Dominique Frangois Arago, a man as versatile as Young
himself, and hardly less profound, if perhaps not quite so
original. Arago at once recognized the merit of Fres-
nel's work, and soon became a convert to the theory.
He told Fresnel that Young had anticipated him as re-
gards the general theory, but that much remained to be
done, and he offered to associate himself with Fresnel
in prosecuting the investigation. Fresnel was not a
little dashed to learn that his original ideas had been
worked out by another while he was a lad, but he
bo\ved gracefully to the situation, and went ahead with
unabated zeal.
The championship of Arago insured the undulatory
theory a hearing before the French Institute, but by no
200
HANS CHRISTIAN OERSTED
DOMINIQUE FRANCOIS ARAGO
ACGCSTIN JEAN FRE9NEL
JAMES CLERK MAXWKW,
THE CENTURY'S PROGRESS IN PHYSICS
means sufficed to bring about its general acceptance. On
the contrary, a bitter feud ensued, in which Arago was
opposed by the "Jupiter Olympius of the Academy,"
Laplace, by the only less famous Poisson, and by the
younger but hardly less able Biot. So bitterly raged the
feud that a life-long friendship between Arago and Biot
was ruptured forever. The opposition managed to delay
the publication of Fresnel's papers, but Arago continued
to fight with his customary enthusiasm and pertinacity,
and at last, in 1823, the Academy yielded, and voted
Fresnel into its ranks, thus implicitly admitting the
value of his work.
It is a humiliating thought that such controversies as
this must mar the progress of scientific truth ; but fort-
unately the story of the introduction of the undulatory
theory has a more pleasant side. Three men, great both
in character and in intellect, were concerned in pressing
its claims — Young, Fresnel and Arago — and the rela-
tions of these men form a picture unmarred by any
of those petty jealousies that so often dim the lustre
of great names. Fresnel freely acknowledged Young's
priority so soon as his attention was called to it ; and
Young applauded the work of the Frenchman, and
aided with his counsel in the application of the undula-
tory theory to the problems of polarization of light,
which still demanded explanation, and which Fresnel's
fertility of experimental resource and profundity of
mathematical insight sufficed in the end to conquer.
After Fresnel's admission to the Institute in 1823 the
opposition weakened, and gradually the philosophers
came to realize the merits of a theory which Young
had vainly called to their attention a full quarter-
century before. Now, thanks largely to Arago, both
303
THE STORY OF NINETEENTH-CENTURY SCIENCE
Young and Fresnel received their full meed of apprecia-
tion. Fresnel was given the Rumford medal of the
Royal Society of England in 1825, and chosen one of the
foreign members of the Society two years later, while
Young in turn was elected one of the eight foreign
members of the French Academy. As a fitting culmi-
nation of the chapter of felicities between the three
friends, it fell to the lot of Young, as Foreign Secretary
of the Royal Society, to notify Fresnel of the honors
shown him by England's representative body of sci-
entists; while Arago, as Perpetual Secretary of the
French Institute, conveyed to Young in the same year
the notification that he had been similarly honored by
the savants of France.
A few months later Fresnel was dead, and Young
survived him only two years. Both died premature-
ly.; but their great work was done, and the world will
remember always and link together these two names in
connection with a theory which in its implications and
importance ranks little below the theory of universal
gravitation.
ii
The full importance of Young's studies of light might
perhaps have gained earlier recognition had it not
chanced that, at the time when they were made, the
attention of the philosophic world was turned with the
fixity and fascination of a hypnotic stare upon another
field, which for a time brooked no rival. How could
the old familiar phenomenon light interest any one
when the new agent galvanism was in view? As well
ask one to fix attention on a star while a meteorite
blazes across the sky.
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THE CENTURY'S PROGRESS IN PHYSICS
The question of the hour was whether in galvanism
the world had to do with a new force, or whether it is
identical with electricity, masking under a new form.
Yery early in the century the profound, if rather cap-
tious, Dr. Wollaston made experiments which seemed to
show that the two are identical ; and by 1807 Dr. Young
could write in his published lectures : "The identity of
the general causes of electrical and of galvanic effects is
now doubted by few." To be entirely accurate, he
should have added, " by few of the leaders of scientific
thought," for the lesser lights were by no means so fully
agreed as the sentence cited might seem to imply.
But meantime an even more striking affinity had been
found for the new agent galvanism. From the first it
had been the chemists rather than the natural philoso-
phers— the word physicist was not then in vogue — who
had chiefly experimented with Yolta's battery ; and the
acute mind of Humphry Davy at once recognized the
close relationship between chemical decomposition and
the appearance of the new " imponderable." The great
Swedish chemist Berzelius also had an inkling of the
same thing. But it was Davy who first gave the
thought full expression, in a Bakerian lecture before
the Royal Society in 1806 — the lecture which gained
him not only the plaudits of his own countrymen, but
the Napoleonic prize of the French Academy at a time
when the political bodies of the two countries were in
the midst of a sanguinary war. " Science knows no
country," said the young Englishman, in accepting the
French testimonial, against the wishes of some of the
more narrow-minded of his friends. " If the two coun-
tries or governments are at war, the men of science are
not. That would, indeed, be a civil war of the worst
205
THE STORY OF NINETEENTH-CENTURY SCIENCE
description. We should rather, through the instru-
mentality of men of science, soften the asperities of
national hostility."
Here it was that Davy explicitly" stated his belief
that "chemical and electrical attraction are produced
by the same cause, acting in one case on particles, in
the other on masses," and that " the same property,
under different modifications, is the cause of all the
phenomena exhibited by different voltaic combinations."
The phenomena of galvanism were thus linked with
chemical action on the one hand, and with frictional
electricity on the other, in the first decade of the cen-
tury, showing that electricity is by no means the iso-
lated "fluid" that it had been thought. But there the
matter rested for another decade. The imaginative
Davy, whose penetrative genius must have carried him
further had it not been diverted, became more and more
absorbed in the chemical side of the problem ; and
Young, having severed his connection Avith the Royal
Institution, was devoting himself to developing his med-
ical practice, and in intervals of duty to deciphering
Egyptian hieroglyphics. Parenthetically it may be
added that Young was far too much in advance of his
time to make a great success as a practitioner (people
demand sophistry rather than philosophy of their fam-
ily physician), but that his success with the hiero-
glyphics was no less novel and epoch-making than his
work in philosophy.
For a time no master-generalizer came to take the place
of these men in the study of the "imponderables "as such,
and the phenomena of electricity occupied an isolated cor-
ner in the realm of science, linked, as has been said rather
to chemistry than to the field we now term physics.
206
THE CENTURY'S PROGRESS IN PHYSICS
But in the year 1819 there flashed before the philo-
sophic world, like lightning from a clear sky, the report
that Hans Christian Oersted, the Danish philosopher,
had discovered that the magnetic needle may be deflect-
ed by the passage near it of a current of electricity.
The experiment was repeated everywhere. Its validity
was beyond question, its importance beyond estimate.
Many men had vaguely dreamed that there might be
some connection between electricity and magnetism —
chiefly because each shows phenomena of seeming at-
traction and repulsion — but here was the first experi-
mental evidence that any such connection actually ex-
ists. The wandering eye of science was recalled to elec-
tricity as suddenly and as irresistibly as it had been in
1800 by the discovery of the voltaic pile. But now it
was the physical rather than the chemical side of the
subject that chiefly demanded attention.
At once Andre Marie Ampere, whom the French love
to call the Newton of electricity, appreciated the far-
reaching importance of the newly disclosed relationship,
and, combining mathematical and experimental studies,
showed how close is the link between electricity and
magnetism, and suggested the possibility of signalling
at a distance by means of electric wires associated with
magnetic needles. Gauss, the great mathematician, and
Weber, the physicist, put this idea to a practical test by
communicating with one another at a distance of sev-
eral roods, in Gottingen, long before "practical" teleg-
raphy grew out of Oersted's discovery.
A new impetus thus being given to the investigators,
an epoch of electrical discovery naturally followed. For
a time interest centred on the French investigators, in
particular upon the experiments of the ever- receptive
207
THE STORY OF NINETEENTH-CENTURY SCIENCE
Arago, who discovered in 1825 that magnets may be
produced at will by electrical induction. But about
1830 the scene shifted to London ; for then the protege
of Davy, and his successor in the Royal Institution,
Michael Faraday, the " man who added to the powers
of his intellect all the graces of the human heart." began
that series of electrical experiments at the Royal Insti-
tution which were destined to attract the dazed atten-
tion of the philosophic world, and stamp their originator
as " the greatest experimental philosopher the world
has ever seen." Nor does the rank of prince of experi-
menters do Faraday full justice, for he was far more
than a mere experimenter. He had not, perhaps, quite
the intuitive insight of Davy, and he utterly lacked the
profound mathematical training of Young. None the
less was he a man who could dream dreams on occasion,
and, as Maxwell has insisted, think in mathematical
channels if not with technical symbols. Only his wagon
must always traverse earth though hitched to a star.
His dreams guided him onward, but ever the hand of
experiment kept check over the dreams.
It was in 1831 that Faraday opened up the field of
magneto-electricity. Reversing the experiments of his
predecessors, who had found that electric currents may
generate magnetism, he showed that magnets have
power under certain circumstances to generate electric-
ity ; he proved, indeed, the interconvertibility of elec-
tricity and magnetism. Then he showed that all bodies
are more or less subject to the influence of magnetism,
and that even light may be affected by magnetism as to
its phenomena of polarization. He satisfied himself
completely of the true identity of all the various forms
of electricity, and of the convertibility of electricity and
208
THE CENTURY'S PROGRESS IN PHYSICS
chemical action. Thus he linked together light, chemi-
cal affinity, magnetism, and electricity. And, moreover,
he knew full well that no one of these can be produced
in indefinite supply from another. Nowhere, he says,
"is there a pure creation or production of power with-
out a corresponding exhaustion of something to supply
it."
When Faraday wrote those words in 1840 he was
treading on the very heels of a greater generalization
than any which he actually formulated ; nay, he had it
fairly within his reach. He saw a great truth without
fully realizing its import ; it was left for others, ap-
proaching the same truth along another path, to point
out its full significance.
in
The great generalization which Faraday so narrowly
missed is the truth which since then has become familiar
as the doctrine of the conservation of energy — the law
that in transforming energy from one condition to an-
other we can never secure more than an equivalent
quantity; that, in short, "to create or annihilate ener-
gy is as impossible as to create or annihilate matter;
and that all the phenomena of the material universe
consist in transformations of energy alone." Some phi-
losophers think this the greatest generalization ever
conceived by the mind of man. Be that as it' may, it is
surely one of the great intellectual landmarks of our
century. It stands apart, so stupendous and so far-
reaching in its implications that the generation which
first saw the law developed could little appreciate it ;
only now, through the vista of half a century, do we
begin to see it in its true proportions,
o 209
THE STORY OF NINETEENTH-CKNTURY SCIENCE
A vast generalization such as this is never a mush-
room growth, nor does it usually spring full grown from
the mind of any single man. Always a number of
minds are very near a truth before any one mind fully
grasps it. Pre-eminently true is this of the doctrine of
conservation of energy. Not Faraday alone, but half a
dozen different men had an inkling of it before it gained
full expression ; indeed, every man who advocated the
undulatory theory of light and heat was verging towards
the goal. The doctrine of Young and Fresnel was as n
highway leading surely on to the wide plain of conser-
vation. The phenomena of electro-magnetism furnished
another such highway. But there was yet another road
which led just as surely and even more readily to the
same goal. This was the road furnished by the phe-
nomena of heat, and the men who travelled it were des-
tined to outstrip their fellow- workers ; though, as we
have seen, wayfarers on other roads were within hailing
t */
distance when the leaders passed the mark.
In order to do even approximate justice to the men
who entered into the great achievement, we must recall
that just at the close of the last century Count TCumford
and Humphry Davy independently showed that labor
may be transformed into heat ; and correctly interpreted
this fact as meaning the transformation of molar into
molecular motion. We can hardly doubt that each of
these men of genius realized, vaguely, at any rate, that
there must be a close correspondence between the
amount of the molar and the molecular motions; hence
that each of them was in sight of the law of the me-
chanical equivalent of heat. But neither of them quite
grasped or explicitly stated what each must vaguely
have seen ; and for just a quarter of a century no one
210
MICHAEL FARADAY
THE CENTURY'S PROGRESS IN PHYSICS
else even came abreast their line of thought, let alone
passing it.
But then, in 1824, a French philosopher, Sadi Carnot,
caught step with the great Englishmen, and took a long
leap ahead by explicitly stating his belief that a definite
quantity of work could be transformed into a definite
quantity of heat, no more, no less. Carnot did not, in-
deed, reach the clear view of his predecessors as to the
nature of heat, for he still thought it a form of " impon-
derable" fluid; but he reasoned none the less clearly as
to its mutual convertibility with mechanical work. But
important as his conclusions seem now that we look
back upon them with clearer vision, they made no im-
pression whatever upon his contemporaries. Carnot's
work in this line was an isolated phenomenon of histori-
cal interest, but it did not enter into the scheme of the
completed narrative in any such way as did the work of
Kumford and Davy.
The man who really took up the broken thread where
Kumford and Davy had dropped it, and wove it into a
completed texture, came upon the scene in 1840. His
home was in Manchester, England ; his occupation that
of a manufacturer. He was a friend and pupil of the
great Dr. Dalton. His name was James Prescott Joule.
When posterity has done its final juggling with the
names of our century, it is not unlikely that the name of
this Manchester philosopher will be a household word
like the names of Aristotle, Copernicus, and Newton.
For Joule's work it was, done in the fifth decade of our
century, which demonstrated beyond all cavil that there
is a precise and absolute equivalence between mechani-
cal work and heat ; that whatever the form of mani-
festation of molar motion, it can generate a definite and
213
THE STORY OF NINETEENTH-CENTURY SCIENCE
measurable amount of heat, and no more. Joule found,
for example, that at the sea-level in Manchester a pound
weight falling through seven hundred and seventy-two
feet could generate enough heat to raise the temperature
of a pound of water one degree Fahrenheit. There was
nothing haphazard, nothing accidental, about this ; it
bore the stamp of unalterable law. And Joule himself
saw, what others in time were made to see, that this
truth is merely a particular case within a more general
law. If heat cannot be in any sense created, but only
made manifest as a transformation of another kind of
motion, then must not the same thing be true of all
those other forms of "force" — light, electricity, magnet-
ism— which had been shown to be so closely associated,
so mutually convertible, with heat? All analogy seemed
to urge the truth of this inference ; all experiment tend-
ed to confirm it. The law of the mechanical equivalent
of heat then became the main corner-stone of the greater
law of the conservation of energy.
But while this citation is fresh in mind, we must turn
our attention with all haste to a country across the
Channel — to Denmark, in short— and learn that even as
Joule experimented with the transformation of heat, a
philosopher of Copenhagen, Colding by name, had hit
upon the same idea, and carried it far towards a demon-
stration. And then, without pausing, we must shift yet
again, this time to Germany, and consider the work of
three other men, who independently were on the track
of the same truth, and two of whom, it must be admit-
ted, reached it earlier than either Joule or Colding,
if neither brought it to quite so clear a demonstra-
tion. The names of these three Germans are Mohr,
Mayer, and Helmholtz. Their share in establishing
214
THE CENTURY'S PROGRESS IN PHYSICS
the great doctrine of conservation must now claim our
attention.
As to Karl Friedrich Mohr, it may be said that his
statement of the doctrine preceded that of any of bis
fellows, yet that otherwise it was perhaps least impor-
tant. In 1837 this thoughtful German had grasped the
main truth, and given it expression in an article pub-
lished in the Zeitschrift fur P/iysik, etc. But the article
attracted no attention whatever, even from Mohr's own
countrymen. Still, Mohr's title to rank as one who
independently conceived the great truth, and perhaps
first conceived it before any other man in the world
saw it as clearly, even though he did not demonstrate
its validity, is not to be disputed.
It was just five years later, in 1842, that Dr. Julius
Robert Mayer, practising physician in the little German
town of Heilbronn, published a paper in Liebig's Annalen
on "The Forces of Inorganic Nature," in which not
merely the mechanical theory of heat, but the entire
doctrine of the conservation of energy, is explicitly if
briefly stated. Two years earlier Dr. Mayer, while
surgeon to a Dutch India vessel cruising in the tropics,
had observed that the venous blood of a patient seemed
redder than venous blood usually is observed to be in
temperate climates. He pondered over this seemingly
insignificant fact, and at last reached the conclusion
that the cause must be the lesser amount of oxidation
required to keep up the body temperature in the tropics.
Led by this reflection to consider the body as a machine
dependent on outside forces for its capacity to act, he
passed on into a novel realm of thought, which brought
him at last to independent discovery of the mechanical
theory of heat, and to the first full and comprehensive
210
THE STORY OF NINETEENTH-CENTURY SCIENCE
appreciation of the great law of conservation. Blood-
letting, the modern physician holds, was a practice of
very doubtful benefit, as a rule, to the subject ; but once,
at least, it led to marvellous results. No straw is so small
that it may not point the receptive mind of genius to
new and wonderful truths.
Here, then, was this obscure German physician, lead-
ing the humdrum life of a village practitioner, yet seeing
such visions as no human being in the world had ever
seen before.
The great principle he had discovered became the
dominating thought of his life, and filled all his leisure
hours. He applied it far and wide, amidst all the phe-
nomena of the inorganic and organic worlds. It taught
him that both vegetables and animals are machines,
bound by the same laws that hold sway over inorgan-
ic matter, transforming energy, but creating nothing.
Then his mind reached out into space and met a universe
made up of questions. Each star that blinked down at
him as he rode in answer to a night call seemed an inter-
rogation-point asking, How do I exist? Why have I
not long since burned out if your theory of conservation
be true ? No one hitherto had even tried to answer that
question; few had so much as realized that it demanded
an answer. But the Heilbronn physician understood
the question and found an answer. His meteoric hy-
pothesis, published in 1848, gave for the first time a
tenable explanation of the persistent light and heat of
our sun and the myriad other suns — an explanation to
which we shall recur in another connection.
All this time our isolated philosopher, his brain aflame
with the glow of creative thought, was quite unaware
that any one else in the world was working along the
216
THE CENTURY'S PROGRESS IN PHYSICS
same lines. And the outside world was equally heedless
of the work of the Heilbronn physician. There was no
friend to inspire enthusiasm and give courage, no kindred
spirit to react on this masterful but lonely mind. And
this is the more remarkable because there are few other
cases where a master -originator in science has come
upon the scene except as the pupil or friend of some
other master-originator. Of the men we have noticed
in the present connection, Young was the friend and
confrere of Davy ; Davy, the protege of Rumford ; Far-
raday, the pupil of Davy ; Fresnel, the co-worker with
Arago ; Colding, the confrere of Oersted ; Joule, the
pupil of Dalton. But Mayer is an isolated phenomenon
— one of the lone mountain-peak intellects of the century.
That estimate may be exaggerated which has called him
the Galileo of the nineteenth century, but surely no luke-
warm praise can do him justice.
Yet for a long time his work attracted no attention
whatever. In 1847, when another German physician,
Hermann von Helmholtz, one of the most massive and
towering intellects of any age, had been independently
led to comprehension of the doctrine of conservation of
energy, and published his treatise on the subject, he had
hardly heard of his countryman Mayer. When he did
hear of him, however, he hastened to renounce all claim
to the doctrine of conservation, though the world at
large gives him credit of independent even though sub-
sequent discovery.
Meantime in England Joule was going on from one
experimental demonstration to another, oblivious of his
German competitors and almost as little noticed by his
own countrymen. He read his first paper before the
chemical section of the British Association for the
217
THE STORY OF NINETEENTH-CENTURY SCIENCE
Advancement of Science in 1843, and no one heeded it
in the least. Two years later he wished to read another
paper, but the chairman hinted that time was limited,
and asked him to confine himself to a brief verbal synop-
sis of the results of his experiments. Had the chair-
man but known it, he was curtailing a paper vastly more
important than all the other papers of the meeting put
together. However, the synopsis was given, and one
man was there to hear it who had the genius to appre-
ciate its importance. This was William Thomson, the
present Lord Kelvin, now known to all the world as
among the greatest of natural philosophers, but then
only a novitiate in science. He came to Joule's aid,
started rolling the ball of controversy, and subsequently
associated himself with the Manchester experimenter in
pursuing his investigations.
But meantime the acknowledged leaders of British
science viewed the new doctrine askance. Faraday,
Brewster, Herschel — those were the great names in
physics at that da\T, and no one of them could quite
accept the new views regarding energy. For several
years no older physicist, speaking with recognized
authority, came forward in support of the doctrine of
conservation. This culminating thought of our first
half-centur\r came silently into the world, unheralded
and unopposed. The fifth decade of the century had
seen it elaborated and substantially demonstrated in at
least three different countries, yet even the leaders of
thought did not so much as know of its existence. In
1853 Whe well, the historian of the inductive sciences, pub-
lished a second edition of his history, and, as Huxley has
pointed out, he did not so much as refer to the revolution-
izing thought which even then was a full decade old,
218
JAMES PRESCOTT JOULE
WILLIAM THOMSON (LORD KELVIN)
JOHN TYNDALL
THE CENTURY'S PROGRESS IN PHYSICS
By this time, however, the battle was brewing. The
rising generation saw the importance of a law which
their elders could not appreciate, and soon it was noised
abroad that there were more than one claimant to the
honor of discovery. Chiefly through the efforts of Pro-
fessor Tyndall, the work of Mayer became known to the
British public, and a most regrettable controversy ensued
between the partisans of Mayer and those of Joule — a
bitter controversy, in which Davy's contention that
science knows no country was not always regarded, and
which left its scars upon the hearts and minds of the
great men whose personal interests were involved.
And so to this day the question who is the chief dis-
coverer of the law of conservation of energy is not sus-
ceptible of a categorical answer that would satisfy all
philosophers. It is generally held that the first choice
lies between Joule and Mayer. Professor Tyndall has
expressed the belief that in future each of these men
will be equally remembered in connection with this
work. But history gives us no warrant for such a hope.
Posterity in the long-run demands always that its heroes
shall stand alone. Who remembers now that Robert
Hooke contested with Newton the discovery of the doc-
trine of universal gravitation? The judgment of pos-
terity is unjust, but it is inexorable. And so we can
little doubt that a century from now one name will be
mentioned as that of the originator of the great doctrine
of conservation of energy. The man whose name is thus
remembered will perhaps be spoken of as the Galileo,
the Newton, of the nineteenth century; but whether
the name thus dignified by the final verdict of history
will be that of Colding, Mohr, Mayer, Helmholtz, or
Joule, it is not for our century to decide.
'
THE STORY OF NINETEENTH-CENTURY SCIENCE
IV
The gradual permeation of the field by the great
doctrine of conservation simply repeated the history
of the introduction of every novel and revolutionary
thought. Necessarily the elder generation, to whom
all forms of energy were imponderable fluids, must pass
away before the new conception could claim the field.
Even the word energy, though Young had introduced
it in 1807, did not come into general use till some time
after the middle of the century. To the generality of
philosophers (the word physicist was even less in favor
at this time) the various forms of energy were still
subtle fluids, and never was idea relinquished with
greater unwillingness than this. The experiments of
Young and Fresnel had convinced a large number of
philosophers that light is a vibration and not a sub-
stance; but so great an authority as Biot clung to the
old emission idea to the end of his life, in 1862, and held
a following.
Meantime, however, the company of brilliant young
men who had just served their apprenticeship when the
doctrine of conservation came upon the scene had grown
into authoritative positions, arid were battling actively
for the new ideas. Confirmatory evidence that energy
is a molecular motion and not an " imponderable " form
of matter accumulated day by day. The experiments of
two Frenchmen, Hippolyte L. Fizeau and Leon Foucault,
served finally to convince the last lingering sceptics that
light is an undulation ; and by implication brought heat
into the same category, since James David Forbes, the
Scotch physicist, had shown in 1837 that radiant heat
conforms to the same laws of polarization and double
222
THE CENTURY'S PROGRESS IN PHYSICS
refraction that govern light. But, for that matter, the
experiments that had established the mechanical equiva-
lent of heat hardly left room for doubt as to the imma-
teriality of this "imponderable." Doubters had, indeed,
expressed scepticism as to the validity of Joule's exper-
iments, but the further researches, experimental and
mathematical, of such workers as Thomson (Lord Kel-
vin), Rankine, and Tyndall in Great Britain, of Helm-
holtz and Clausius in Germany, and of Regnault in
France, dealing with various manifestations of heat,
placed the evidence beyond the reach of criticism.
Out of these studies, just at the middle of the cen-
tury, to which the experiments of Mayer and Joule had
led, grew the new science of thermo-dynamics. Out of
them also grew in the mind of one of the investigators
a new generalization, only second in importance to the
doctrine of conservation itself. Professor William
Thomson (Lord Kelvin) in his studies in thermo-dynam-
ics was early impressed with the fact that whereas all
the molar motion developed through labor or gravity
could be converted into heat, the process is not fully re-
versible. Heat can, indeed, be converted into molar
motion or work, but in the process a certain amount of
the heat is radiated into space and lost. The same
thing happens whenever any other form of energy is
converted into molar motion. Indeed, every transmuta-
tion of energy, of whatever character, seems compli-
cated by a tendency to develop heat, part of which is
lost. This observation led Professor Thomson to his
doctrine of the dissipation of energy, which he formu-
lated before the Royal Society of Edinburgh in 1852,
and published also in the Philosophical Magazine the
same year, the title borne being, "On a Universal Ten-
223
THE STORY OF NINETEENTH-CENTURY SCIENCE
dency in Nature to the Dissipation of Mechanical En-
ergy."
From the principle here expressed Professor Thomson
drew the startling conclusion that, " since any restora-
tion of this mechanical energy without more than an
equivalent dissipation is impossible," the universe, as
known to us, must be in the condition of a machine
gradually running down ; and in particular that the
world we live on has been within a finite time unfit for
human habitation, and must again become so within a
finite future. This thought seems such a commonplace
to-day that it is difficult to realize how startling it ap-
peared half a century ago. A generation trained, as
ours has been, in the doctrines of conservation and dis-
sipation of energy as the very alphabet of physical sci-
ence can but ill appreciate the mental attitude of a gen-
eration which for the most part had not even thought it
problematical whether the sun could continue to give
out heat and light forever. But those advance thinkers
who had grasped the import of the doctrine of conser-
vation could at once appreciate the force of Thomson's
doctrine of dissipation, and realize the complementary
character of the two conceptions.
Here and there a thinker like Rankine did, indeed, at-
tempt to fancy conditions under which the energy lost
through dissipation might be restored to availability,
but no such effort has met with success, and in time
Professor Thomson's generalization and his conclusions
as to the consequences of the law involved came to be
universally accepted.
The introduction of the new views regarding the nat-
ure of energy followed, as I have said, the course of
every other growth of new ideas. Young and imagina-
224
THE CENTURY'S PROGRESS IN PHYSICS
tive men could accept the new point of view ; older phi-
losophers, their minds channelled by preconceptions,
could not get into the new groove. So strikingly true
is this in the particular case now before us that it is
worth while to note the ages at the time of the revolu-
tionary experiments of the men whose work has been
mentioned as entering into the scheme of evolution of
the idea that energy is merely a manifestation of matter
in motion. Such a list will tell the story better than a
volume of commentary.
Observe, then, that Davy made his epochal experi-
ment of melting ice by friction when he was a youth of
twenty. Young was no older when he made his first
communication to the Royal Society, and was in his
twenty -seventh year when he first actively espoused the
undulatory theory. Fresnel was twenty-six when he
made his first important discoveries in the same field ;
and Arago, who at once became his champion, was then
but two vears his senior, though for a decade he had
«/
been so famous that one involuntarily thinks of him as
belonging to an elder generation.
Forbes was under thirty when he discovered the po-
larization of heat, which pointed the way to Mohr, then
thirty-one, to the mechanical equivalent. Joule was
twenty-two in 1840, when his great work was begun ;
and Mayer, whose discoveries date from the same year,
was then twenty-six, which was also the age of Helm- '
holtz when he published his independent discovery of
the same law. William Thomson was a youth just past
his majority when he came to the aid of Joule before
the British Society, and but seven jears older when he
formulated his own doctrine of dissipation of energy.
And Clausius and Rankine, who are usually mentioned
p 225
TilE STORY OF NINETEENTH-CENTURY SCIENCE
with Thomson as the great developers of thermo-dynam-
ics, were both far advanced with their novel studies
before they were thirty. We may well agree with the
father of inductive science that " the man who is young
in years may be old in hours."
Yet we must not forget that the shield has a reverse
side. For was not the greatest of observing astrono-
mers, Herschel, past thirty-five before he ever saw a
telescope, and past fifty before he discovered the heat
rays of the spectrum ? And had not Faraday reached
middle life before he turned his attention especially to
electricity ? Clearly, then, to make his phrase complete,
Bacon must have added that "the man who is old in
years may be young in imagination." Here, however,
even more appropriate than in the other case — more's
the pity — would have been the application of his quali-
fying clause: "but that happeneth rarely."
There are only a few great generalizations as yet
thought out in any single field of science. Naturally,
then, after a great generalization has found definitive
expression, there is a period of lull before another for-
ward move. In the case of the doctrines of energy, the
lull has lasted half a century. Throughout this period,
it is true, a multitude of workers have been delving in
the field, and to the casual observer it might seem as if
their activity had been boundless, while the practical
applications of their ideas — as exemplified, for example,
in the telephone, phonograph, electric light, and so on—
have been little less than revolutionary. Yet the most
competent of living authorities, Lord Kelvin, could as-
226
sert in 1895 that in fifty years he had learned nothing
new regarding the nature of energy.
This, however, must not be interpreted as meaning
that the world has stood still during these two genera-
tions. It means rather that the rank and file have been
moving forward along the road the leaders had already
travelled. Only a few men in the world had the range
of thought regarding the new doctrine of energy that
Lord Kelvin had at the middle of the century. The
few leaders then saw clearly enough that if one form of
energy is in reality merely an undulation or vibration
among the particles of 'k ponderable " matter or of ether,
all other manifestations of energy must be of the same
nature. But the rank and file were not even within
sight of this truth for a long time after they had partly
grasped the meaning of the doctrine of conservation.
When, late in the fifties, that marvellous young Scotch-
man, James Clerk Maxwell, formulating in other words
an idea of Faraday's, expressed his belief that electrici-
ty and magnetism are but manifestations of various con-
ditions of stress and motion in the ethereal medium
(electricity a displacement of strain, magnetism a whirl
in the ether), the idea met with no immediate populari-
ty. And even less cordial was the reception given the
same thinker's theory, put forward in 1863, that the
ethereal undulations producing the phenomenon we call
light differ in no respect except in their wave-length
from the pulsations of electro-magnetism.
At about the same time Helmholtz formulated a
somewhat similar electro-magnetic theory of light; but
even the weight of this combined authority could not
give the doctrine vogue until very recently, when the
experiments of Heinrich Hertz, the pupil of Helmholtz,
227
THE STORY OF NINETEENTH-CENTURY SCIENCE
have shown that a condition of electrical strain may be
developed into a wave system by recurrent interruptions
of the electric state in the generator, and that such
waves travel through the ether with the rapidity of
light. Since then the electro-magnetic theory of light
has been enthusiastically referred to as the greatest gen-
eralization of the century ; but the sober thinker must
see that it is really only what Hertz himself called it-
one pier beneath the great arch of conservation. It is
an interesting detail of the architecture, but the part
cannot equal the size of the whole.
More than that, this particular pier is as yet by no
means a very firm one. It has, indeed, been demon-
strated that waves of electro-magnetism pass through
space with the speed of light, but as yet no one has de-
veloped electric waves even remotely approximating the
shortness of the visual rays. The most that can posi-
tively be asserted, therefore, is that all the known forms
of radiant energy — heat, light, electro - magnetism-
travel through space at the same rate of speed, and con-
sist of traverse vibrations — " lateral quivers," as Fresnel
said of light — known to differ in length, and not posi-
tively known to differ otherwise. It has, indeed, been
suggested that the newest form of radiant energy, the
famous X ray of Professor Rontgen's discovery, is a
longitudinal vibration, but this is a mere surmise. Be
that as it may, there is no one now to question that all
forms of radiant energy, whatever their exact affinities,
consist essentially of undulatory motions of one uniform
medium.
A full century of experiment, calculation, and con-
troversy has thus sufficed to correlate the " impondera-
ble fluids " of our forebears, and reduce them all to man-
THE CENTURY'S PROGRESS IN PHYSICS
ifestations of motion among particles of matter. At
first glimpse that seems an enormous change of view.
And yet, when closely considered, that change in
thought is not so radical as the change in phrase might
seem to imply. For the nineteenth-century physicist, in
displacing the "imponderable fluids" of many kinds —
one each for light, heat, electricity, magnetism — has
been obliged to substitute for them one all-pervading
fluid, whose various quivers, waves, ripples, whirls, or
strains produce the manifestations which in popular
parlance are termed forms of force. This all-pervading
fluid the physicist terms the ether, and he thinks of it
as having no weight. In effect, then, the physicist has
dispossessed the many imponderables in favor of a single
imponderable — though the word imponderable has been
banished from his vocabulary. In this view the ether —
which, considered as a recognized scientific verity, is es-
sentially a nineteenth-century discovery — is about the
most interesting thing in the universe. Something more
as to its properties, real or assumed, we shall have oc-
casion to examine as we turn to the obverse side of
physics, which demands our attention in the next chap-
ter.
CHAPTER VII
THE ETHER AND PONDERABLE MATTER
" WHATEVER difficulties we may have in forming a
consistent idea of the constitution of the ether, there
can be no doubt that the interplanetary and interstellar
spaces are not empty, but are occupied by a material
substance or body which is certainly the largest and
probably the most uniform body of which we have any
knowledge."
Such was the verdict pronounced some twenty years
ago by James Clerk Maxwell, one of the very greatest
of nineteenth-century physicists, regarding the existence
of an all-pervading plenum in the universe, in which
every particle of tangible matter is immersed. And this
verdict may be said to express the attitude of the entire
philosophical world of our day. Without exception, the
authoritative physicists of our time accept this plenum
as a verity, and reason about it with something of the
same confidence they manifest in speaking of " pondera-
ble " matter or of energy. It is true there are those among
them who are disposed to deny that this all-pervading
plenum merits the name of matter. But that it is a
something, and a vastly important something at that, all
are agreed. Without it, they allege, we should know
230
THE ETHER AND PONDERABLE MATTER
nothing of light, of radiant heat, of electricity, or mag-
netism ; without it there would probably be no such
thing as gravitation ; nay, they even hint that without
this strange something, ether, there would be no such
thing as matter in the universe. If these contentions of
the modern physicist are justified, then this intangible
ether is incomparably the most important as well as the
"largest and most uniform substance or body" in the
universe. Its discovery may well be looked upon as the
most important feat of our century.
For a discovery of our century it surely is, in the
sense that all the known evidences of its existence have
been gathered in this epoch. True, dreamers of all ages
have, for metaphysical reasons, imagined the existence
of intangible fluids in space — they had, indeed, peopled
space several times over with different kinds of ethers,
as Maxwell remarks — but such vague dreamings no more
constituted the discovery of the modern ether than the
dream of some pre-Columbian visionary that land might
lie beyond the unknown waters constituted the discov-
ery of America. In justice it must be admitted that
Huyghens, the seventeenth-century originator of the un-
dulatory theory of light, caught a glimpse of the true
ether; but his contemporaries and some eight genera-
tions of his successors were utterly deaf to his claims;
so he bears practically the same relation to the nine-
teenth-century discoverers of ether that the Norseman
bears to Columbus.
The true Columbus of the ether was Thomas Young.
His discovery was consummated in the early days of the
present century, when he brought forward the first con-
clusive proofs of the undulatory theory of light. To
say that light consists of undulations is to postulate
231
THE STORY OF NINETEENTH-CENTURY SCIENCE
something which undulates; and this something could
not be air, for air exists only in infinitesimal quantity, if
at all, in the interstellar spaces, through which light
freely penetrates. But if not air, what then? Why,
clearly, something more intangible than air; something
supersensible, evading all direct efforts to detect it, yet
existing everywhere in seemingly vacant space, and also
interpenetrating the substance of all transparent liquids
and solids, if not, indeed, of all tangible substances.
This intangible something Young rechristened the Lu-
miniferous Ether.
In the early days of his discovery Young thought of
the undulations which produce light and radiant heat as
being longitudinal — a forward and backward pulsation,
corresponding to the pulsations of sound — and as such
pulsations can be transmitted by a fluid medium with
the properties of ordinary fluids, he was justified in
thinking of the ether as being like a fluid in its proper-
ties, except for its extreme intangibility. But about
1818 the experiments of Fresnel and Arago with polar-
ization of light made it seem very doubtful whether the
theory of longitudinal vibrations is sufficient, and it was
suggested by Young, and independently conceived and
demonstrated by Fresnel, that the luminiferous undula-
tions are not longitudinal, but transverse; and all the
more recent experiments have tended to confirm this
view. But it happens that ordinary fluids — gases and
liquids — cannot transmit lateral vibrations ; only rigid
bodies are capable of such a vibration. So it became
necessary to assume that the luminiferous ether is a body
possessing elastic rigidity — a familiar property of tangi-
ble solids, but one quite unknown among fluids.
The idea of transverse vibrations carried with it an-
232
THE ET1IER AND PONDERABLE MATTER
other puzzle. Why does not the ether, when set aquiver
with the vibration which gives us the sensation we call
light, have produced in its substance subordinate quiv-
ers, setting out at right angles from the path of the
original quiver? Such perpendicular vibrations seem
not to exist, else we might see around a corner ; how
explain their absence? The physicists could think of
but one way: they must assume that the ether is in-
compressible. It must fill all space — at any rate, all
space with which human knowledge deals — perfectly
full.
These properties of the ether, incompressibility and
elastic rigidity, are quite conceivable by themselves;
but difficulties of thought appear when we reflect upon
another quality which the ether clearly must possess —
namely, frictionlessness. Per hypothesis this rigid, in-
compressible body pervades all space, imbedding every
, particle of tangible matter; yet it seems not to retard the
movements of this matter in the slightest degree. This
is undoubtedly the most difficult to comprehend of the
alleged properties of the ether. The physicist explains
it as due to the perfect elasticity of the ether, in virtue
of which it closes in behind a moving particle with a
push exactly counterbalancing the stress required to
penetrate it in front.
To a person unaccustomed to think of seemingly
solid matter as really composed of particles relatively
wide apart, it is hard to understand the claim that
ether penetrates the substance of solids — of glass, for
example — and, to use Young's expression, which we
have previously quoted, moves among them as freely
as the wind moves through a grove of trees. This
thought, however, presents few difficulties to the mind
283
THE STORY OF NINETEENTH-CENTURY SCIENCE
accustomed to philosophical speculation. But the ques-
tion early arose in the mind of Fresnel whether the
ether is not considerably affected by contact with the
particles of solids. Some of his experiments led him to
believe that a portion of the ether which penetrates
among the molecules of tangible matter is held captive,
so to speak, and made to move along with these par-
ticles. He spoke of such portions of the ether as
" bound " ether, in contradistinction to the great mass
of " free" ether. Half a century after Fresnel's death,
when the ether hypothesis had become an accepted ten-
et of science, experiments were undertaken by Fizeau
in France, and by Maxwell in England, to ascertain
whether any portion of ether is really thus bound to
particles of matter ; but the results of the experiments
were negative, and the question is still undetermined.
While the undulatory theory of light was still fighting-
its way, another kind of evidence favoring the existence .
of an ether was put forward by Michael Faraday, who,
in the course of his experiments in electrical and mag-
netic induction, was led more and more to perceive def-
inite lines or channels of force in the medium subject to
electro-magnetic influence. Faraday's mind, like that
of Newton and many other philosophers, rejected the
idea of action at a distance, and he felt convinced that
the phenomena of magnetism and of electric induction
told strongly for the existence of an invisible plenum
everywhere in space, which might very probably be
the same plenum that carried the undulations of light
and radiant heat.
Then, about the middle of the century, came that final
revolution of thought regarding the nature of energy
which we have already outlined in the preceding chap-
234
THE ETIIEli AND PONDERABLE MATTER
ter, and with that the case for ether was considered to
be fully established. The idea that energy is merely a
" mode of motion " (to adopt TyndalPs familiar phrase),
combined with the universal rejection of the notion of
action at a distance, made the acceptance of a plenum
throughout space a necessity of thought — so, at any
rate, it has seemed to most physicists of recent decades.
The proof that all known forms of radiant energy move
through space at the same rate of speed is regarded as
practically a demonstration that but one plenum — one
ether — is concerned in their transmission. It has, in-
deed, been tentatively suggested, by Professor J. Oliver
Lodge, that there may be two ethers, representing the
two opposite kinds of electricity, but even the author
of this hypothesis would hardly claim for it a high de-
gree of probability.
The most recent speculations regarding the properties
of the ether have departed but little from the early ideas
of Young and Fresnel. It is assumed on all sides that
the ether is a continuous, incompressible body, possess-
ing rigidity and elasticity. Lord Kelvin has even cal-
culated the probable density of this ether, and its coeffi-
cient of rigidity. As might be supposed, it is all but
infinitely tenuous as compared with any tangible solid,
and its rigidity is but infinitesimal as compared with
that of steel. In a word, it combines properties of
tangible matter in a way not known in any tangible
substance. Therefore we cannot possibly conceive its
true condition correctly. The nearest approximation,
according to Lord Kelvin, is furnished by a mould of
transparent jell}'. It is a crude, inaccurate analogy, of
course, the density and resistance of jelly in particular
being utterly different from those of the ether ; but the
235
THE STORY OF NINETEENTH-CENTURY SCIENCE
quivers that run through the jelly when it is shaken,
and the elastic tension under which it is placed when its
mass is twisted about, furnish some analogy to the quiv-
ers and strains in the ether, which are held to constitute
radiant energy, magnetism, and electricity.
The great physicists of the day being at one regarding
the existence of this all-pervading ether, it would be a
manifest presumption for any one standing without the
pale to challenge so firmly rooted a belief. And, in-
deed, in any event, there seems little ground on which
to base such a challenge. Yet it may not be altogether
amiss to reflect that the physicist of to-day is no more
certain of his ether than was his predecessor of the
eighteenth century of the existence of certain alleged
substances which he called phlogiston, caloric, corpuscles
of light, and magnetic and electric fluids. It would be
but the repetition of history should it chance that be-
fore the close of another century the ether should have
taken its place along with these discarded creations of
the scientific imagination of earlier generations. The
philosopher of to-day feels very sure that an ether ex-
ists ; but when he says there is " no doubt " of its exist-
ence he speaks incautiously, and steps beyond the bounds
of demonstration. He does not know that action cannot
take place at a distance ; he does not know that empty
space itself may not perform the functions which he
ascribes to his space-filling ether.
n
Meantime, however, the ether, be it substance or be
it only dream-stuff, is serving an admirable purpose in
furnishing a fulcrum for modern physics. Not alone
THE ETHER AND PONDERABLE MATTER
to the student of energy has it proved invaluable, but to
the student of matter itself as well. Out of its hypo-
HERMANN LTTDWIO FERDINAND TTELMHOLTZ
From a photograph by Loescher and Petsch. Berlin
THE STORY OF NINETEENTH-CENTURY SCIENCE
thetical mistiness has been reared the most tenable
theory of the constitution of ponderable matter which
has yet been suggested — or, at any rate, the one that
will stand as the definitive nineteenth-century guess at
this " riddle of the ages." I mean, of course, the vortex
theory of atoms — that profound and fascinating doctrine
which suggests that matter, in all its multiform phases,
is nothing more or less than ether in motion.
The author of this wonderful conception is Lord Kel-
vin. The idea was born in his mind of a happy union
of mathematical calculations with concrete experiments.
The mathematical calculations were largely the work of
Hermann von Helmholtz, who, about the year 1858, had
undertaken to solve some unique problems in vortex
motions. Helmholtz found that a vortex whirl, once es-
tablished in a frictionless medium, must go on, theoret-
ically, unchanged forever. In a limited medium such a
whirl may be Y-shaped, with its ends at the surface of
the medium. We may imitate such a vortex by drawing
the bowl of a spoon quickly through a cup of water.
But in a limitless medium the vortex whirl must always
be a closed ring, which may take the simple form of a
hoop or circle, or which may be indefinitely contorted,
looped, or, so to speak, knotted. Whether simple or
contorted, this endless chain of whirling matter (the
particles revolving about the axis of the loop as the par-
ticles of a string revolve when the string is rolled be-
tween the fingers) must, in a frictionless medium, retain
its form, and whirl on with undiminished speed forever.
While these theoretical calculations of Helmholtz were
fresh in his mind, Lord Kelvin (then Sir William Thom-
son) was shown by Professor P. G. Tait, of Edinburgh,
an apparatus constructed for the purpose of creating
238
THE ETHER AND PONDERABLE MATTER
vortex rings in air. The apparatus, which any one may
duplicate, consisted simply of a box with a hole bored
in one side, and a piece of canvas stretched across the
opposite side in lieu of boards. Fumes of chloride of
ammonia are generated within the box, merely to render
the air visible. By tapping with the hand on the canvas
side of the box, vortex rings of the clouded air are driven
out, precisely similar in appearance to those smoke-rings
which some expert tobacco-smokers can produce by tap-
ping on their cheeks, or to those larger ones which we
sometimes see blown out from the funnel of a locomo-
tive.
The advantage of Professor Tait's apparatus is its
manageableness, and the certainty with which the de-
sired result can be produced. Before Lord Kelvin's in-
terested observation it threw out rings of various sizes,
which moved straight across the room at varying rates
of speed, according to the initial impulse, and which be-
haved very strangely when coming in contact with one
another. If, for example, a rapidly moving ring over-
took another moving in the same path, the one in ad-
vance seemed to pause, and to spread out its periphery
like an elastic band, while the pursuer seemed to con-
tract, till it actually slid through the orifice of the other,
after which each ring resumed its original size, and con-
tinued its course as if nothing had happened. When, on
the other hand, two rings moving in slightly different di-
rections came near each other, they seemed to have an
attraction for each other ; yet if they impinged, they
bounded away, quivering like elastic solids. If an effort
were made to grasp or to cut one of these rings, the subtle
thing shrunk from the contact, and slipped away as if it
were alive.
239
THE STORY OF NINETEEXTII-CENTURY SCIENCE
And all the while the body which thus conducted
itself consisted simply of a whirl in the air, made visi-
ble, but not otherwise influenced, by smoky fumes.
Presently the friction of the surrounding air wore the
ring away, and it faded into the general atmosphere—
often, however, not until it had persisted for many sec-
onds, and passed clear across a large room. Clearly, if
there were no friction, the ring's inertia must make it a
permanent structure. Only the frictionless medium was
lacking to fulfil all the conditions of Helmholtz's inde-
structible vortices. And at once Lord Kelvin bethought
him of the frictionless medium which physicists had now
begun to accept — the all-pervading ether. What if vor-
tex rings were started in this ether, must they not have
the properties which the vortex rings in air had exhib-
ited— inertia, attraction, elasticity ? And are not these
the properties of ordinary tangible matter? Is it not
probable, then, that what we call matter consists merely
of aggregations of infinitesimal vortex rings in the
ether?
Thus the vortex theory of atoms took form in Lord
Kelvin's mind, and its expression gave the world what
many philosophers of our time regard as the plausible
conception of the constitution of matter hitherto formu-
lated. It is only a theory, to be sure ; its author would
be the last person to claim finality for it. "It is only a
dream," Lord Kelvin said to me, in referring to it not long
ago. But it has a basis in mathematical calculation and
in analogical experiment such as no other theory of mat-
ter can lay claim to, and it has a unifying or monistic
tendency that makes it, for the philosophical mind, little
less than fascinating. True or false, it is the definitive
theory of matter of the nineteenth century.
240
THE ETHER AND PONDERABLE MATTER
in
Quite aside from the question of the exact constitu-
tion of the ultimate particles of matter, questions as to
the distribution of such particles, their mutual relations,
properties, and actions, have come in for a full share of
attention during our century, though the foundations
for the modern speculations were furnished in a pre-
vious epoch. The most popular eighteenth - century
speculation as to the ultimate constitution of matter
was that of the learned Italian priest, Roger Joseph
Boscovich, published in 1758, in his Theoria Philoso-
phies Naturalis. " In this theory," according to an
early commentator, " the whole mass of which the
bodies of the universe are composed is supposed to con-
sist of an exceedingly great yet finite number of simple,
indivisible, inextended atoms. These atoms are endued
by the Creator with repulsive and attractive forces,
which vary according to the distance. At very small
distances the particles of matter repel each other ; and
this repulsive force increases beyond all limits as the
distances are diminished, and will consequently forever
prevent actual contact. When the particles of matter
are removed to sensible distances, the repulsive is ex-
changed for an attractive force, which decreases in in-
verse ratio with the squares of the distances, and extends
beyond the spheres of the most remote comets."
This conception of the atom as a mere centre of force
was hardly such as could satisfy any mind other than
the metaphysical. No one made a conspicuous attempt
to improve upon the idea, however, till just at the close
of the century, when Humphry Davy was led, in the
course of his studies of heat, to speculate as to the
q 341
THE STORY OF NINETEENTH-CENTURY SCIENCE
changes that occur in the intimate substance of matter
under altered conditions of temperature. Davy, as \ve
have seen, regarded heat as a manifestation of motion
among the particles of matter. As all bodies with
which we come in contact have some temperature, Davy
inferred that the intimate particles of every substance
must be perpetually in a state of vibration. Such vibra-
tions, he believed, produced the " repulsive force" which
(in common with Boscovich) he admitted as holding the
particles of matter at a distance from one another. To
heat a substance means merely to increase the rate of
vibration of its particles; thus also, plainly, increasing
the repulsive forces, and expanding the bulk of the mass
as a whole. If the degree of heat applied be sufficient,
the repulsive force may become strong enough quite to
overcome the attractive force, and the particles will sep-
arate and tend to fly away from one another, the solid
then becoming a gas.
Not much attention was paid to these very suggestive
ideas of Davy, because they were founded on the idea
that heat is merely a motion, which the scientific world
then repudiated ; but half a century later, when the new
theories of energy had made their way, there came a
revival of practically the same ideas of the particles of
matter (molecules they were now called) which Davy
had advocated. Then it was that Clausius in Germany
and Clerk Maxwell in England took up the investigation,
of what came to be known as the kinetic theory of gases
—the now familiar conception that all the phenomena
of gases are due to the helter-skelter flight of the show-
ers of widely separated molecules of which they are
composed. The specific idea that the pressure or
"spring" of gases is due to such molecular impacts was
243
THE ETIIER AXD PONDERABLE MATTER
due to Daniel Bournelli, who advanced it early in the
eighteenth century. The idea, then little noticed, had
been revived about a century later by William Hera-
path, and again with some success by J. J. "Waterston,
of Bombay, about 18i6; but it gained no distinct foot-
ing until taken in hand by Clausius in 1857 and by
Maxwell in 1859.
The investigations of these great physicists not only
served fully to substantiate the doctrine, but threw a
flood of light upon the entire subject of molecular dy-
namics. Soon the physicists came to feel as certain of
the existence of these showers of flying molecules mak-
ing up a gas as if they could actually see and watch
their individual actions. Through study of the viscosity
of gases — that is to say, of the degree of frictional oppo-
sition they show to an object moving through them or
to another current of gas — an idea was gained, with the
aid of mathematics, of the rate of speed at which the
particles of the gas are moving, and the number of col-
lisions which each particle must experience in a given
time, and of the length of the average free path trav-
ersed by the molecule between collisions. These meas-
urements were confirmed by study of the rate of diffusion
at which different gases mix together, and also by the
rate of diffusion of heat through a gas, both these phe-
nomena being chiefly due to the helter-skelter flight of
the molecules.
It is sufficiently astonishing to be told that such
measurements as these have been made at all, but the
astonishment grows when one hears the results. It ap-
pears from Maxwell's calculations that the mean free
path, or distance traversed by the molecules between
collisions in ordinar}^ air, is about one half-millionth of
243
THE STORY OF NINETEENTH-CENTURY SCIENCE
an inch ; while the speed of the molecules is such that
each one experiences about eight billions of collisions
per second ! It would be hard, perhaps, to cite an illus-
tration showing the refinements of modern physics bet-
ter than this ; unless, indeed, one other result that fol-
lowed directly from these calculations be considered
such — the feat, namely, of measuring the size of the
molecules themselves. Clausius was the first to point
out how this might be done from a knowledge of the
length of free path ; and the calculations were made by
Loschmidt in Germany, and by Lord Kelvin in England,
independently.
The work is purely mathematical, of course, but the
results are regarded as unassailable ; indeed, Lord Kelvin
speaks of them as being absolutely demonstrative within
certain limits of accuracy. This does not mean, how-
ever, that they show the exact dimensions of the mole-
cule ; it means an estimate of the limits of size within
which the actual size of the molecule may lie. These
limits, Lord Kelvin estimates, are about the one ten-
millionth of a centimetre for the maximum, and the one
one-hundred-millionth of a centimetre for the minimum.
Such figures convey no particular meaning to our blunt
senses, but Lord Kelvin has given a tangible illustration
that aids the imagination to at least a vague comprehen-
sion of the unthinkable smallness of the molecule. He
estimates that if a ball, say of water or glass, about " as
large as a football, were to be magnified up to the size
of the earth, each constituent molecule being magnified
in the same proportion, the magnified structure would
be more coarse-grained than a heap of shot, but proba-
bly less coarse-grained than a heap of footballs."
Several other methods have been employed to estimate
244
THE ETI1ER AND PONDERABLE MATTER
the size of molecules. One of these is based upon the
phenomena of contact electricity ; another upon the
wave-theory of light; and another upon capillary at-
traction, as shown in the tense film of a soap-bubble !
No one of these methods gives results more definite than
that due to the kinetic theory of gases, just outlined ;
but the important thing is that the results obtained by
these different methods (all of them due to Lord Kelvin)
agree with one another in fixing the dimensions of the
molecule at somewhere about the limits already men-
tioned. We may feel very sure indeed, therefore, that
the ultimate particles of matter are not the unextended,
formless points which Boscovich and his followers of the
last century thought them.
IV
Whatever the exact form of the molecule, its outline is
subject to incessant variation ; for nothing in molecular
science is regarded as more firmly established than that
the molecule, under all ordinary circumstances, is in a
state of intense but variable vibration. The entire en-
ergy of a molecule of gas, for example, is not measured
by its momentum, but by this plus its energy of vibra-
tion and rotation, due to the collisions already referred
to. Clausius has even estimated the relative importance
of these two quantities, showing that the translational
motion of a molecule of gas accounts for only three-
fifths of its kinetic energy. The total energy of the
molecule (which we call " heat ") includes also another
factor, namely, potential energy, or energy of position,
due to the work that has been done on expanding, in
overcoming external pressure, and internal attraction
245
THE STORY OF NINETEENTH-CENTURY SCIENCE
between the molecules themselves. This potential en-
ergy (which will be recovered when the gas contracts) is
the "latent heat" of Black, which so long puzzled the
philosophers. It is latent in the same sense that the en-
ergy of a ball thrown into the air is latent at the mo-
ment when the ball poises at its greatest height before
beginning to fall.
It thus appears that a variety of motions, real and po-
tential, enter into the production of the condition we
term heat. It is, however, chiefly the translational mo-
tion which is measurable as temperature ; and this, too,
which most obviously determines the physical state of
the substance that the molecules collectively compose —
whether, that is to say, it shall appear to our blunt per-
ceptions as a gas, a liquid, or a solid. In the gaseous
state, as we have seen, the translational motion of the
molecules is relatively enormous, the molecules being
widely separated. It does not follow, as we formerly
supposed, that this is evidence of a repulsive power act-
ing between the molecules. The physicists of to-day,
headed by Lord Kelvin, decline to recognize any such
power. They hold that the molecules of a gas fly in
straight lines in virtue of their inertia, quite indepen-
dently of one another, except at times of collision, from
which they rebound in virtue of their elasticity ; or an
approach to collision, in which latter case, coming with-
in the range of mutual attraction, two molecules may
circle about one another, as a comet circles about the
sun, then rush apart again, as the comet rushes from
the sun.
It is obvious that the length of the mean free path of
the molecules of a gas may be increased indefinitely by
decreasing the number of the molecules themselves in a
346
THE ETHER AND PONDERABLE MATTER
circumscribed space. It has been shown b}^ Professors
Tait and Dewar that a vacuum may be produced arti-
ficially of such a degree of rarefaction that the mean
free path of the remaining molecules is measurable in
inches. The calculation is based on experiments made
with the radiometer of Professor Crookes, an instru-
ment which in itself is held to demonstrate the truth of
the kinetic theory of gases. Such an attenuated gas as
this is considered by Professor Crookes as constituting a
fourth state of matter, which he terms ultra-gaseous.
If, on the other hand, a gas is subjected to pressure,
its molecules are crowded closer together, and the length
of their mean free path is thus lessened. Ultimately, the
pressure being sufficient, the molecules are practically
in continuous contact. Meantime the enormously in-
creased number of collisions has set the molecules more
and more actively vibrating, and the temperature of the
gas has increased, as, indeed, necessarily results in ac-
cordance with the law of the conservation of energy.
No amount of pressure, therefore, can suffice by itself to
reduce the gas to a liquid state. It is believed that
even at the centre of the sun, where the pressure is al-
most inconceivably great, all matter is to be regarded as
really gaseous, though the molecules must be so packed
together that the consistency is probably more like that
of a solid.
If, however, coincidently with the application of press-
ure, opportunity be given for the excess of heat to be
dissipated to a colder surrounding medium, the mole-
cules, giving off their excess of energy, become relative-
ly quiescent, and at a certain stage the gas becomes a
liquid. The exact point at which this transformation
occurs, however, differs enormously for different sub-
347
THE STORY OF NINETEENTH-CEiNTURY SCIENCE
stances. In the case of water, for example, it is a tem-
perature more than four hundred degrees above zero,
Centigrade; while for atmospheric air it is 191° Centi-
grade below zero, or more than a hundred and fifty de-
grees below the point at which mercury freezes.
Be it high or low, the temperature above which any
substance is always a gas, regardless of pressure, is
called the critical temperature, or absolute boiling-point,
of that substance. It does not follow, however, that
below this point the substance is necessarily a liquid.
This is a matter that will be determined by external
conditions of pressure. Even far below the critical tem-
perature the molecules have an enormous degree of ac-
tivity, and tend to fly asunder, maintaining what ap-
pears to be a gaseous, but what technically is called a
vaporous, condition — the distinction being that pressure
alone suffices to reduce the vapor to the liquid state.
Thus water may change from the gaseous to the liquid
state at four hundred degrees above zero, but under
conditions of ordinary atmospheric pressure it does not
do so until the temperature is lowered three hundred
degrees further. Below four hundred degrees, however,
it is technically a vapor, not a gas ; but the sole differ-
ence, it will be understood, is in the degree of molecular
activity.
It thus appears that the prevalence of water in a
vaporous and liquid rather than in a " permanently "
gaseous condition here on the globe is a mere incident
of telluric evolution. Equally incidental is the fact that
the air we breathe is " permanently " gaseous and not
liquid or solid, as it might be were the earth's surface
temperature to be lowered to a degree which, in the
larger view, may be regarded as trifling. Between the
348
TUE ETHER AND PONDERABLE MATTER
atmospheric temperature in tropical and in arctic regions
there is often a variation of more than one hundred de-
grees ; were the temperature reduced another hundred,
the point would be reached at which oxygen gas becomes
a vapor, and under increased pressure would be a liquid.
Thirty-seven degrees more would bring us to the critical
temperature of nitrogen.
Nor is this a mere theoretical assumption ; it is a
determination of experimental science, quite indepen-
dent of theory. The physicist in the laboratory has
produced artificial conditions of temperature enabling
him to change the state of the most persistent gases.
Some fifty years since, when the kinetic theory was in
its infancy, Faraday liquefied carbonic acid gas, among
others, and the experiments thus inaugurated have been
extended by numerous more recent investigators, notably
by Cailletet in Switzerland, by Pictet in France, and by
Dr. Thomas Andrews and Professor James Dewar in
England. In the course of these experiments not only
has air been liquefied, but hydrogen also, the most subtle
of gases ; and it has been made more and more apparent
that gas and liquid are, as Andrews long ago asserted,
" only distant stages of a long series of continuous phys-
ical changes." Of course if the temperature be lowered
still further, the liquid becomes a solid ; and this change
also has been effected in the case of some of the most
" permanent " gases, including air.
The degree of cold — that is, of absence of heat — thus
produced is enormous, relatively to anything of which
we have experience in nature here at the earth now,
yet the molecules of solidified air, for example, are not
absolutely quiescent. In other words, they still have a
temperature, though so very low. But it is clearly con-
249
THE STORY OF NINETEENTH-CENTURY SCIENCE
ceivable that a stage might be reached at which the
molecules became absolutely quiescent, as regards either
translational or vibratory motion. Such a heatless con-
dition has been approached, but as yet not quite attained,
in laboratory experiments. It is called the absolute
zero of temperature, and is estimated to be equivalent
to 273° Centigrade below the freezing-point of water, or
ordinary zero.
A temperature (or absence of temperature) closely
approximating this is believed to obtain in the ethereal
ocean of interplanetary and interstellar space, which
transmits, but is thought not to absorb, radiant energy.
We here on the earth's surface are protected from ex-
posure to this cold, which would deprive every organic
thing of life almost instantaneously, solely by the thin
blanket of atmosphere with which the globe is coated.
It would seem as if this atmosphere, exposed to such a
temperature at its surface, must there be incessantly
liquelied, and thus fall back like rain to be dissolved
into gas again while it still is many miles above the
earth's surface. This may be the reason why its scurry-
ing molecules have not long ago wandered off into space,
and left the world without protection.
But whether or not such liquefaction of the air now
occurs in our outer atmosphere, there can be no question
as to what must occur in its entire depth were we per-
manently shut off from the heating influence of the sun,
as the astronomers threaten that we may be in a future
age. Each molecule, not alone of the atmosphere, but of
the entire earth's substance, is kept aquiver by the energy
which it receives, or has received, directly or indirectly,
from the sun. Left to itself, each molecule would wear
out its energy and fritter it off into the space about it,
250
THE ETHER AND PONDERABLE MATTER
ultimately running completely down, as surely as any
human-made machine whose power is not from time to
time restored. If then it shall come to pass in some
future age that the sun's rays fail us, the temperature
of the globe must gradually sink towards the absolute
zero. That is to say, the molecules of gas which now
fly about at such inconceivable speed must drop helpless
to the earth ; liquids must in turn become solids ; and
solids themselves, their molecular quivers utterly stilled,
may perhaps take on properties the nature of which we
cannot surmise.
Yet even then, according to the current hypothesis,
the heatless molecule will still be a thing instinct with
life. Its vortex whirl will still go on, uninfluenced by
the dying out of those subordinate quivers that produced
the transitory effect which we call temperature. For
those transitory thrills, though determining the physical
state of matter as measured by our crude organs of sense,
were no more than non-essential incidents; but the vortex
whirl is the essence of matter itself.
CHAPTER VIII
THE CENTURY'S PROGRESS IN CHEMISTRY
SMALL beginnings have great endings — sometimes.
As a case in point, note what came of the small original
effort of a self-trained back-country Quaker youth named
John Dal ton, who along towards the close of the last
century became interested in the weather, and was led
to construct and use a crude rain-gauge to test the
amount of the waterfall. The simple experiments thus
inaugurated led to no fewer than two hundred thousand
recorded observations regarding the weather, which
formed the basis for some of the most epochal discov-
eries in meteorology, as we have seen. But this was
only a beginning. The simple rain-gauge pointed the
way to the most important generalization of our century
in a field of science with which, to the casual observer,
it might seem to have no alliance whatever. The won-
derful theory of atoms, on which the whole gigantic
structure of modern chemistry is founded, was the logical
outgrowth, in the mind of John Dalton, of those early
studies in meteorology.
The way it happened was this : From studying the
rainfall, Dalton turned naturally to the complementary
process of evaporation. He was soon led to believe that
353
THE CENTURY'S PROGRESS IN CHEMISTRY
vapor exists in the atmosphere as an independent gas.
But since two bodies cannot occupy the same space at
the same time, this implies that the various atmospheric
gases are really composed of discrete particles. These ,
ultimate particles are so small that we cannot see them
— cannot, indeed, more than vaguely imagine them—
yet each particle of vapor, for example, is just as much
a portion of water as if it were a drop out of the ocean,
or, for that matter, the ocean itself. But again, water
is a compound substance, for it may be separated, as
Cavendish had shown, into the two elementary sub-
stances hvdrogen and oxvgren. Hence the atom of
*/ •/ o
water must be composed of two lesser atoms joined
together. Imagine an atom of hydrogen and one of
oxygen. Unite them, and we have an atom of water ;
sever them, and the water no longer exists ; but whether
united or separate the atoms of hydrogen and of oxygen
remain hydrogen and oxygen and nothing else. Differ-
ently mixed together or united, atoms produce different
gross substances; but the elementary atoms never change
their chemical nature — their distinct personality.
It was about the year 1803 that Dalton first gained a
full grasp of the conception of the chemical atom. At
once he saw that the hypothesis, if true, furnished a
marvellous key to secrets of matter hitherto insoluble —
questions relating to the relative proportions of the
atoms themselves. It is known, for example, that a
certain bulk of hydrogen gas unites with a certain bulk
of oxygen gas to form water. If it be true that this
combination consists essentially of the union of atoms
one with another (each single atom of hydrogen united
to a single atom of oxygen), then the relative weights
of the original masses of hydrogen and of oxygen must
203
THE STORY OF NINETEENTH-CENTURY SCIENCE
be also the relative weights of each of their respective
atoms. If one pound of hydrogen unites with five and
one-half pounds of oxygen (as, according to Dalton's
experiments, it did), then the weight of the oxygen
JOTTN D ALTON
atom must be five and one-half times that of the hydro-
gen atom. Other compounds may plainly be tested in
the same way. Dalton made numerous tests before he
published his theory. He found that hydrogen enters
into compounds in smaller proportions than any other
element known to him, and so, for convenience, deter-
mined to take the weight of the hydrogen atom as unity.
254
THE CENTURY'S PROGRESS IN CHEMISTRY
The atomic weight of oxygen then becomes (as given in
Dalton's first table of 1803) 5.5 ; that of water (hydrogen
plus oxygen) being of course 6.5. The atomic weights
of about a score of substances are given in Dalton's first
paper, which was read before the Literary and Philo-
sophical Society of Manchester, October 21, 1803. 1
wonder if Dalton himself, great and acute intellect
though he had, suspected, when he read that paper, that
he was inaugurating one of the most fertile movements
ever entered on in the whole history of science ?
IT
Be that as it may, it is certain enough that Dalton's
contemporaries were at first little impressed with the
novel atomic theory. Just at this time, as it chanced, a
dispute was waging in the field of chemistry regarding
a matter of empirical fact which must necessarily be
settled before such a theory as that of Dalton could
even hope for a hearing. This was the question whether
or not chemical elements unite with one another always
in definite proportions. Berthollet, the great co-worker
with Lavoisier, and now the most authoritative of living
chemists, contended that substances combine in almost
indefinitely graded proportions between fixed extremes.
He held that solution is really a form of chemical com-
bination— a position which, if accepted, left no room for
argument.
But this contention of the master was most actively
disputed, in particular by Louis Joseph Proust, and alJ
chemists of repute were obliged to take sides with one
or the other. For a time the authority of Berthollet
held out against the facts, but at last accumulated evi-
255
THE STORY OF NINETEENTH-CENTURY SCIENCE
dence told for Proust and his followers, and towards the
close of the first decade of our century it came to be
generally conceded that chemical elements combine with
one another in fixed and definite proportions.
More than that. As the analysts were led to weigh
carefully the quantities of combining elements, it was
observed that the proportions are not only definite, but
that they bear a very curious relation to one another.
It element A combines with two different proportions of
element B to form two compounds, it appeared that the
weight of the larger quantity of B is an exact multiple
of that of the smaller quantity. This curious relation
was noticed by Dr. Wollaston, one of the most accurate
of observers, and a little later it was confirmed by Johan
Jakob Berzelius, the great Swedish chemist, who was to
be a dominating influence in the chemical world for a
generation to come. But this combination of elements
in numerical proportions was exactly what Dalton had
noticed as early as 1802, and what had led him directly
to the atomic weights. So the confirmation of this
essential point by chemists of such authority gave the
strongest confirmation to the atomic theory.
During these same years the rising authority of the
French chemical world, Joseph Louis Gay-Lussac, was
conducting experiments with gases, which he had un-
dertaken at first in conjunction with Humboldt, but
which later on were conducted independently. In 1809,
the next year after the publication of the first volume
of Dalton's New System of Chemical Philosophy, Gay-
Lussac published the results of his observations, and
among other things brought out the remarkable fact
that gases, under the same conditions as to temperature
and pressure, combine always in definite numerical
256'
THE CENTURY'S PROGRESS IN CHEMISTRY
proportions as to volume. Exactly two volumes of
hydrogen, for example, combine with one volume of
oxygen to form water. Moreover, the resulting com-
pound gas always bears a simple relation to the com-
bining volumes. In the case just cited the union of two
JOSEPH LOUIS GAY-I,USSAC
volumes of hydrogen and one of oxygen results in pre-
cisely two volumes of water vapor.
Naturally enough the champions of the atomic theory
seized upon these observations of Gay-Lussac as lending
strong support to their hypothesis — all of them, that is,
but the curiously self-reliant and self-sufficient author of
the atomic theory himself, who declined to accept the
B 257
THE STORY OF NINETEENTH-CENTURY SCIENCE
observations of the French chemist as valid. Yet the
observations of Gay-Lussac were correct, as countless
chemists since then have demonstrated anew, and his
theory of combination by volumes became one of the
foundation-stones of the atomic theory, despite the op-
position of the author of that theory.
The true explanation of Gay-Lussac's law of combina-
tion by volumes was thought out almost immediately by
an Italian savant, Amadeo Avogadro, and expressed in
terms of the atomic theory. The fact must be, said
Avogadro, that under similar physical conditions every
form of gas contains exactly the same number of ulti-
mate particles in a given volume. Each of these ulti-
mate physical particles may be composed of two or more
atoms (as in the case of water vapor), but such a com-
pound atom conducts itself as if it were a simple and
indivisible atom, as regards the amount of space that sep-
arates it from its fellows under given conditions of press-
ure and temperature. The compound atom, composed
of two or more elementary atoms, Avogadro proposed
to distinguish, for purposes of convenience, by the name
molecule. It is to the molecule, considered as the
unit of physical structure, that Avogadro's law applies.
This vastly important distinction between atoms and
molecules, implied in the law just expressed, was pub-
lished in 1811. Four years later, the famous French
physicist Ampere outlined a similar theory, and utilized
the law in his mathematical calculations. And with that
the law of Avogadro dropped out of sight for a full gen-
eration. Little suspecting that it was the very key to
the inner mysteries of the atoms for which they were
seeking, the chemists of the time cast it aside, and let
it fade from the memory of their science.
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THE CENTURY'S PROGRESS IN CHEMISTRY
This, however, was not strange, for of course the law
of Avogadro is based on the atomic theory, and in 1811
the atomic theory was itself still being weighed in the
balance. The law of multiple proportions found general
acceptance as an empirical fact ; but many of the leading
lights of chemistry still looked askance at D.alton's ex-
planation of this law. Thus Wollaston, though from
the first he inclined to acceptance of the Daltonian view,
cautiously suggested that it would be well to use the
non-committal word "equivalent" instead of "atom";
and Davy, for a similar reason, in his book of 1812,
speaks only of " proportions," binding himself to no
theory as to what might be the nature of these propor-
tions.
At least two great chemists of the time, however, adopt-
ed the atomic view with less reservation. One of these
was Thomas Thomson, professor at Edinburgh, who in
1807 had given an outline of Dalton's theory in a widely
circulated book, which first brought the theory to the
general attention of the chemical world. The other,
and even more noted advocate of the atomic theory,
was Johan Jakob Berzelius. This great Swedish chem-
ist at once set to work to put the atomic theory to such
tests as might be applied in the laboratory. He was an
analyst of the utmost skill, and for years he devoted
himself to the determination of the combining weights,
"equivalents," or "proportions" of the different ele-
ments. These determinations, in so far as they were
accurately made, were simple expressions of empirical
facts, independent of any theory ; but gradually it be-
came more and more plain that these facts all har-
monize with the atomic theory of Dalton. So by com-
mon consent the proportionate combining weights of
259
THE STORY OF NINETEENTH-CENTURY SCIENCE
the elements came to be known as atomic weights —
the name Dalton had given them from the first — and
the tangible conception of the chemical atom as a body
of definite constitution and weight gained steadily in
favor.
From the outset the idea had had the utmost tangibil-
ity in the mind of Dalton. He had all along represented
the different atoms by geometrical symbols — as a circle
for oxygen, a circle enclosing a dot for hydrogen, and
the like — and had represented compounds by placing
these symbols of the elements in juxtaposition. Berzelius
proposed to improve upon this method by substituting
for the geometrical symbol the initial of the Latin name
of the element represented — O for oxygen, H for hy-
drogen, and so on — a numerical coefficient to follow
the letter as an indication of the number of atoms pres-
ent in any given compound. This simple system soon
gained general acceptance, and with slight modifica-
tions it is still universally employed. Every school-
boy now is aware that H2O is the chemical way of ex-
pressing the union of two atoms of hydrogen with one
of oxygen to form a molecule of water. But such a
formula would have had no meaning for the wisest
chemist before the day of Berzelius.
The universal fame of the great Swedish authority
served to give general currency to his symbols and
atomic weights, and the new point of view thus devel-
oped led presently to two important discoveries which
removed the last lingering doubts as to the validity
of the atomic theory. In 1819 two French physicists,
Dulong and Petit, while experimenting with heat, dis-
covered that the specific heats of solids (that is to say,
the amount of heat required to raise the temperature of
260
THE CENTURY'S PROGRESS IN CHEMISTRY
a given mass to a given degree) vary inversely as their
atomic weights. In the same year Eilhard Mitscherlich,
a German investigator, observed that compounds having
the same number of atoms to the molecule are disposed
to form the same angles of crystallization — a property
which he called isomorphism.
JOHAN JAKOB BERZEHUS
Here, then, were two utterly novel and independent
sets of empirical facts which harmonize strangely with
the supposition that substances are composed of chemical
atoms of a determinate weight. This surely could not
be coincidence — it tells of law. And so as soon as the
claims of Dulong and Petit and of Mitscherlich had
been substantiated by other observers, the laws of the
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THE STORY OF NINETEENTH-CENTURY SCIENCE
specific heat of atoms, and of isomorphism, took their
place as new levers of chemical science. With the aid
of these new tools an impregnable breastwork of facts
was soon piled about the atomic theory. And John
Dalton, the author of that theory, plain, provincial
Quaker, working on to the end in semi-retirement, be-
came known to all the world and for all time as a mas-
ter of masters.
in
During those early years of our century, when Dalton
was grinding away at chemical fact and theory in his
obscure Manchester laboratory, another Englishman held
the attention of the chemical world with a series of the
most brilliant and widely heralded researches. Hum-
phry Davy had come to London in 1801, at the instance
of Count Rumford, to assume the chair of chemical phi-
losophy in the Royal Institution, which the famous
American had just founded.
Here, under Davy's direction, the largest voltaic bat-
tery yet constructed had been put in operation, and with
its aid the brilliant young experimenter was expected al-
most to perform miracles. And indeed he scarcety disap-
pointed the expectation, for with the aid of his battery
he transformed so familiar a substance as common pot-
ash into a metal which wras not only so light that it
floated on water, but possessed the seemingly mirac-
ulous property of bursting into flames as soon as it
came in contact with that fire-quenching liquid. If
this were not a miracle, it had for the popular eye all
the appearance of the miraculous.
What Davy really had done was to decompose the
potash, which hitherto had been supposed to be elemen-
262
THE CENTURY'S PROGRESS IN CHEMISTRY
ttirv, liberating its oxy gen, and thus isolating its metallic
base, which he named potassium. The same thing \vas
done with soda, and the closely similar metal sodium
was discovered — metals of a unique type, possessed of a
strange avidity for oxygen, and capable of seizing on it
even when it is bound up in the molecules of water.
Considered as mere curiosities, these discoveries were in-
teresting, but aside from that they were of great theo-
retical importance, because they showed the compound
nature of some familiar chemicals that had been re-
garded as elements. Several other elementary earths
met the same fate when subjected to the electrical in-
fluence, the metals barium, calcium, and strontium being
thus discovered. Thereafter Davy always referred to
the supposed elementary substances (including oxygen,
hydrogen, and the rest) as " undecompounded" bodies.
These resist all present efforts to decompose them, but
how can one know what might not happen were they
subjected to an influence, perhaps some day to be dis-
covered, which exceeds the battery in power as the bat-
tery exceeds the blow-pipe?
Another and even more important theoretical result
that flowed from Davy's experiments during th'is first
decade of the century was the proof that no elementary
substances other than hydrogen and oxygen are produced
when pure water is decomposed by the electric current.
It was early noticed by Davy and others that when a
strong current is passed through water, alkalies appear
at one pole of the battery and acids at the other, and
this though the water used were absolutely pure. This
seemingly told of the creation of elements — a transmuta-
tion but one step removed from the creation of matter
itself — -under the influence of the new "force." It was
263
THE STORY OF NINETEENTH-CENTURY SCIENCE
one of Davy's greatest triumphs to prove, in the series
of experiments recorded in His famous Bakerian lecture
of 1806, that the alleged creation of elements did not
take place, the substances found at the poles of the bat-
tery having been dissolved from the walls of the vessels
in which the water experimented upon had been placed.
Thus the same implement which had served to give a
certain philosophical warrant to the fading dreams of
alchemy banished those dreams peremptorily from the
domain of present science.
Though the presence of the alkalies and acids in the
water was explained, however, their respective migra-
tions to the negative and positive poles of the battery
remained to be accounted for. Davy's classical expla-
nation assumed that different elements differ among
o
themselves as to their electrical properties, some being
positively, others negatively, electrified. Electricity
and "chemical affinity," he said, apparently are mani-
festations of the same force, acting in the one case on
masses, in the other on particles. Electro-positive par-
ticles unite with electro-negative particles to form chem-
ical compounds, in virtue of the familiar principle that
opposite electricities attract one another. When com-
pounds are decomposed by the battery, this mutual at-
traction is overcome by the stronger attraction of the
poles of the battery itself.
This theory of binary composition of all chemical
compounds, through the union of electro-positive and
electro-negative atoms or molecules, was extended by
Berzelius, and made the basis of his famous s}rstem of
theoretical chemistry. This theory held that all inor-
ganic compounds, however complex their composition,
are essentially composed of such binary combinations.
264
T11E CENTURY'S PROGRESS IX CHEMISTRY
For many years this view enjoyed almost undisputed
sway. It received what seemed strong confirmation
when Faraday showed the definite connection between
the amount of electricity employed and the amount of
decomposition produced in the so-called electrolyte.
But its claims were really much too comprehensive, as
subsequent discoveries proved.
IV
When Berzelius first promulgated his binary theory
he was careful to restrict its unmodified application to
the compounds of the inorganic world. At that time,
and for a long time thereafter, it was supposed that sub-
stances of organic nature had some properties that kept
them aloof from the domain of inorganic chemistry. It
was little doubted that a so-called " vital force " oper-
ated here, replacing or modifying the action of ordinary
" chemical affinity." It was, indeed, admitted that or-
ganic compounds are composed of familiar elements —
chiefly carbon, oxygen, hydrogen, and nitrogen — but
these elements were supposed to be united in ways that
could not be imitated in the domain of the non-living.
It was regarded almost as an axiom of chemistry that
no organic compound whatever could be put together
from its elements — synthesized — in the laboratory. To
effect the synthesis of even the simplest organic com-
pound it was thought that the " vital force" must be in
operation.
Therefore a veritable sensation was created in the
chemical world when, in the year 1828, it was an-
nounced that the young German chemist Fried rich
Wohler, formerly pupil of Berzelius, and already known
365
THE STORY OF NINETEENTH -CENTURY SCIENCE
as a coining master, had actually synthesized the well-
known organic product urea in his laboratory at Sacrow.
The "exception which proves the rule" is something
never heard of in the domain of logical science. Nat-
ural law knows no exceptions. So the synthesis of a
single organic compound sufficed at a blow to break
down the chemical barrier which the imagination of the
fathers of the science had erected between animate and
inanimate nature. Thenceforth the philosophical chem-
ist would regard the plant and animal organisms as
chemical laboratories in which conditions are peculiarly
favorable for building up complex compounds of a few
familiar elements, under the operation of universal
chemical laws. The chimera " vital force " could no
longer gain recognition in the domain of chemistry.
Now a wave of interest in organic chemistry swept
over the chemical world, and soon the study of carbon
compounds became as much the fashion as electro-chem-
istry had been in the preceding generation.
Foremost among the workers who rendered this epoch
of organic chemistry memorable were Justus Liebig in
Germany and Jean Baptiste Andre Dumas in France,
and their respective pupils, Charles Frederic Gerhardt
and Augustus Laurent. Wohler, too, must be named in
the same breath, as also must Louis Pasteur, who,
though somewhat younger than the others, came upon
the scene in time to take chief part in the most impor-
tant of the controversies that grew out of their labors.
Several years earlier than this the way had been
paved for the study of organic substances by Gay-Lus-
sac's discovery, made in 1815, that a certain compound
of carbon and nitrogen, which he named cyanogen, has
a peculiar degree of stability which enables it to retain
266
THE CENTURY'S PROGRESS IN CHEMISTRY
its identity, and enter into chemical relations after the
«/ '
manner of a simple body. A year later Ampere discov-
ered that nitrogen and hydrogen, when combined in cer-
tain proportions to form what he called ammonium,
JUSTUS VON LIKBIG
have the same property. Berzelius had seized upon this
discovery of the compound radical, as it was called, be-
cause it seemed to lend aid to his dualistic theory. He
conceived the idea that all organic compounds are bi-
nary unions of various compound radicals with an atom
of oxygen, announcing this theory in 1818. Ten years
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THE STORY OF NINETEENTH-CENTURY SCIENCE
later, Liebig and "Wohler undertook a joint investigation
which resulted in proving that compound radicals are
indeed very abundant among organic substances. Thus
the theory of Berzelius seemed to be substantiated, and
organic chemistry came to be defined as the chemistry
of compound radicals.
But even in the day of its seeming triumph the dual-
istic theory was destined to receive a rude shock. This
came about through the investigations of Dumas, who
proved that in a certain organic substance an atom of
hydrogen may be removed, and an atom of chlorine
substituted in its place without destroying the integrity
of the original compound — much as a child might sub-
stitute one block for another in its play-house. Such a
substitution would be quite consistent with the dualistic
theory, were it not for the very essential fact that hy-
drogen is a powerfully electro-positive element, while
chlorine is as strongly electro-negative. Hence the
compound radical which united successively with these
two elements must itself be at one time electro-positive,
at another electro-negative — a seeming inconsistency
which threw the entire Berzelian theory into disfavor.
In its place there was elaborated, chiefly through the
efforts of Laurent and Gerhard t, a conception of the
molecule as a unitary structure, built up through the
aggregation of various atoms, in accordance with " elec-
tive affinities" whose nature is not yet understood. A
doctrine of " nuclei " and a doctrine of " types " of molec-
ular structure were much exploited, and, like the doc-
trine of compound radicals, became useful as aids to
memory and guides for the analyst, indicating some of
the plans of molecular construction, though by no means
penetrating the mysteries of chemical affinity. They
268
THE CENTURY'S PROGRESS IN CHEM1STRV
are classifications rather than explanations of chemical
unions. But at least they served an important purpose
in giving definiteness to the idea of a molecular struct-
ure built of atoms as the basis of all substances. Now
at last the word molecule came to have a distinct mean-
ing, as distinct from "atom," in the minds of -the gener-
ality of chemists, as it had had for Avogadro a third of
a century before. Avogadro's hypothesis that there are
equal numbers of these molecules in equal volumes of
gases, under fixed conditions, was revived by Gerhard t,
and a little later, under the championship of Cannizzaro,
was exalted to the plane of a fixed law. Thenceforth
the conception of the molecule was to be as dominant a
thought in chemistry as the idea of the atom had be-
come in a previous epoch.
Of course the atom itself was in no sense displaced,
but Avogadro's law soon made it plain that the atom had
often usurped territory that did not really belong to it.
In many cases the chemists had supposed themselves
dealing with atoms as units where the true unit was the
molecule. In the case of elementary gases, such as hy-
drogen and oxygen, for example, the law of equal num-
bers of molecules in equal spaces made it clear that the
atoms do not exist isolated, as had been supposed. Since
two volumes of hydrogen unite with one volume of oxy-
gen to form two volumes of water vapor, the simplest
mathematics shows, in the light of Avogadro's law, not
only that each molecule of water must contain two hy-
drogen atoms (a point previously in dispute), but that
the original molecules of hydrogen and oxygen must
269
THE STORY OF NINETEENTH-CENTURY SCIENCE
have been composed in each case of two atoms — else
how could one volume of oxygen supply an atom for
every molecule of two volumes of water?
What, then, does this imply ? Why, that the ele-
mentary atom has an avidity for other atoms, a long-
ing for companionship, an "affinity " — call it what you
will — which is bound to be satisfied if other atoms are
in the neighborhood. Placed solely among atoms of
its own kind, the oxygen atom seizes on a fellow oxy-
gen atom, and in all' their mad dancings these two
mates cling together — possibly revolving about one an-
other in miniature planetary orbits. Precisely the same
thing occurs among the hydrogen atoms. But now
suppose the various pairs of oxygen atoms come near
other pairs of hydrogen atoms (under proper conditions
Avhich need not detain us here), then each oxygen atom
loses its attachment for its fellow, and flings itself madly
into the circuit of one of the hydrogen couplets, and—
presto ! — there are only two molecules for every three
there were before, and free oxygen and hydrogen have
become water. The whole process, stated in chemical
phraseology, is summed up in the statement that under
the given conditions the oxygen atoms had a greater
affinity for the hydrogen atoms than for one another.
As chemists studied the actions of various kinds of
atoms, in regard to their unions with one another to
form molecules, it gradually dawned upon them that
not all elements are satisfied with the same number of
companions. Some elements ask only one, and refuse
to take more ; while others link themselves, when occa-
sion offers, with two, three, four, or more. Thus we
saw that oxygen forsook a single atom of its own kind
and linked itself with two atoms of hydrogen. Clearly,
270
THE CENTURY'S PROGRESS IN CHEMISTRY
then, the oxygen atom, like a creature with two hands,
is able to clutch two other atoms. But we have no
proof that under any circumstances it could hold more
than two. Its affinities seem satisfied when it has two
bonds. But, on the other hand, the atom of nitrogen
is able to hold three atoms of hydrogen, and does so in
the molecule of ammonium (NH3); while the carbon
atom can hold four atoms' of hydrogen or two atoms
of oxygen.
Evidently, then, one atom is not always equivalent to
another atom of a different kind in combining powers.
A recognition of this fact by Frankland about 1852, and
its further investigation by others (notably A. Kekule
and A. S. Couper), led to the introduction of the word
equivalent into chemical terminology in a new sense,
and in particular to an understanding of the affinities
or" valency " of different elements, which proved of the
most fundamental importance. Thus it was shown that,
of the four elements that enter most prominently into
organic compounds, hydrogen can link itself with only
a single bond to any other element — it has, so to speak,
but a single hand with which to grasp — while oxygen
has capacity for two bonds, nitrogen for three (possi-
bly for five), and carbon for four. The words mono-
valent, divalent, trivalent, tretravalent, etc., were coined
to express this most important fact, and the various ele-
ments came to be known as monads, diads, triads, etc.
Just why different elements should differ thus in valency
no one as yet knows ; it is an empirical fact that they
do. And once the nature of any element has been deter-
mined as regards its valency, a most important insight
into the possible behavior of that element has been
secured. Thus a consideration of the fact that hydro-
271
THE STORY OF NINETEENTH-CENTURY SCIENCE
gen is monovalent, while oxygen is divalent, makes it
plain that we must expect to find no more than three
compounds of these two elements, namely, H — O—
(written HO by the chemist, and called hydroxyl);
H— O— H (H2O, or water), and H— O— O— H (H2O2,
or hydrogen peroxide). It will be observed that in the
first of these compounds the atom of oxygen stands, so
to speak, with one of its hands free, eagerly reaching
out, therefore, for another companion, and hence, in the
language of chemistry, forming an unstable compound.
Again, in the third compound, though all hands are
clasped, yet one pair links oxygen with oxygen ; and
this also must be an unstable union, since the avidity of
an atom for its own kind is relatively weak. Thus the
well-known properties of hydrogen peroxide are ex-
plained, its easy decomposition, and the eagerness with
which it seizes upon the elements of other compounds.
But the molecule of water, on the other hand, has its
atoms arranged in a state of stable equilibrium, all their
affinities being satisfied. Each hydrogen atom has sat-
isfied its own affinity by clutching the oxygen atom;
and the oxygen atom has both its bonds satisfied by
clutching back at the two hydrogen atoms. Therefore
the trio, linked in this close bond, have no tendency to
reach out for any other companion, nor, indeed, any
power to hold another should it thrust itself upon them.
They form a "stable" compound, which under all ordi-
nary circumstances will retain its identity as a molecule
of water, even though the physical mass of which it is
a part changes its condition from a solid to a gas — from
ice to vapor.
But a consideration of this condition of stable equi-
librium in the molecule at once suggests a new question :
272
THE CENTURY'S PROGRESS IN CHEMISTRY
Ho\v can an aggregation of atoms, having all their
affinities satisfied, take any further part in chemical
reactions? Seemingly such a molecule, whatever its
physical properties, must be chemically inert, incapable
of any atomic readjustments. And so in point of fact
it is, so long as its component atoms cling to one another
unremittingly. But this, it appears, is precisely what the
atoms are little prone to do. It seems that they are
fickle to the last degree in their individual attachments,
and are as prone to break away from bondage as they are
to enter into it. Thus the oxygen atom which has just
flung itself into the circuit of two hydrogen atoms, the
next moment flings itself free again and seeks new com-
panions. It is for all the world like the incessant change
of partners in a rollicking dance.
This incessant dissolution and reformation of molecules
in a substance which as a whole remains apparently un-
changed was first fully appreciated by Ste.-Claire Deville,
and by him named dissociation. It is a process which
goes on much more activety in some compounds than in
others, and very much more actively under some physi-
cal conditions (such as increase of temperature) than un-
der others. But apparently no substances at ordinary
temperatures, and no temperature above the absolute
zero, are absolutely free from its disturbing influence.
Hence it is that molecules having all the valency of
their atoms fullv satisfied do not lose their chemical
activity — since each atom is momentarily free in the
exchange of partners, and may seize upon different
atoms from its former partners, if those it prefers are
at hand.
While, however, an appreciation of this ceaseless
activity of the atom is essential to a proper understand-
s 273
THE STORY OF NINETEENTH-CENTURY SCIENCE
ing of its chemical efficiency, yet from another point of
view the " saturated " molecule — that is, the molecule
whose atoms have their valency all satisfied — may be
thought of as a relatively fixed or stable organism.
Even though it may presently be torn down, it is for
the time being a completed structure; and a considera-
tion of the valency of its atoms gives the best clew that
has hitherto been obtainable as to the character of its
architecture. How important this matter of architecture
of the molecule — of space relations of the atoms — may
be was demonstrated as long ago as 1823, when Liebig and
Wohler proved, to the utter bewilderment of the chem-
ical world, that two substances may have precisely the
same chemical constitution — the same number and kind
of atoms — and yet differ utterly in physical properties.
The word isomerism was coined by Berzelius to express
this anomalous condition of things, which seemed to
negative the most fundamental truths of chemistry.
Naming the condition by no means explained it, but
the fact was made clear that something besides the
mere number and kind of atoms is important in the
architecture of a molecule. It became certain that
atoms are not thrown together haphazard to build a
molecule, any more than bricks are thrown together
at random to form a house.
How delicate may be the gradations of architectural
design in building a molecule was well illustrated about
1850, when Pasteur discovered that some carbon com-
pounds— as certain sugars— can only be distinguished
from one another, when in solution, by the fact of their
twisting or polarizing a ray of light to the left or to
the right, respectively. But no inkling of an explana-
tion of these strange variations of molecular structure
274
THE CENTURY'S PROGRESS IX CHEMISTRY
came until the discovery of the law of valency. Then
much of the mystery was cleared away ; for it was
plain that since each atom in a molecule can hold to
itself only a fixed number of other atoms, complex
molecules must have their atoms linked in definite
chains or groups. And it is equally plain that where
the atoms are numerous, the exact plan of grouping
may sometimes be susceptible of change without doing
violence to the law of valency. It is in such cases that
isomerism is observed to occur.
By paying constant heed to this matter of the affini-
ties, chemists are able to make diagrammatic pictures of
the plan of architecture of any molecule whose com-
position is known. In the simple molecule of water
(H2O), for example, the two hydrogen atoms must have
released one another before they could join the oxygen,
and the manner of linking must apparently be that rep-
resented in the graphic formula H — O — H. With mole-
cules composed of a large number of atoms, such graphic
representation of the scheme of linking is of course in-
creasingly difficult, yet, with the affinities for a guide, it
is always possible. Of course no one supposes that such
a formula, written in a single plane, can possibly repre-
sent the true architecture of the molecule : it is at best
suggestive or diagrammatic rather than pictorial. Never-
theless, it affords hints as to the structure of the mole-
cule such as the fathers of chemistry would not have
thought it possible ever to attain.
VI
These utterly novel studies of molecular architecture
may seem at first sight to take from the atom much of
275
THE STORY OF NINETEENTH-CENTURY SCIENCE
its former prestige as the all-important personage of the
chemical world. Since so much depends upon the mere
position of the atoms, it may appear that comparatively
little depends upon the nature of the atoms themselves.
But such a view is incorrect, for on closer consideration
it will appear that at no time has the atom been seen to
renounce its peculiar personality. Within certain limits
the character of a molecule may be altered by changing
the positions of its atoms (just as different buildings may
be constructed of the same bricks), but these limits are
sharply defined, and it would be as impossible to exceed
them as it would be to build a stone building with bricks.
From first to last the brick remains a brick, whatever
the style of architecture it helps to construct; it never
becomes a stone. And just as closely does each atom
retain its own peculiar properties, regardless of its sur-
roundings.
Thus, for example, the carbon atom may take part in
the formation at one time of a diamond, again of a piece
of coal, and yet again of a particle of sugar, of wood
fibre, of animal tissue, or of a gas in the atmosphere;
but from first to last — from glass-cutting gem to in-
tangible gas — there is no demonstrable change whatever
in any single property of the atom itself. So far as we
know, its size, its weight, its capacity for vibration or
rotation, and its inherent affinities, remain absolutely
unchanged throughout all these varying fortunes of po-
sition and association. And the same thing is true of
every atom of all of the sixty-odd elementary substances
with which the modern chemist is acquainted. Every
one appears always to maintain its unique integrity,
gaining nothing and losing nothing.
All this being true, it would seem as if the position of
276
THE CENTURY'S PROGRESS IX CHEMISTRY
the Daltonian atom as a primordial bit of matter, inde-
structible and non-transmutable, had been put to the
test by the chemistry of our century, and not found
wanting. Since those early clays of the century when
the electric battery performed its miracles and seeming-
ly reached its limitations in the hands of Davy, many
ROBERT WILLIAM BUNSEN
new elementary substances have been discovered, but no
single element has been displaced from its position as an
undecomposable body. Rather have the analyses of the
277
THE STORY OF NINETEENTH-CENTURY SCIENCE
chemist seemed to make it more and more certain that
all elementary atoms are in truth what John Herscbel
called them, "manufactured articles" -primordial,
changeless, indestructible.
And yet, oddly enough, it has chanced that hand in
hand with the experiments leading to such a goal have
gone other experiments and speculations of exactly the
opposite tenor. In each generation there have been
chemists among the leaders of their science who have
refused to admit that the so-called elements are really
elements at all in any final sense, and who have sought
eagerly for proof which might warrant their scepticism.
The first bit of evidence tending to support this view
was furnished by an English physician, Dr. William
Prout, who in 1815 called attention to a curious relation
to be observed between the atomic weight of the vari-
ous elements. Accepting the figures given by the au-
thorities of the time (notably Thomson and Berzelius), it
appeared that a strikingly large proportion of the
atomic weights were exact multiples of the weight of
hydrogen, and that others differed so slightly that errors
of observation might explain the discrepancy. Prout
felt that this could not be accidental, and he could think
of no tenable explanation, unless it be that the atoms of
the various alleged elements are made up of different
fixed numbers of hydrogen atoms. Could it be that the
one true element — the one primal matter — is hydrogen,
and that all other forms of matter are but compounds
of this original substance?
Prout advanced this startling idea at first tentatively,
in an anonymous publication ; but afterwardshe espoused
it openly and urged its tenability. Coming just after
Davy's dissociation of some supposed elements, the idea
278
THE CENTURY'S PROGRESS IN CHEMISTRY
proved alluring, and for a time gained such popularity
that chemists were disposed to round out the observed
atomic weights of all elements into whole numbers.
GtJSTAVE ROBERT KIRCHHOFF
But presently renewed determinations of the atomic
weights seemed to discountenance this practice, and
Prout's alleged law fell into disrepute. It was revived,
however, about 1840, by Dumas, whose great authority
secured it a respectful hearing, and whose careful rede-
termination of the weight of carbon, making it exactly
twelve times that of hydrogen, aided the cause.
S79
THE STORY OF NINETEENTH -CENTURY SCIENCE
Subsequently Stas, the pupil of Dumas, undertook a
long series of determinations of atomic weights, with
the expectation of confirming the Proutian hypothesis.
But his results seemed to disprove the hypothesis, for
the atomic weights of many elements differed from
whole numbers by more, it was thought, than the limits
of error of the experiments. It is noteworthy, however,
that the confidence of Dumas was not shaken, though
he was led to modify the hypothesis, and, in accordance
with previous suggestions of Clark and of Marignac, to
recognize as the primordial element, not hydrogen it-
self, but an atom half the weight, or even one-fourth
the weight, of that of hydrogen, of which primordial
atom the hydrogen atom itself is compounded. But
even in this modified form the hypothesis found great
opposition from experimental observers.
In 1864:, however, a novel relation between the
weights of the elements and their other characteristics
was called to the attention of chemists by Professor
John A. R. Newlands, of London, who had noticed that
if the elements are arranged serially in the numerical
order of their atomic weights, there is a curious recur-
rence of similar properties at intervals of eight elements.
This so-called "law of octaves" attracted little immedi-
ate attention, but the facts it connotes soon came under
the observation of other chemists, notably of Professors
Gustav Hinrichs in America, Dmitri Mendeleeff in Rus-
sia, and Lothar Meyer in Germany. Mendeleeff gave
the discovery fullest expression, expositing it in 1869,
under the title of " periodic law."
Though this early exposition of what has since been
admitted to be a most important discovery was very
fully outlined, the generality of chemists gave it little
280
LOUIS JACQUES MANDE DAGUERRE
From a daguerreotype made in Paris for Meade Brothers. New York, now n possession oJ
Abraham Bogardus, New York
THE CENTURY'S PROGRESS IN CHEMISTRY
heed till a decade or so later, when three new elements,
gallium, scandium, and germanium, were discovered,
which, on being analyzed, were quite unexpectedly
found to lit into three gaps which Mendeleeff had left
in his periodic scale. In effect, the periodic law had en-
abled Mendeleeff to predicate the existence of the new
elements years before they were discovered. Surely a
system that leads to such results is no mere vagary. So
very soon the periodic law took its place as one of the
most important generalizations of chemical science.
This law of periodicity was put forward as an expres-
sion of observed relations independent of hypothesis;
but of course the theoretical bearings of these facts
could not be overlooked. As Professor J. H. Gladstone
has said, it forces upon us " the conviction that the ele-
ments are not separate bodies created without reference
to one another, but that they have been originally fash-
ioned, or have been built up, from one another, accord-
ing to some general plan." It is but a short step from
that proposition to the Proutian hypothesis.
But the atomic weights are not alone in suggesting
the compound nature of the alleged elements. Evi-
dence of a totally different kind has contributed to the
same end, from a source that could hardly have been
imagined when the Proutian hypothesis was formulated,
through the addition of a novel weapon to the arma-
mentarium of the chemist — the spectroscope. The per-
fection of this instrument, in the hands of two German
scientists, Gustav Robert Kirchhoff and Robert Wilhelm
Bunsen, came about through the investigation, towards
the middle of the century, of the meaning of the dark
lines which had been observed in the solar spectrum by
Fraunhofer as early as 1815, and by Wollaston a decade
283
THE STORY OF NINETEENTH-CENTURY SCIENCE
earlier. It was suspected by Stokes and by Fox Talbot
in England, but first brought to demonstration by Kirch-
hoff and Bunsen, that these lines, which were known to
occupy definite positions in the spectrum, are really in-
dicative of particular elementary substances. By means
of the spectroscope, which is essentially a magnifying
lens attached to a prism of glass, it is possible to locate
the lines with great accuracy, and it was soon shown
that here was a new means of chemical analysis of the
most exquisite delicacy. It was found, for example,
that the spectroscope could detect the presence of a
quantity of sodium so infinitesimal as the one two-
hundred-thousandth of a grain. But what was even more
important, the spectroscope put no limit upon the dis-
tance of location of the substance it tested, provided
only that sufficient light came from it. The experi-
ments it recorded might be performed in the sun, or in
the most distant stars or nebulae ; indeed, one of the
earliest feats of the instrument was to wrench from the
sun the secret of his chemical constitution.
To render the utility of the spectroscope complete,
however, it was necessary to link with it another new
chemical agency, namely, photography. This now fa-
miliar process is based on the property of light to de-
compose certain unstable compounds of silver, and thus
alter their chemical composition. "We have seen that
Davy and Wedgwood barely escaped the discovery of
the value of the photographic method. Their successors
quite overlooked it until about 1826, when Louis J. M.
Daguerre, the French chemist, took the matter in hand,
and after many years of experimentation brought it to
relative perfection in 1839, in which year the famous
daguerreotype first brought the matter to popular at-
284
THE CENTURY'S PROGRESS IN CHEMISTRY
tention. In the same year Mr. Fox Talbot read a paper
on the subject before the Royal Society, and soon after-
wards the efforts of Herschel and numerous other natu-
ral philosophers contributed to the advancement of the
new method.
JOHN W. DRAPER
In 1843 Dr. John "W. Draper, the famous English-
American chemist and physiologist, showed that by
photography the Fraunhofer lines in the solar spectrum
might be mapped with absolute accuracy ; also proving
that the silvered film revealed many lines invisible to
the unaided eye. The value of this method of observa-
tion was recognized at once, and, as soon as the spectro-
285
THE STORY OF NINETEENTfl-CKNTURY SCIENCE
scope was perfected, the photographic method, in con-
junction with its use, became invaluable to the chemist.
By this means comparisons of spectra may be made
with a degree of accuracy not otherwise obtainable;
and in case of the stars, whole clusters of spectra may
be placed on record at a single observation.
As the examination of the sun and stars proceeded,
chemists were amazed or delighted, according to their
various preconceptions, to witness the proof that many
familiar terrestrial elements are to be found in the ce-
lestial bodies. But what perhaps surprised them most
was to observe the enormous preponderance in the si-
deral bodies of the element hydrogen. Not only are
there vast quantities of this element in the sun's atmos-
phere, but some other suns appeared to show hydrogen
lines almost exclusively in their spectra. Presently it
appeared that the stars of which this is true are those
white stars, such as Sirius, which had been conjectured
to be the hottest; whereas stars that are only red-hot,
like our sun, show also the vapors of many other ele-
ments, including iron and other metals.
In 18T8 Mr. J. Norman Lockyer, in a paper before
the Royal Society, called attention to the possible sig-
nificance of this series of observations. He urged that
the fact of the sun showing fewer elements than are ob-
served here on the cool earth, while stars much hotter
than the sun show chiefly one element, and that one
hydrogen, the lightest of known elements, seemed to give
color to the possibility that our alleged elements are
really compounds, which at the temperature of the hot-
test stars may be decomposed into hydrogen, the latter
"element " itself being also doubtless a compound, which
might be resolved under yet more trying conditions.
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THE CENTURY'S PROGRESS IN CHEMISTRY
Here, then, was what might be termed direct experi-
mental evidence for the hypothesis of Prout. Unfortu-
nately, however, it is evidence of a kind which only a
few experts are competent to discuss — so very delicate a
matter is the spectral analysis of the stars. What is
still more unfortunate, the experts do not agree among
themselves as to the validity of Mr. Lockyer's conclu-
sions. Some, like Professor Crookes, have accepted
them with acclaim, hailing Lockyer as "the Darwin of
the inorganic world," while others have sought a differ-
ent explanation of the facts he brings forward. As yet
it cannot be said that the controversy has been brought
to final settlement. Still, it is hardly to be doubted
that now, since the periodic law has seemed to join
hands with the spectroscope, a belief in the compound
nature of the so-called elements is rapidly gaining
ground among chemists. More and more general be-
comes the belief that the Daltonian atom is really a
compound radical, and that back of the seeming di-
versity of the alleged elements is a single unique form
of primordial matter. But it should not be forgotten
that this view, whatever its attractiveness, still lurks in
the domain of theory. There is no proof that the Dal-
tonian atom has yet been divided in the laboratory.
CHAPTER IX
THE CENTURY'S PROGRESS IN BIOLOGY
I
THEORIES OF ORGANIC EVOLUTION
WHEN Coleridge said of Humphry Davy that lie might
have been the greatest poet of his time had he not
chosen rather to be the greatest chemist, it is possible
that the enthusiasm of the friend outweighed the cau-
tion of the critic. But however that may be, it is be-
yond dispute that the man who actually was the great-
est poet of that time might easily have taken the very
highest rank as a scientist had not the Muse distracted
his attention. Indeed, despite these distractions, Johann
Wolfgang von Goethe achieved successes in the field of
pure science that would insure permanent recognition
for his name had he never written a stanza of poetry.
Such is the versatility that marks the highest genius.
It was in 1790 that Goethe published the work that
laid the foundations of his scientific reputation — the
work on the Metamorphoses of Plants, in which he ad-
vanced the novel doctrine that all parts of the flower are
modified or metamorphosed leaves. This was followed
presently by an extension of the doctrine of metamor-
THE CENTURY'S PROGRESS IN BIOLOGY
phosis to the animal kingdom, in the doctrine which
Goethe and Oken advanced independently, that the ver-
tebrate skull is essentially a modified and developed ver-
tebra. These were conceptions worthy of a poet; im-
possible, indeed, for any mind that had not the poetic
faculty of correlation. But in this case the poet's vision
was prophetic of a future view of the most prosaic sci-
ence. The doctrine of metamorphosis of parts soon
came to be regarded as a fundamental feature in the
science of living things.
But the doctrine had implications that few of its
early advocates realized. If all the parts of a flower-
sepal, petal, stamen, pistil, with their countless devia-
tions of contour and color — are but modifications of the
leaf, such modification implies a marvellous differentia-
tion and development. To assert that a stamen is a
metamorphosed leaf means, if it means anything, that in
the long sweep of time the leaf has by slow or sudden
gradations changed its character through successive
generations, until the offspring, so to speak, of a true
leaf has become a stamen. But if such a metamorphosis
as this is possible — if the seemingly wide gap between
leaf and stamen may be spanned by the modification of
a line of organisms — where does the possibility of modi-
fication of organic type find its bounds? Why may
not 1;he modification of parts go on along devious lines
until the remote descendants of an organism are utterly
unlike that organism? Why may we not thus account
for the development of various species of beings all
sprung from one parent stock? That too is a poet's
dream; but is it only a dream? Goethe thought not.
Out of his studies of metamorphosis of parts there grew
in his mind the belief that the multitudinous species of
T 289
THE STORY OF NINETEENTH-CENTURY SCIENCE
plants and animals about us have been evolved from
fewer and fewer earlier parent types, like twigs of a
giant tree drawing their nurture from the same primal
ERASMUS DARWIN
root. It was a bold and revolutionary thought; and
the world regarded it as but the vagary of a poet.
Just at the time when this thought was taking form
in Goethe's brain, the same idea was germinating in the
mind of another philosopher, an Englishman of interna-
tional fame, Dr. Erasmus Darwin, who, while he lived,
enjoyed the widest popularity as a poet, the rhymed
couplets of his Botanic Garden being quoted every-
290
THE CENTURY'S PROGRESS IN BIOLOGY
where with admiration. And posterity, repudiating the
verse which makes the body of the book, yet grants
permanent value to the book itself, because, forsooth,
its copious explanatory footnotes furnish an outline of
the status of almost every department of science of
the time.
But even though he lacked the highest art of the versi-
fier, Darwin had, be}rond peradventure, the imagination
of a poet coupled with profound scientific knowledge;
and it was his poetic insight, correlating organisms seem-
ingly diverse in structure, and imbuing the lowliest
flower with a vital personality, which led him to sus-
pect that there are no lines of demarcation in nature.
"Can it be," he queries,- " that one form of organism
has developed from another ; that different species are
really but modified descendants of one parent stock?"
The alluring thought nestled in his mind and was nurt-
ured there, and grew into a fixed belief, which was
given fuller expression in his Zoonomia, and in the
posthumous Temple of Nature. But there was little
proof of its validity forthcoming that could satisfy any
one but a poet, and when Erasmus Darwin died, in 1802,
the idea of transmutation of species was still but an un-
substantiated dream.
It was a dream, however, which was not confined to
Goethe and Darwin. Even earlier the idea had come
more or less vaguely to another great dreamer — and
worker — of Germany, Immanuel Kant, and to several
great Frenchmen, including De Maillet, Maupertuis,
Robinet, and the famous naturalist Buffon — a man who
had the imagination of a poet, though his message was
couched in most artistic prose. Not long after the mid-
dle of the eighteenth century Buffon had put forward
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THE STORY OF NINETEENTH-CENTURY SCIENCE
the idea of transmutation of species, and he reiterated
it from time to time from then on till his death in 1788.
But the time was not yet ripe for the idea of transmu-
tation of species to burst its bonds.
And yet this idea, in a modified or undeveloped form,
had taken strange hold upon the generation that was
upon the scene at the close of the eighteenth century.
Vast numbers of hitherto unknown species of animals
had been recently discovered in previously unexplored
regions of the globe, and the wise men were sorely puz-
zled to account for the disposal of all of these at the
time of the Deluge. It simplified matters greatly to
suppose that many existing species had been developed
since the episode of the Ark by modification of the
original pairs. The remoter bearings of such a theory
were overlooked for the time, and the idea that Amer-
ican animals and birds, for example, were modified
descendants of Old World forms — the jaguar of the
leopard, the puma of the lion, and so on — became a cur-
rent belief with that class of humanity who accept al-
most any statement as true that harmonizes with their
prejudices, without realizing its implications.
Thus it is recorded with eclat that the discovery of
the close proximity of America at the northwest with
Asia removes all difficulties as to the origin of the
Occidental faunas and floras, since Oriental species
might easily have found their way to America on the
ice, and have been modified as we find them bv " the
7 «/
well-known influence of climate." And the persons who
gave expression to this idea never dreamed of its real
significance. In truth, here was the doctrine of evolu-
tion in a nutshell, and, because its ultimate bearings
were not clear, it seemed the most natural of doctrines.
292
THE CENTURY'S PROGRESS IX BIOLOGY
But most of the persons who advanced it would have
turned from it aghast could they have realized its im-
port. As it was, however, only here and there a man
like Buffon reasoned far enough to inquire what might
be the limits of such assumed transmutation ; and only
here and there a Darwin or a Goethe reached the con-
viction that there are no limits.
ii
And even Goethe and Darwin had scarcely passed be-
yond that tentative stage of conviction in which they
held the thought of transmutation of species as an ancil-
lary belief, not yet ready for full exposition There
was one of their contemporaries, however, who, holding
the same conception, was moved to give it full explica-
tion. This was the friend and disciple of Buffon, Jean
Baptiste de Lamarck. Possessed of the spirit of a poet
and philosopher, this great French man had also the widest
range of technical knowledge, covering the entire field
of animate nature. The first half of his long life was
devoted chiefly to botany, in which he attained high
distinction. Then, just at the beginning of our cen-
tury, he turned to zoology, in particular to the lower
forms of animal life. Studying these lowly organisms,
existing and fossil, he was more and more impressed
with the gradations of form everywhere to be seen ;
the linking of diverse families through intermediate
ones ; and in particular with the predominance of low
types of life in the earlier geological strata. Called upon
constantly to classify the various forms of life in the
course of his systematic writings, he found it more and
more difficult to draw sharp lines of demarcation, and at
393
THE STOR\f OF NINETEENTH-CENTURY SCIENCE
last the suspicion long harbored grew into a settled con-
viction that there is really no such thing as a species of
organism in nature ; that " species " is a tigment of the
human imagination, whereas in nature there are only
individuals.
That certain sets of individuals are more like one an-
other than like other sets is of course patent, but this
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THE CENTURY'S PROGRESS IN BIOLOGY
only means, said Lamarck, that these similar groups
have had comparatively recent common ancestors, while
dissimilar sets of beings are more remotely related in
consanguinity. But trace back the lines of descent far
enough, and all will culminate in one original stock.
All forms of life whatsoever are modified descendants
of an original organism. From lowest to highest, then,
there is but one race, one species, just as all the mul-
titudinous branches and twigs from one root are but
one tree. For purposes of convenience of description,
we may divide organisms into orders, families, genera,
species, just as we divide a tree into root, trunk,
branches, twigs, leaves ; but in the one case, as in the
other, the division is arbitrary and artificial.
In Philosophie Zoologique (1809), Lamarck first ex-
plicitly formulated his ideas as to the transmutation of
species, though he had outlined them as early as 1801.
In this memorable publication not only did he state his
belief more explicitly and in fuller detail than the idea
had been expressed by any predecessor, but he took an-
other long forward step, carrying him far beyond all his
forerunners except Darwin, in that he made an attempt
to explain the way in which the transmutation of spe-
cies had been brought about. The changes have been
wrought, he said, through the unceasing efforts of each
organism to meet the needs imposed upon it by its envi-
ronment. Constant striving means the constant use of
certain organs,'and such use leads to the development
of those organs. Thus a bird running by the sea-shore
is constantly tempted to wade deeper and deeper in
pursuit of food; its incessant efforts tend to develop
its legs, in accordance with the observed principle that
the use of any organ tends to strengthen and develop it.
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THE STORY OF NINETEENTH-CENTURY SCIENCE
But such slightly increased development of the legs is
transmitted to the offspring of the bird, which in turn
develops its already improved legs by its individual ef-
forts, and transmits the improved tendency. Generation
after generation this is repeated, until the sum of the
infinitesimal variations, all in the same direction, results
in the production of the long-legged wading-bird. In
a similar way, through individual effort and transmitted
tendency, all the diversified organs of all creatures have
been developed — the fin of the fish, the wing of the bird,
the hand of man ; nay, more, the fish itself, the bird, the
man, even. Collectively the organs make up the entire
organism; and what is true of the individual organs
must be true also of their ensemble, the living being.
Whatever might be thought of Lamarck's explanation
of the cause of transmutation — which really was that
already suggested by Erasmus Darwin — the idea of the
evolution for which he contended was but the logical
extension of the conception that American animals are
the modified and degenerated descendants of European
animals. But people as a rule are little prone to follow
ideas to their logical conclusions, and in this case the
conclusions were so utterly opposed to the proximal
bearings of the idea that the whole thinking world
repudiated them with acclaim. The very persons who
had most eagerly accepted the idea of transmutation of
European species into American species, and similar lim-
ited variations through changed environment, because
of the relief thus given the otherwise overcrowded Ark,
were now foremost in denouncing such an extension of
the doctrine of transmutation as Lamarck proposed.
And, for that matter, the leaders of the scientific world
were equally antagonistic to the Laraarckian hypothesis.
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THE CENTURY'S PROGRESS IN BIOLOGY
Cuvier in particular, once the pupil of Lamarck, but now
his colleague, and in authority more than his peer, stood
out against the transmutation doctrine with all his force.
He argued for the absolute fixity of species, bringing to
bear the resources of a mind which, as a mere repository
of facts, perhaps never was excelled. As a final and
tangible proof of his position, he brought forward the
bodies of ibises that had been embalmed by the ancient
Egyptians, and showed by comparison that these do not
differ in the slightest particular from the ibises that visit
the Nile to-day. Lamarck replied that this proved noth-
ing except that the ibis had become perfectly adapted
to its Egyptian surroundings in an early day, historically
speaking, and that the climatic and other conditions of
the Nile Valley had not since then changed. His the-
ory, he alleged, provided for the stability of species
under fixed conditions quite as well as for transmuta-
tion under varying conditions.
But, needless to say, the popular verdict lay with Cu-
vier; talent won for the time against genius, and La-
marck was looked upon as as impious visionary. His
faith never wavered, however. He believed that he had
gained a true insight into the processes of animate nat-
ure, and he reiterated his hypotheses over and over, par-
ticularly in the introduction to his Histoire naturelle des
Animaux sans Vertebras, in 1815, and in his Systeme des
Connaissances positives de Vllomme, in 1820. He lived
on till 1829, respected as a naturalist, but almost unrec-
ognized as a prophet.
in
While the names of Darwin and Goethe, and in par-
ticular that of Lamarck, must always stand out in high
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THE STORY OF NINETEENTH-CENTURY SCIENCE
relief in this generation as the exponents of the idea of
transmutation of species, there are a few others which
must not be altogether overlooked in this connection.
Of these the most conspicuous is that of Gottfried Rein-
hold Treviranus, a German naturalist physician, profess-
or of mathematics in the lyceum at Bremen.
It was an interesting coincidence that Treviranus
should have published the first volume of his Biologie,
oder Philosophie der lebenden Natur, in which his views
on the transmutation of species were expounded, in 1802,
the same twelvemonth in which Lamarck's first exposi-
tion of the same doctrine appeared in his Reclierches sur
V Organisation des Corps Vivants. It is singular, too,
that Lamarck, in his Hydrogeologie of the same date,
should independently have suggested " biology " as an
appropriate word to express the general science of living
things. It is significant of the tendency of thought of
the time that the need of such a unifying word should
have presented itself simultaneously to independent
thinkers in different countries.
That same memorable year, Lorenz Oken, another
philosophical naturalist, professor in the University of
Zurich, published the preliminary outlines of his Phi-
losophie der Natur, which, as developed through later
publications, outlined a theory of spontaneous generation
and of evolution of species. Thus it appears that this
idea was germinating in the minds of several of the
ablest men of the time during the first decade of our
century. But the singular result of their various expli-
cations was to give sudden check to that undercurrent
of thought which for some time had been setting tow-
ards this conception. As soon as it was made clear
whither the concession that animals may be changed by
THE CENTURY'S PROGRESS IN BIOLOGY
their environment must logically trend, the recoil from
the idea was instantaneous and fervid. Then for a gen-
eration Cuvier was almost absolutely dominant, and his
verdict was generally considered final.
ETIENNE GEOFFKOY SAINT-HILAIHE
There was, indeed, one naturalist of authority in
France who had the hardihood to stand out against
Cuvier and his school, and who was in a position to
gain a hearing, though by no means to divide the fol-
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THE STORY OF NINETEENTH-CENTURY SCIENCE
lowing. This was Etienne Geoffrey Saint-Hilaire, the
famous author of the Philosophic Anatomigue, and for
many years the colleague of Lamarck at the Jarclin des
Plantes. Like Goethe, Geoffroy was pre-eminently an
anatomist, and, like the great German, he had early
been impressed with the resemblances between the anal-
ogous organs of different classes of beings. He con-
ceived the idea that an absolute unity of type prevails
throughout organic nature as regards each set of organs.
Out of this idea grew his gradually formed belief that
similarity of structure might imply identity of origin—
that, in short, one species of animal might have devel-
oped from another.
Geoffrey's grasp of this idea of transmutation was by
no means so complete as that of Lamarck, and he seems
never to have fully determined in his own mind just
what might be the limits of such development of species.
Certainly he nowhere includes all organic creatures in
one line of descent, as Lamarck had done; nevertheless
he held tenaciously to the truth as he saw it, in open op-
position to Cuvier, with whom he held a memorable de-
bate at the Academy of Sciences in 1830 — the debate
which so aroused the interest and enthusiasm of Goethe,
but which, in the opinion of nearly every one else, re-
sulted in crushing defeat for Geoffroy, and brilliant,
seemingly final, victory for the advocate of special cre-
ation and the fixity of species.
With that all ardent controversy over the subject
seemed to end, and for just a quarter of a century to
come there was published but a single argument for
transmutation of species which attracted any general at-
tention whatever. This oasis in a desert generation was
a little book called Vestiges of the Natural History of
300
THE CENTURY'S PROGRESS IN BIOLOGY
Creation, which appeared anonymously in England in
1844, and which passed through numerous editions, and
was the subject of no end of abusive and derisive com-
ment. The authorship of this book remained for forty
years a secret, but it is now conceded to have been the
work of Robert Chambers, the well-known English
author and publisher. The book itself is remarkable as
being an avowed and unequivocal exposition of a gener-
al doctrine of evolution, its view being as radical and
comprehensive as that of Lamarck himself. But it was
a resume of earlier efforts rather than a new departure,
to say nothing of its technical shortcomings, and, while
it aroused bitter animadversions, and cannot have been
without effect in creating an undercurrent of thought in
opposition to the main trend of opinion of the time, it
can hardly be said to have done more than that. In-
deed, some critics have denied it even this merit. After
its publication, as before, the conception of transmuta-
tion of species remained in the popular estimation, both
lay and scientific, an almost forgotten " heresy."
It is true that here and there a scientist of greater or
less repute — as Yon Buch, Meckel, and Yon Baer in
Germany, Bory Saint Yincent in France, Wells, Grant,
and Matthew in England, and Leidy in America — had
expressed more or less tentative dissent from the doc-
trine of special creation and immutability of species, but
their unaggressive suggestions, usually put forward in
obscure publications, and incidentally, were utterly over-
looked and ignored. And so, despite the scientific ad-
vances along many lines at the middle of the century,
the idea of the transmutability of organic races had no
such prominence, either in scientific or unscientific cir-
cles, as it had acquired fifty years before. Special cre-
801
THE STORY OF NINETEENTH-CENTURY SCIENCE
ation held the day, apparently unchallenged and unop-
posed.
IV
But even at this time the fancied security of the spe-
cial-creation hypothesis was by no means real. Though
it seemed so invincible, its real position was that of an
apparently impregnable fortress beneath which, all un-
beknown to the garrison, a powder-mine has been dug
and lies ready for explosion. For already there existed
in the secluded work-room of an English naturalist, a
manuscript volume and a portfolio of notes which might
have sufficed, if given publicity, to shatter the entire
structure of the special-creation hypothesis. The natu-
ralist who, by dint of long and patient effort, had con-
structed this powder-mine of facts was Charles Robert
Darwin, grandson of the author of Zoonomia.
As long ago as July 1, 1837, young Darwin, then
twenty-eight years of age, had opened a private jour-
nal, in which he purposed to record all facts that
came to him which seemed to have any bearing on
the moot point of the doctrine of transmutation of spe-
cies. Four or five years earlier, during the course of
that famous trip around the world with Admiral Fitz-
roy, as naturalist to the Beagle, Darwin had made the
personal observations which first tended to shake his be-
lief in the fixity of species. In South America, in the
Pampean formation, he had discovered "great fossil an-
imals covered with armor like that on the existing arma-
dillos," and had been struck with this similarity of type
between ancient and existing faunas of the same region.
He was also greatly impressed by the manner in which
closely related species of animals were observed to re-
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THE CENTURY'S PROGRESS IN BIOLOGY
place one another as he proceeded southward over the
continent ; and " by the South American character of
most of the productions of the Galapagos Archipelago,
and more especially by the manner in which they differ
slightly on each island of the group, none of the islands
appearing to be very ancient in a geological sense."
At first the full force of these observations did not
strike him ; for, under sway of Lyell's geological con-
ceptions, he tentatively explained the relative absence
of life on one of the Galapagos Islands by suggesting
that perhaps no species had been created since that isl-
and arose. But gradually it dawned upon him that
such facts as he had observed "could only be explained
on the supposition that species gradually become modi-
fied." From then on, as he afterwards asserted, the sub-
ject haunted him ; hence the journal of 1837.
It will thus be seen that the idea of the variability of
species came to Charles Darwin as an. inference from
personal observations in the field, not as a thought bor-
rowed from books. He had, of course, read the works
of his grandfather much earlier in life, but the argu-
ments of the Zoonomia and Temple of Nature had not
served in the least to weaken his acceptance of the cur-
rent belief in fixity of species. Nor had he been more
impressed with the doctrine of Lamarck, so closely sim-
ilar to that of his grandfather. Indeed, even after his
South American experience had aroused him to a new
point of view he was still unable to see anything of
value in these earlier attempts at an explanation of the
variation of species. In opening his journal, therefore,
he had no preconceived notion of upholding the views of
these or any other makers of hypotheses, nor at the
time had he formulated any hypothesis of his own. His
THE STORY OF NINETEENTH-CENTURY SCIENCE
mind was open and receptive; he was eager only for
facts which might lead him to an understanding of a
CHARLES ROBERT DARWIN
problem which seemed utterly obscure. It was some-
thing to feel sure that species have varied ; but how
have such variations been brought about?
It was not long before Darwin found a clew which he
thought might lead to the answer he sought. In cast-
ing about for facts he had soon discovered that the
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THE CENTURY'S PROGRESS IN BIOLOGY
most available field for observation lay among domesti-
cated animals, whose numerous variations within specific
lines are familiar to every one. Thus under domestica-
tion creatures so tangibly different as a mastiff and a
terrier have sprung from a common stock. So have the
Shetland pony, the thoroughbred, and the draught-
horse. In short, there is no domesticated animal that
lias not developed varieties deviating more or less wide-
ly from the parent stock. Now how has this been ac-
complished ? Why, clearly, by the preservation, through
selective breeding, of seemingly accidental variations.
Thus one horseman, by constantly selecting animals
that " chance" to have the right build and stamina,
finally develops a race of running-horses ; while another
horseman, by selecting a different series of progenitors,
has developed a race of slow, heavy draught-animals.
So far so good; the preservation of "accidental" va-
riations through selective breeding is plainly a means by
which races may be developed that are very different
from their original parent form. But this is under
man's supervision and direction. By what process could
such selection be brought about among creatures in a
state of nature ? Here surely was a puzzle, and one that
must be solved before another step could be taken in
this direction.
The key to the solution of this puzzle came into Dar-
win's mind through a chance reading of the famous
essay on " Population " which Thomas Robert Malthus
had published almost half a century before. This essay,
expositing ideas by no means exclusively original with
Malthus, emphasizes the fact that organisms tend to
increase at a geometrical ratio through successive gen-
erations, and hence would overpopulate the earth if not
u 305
THE STORY OF NINETEENTH-CENTURY SCIENCE
somehow kept in check. Cogitating this thought, Dar-
win gained a new insight into the processes of nature.
He saw that in virtue of this tendency of each race of
beings to overpopulate the earth, the entire organic
world, animal and vegetable, must be in a state of
perpetual carnage and strife, individual against indi-
vidual, fighting for sustenance and life.
That idea fully imagined, it becomes plain that a select-
ive influence is all the time at work in nature, since only
a few individuals, relatively, of each generation can come
to maturity, and these few must, naturally, be those
best fitted to battle with the particular circumstances
in the midst of which they are placed. In other words,
the individuals best adapted to their surroundings will,
on the average, be those that grow to maturity and
produce offspring. To these offspring will be trans-
mitted the favorable peculiarities. Thus these pecul-
iarities will become permanent, and nature will have
accomplished precisely what the human breeder is seen
to accomplish. Grant that organisms in a state of
nature vary, however slightly, one from another (which
is indubitable), and that such variations will be trans-
mitted by a parent to its offspring (which no one then
doubted); grant, further, that there is incessant strife
among the various organisms, so that only a small pro-
portion can come to maturity — grant these things, said
Darwin, and we have an explanation of the preservation
of variations which leads on to the transmutation of
species themselves.
This wonderful coign of vantage Darwin had reached
by 1839. Here was the full outline of his theory ; here
were the ideas which afterwards came to be embalmed
in familiar speech in the phrases " spontaneous varia-
306
THE CENTURY'S PROGRESS IN BIOLOGY
tion," and the "survival of the fittest," through "nat-
ural selection." After such a discovery any ordinary
man would at once have run through the streets of
science, so to speak, screaming " Eureka !" Not so Dar-
win. He placed the manuscript outline of his theory in
his portfolio, and went on gathering facts bearing on his
discovery. In 1844 he made an abstract in a manuscript
book of the mass of facts by that time accumulated.
He showed it to his friend Hooker, made careful provi-
sion for its publication in the event of his sudden death,
then stored it away in his desk, and went ahead with
the gathering of more data. This was the unexploded
powder-mine to which I have just referred.
Twelve years more elapsed ; years during which the
silent worker gathered a prodigious mass of facts, an-
swered a multitude of objections that arose in his own
mind, vastly fortified his theory. All this time the toiler
was an invalid, never knowing a day free from illness
and discomfort, obliged to husband his strength, never
able to work more than an hour and a half at a stretch ;
yet he accomplished what would have been vast achieve-
ments for half a dozen men of robust health. Two
friends among the eminent scientists of the day knew of
his labors — Sir Joseph Hooker, the botanist, and Sir
Charles Lyell, the geologist. Gradually Hooker had
come to be more than half a convert to Darwin's views.
Lyell was still sceptical, yet he urged Darwin to publish
his theory without further delay, lest he be forestalled.
At last the patient worker decided to comply with this
advice, and in 1856 he set to work to make another and
fuller abstract of the mass of data he had gathered.
And then a strange thing happened. After Darwin
had been at work on his " abstract " about two years,
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THE STORY OF NINETEENTH-CENTURY SCIENCE
but before he had published a line of it, there came to
him one day a paper in manuscript, sent for his approval
by a naturalist friend, named Alfred Russell Wallace,
who had been for some time at work in the East India
ALFRED RUSSELL WALLACE
Archipelago. He read the paper, and, to his amaze-
ment, found that it contained an outline of the same
308
THE CENTURY'S PROGRESS IN BIOLOGY
theory of " natural selection " which he himself had
originated and for twenty years had worked upon.
Working independently, on opposite sides of the globe,
Darwin and Wallace had hit upon the same explanation
of the cause of transmutation of species. " Were Wal-
lace's paper an abstract of my unpublished manuscript
of 1844," said Darwin, " it could not better express my
ideas."
Here was a dilemma. To publish this paper with no
word from Darwin would give Wallace priority, and
wrest from Darwin the credit of a discovery which he
had made years before his co-discoverer entered the
field. Yet, on the other hand, could Darwin honorably
do otherwise than publish his friend's paper and himself
remain silent? It was a complication well calculated to
try a man's soul. Darwin's was equal to the test.
Keenly alive to the delicacy of the position, he placed
the whole matter before his friends Hooker and Lyell,
and left the decision as to a course of action absolutely
to them. Needless to say, these great men did the one
thing which insured full justice to all concerned. They
counselled a joint publication, to include on the one
hand Wallace's paper, and on the other an abstract of
Darwin's ideas, in the exact form in which it had been
outlined by the author in a letter to Asa Gray in the
previous year — an abstract which was in Gray's hands
before Wallace's paper was in existence. This joint
production, together with a full statement of the facts
of the case, was presented to the Linnaean Society of
London by Hooker and Lyell on the evening of July 1,
1858, this being, by an odd coincidence, the twenty-first
anniversary of the day on which Darwin had opened
his journal to collect facts bearing on the "species ques-
309
THE STORY OF NINETEENTH-CENTURY SCIENCE
tion." Not often before in the history of science has it
happened that a great theory has been nurtured in its
author's brain through infancy and adolescence to its
full legal majority before being sent out into the world.
Thus the fuse that led to the great powder-mine had
been lighted. The explosion itself came more than a
year later, in November, 1859, when Darwin, after thir-
teen months of further effort, completed the outline of
his theory, which was at first begun as an abstract for
the Linnaean Society, but which grew to the size of an
independent volume despite his efforts at condensation,
and which was given that ever-to-be-famous title, The
Origin of Species by means of Natural Selection, or the
Preservation of Favored Races in the Struggle for Life.
And what an explosion it was ! The joint paper of 1858
had made a momentary flare, causing the hearers, as
Hooker said, to " speak of it with bated breath," but be-
yond that it made no sensation. What the result was
when the Origin itself appeared, no one of our genera-
tion need be told. The rumble and roar that it made in
the intellectual world have not yet altogether ceased to
echo after forty years of reverberation.
v
To the Origin of Species, then, and to its author,
Charles Darwin, must always be ascribed chief credit
for that vast revolution in the fundamental beliefs of
our race which has come about since 1859, and made
the second half of the century memorable. But it must
not be overlooked that no such sudden metamorphosis
could have been effected had it not been for the aid of a
few notable lieutenants, who rallied to the standards of
310
THOMAS HENRY HUXLEY
From a photograph by W. and D. Downey, London
T11E CENTURY'S PROGRESS IN BIOLOGY
the leader immediately after the publication of the Ori-
gin. Darwin had all along felt the utmost confidence
in the ultimate triumph of his ideas. "Our posterity,"
he declared in a letter to Hooker, " will marvel as much
about the current belief [in special creation] as we do
about fossil shells having been thought to be created as
we now see them." But he fully realized that for the
present success of his theory of transmutation the cham-
pionship of a few leaders of science was all-essential.
He felt that if he could make converts of Hooker and
Lyell and of Thomas Henry Huxley at once, .all would
be well.
His success in this regard, as in others, exceeded his
expectations. Hooker was an ardent disciple from read-
ing the proof-sheets before the book was published ;
Lyell renounced his former beliefs and fell into line a
few months later ; while Huxley, so soon as he had mas-
tered the central idea of natural selection, marvelled
that so simple yet all-potent a thought had escaped him
so long, and then rushed eagerly into the fray, wielding
the keenest dialectic blade that was drawn during the
entire controversy. Then, too, unexpected recruits were
found in Sir John Lubbock and John Tyndall, who car-
ried the war eagerly into their respective territories;
while Herbert Spencer, who had advocated a doctrine
of transmutation on philosophic grounds some years be-
fore Darwin published the key to the mystery — and who
himself had barely escaped independent discovery of
that key — lent his masterful influence to the cause. In
America, the famous botanist Asa Gray, who had long
been a correspondent of Darwin's, but whose advocacy
of the new theory had not been anticipated, became an
ardent propagandist; while in Germany Ernst Heinrich
313
THE STORY OF NINETEENTH-CENTURY SCIENCE
Haeckel, the youthful but already noted zoologist, took
up the fight with equal enthusiasm.
ASA GRAY
Against these few doughty champions — with here and
there another of less general renown — was arrayed, at
the outset, practically all Christendom. The interest of
the question came home to every person of intelligence,
whatever his calling, and the more deeply as it became
more and more clear, how far-reaching are the real bear-
314
THE CENTURY'S PROGRESS IX BIOLOGY
ings of the doctrine of natural selection. Soon it was
seen that should the doctrine of the survival of the
favored races through the struggle for existence win,
there must come with it as radical a change in man's
estimate of his own position as had come in the day
when, through the efforts of Copernicus and Galileo, the
world was dethroned from its supposed central position
in the universe. The whole conservative majority of
mankind recoiled from this necessity with horror. And
this conservative majority included not laymen merely,
but a vast preponderance of the leaders of science also.
With the open-minded minority, on the other hand,
the theory of natural selection made its way by leaps
and bounds. Its delightful simplicity — which at first
sight made it seem neither new nor important — coupled
with the marvellous comprehensiveness of its implica-
tions, gave it a hold on the imagination, and secured it
a hearing where other theories of transmutation of spe-
cies had been utterly scorned. Men who had found
Lamarck's conception of change through voluntary ef-
fort ridiculous, and the vaporings of the Vestiges alto-
gether despicable, men whose scientific cautions held
them back from Spencer's deductive argument, took
eager hold of that tangible, ever-present principle of
natural selection, and were led on and on to its goal.
Hour by hour the attitude of the thinking world tow-
ards this new principle changed ; never before was so
great a revolution wrought so suddenly.
Nor was this merely because " the times were ripe "
or " men's minds prepared for evolution." Darwin
himself bears witness that this was not altogether so.
All through the years in which he brooded this theory
he sounded his scientific friends, and could find among
315
THE STO1IY OF NINETEENTH-CENTURY SCIENCE
them not one who acknowledged a doctrine of transmu-
tation. The reaction from the standpoint of Lamarck
and Erasmus Darwin and Goethe had been complete,
and when Charles Darwin avowed his own conviction
he expected always to have it met with ridicule or
contempt. In 1857 there was but one man speaking
with any large degree of authority in the world who
openly avowed a belief in transmutation of species — that
man being Herbert Spencer. But the Origin of Species
came, as Huxley has said, like a flash in the darkness, en-
abling the benighted voyager to see the way. The score
of years during which its author had waited and worked
had been years well spent. Darwin had become, as he
himself says, a veritable Croesus, " overwhelmed with
his riches in facts " — facts of zoology, of selective artifi-
cial breeding, of geographical distribution of animals, of
embryology, of paleontology. He had massed his facts
about his theory, condensed them and recondensed, un-
til his volume of five hundred pages was an encyclo-
paedia in scope. During those long years of musing he
had thought out almost every conceivable objection to
his theory, and in his book every such objection was
stated with fullest force and candor, together with such
reply as the facts at command might dictate. It was
the force of those twenty years of effort of a master
mind that made the sudden breach in the breastwork of
current thought.
Once this breach was effected, the work of conquest
went rapidly on. Day by day squads of the enemy
capitulated and struck their arms. By the time another
score of years had passed the doctrine of evolution had
become the working hypothesis of the scientific world,
The revolution had been effected.
316
THE CENTURY'S PROGRESS IN BIOLOGY
And from amid the wreckage of opinion and belief
stands forth the figure of Charles Darwin, calm, imper-
turbable, serene; scatheless to ridicule, contumely, abuse ;
unspoiled by ultimate success ; unsullied alike by the
strife and the victory — take him for all in all, for char-
acter, for intellect, for what he was and what he did,
perhaps the most Socratic figure of the century. When,
in 1882, he died, friend and foe alike conceded that one of
the greatest sons of men had rested from his labors, and
all the world felt it fitting that the remains of Charles
Darwin should be entombed in Westminster Abbey,
close beside the honored grave of Isaac Newton. Nor
were there many who would dispute the justice of Hux-
ley's estimate of his accomplishment : " He found a great
truth trodden under foot. Reviled by bigots, and ridiculed
by all the world, he lived long enough to see it, chiefly by
his own efforts, irrefragably established in science, in-
separably incorporated with the common thoughts of men,
and only hated and feared by those who would revile, but
dare not."
VI
Wide as are the implications of the great truth which
Darwin and his co-workers established, however, it
leaves quite untouched the problem of the origin of
those "favored variations" upon which it operates.
That such variations are due to fixed and determinate
causes no one understood better than Darwin ; but in
his original exposition of his doctrine he made no as-
sumption as to what these causes are. He accepted the
observed fact of variation — as constantly witnessed, for
example, in the differences between parents and off-
spring— and went ahead from this assumption.
317
THE STORY OF NINETEENTH-CENTURY SCIENCE
But as soon as the validity of the principle of natural
selection came to be acknowledged, speculators began to
search for the explanation of those variations which, for
purposes of argument, had been provisionally called
" spontaneous." Herbert Spencer had all along dwelt
on this phase of the subject, expounding the Lamarck-
ian conceptions of the direct influence of the environ-
ment (an idea which had especially appealed to Buffon
and to Geoffroy Saint-Hilaire), and of effort in response
to environment and stimulus as modifying the individu-
*- o
al organism, and thus supplying the basis for the opera-
tion of natural selection. Haeckel also became an advo-
cate of this idea, and presently there arose a so-called
school of neo-Lamarckians, which developed particular
strength and prominence in America, under the leader-
ship of Professors A. Hyatt and E. D. Cope.
But just as the tide of opinion was turning strongly in
this direction, an utterly unexpected obstacle appeared
in the form of the theory of Professor August Weis-
mann, put forward in 1883, which antagonized the La-
marckian conception (though not touching the Darwin-
ian, of which Weismann is a firm upholder) by denying
that individual variations, however acquired by the ma-
ture organism, are transmissible. The flurry which this
denial created has not yet altogether subsided, but sub-
sequent observations seem to show that it was quite dis-
proportionate to the real merits of the case. Notwith-
standing Professor Weismann's objections, the balance
of evidence appears to favor the view that the Lamarck-
ian factor of acquired variations stands as the comple-
ment of the Darwinian factor of natural selection in ef-
fecting the transmutation of species.
Even though this partial explanation of what Pro-
318
THE CENTURY'S PROGRESS IN BIOLOGY
fessor Cope calls the " origin of the fittest " be accepted,
there still remains one great life problem which the doc-
trine of evolution does not touch. The origin of species,
genera, orders, and classes of beings through endless
transmutations is in a sense explained ; but what of the
first term of this long series? Whence came that pri-
mordial organism whose transmuted descendants make
up the existing faunas and floras of the globe?
ERNEST HAECKEL
There was a time, soon after the doctrine of evolution
gained a hearing, when the answer to that question
seemed to some scientists of authority to have been
319
THE STORY OF NINETEENTH-CENTURY SCIE.N'CE
given by experiment. Recurring to a former belief, and
repeating some earlier experiments, the director of the
Museum of Natural History at Rouen, M. F. A. Pouchet,
reached the conclusion that organic beings are sponta-
neously generated about us constantly, in the familiar
processes of putrefaction, which were known to be due
to the agency of microscopic bacteria. But in 1862
Louis Pasteur proved that this seeming spontaneous
generation is in reality due to the existence of germs in
the air. Notwithstanding the conclusiveness of these
experiments, the claims of Pouchet were revived in Eng-
land ten years later by Professor Bastian ; but then the
experiments of John Tyndall, fully corroborating the
results of Pasteur, gave a final quietus to the claim of
" spontaneous generation " as hitherto formulated.
There for the moment the matter rests. But the end
is not yet. Fauna and flora are here, and, thanks to
Lamarck and Wallace and Darwin, their development,
through the operation of those "secondary causes"
which we call laws of nature, has been proximally ex-
plained. The lowest forms of life have been linked with
the highest in unbroken chains of descent. Meantime,
through the efforts of chemists and biologists, the gap
between the inorganic and the organic worlds, which
once seemed almost infinite, has been constantly nar-
rowed. Already philosophy can throw a bridge across
that gap. But inductive science, which builds its own
bridges, has not yet spanned the chasm, small though it
appear. Until it shall have done so, the bridge of or-
ganic evolution is not quite complete: yet even as it
stands to-day it is the most stupendous scientific struct-
ure of our century.
320
CHAPTER X
THE CENTURY'S PROGRESS IN ANATOMY AND
PHYSIOLOGY
THE focal points of the physiological world towards
the close of the eighteenth century were Italy and Eng-
land, but when Spallanzani and Hunter passed away the
scene shifted to France. The time was peculiarly pro-
pitious, as the recent advances in many lines of science
had brought fresh data for the student of animal life
which were in need of classification, and, as several
minds capable of such a task were in the field, it was
natural that great generalizations should have come to
be quite the fashion. Thus it was that Cuvier came for-
ward with a brand-new classification of the animal king-
dom, establishing four great types of being, which he
called vertebrates, molluscs, articulates, and radiates.
Lamarck had shortly before established the broad dis-
tinction between animals with and those without a back-
bone; Cuvier's classification divided the latter — the in-
vertebrates— into three minor groups. And this divis-
ion, familiar ever since to all students of zoology, has
only in very recent years been supplanted, and then not
by revolution, but by a further division, which the elab-
orate recent studies of lower forms of life seemed to
make desirable.
x 321
THE STORY OF NINETEENTH-CENTURY SCIENCE
In the course of those studies of comparative anato-
my which led to his new classification, Cuvier's atten-
tion was called constantly to the peculiar co-ordination
of parts in each individual organism. Thus an animal
with sharp talons for catching living prey — as a member
of the cat tribe — has also sharp teeth, adapted for tear-
ing up the flesh of its victim, and a particular type of
stomach, quite different from that of herbivorous creat-
ures. This adaptation of all the parts of the animal to
one another extends to the most diverse parts of the or
ganism, and enables the skilled anatomist, from the ob-
servation of a single typical part, to draw inferences as
to the structure of the entire animal — a fact which was
of vast aid to Cuvier in his studies of paleontology. It
did not enable Cuvier, nor does it enable any one else,
to reconstruct fully the extinct animal from observation
of a single bone, as has sometimes been asserted, but
what it really does establish, in the hands of an expert,
is sufficiently astonishing.
Of course this entire principle, in its broad outlines, is
something with which every student of anatomy had
been familiar from the time when anatomy was first
studied, but the full expression of the " law of co-ordina-
tion," as Cuvier called it, had never been explicitly made
before; and notwithstanding its seeming obviousness, the
exposition which Cuvier made of it in the introduction
to his classical work on comparative anatomy, which
was published during the first decade of the century,
ranks as a great discovery. It is one of those general-
izations which serve as guide-posts to other discover-
ries.
Much the same thing may be said of another general-
ization regarding the animal body, which the brilliant
> 322
PROGRESS IN ANATOMY AND PHYSIOLOGY
young French physician Marie Franpois Bichat made in
calling attention to the fact that each vertebrate organ-
ism, including man, has really two quite different sets of
MAHIE FRANCOIS XAVIER BICHAT
From a medallion by David d' Angers
organs — one set under volitional control, and serving the
end of locomotion, the other removed from volitional
control, and serving the ends of the " vital processes" of
digestion, assimilation, and the like. He called these-
sets of organs the animal system and the organic sys-
tem, respectively. The division thus pointed out was
not quite new, for Grimaud, professor of physiology in
the universit}^ of Montpellier, had earlier made what
was substantially the same classification of the functions
into " internal or digestive and external or locomotive ";
323
THE STORY OF NINETEENTH-CENTURY SCIENCE
but it was Bichat's exposition that gave currency to the
idea.
Far more important, however, was another classifica-
tion which Bichat put forward in his work on anatomy,
published just at the beginning of the century. This was
the division of all animal structures into what Bichat
called tissues, and the pointing out that there are really
only a few kinds of these in the body, making up all
the diverse organs. Thus muscular organs form one
system ; membranous organs another ; glandular organs
a third ; the vascular mechanism a fourth, and so on.
The distinction is so obvious that it seems rather diffi-
cult to conceive that it could have been overlooked by
the earliest anatomists ; but, in point of fact, it is only
obvious because now it has been familiarly taught for
almost a century. It had never been given explicit ex-
pression before the time of Bichat, though it is said that
Bichat himself was somewhat indebted for it to his mas-
ter, the famous alienist, Pinel.
Howeverthat may be, it is certain that all subsequent
anatomists have found Bichat's classification of the tis
sues of the utmost value in their studies of the animal
functions. Subsequent advances were to show that the
distinction between the various tissues is not really so
fundamental as Bichat supposed, but that takes nothing
from the practical value of the famous classification.
ii
At the same time when these broad microscopical dis-
tinctions were being drawn there were other workers
who were striving to go even deeper into the intricacies
of the animal mechanism with the aid of the microscope.
324
PROGRESS IN ANATOMY AND PHYSIOLOGY
This undertaking, however, was beset with very great
optical difficulties, and for a long time little advance
was made upon the work of preceding generations.
Two great optical barriers, known technically as spher-
ical and chromatic aberration — the one due to a failure
of the rays of light to fall all in one plane when focalized
through a lens, the other due to the dispersive action of
the lens in breaking the white light into prismatic col-
ors— confronted the makers of microscopic lenses, and
seemed all but insuperable. The making of achromatic
lenses for telescopes had been accomplished, it is true,
by Dolland in the previous century, by the union of
lenses of crown glass with those of flint glass, these two
materials having different indices of refraction and dis-
persion. But, aside from the mechanical difficulties
which arise when the lens is of the minute dimensions
required for use with the microscope, other perplexities
are introduced by the fact that the use of a wide pencil
of light is a desideratum, in order to gain sufficient illu-
mination when large magnification is to be secured.
In the attempt to overcome these difficulties, the fore-
most physical philosophers of the time came to the aid
of the best opticians. Very early in the century, Dr.
(afterwards Sir David) Brewster, the renowned Scotch
physicist, suggested that certain advantages might ac-
crue from the use of such gems as have high refractive
and low dispersive indices, in place of lenses made of
glass. Accordingly lenses were made of diamond, of
sapphire, and so on, and with some measure of success.
But in 1812 a much more important innovation was intro-
duced by Dr. William Hyde "VVollaston, one of the great-
est and most versatile, and since the death of Cavendish
by far the most eccentric, of English natural philosophers.
325
TilE STORY OF NINETEENTH-CENTURY SCIENCE
This was the suggestion to use two plano-convex lenses,
placed at a prescribed distance apart, in lieu of the sin-
gle double convex lens generally used. This combina-
tion largely overcame the spherical aberration, and it
gained immediate fame as the " Wollaston doublet."
To obviate loss of light
in such a doublet from in-
crease of reflecting surfaces,
Dr. Brewster suggested fill-
ing the interspace between
the two lenses with a ce-
ment having the same index
of refraction as the lenses
themselves — an improve-
ment ot manifest advan-
tage. An improvement yet
more important was made
by Dr. Wollaston himself,
in the introduction of the
diaphragm to limit the field
of vision between the lenses,
instead of in front of the anterior lens. A pair of lenses
thus equipped, Dr. Wollaston called the periscopic micro-
scope. Dr. Brewster suggested that in such a lens the
same object might be attained with greater ease by grind-
ing an equatorial groove about a thick or globular lens
and filling the groove with an opaque cement. This ar-
rangement found much favor, and came subsequently to
be known as a Coddington lens, though Mr. Coddington
laid no claim to being its inventor.
Sir John Herschel, another of the very great physicists
of the time, also gave attention to the problem of im-
proving the microscope, and in 1821 he introduced what
336
WILLIAM HYDE WOLLASTON
PROGRESS IN ANATOMY AND PHYSIOLOGY
was called an aplanatic combination of lenses, in which,
as the name implies, the spherical aberration was largely
done away with. It was thought that the use of this
Herschel aplanatic combination as an eye - piece, com-
bined with the Wollaston doublet for the objective, came
as near perfection as the compound microscope was like-
ly soon to come. But in reality the instrument thus
constructed, though doubtless superior to any predeces-
sor, was so defective that for practical purposes the sim-
ple- microscope, such as the doublet or the Coddington,
was preferable to the more complicated one.
Many opticians, indeed, quite despaired of ever being
able to make a satisfactory refracting compound micro-
scope, and some of them had taken up anew Sir Isaac
Newton's suggestion in reference to a reflecting micro-
scope. In particular, Professor Giovanni Battista Amici,
a very famous mathematician and practical optician of
Modena, succeeded in constructing a reflecting micro-
scope which was said to be superior to any compound
microscope of the time, though the events of the ensu-
ing years were destined to rob it of all but historical
value. For there were others, fortunately, who did not
despair of the possibilities of the refracting microscope,
and their efforts were destined before long to be crowned
with a degree of success not even dreamed of by any
preceding generation.
The man to whom chief credit is due for directing
those final steps that made the compound microscope a
practical implement instead of a scientific toy was the
English amateur optician Joseph Jackson Lister. Com-
bining mathematical knowledge with mechanical ingenu-
ity, and having the practical aid of the celebrated opti-
cian Tulley, he devised formulas for the combination
327
THE STORY OF NINETEENTH-CENTURY SCIENCE
of lenses of crown glass with others of flint glass, so
adjusted that the refractive errors of one were corrected
or compensated by the other, with the result of produc-
ing lenses of hitherto unequalled powers of definition;
lenses capable of showing an image highly magnified,
yet relatively free from those distortions and fringes of
color that had heretofore been so disastrous to true in-
terpretation of magnified structures.
Lister had begun his studies of the lens in 1821,
but i-t was not until 1830 that he contributed to the
Royal Society the famous paper detailing his theories
and experiments. Soon after this various Continental
opticians who had long been working along similar lines
took the matter up, and their expositions, in particular
that of Amici, introduced the improved compound mi-
croscope to the attention of microscopists everywhere.
And it required but the most casual trial to convince
the experienced observers that a new implement of sci-
entific research had. been placed in their hands which
carried them a long step nearer the observation of the
intimate physical processes which lie at the foundation
of vital phenomena. For the physiologist, this perfec-
tion of the compound microscope had the same signifi-
cance that the discovery of America had for the fifteenth-
century geographers — it promised a veritable world of
utterly novel revelations. Nor was the fulfilment of
that promise long delayed.
in
Indeed, so numerous and so important were the dis-
coveries now made in the realm of minute anatomy that
the rise of histology to the rank of an independent sci-
328
PROGRESS IN ANATOMY AND PHYSIOLOGY
ence may be said to date from this period. Hitherto,
ever since the discovery of magnify ing -glasses, there
had been here and there a man, such as Leuwenhoek or
Malpighi, gifted with exceptional vision, and perhaps
unusually happy in his conjectures, who made important
contributions to the knowledge of the minute structure
of organic tissues ; but now of a sudden it became pos-
sible for the veriest tyro to confirm or refute the la-
borious observations of these pioneers, while the skilled
observer could step easily beyond the barriers of vision
hitherto quite impassable. And so, naturally enough,
the physiologists of the fourth decade of our century
rushed as eagerly into the new realm of the microscope
as, for example, their successors of to-day are exploring
the realm of the X ray.
Lister himself, who had become an eager interrogator
of the instrument he had perfected, made many impor-
tant discoveries, the most notable being his final set-
tlement of the long -mooted question as to the true
form of the red corpuscles of the human blood. In
reality, as everybody knows nowadays, these are bicon-
cave disks, but owing to their peculiar figure it is easily
possible to misinterpret the appearances they present
when seen through a poor lens, and though Dr. Thomas
Young and various other observers had come very near
the truth regarding them, unanimity of opinion was pos-
sible only after the verdict of the perfected microscope
was given.
These blood corpuscles are so infinitesimal in size that
something like five millions of them are found in each
cubic millimetre of the blood, yet they are isolated par-
ticles, each having, so to speak, its own personality.
This, of course, had been known to microscopists since
329
THE STORY OF NINETEENTH-CENTURY SCIENCE
the days of the earliest lenses. It had been noticed,
too, by here and there an observer, that certain of the
solid tissues seemed to present something of a granular
texture, as if they too, in their ultimate constitution,
were made up of particles. And now, as better and bet-
ter lenses were constructed, this idea gained ground
constantly, though for a time no one saw its full signif-
icance. In the case of vegetable tissues, indeed, the fact
that little particles encased in a membranous covering,
and called cells, are the ultimate visible units of struct-
ure had long been known.
But it was supposed that
animal tissues differed radi-
cally from this construction.
The elementary particles of
vegetables " were regarded
to a certain extent as indi-
viduals which composed the
MATTHIAS JAK01! SCHLEIDEX
entire plant, while, on the
other hand, no such view
was taken of the elementary
parts of animals."
In the year 1833 a further
insight into the nature of the
ultimate particles of plants
was gained through the ob-
servation of the English microscopist Robert Brown,
who, in the course of his microscopic studies of the epi-
dermis of orchids, discovered in the cells "an opaque
spot," which he named the nucleus. Doubtless the same
"spot" had been seen often enough before by other ob-
servers, but Brown was the first to recognize it as a
component part of the vegetable cell, and to give it
330
PROGRESS IN ANATOMY AND PHYSIOLOGY
a name. That this newly recognized structure must be
important in the economy of the cell was recognized by
Brown himself, and by the celebrated German Meyen,
who dealt with it in his work on vegetable physiology,
published not long afterwards ; but it remained for an-
other German, the professor of botany in the university
of Jena, Dr. M. J. Schleiden, to bring the nucleus to
popular attention, and to assert its all-importance in the
economy of the cell.
Schleiden freely acknowledged his indebtedness to
Brown for first knowledge of the nucleus, but he soon
carried his studies of that structure far beyond those of
its discoverer. He came to believe that the nucleus is
really the most important portion of the cell, in that it
is the original structure from which the remainder of
the cell is developed. Hence he named it the cytoblast.
He outlined his views in an epochal paper published in
Miiller's Archives in 1838, under title of " Beitrage zur
Phytogenesis." This paper is in itself of value, yet the
most important outgrowth of Schleiden's observations of
the nucleus did not spring from his own labors, but from
those of a friend to whom he mentioned his discoveries
the year previous to their publication. This friend was
Dr. Theodor Schwann, professor of physiology in the
university of Louvain.
At the moment when these observations were com-
municated to him Schwann was puzzling over certain
details of animal histology which he could not clearly
explain. His great teacher, Johannes Miiller, had called
attention to the strange resemblance to vegetable cells
shown by certain cells of the chorda dorsalis (the em-
bryonic cord from which the spinal column is devel-
oped), and Schwann himself had discovered a corre-
331
THE STORY OF NINETEENTH-CENTURY SCIENCE
spending similarity in the branchial cartilage of a tad-
pole. Then, too, the researches of Friedrich Henle had
shown that the particles that make up the epidermis of
animals are very cell-like in appearance. Indeed, the
cell-like character of certain animal tissues had come to
be matter of common note among students of minute
anatomy. Sch\vann felt that this similarity could not
be mere coincidence, but he had gained no clew to
further insight until Schleiden called his attention to
the nucleus. Then at once he reasoned that if there
really is the correspondence between \7egetable and ani-
mal tissues that he suspected, and if the nucleus is so im-
portant in the vegetable cell as Schleiden believed, the
nucleus should also be found in the ultimate particles of
animal tissues.
Schwann's researches soon showed the entire correct-
ness of this assumption. A closer stud\r of animal tis-
sues under the microscope showed, particularly in the
case of embryonic tissues, that "opaque spots" such as
Schleiden described are really to be found there in
abundance— forming, indeed, a most characteristic phase
of the structure. The location of. these nuclei at com-
paratively regular intervals suggested that they are
found in de'finite compartments of the tissue, as Schleiden
had shown to be the case with vegetables; indeed, the
walls that separated such cell-like compartments one from
another were in some cases visible. Particularly was
this found to be the case with embryonic tissues, and
the study of these soon convinced Schwann that his
original surmise had been correct, and that all animal
tissues are in their incipiency composed of particles not
unlike the ultimate particles of vegetables — in short, of
what the botanists termed cells. Adopting this name.
332
KAKL ERNST VON BAEK
PROGRESS IN ANATOMY AND PHYSIOLOGY
Schwann propounded what soon became famous as his
cell theory, under title of Mikroskopische Untersuchun-
gen uber die Uebereinstimmung in der Structur und
dem Wachsthum der Thiere und Pflanzen. So expeditious
had been his work, that this book was published early
in 1839, only a few months after the appearance of
Schleiden's paper.
As the title suggests, the main idea that actuated
Schwann was to unify vegetable and animal tissues.
Accepting cell-structure as the basis of all vegetable
tissues, he sought to show that the same is true of ani-
mal tissues, all the seeming diversities of fibre being but
the alteration and development of what were originally
simple cells. And by cell Schwann meant, as did Schlei-
den also, what the word ordinarily implies — a cavity
walled in on all sides. He conceived that the ultimate
constituents of all tissues were really such minute cavi-
ties, the most important part of which was the cell wall,
with its associated nucleus. He knew, indeed, that the
cell might be filled with fluid contents, but he regarded
these as relatively subordinate in importance to the wall
itself. This, however, did not apply to the nucleus,
which was supposed to lie against the cell wall, and in the
beginning to generate it. Subsequently the wall might
grow so rapidly as to dissociate itself from its contents,
thus becoming a hollow bubble or true cell ; but the
nucleus, as long as it lasted, was supposed to continue in
contact with the cell wall. Schleiden had even supposed
the nucleus to be a constituent part of the wall, some-
times lying enclosed between two layers of its substance,
and Schwann quoted this view with seeming approval.
Schwann believed, however, that in the mature cell the
nucleus ceased to be functional, and disappeared.
335
THE STORY OF NINETEENTH-CENTURY SCIENCE
The main thesis as to the similarity of development
of vegetable and animal tissues, and the cellular nature
of the ultimate constitution of both, was supported by a
mass of carefully gathered evidence which a multitude
of microscopists at once confirmed, so Schwann's work
became a classic almost from the moment of its publi-
cation. Of course various other workers at once dis-
puted Schwann's claim to priority of discovery, in particu-
lar the English microscopist Valentin, who asserted, not
without some show of justice, that he was working
closely along the same lines. But so, for that matter,
were numerous others, as Henle, Turpin, Dumortier,
Purkinje, and Miiller, all of whom Schwann himself had
quoted. Moreover, there were various physiologists who
earlier than any of these had foreshadowed the cell the-
ory ; notably Kaspar Friedrich Wolff, towards the close
of the previous century, and Treviranus about 1807.
But, as we have seen in so many other departments of
science, it is one thing to foreshadow a discovery, it is
quite another to give it full expression and make it
germinal of other discoveries. And when Schwann put
forward the explicit claim that " there is one universal
principle of development for the elementary parts of
organisms, however different, and this principle is the
formation of cells," he enunciated a doctrine which was
for all practical purposes absolutely new, and opened
up a novel field for the microscopist to enter. A most
important era in physiology dates from the publication
of his book in 1839.
rv
That Schwann should have gone to embryonic tissues
for the establishment of his ideas was no doubt due very
336
PROGRESS IN ANATOMY AND PHYSIOLOGY
largely to the influence of the great Eussian, Karl Ernst
von Baer, who about ten years earlier had published the
first part of his celebrated work on embryology, and
JOHANNES MULI.ER
whose ideas were rapidly gaining ground, thanks large-
ly to the advocacy of a few men, notably Johannes Miil-
ler in German}7, and William B. Carpenter in England,
and to the fact that the improved microscope had made
minute anatomy popular. Schwann's researches made
it plain that the best field for the study of the animal
cell is here, and a host of explorers entered the field.
The result of their observations was, in the main, to con-
Y 337.
THE STORY OF NINETEENTH-CENTURY SCIENCE
firm the claims of Schwann as to the universal prev-
alence of the cell. The long-current idea that animal
tissues grow only as a sort of deposit from the blood-
vessels was now discarded, and the fact of so-called
plant-like growth of animal cells, for which Schwann
contended, was universally accepted. Yet the full
measure of the affinity between the two classes of cells
was not for some time generally apprehended.
Indeed, since the substance that composes the cell
walls of plants is manifestly very different from the
limiting membrane of the animal cell, it was natural, so
long as the wall was considered the most essential part
of the structurej that the divergence between the two
classes of cells should seem very pronounced. And for
a time this was the conception of the matter that was
uniformly accepted. But as time went on many ob-
servers had their attention called to the peculiar char-
acteristics of the contents of the cell, and were led to
ask themselves whether these might not be more im-
portant than had been supposed. In particular Dr.
Hugo von Mohl, professor of botany in the university of
Tubingen, in the course of his exhaustive studies of the
vegetable cell, was impressed with the peculiar and
characteristic appearance of the cell contents. He ob-
served universally within the cell " an opaque, viscid
fluid, having granules intermingled in it," which made
up the main substance of the cell, and which particular-
ly impressed him because under certain conditions it
could be seen to be actively in motion, its parts sep-
arated into filamentous streams.
Yon Mohl called attention to the fact that this mo-
tion of the cell contents had been observed as long ago
as 1774 by Bonaventura Corti, and rediscovered in 1807
338
PROGRESS IN ANATOMY AND PHYSIOLOGY
by Treviranus, and that these observers had described
the phenomenon under the " most unsuitable name of
' rotation of the cell sap.' " Yon Mohl recognized that
the streaming substance was
something quite different
from sap. He asserted that
the nucleus of the cell lies
within this substance, and
not attached to the cell wall
as Schleiden had contended.
He saw, too, that the chlo-
rophyl granules, and all
other of the cell contents,
are incorporated with the
" opaque, viscid fluid," and
in 1846 he had become so
impressed with the impor-
tance Of this Universal Cell WILLIAM BK.VJAMI.V CAKPK.VTKR
, . . . Photographed by Elliot and Fry, London
substance that he gave it
the name of protoplasm. Yet in so doing he had no inten-
tion of subordinating the cell wall. The fact that Payen
in 1844, had demonstrated that the cell walls of all vege-
tables, high or low, are composed largely of one sub-
stance, cellulose, tended to strengthen the position of
the cell wall as the really essential structure, of which
the protoplasmic contents were only subsidiary prod-
ucts.
Meantime, however, the students of animal histology
were more and more impressed with the seeming pre-
ponderance of cell contents over cell walls in the tissues
they studied. They too found the cell to be filled with
a viscid, slimy fluid, capable of motion. To this Du-
jardin gave the name of sarcode. Presently it came to
339
THE STORY OF NINETEENTH-CENTURY SCIENCE
be known, through the labors of Kolliker, ISfageli, Bis-
choff, and various others, that there are numerous lower
forms of animal life which seem to be composed of this
sarcode, without any cell wall whatever. The same
thing seemed to be true of certain cells of higher organ-
isms, as the blood corpuscles. Particularly in the case
of cells that change their shape markedly, moving about
in consequence of the streaming of their sarcode, did it
seem certain that no cell wall is present ; or that, if pres-
ent, its role must be insignificant.
And so histologists came to question whether, after
all, the cell contents rather than the enclosing wall must
not be the really essential structure, and the weight of
increasing observations finally left no escape from the
conclusion that such is really the case. But attention
being thus focalized on the cell contents, it was at once
apparent that there is a far closer similarity between
the ultimate particles of vegetables and those of ani-
mals than had been supposed. Cellulose and animal
membrane being now regarded as mere by-products, the
way was clear for the recognition of the fact that veg-
etable protoplasm and animal sarcode are marvellously
similar in appearance and general properties. The closer
the observation the more striking seemed this similar-
ity ; and finally, about 1860, it was demonstrated by
Heinrich de Bary and by Max Schultze that the two are
to all intents and purposes identical. Even earlier Re-
mak had reached a similar conclusion, and applied von
Mohl's word protoplasm to animal cell contents, and
now this application soon became universal. Thence-
forth this protoplasm was to assume the utmost impor-
tance in the physiological world, being recognized as the
universal " physical basis of life,*' vegetable and animal
340
MAX SCHULTZE
PROGRESS IN ANATOMY AND PHYSIOLOGY
alike. This amounted to the logical extension and cul-
mination of Schwanu's doctrine as to the similarity of
development of the two animate kingdoms. Yet at the
same time it was in effect the banishment of the cell
that Schwann had defined. The word cell was retained,
it is true, but it no longer signified a minute cavity. It
now implied, as Schultze defined it, "a small mass of
protoplasm endowed with the attributes of life." This
definition was destined presently to meet with yet an-
other modification, as we shall see ; but the conception
of the protoplasmic mass as the essential ultimate struct-
ure, which might or might not surround itself with a
protective covering, was a permanent addition to physi-
ological knowledge. The earlier idea had, in effect, de-
clared the shell the most important part of the egg;
this developed view assigned to the yolk its true posi-
tion.
In one other important regard the theory of Schleiden
and Schwann now became modified. This referred to
the origin of the cell. Schwann had regarded cell
growth as a kind of crystallization, beginning with the
deposit of a nucleus about a granule in the intercellular
substance — the cytoblastema, as Schleiden called it.
But von Mohl, as early as 1835, had called attention to
the formation of new vegetable cells through the divis-
ion of a pre-existing cell. Ehrenberg, another high au-
thorit}7 of the time, contended that no such division oc-
curs, and the matter was still in dispute when Schleiden
came forward with his discovery of so-called free cell
formation within the parent cell, and this for a long
time diverted attention from the process of division
which von Mohl had described. All manner of schemes
of cell formation were put forward during the ensuing
343
THE STORY OF NINETEENTH-CENTURY SCIENCE
years by a multitude of observers, and gained currency
notwithstanding von Mohl's reiterated contention that
there are really but two ways in which the formation
of new cells takes place, namely, "first, through divis-
ion of older cells ; secondly, through the formation of
secondary cells lying free in the cavity of a cell."
HUGO VON MOHL
But gradually the researches of such accurate observ.
ers as linger, Nageli, Kolliker, Reichart, and Remak
tended to confirm the opinion of von Molil that cells
spring only from cells, and finally Rudolf Virchow
brought the matter to demonstration about 1860. His
344
PROGRESS IN ANATOMY AND PHYSIOLOGY
Omnis cellula e cellula became from that time one of
the accepted data of physiology. This was supplement-
ed a little later by Fleming's Omnis nucleus e nucleo,
when still more refined methods of observation had
shown that the part of the cell which always first under-
goes change preparatory to new cell formation is the all-
essential nucleus. Thus the nucleus was restored to the
important position which Schwann and Schleiden had
given it, but with greatly altered significance. Instead
of being a structure generated de novo from non-cellular
substance, and disappearing as soon as its function of
cell-formation was accomplished, the nucleus was now
known as the central and permanent feature of every
cell, indestructible while the cell lives ; itself the divis-
ion-product of a pre-existing nucleus, and the parent, by
division of its substance, of other generations of nuclei.
The word cell received a final definition as "a small
mass of protoplasm supplied with a nucleus."
In this widened and culminating general view of the
cell theory it became clear that every animate organism,
animal or vegetable, is but a cluster of nucleated cells, all
of which, in each individual case, are the direct descendants
of a single primordial cell of the ovum. In the devel-
oped individuals of higher organisms the successive gen-
erations of cells become marvellously diversified in form
and in specific functions; there is a wonderful division
of labor, special functions being chiefly relegated to defi-
nite groups of cells; but from first to last there is no
function developed that is not present, in a primitive
way, in every cell, however isolated; nor does the de-
veloped cell, however specialized, ever forget altogether
any one of its primordial functions or capacities. All
physiology, then, properly interpreted, becomes merely
345
THE STORY OF NINETEENTH -CENTURY SCIENCE
a study of cellular activities ; and the development of
the cell theory takes its place as the great central gen-
eralization in physiology of our century. Something of
the later developments of this theory we shall see in an-
other connection.
Just at the time when the microscope was opening
up the paths that were to lead to the wonderful cell
theory, another novel line of interrogation of the liv-
ing organism was being
put forward by a differ-
ent set of observers. T\vo
great schools of physio-
logical chemistry had arisen
— one under guidance of
Liebig and Wohler in Ger-
many, the other dominated
by the great French master
Jean Baptiste Dumas. Lie-
big had at one time contem-
plated the study of medicine,
and Dumas had achieved dis-
tinction in connection with
Prevost at Geneva in the
JEAN BAPTISTE DUMAS
field of pure physiology be-
fore he turned his attention especially to chemistry. Both
these masters, therefore, and Wohler as well, found ab-
sorbing interest in those phases of chemistry that have
to do with the functions of living tissues; and it was
largely through their efforts and the labors of their fol-
lowers that the prevalent idea that vital processes are
dominated by unique laws was discarded and physiology
346
PROGRESS IN ANATOMY AND PHYSIOLOGY
was brought within the recognized province of the
chemist. So at about the time when the microscope
had taught that the cell is the really essential structure
of the living organism, the chemists had come to under-
stand that every function of the organism is really the
expression of a chemical change — that each cell is, in
short, a miniature chemical laboratory. And it was
this combined point of view of anatomist and chemist,
this union of hitherto dissociated forces, that made pos-
sible the inroads into the unexplored fields of physi-
ology that were effected towards the middle of our cen-
tury.
One of the first subjects reinvestigated and brought
to proximal solution was the long-mooted question of
the digestion of foods. Spallanzani and Hunter had
shown in the previous century that digestion is in some
sort a solution of foods ; but little advance was made
upon their work until 1824, when Prout detected the
presence of hydrochloric acid in the gastric juice. A
decade later Sprott and Boyd detected the existence of
peculiar glands in the gastric mucous membrane; and
Cagniard la Tour and Schwann independently discov-
ered that the really active principle of the gastric juice
is a substance which was named pepsin, and which was
shown by Schwann to be active in the presence of hy-
drochloric acid.
Almost coincidently, in 1836, it was discovered by
Purkinje and Pappenheim that another organ than the
stomach — the pancreas, namely — has a share in diges-
tion, and in the course of the ensuing decade it came to
be known, through the efforts of Eberle, Valentin, and
Claude Bernard, that this organ is all-important in the
digestion of starchy and fatty foods. It was found, too,
347
THE STORY OF NINETEENTH-CENTURY SCIENCE
that the liver and the intestinal glands have each an im-
portant share in the work of preparing foods for absorp-
tion, as also has the saliva — that, in short, a coalition of
forces is necessary for the digestion of all ordinary foods
taken into the stomach.
And the chemists soon discovered that in each one of
the essential digestive juices there is at least one sub-
stance having certain resemblances to pepsin, though
acting on different kinds of food. The point of resem-
blance between all these essential digestive agents is
that each has the remarkable property of acting on
relatively enormous quantities of the substance which
it can digest without itself being destroyed or apparent-
ly even altered. In virtue of this strange property,
pepsin and the allied substances were spoken of as fer-
ments, but more recently it is customary to distingush
them from such organized ferments as yeast by desig-
nating them enzymes. The isolation of these enzymes,
and an appreciation of their mode of action, mark a
long step towards the solution of the riddle of digestion,
but it must be added that we are still quite in the dark
as to the real ultimate nature of their strange activity.
In a comprehensive view, the digestive organs, taken
as a whole, are a gateway between the outside world
and the more intimate cells of the organism. Another
equally important gateway is furnished by the lungs,
and here also there was much obscurity about the exact
method of functioning at the time of the revival of phys-
iological chemistry. That oxygen is consumed and
carbonic acid given off during respiration the chemists
of the age of Priestley and Lavoisier had indeed made
clear, but the mistaken notion prevailed that it was in
the lungs themselves that the important burning of fuel
848
PROGRESS IN ANATOMY AND PHYSIOLOGY
occurs, of which carbonic acid is a chief product. But
now that attention had been called to the importance of
the ultimate cell, this misconception could not long hold
its ground, and as early as 1842 Liebig, in the course of
his studies of animal heat, became convinced that it is
not in the lungs, but in the ultimate tissues to which
they are tributary, that the true consumption of fuel
takes place. Reviving Lavoisier's idea, with modifica-
tions and additions, Liebig contended, and in the face
of opposition finally demonstrated, that the source of
animal heat is really the consumption of the fuel taken
in through the stomach and the lungs. He showed
that all the activities of life are really the product of
energy liberated solely through destructive processes,
amounting, broadly speaking, to combustion occurring
in the ultimate cells of the organism.
Further researches showed that the carriers of oxy-
gen, from the time of its absorption in the lungs till its
liberation in the ultimate tissues, are the red corpuscles,
whose function had been supposed to be the mechanical
one of mixing of the blood. It transpired that the red
corpuscles are composed chiefly of a substance which
Kiihne first isolated in crystalline form in 1865, and
which was named haemoglobin — a substance which has
a marvellous affinity for oxygen, seizing on it eagerly
at the lungs, yet giving it up with equal readiness when
coursing among the remote cells of the body. When
freighted with oxygen it becomes oxyhaemoglobin, and
is red in color ; when freed from its oxygen it takes a
purple hue; hence the widely different appearance of
arterial and venous blood, which so puzzled the early
physiologists.
This proof of the vitally important role played by the
349
THE STORY OF NINETEENTH-CENTURY SCIENCE
red blood corpuscles led, naturally, to renewed studies
of these infinitesimal bodies. It was found that they
may vary greatly in number at different periods in the
life of the same individual, proving that they may be
both developed and destroyed in the adult organism.
Indeed, extended observations left no reason to doubt
that the process of corpuscle formation and destruction
may be a perfectly normal one ; that, in short, every
red blood corpuscle runs its course and dies like any
more elaborate organism. They are formed constantly
in the red marrow of bones, and are destroyed in the
liver, where they contribute to the formation of the
coloring matter of the bile. Whether there are other
seats of such manufacture and destruction of the cor-
puscles is not yet fully determined. Nor are histolo-
gists agreed as to whether the red blood corpuscles
themselves are to be regarded as true cells, or merely as
fragments of cells budded out from a true cell for a
special purpose ; but, in either case, there is not the
slightest doubt that the chief function of the red cor-
puscle is to carry oxygen.
If the oxygen is taken to the ultimate cells before
combining with the combustibles it is to consume, it
goes without saying that these combustibles themselves
must be carried there also. Nor could it be in doubt
that the chiefest of these ultimate tissues, as regards
quantity of fuel required, are the muscles. A general
and comprehensive view of the organism includes, then,
digestive apparatus and lungs as the channels of fuel-
supply ; blood and lymph channels as the transportation
system ; and muscle cells, united into muscle fibres, as
the consumption furnaces, where fuel is burned and
energy transformed and rendered available for the pur-
350
PROGRESS IN ANATOMY ANU PHYSIOLOGY
poses of the organism, supplemented by a set of ex-
cretory organs, through which the waste products —
the ashes — are eliminated from the system.
But there remain, broadly
speaking, two other sets of
organs whose size demon-
strates their importance in
the economy of the organ-
ism, yet whose functions are
not accounted for in this
synopsis. These are those
glandlike organs, such as the
spleen, which have no duct
and produce no visible se-
cretions ; and the nervous
mechanism, whose central
organs are the brain and
spinal cord. What offices
do these sets of organs per-
form in the great labor-specializing aggregation of cells
which we call a living organism?
As regards the ductless glands, the first clew to their
function was given when the great Frenchman Claude
Bernard (the man of whom his admirers loved to say,
" he is not a physiologist merely ; he is physiology it-
self ") discovered what is spoken of as the glycogenic
function of the liver. The liver itself, indeed, is not a
ductless organ, but the quantity of its biliary output
seems utterly disproportionate to its enormous size, par-
ticularly when it is considered that in the case of the
human species the liver contains normally about one-
fifth of all the blood in the entire body. Bernard dis-
covered that the blood undergoes a change of composi-
.. 351
CLACDE UEKXAKD
THE STORY OF NINETEENTH-CENTURY SCIENCE
tion in passing through the liver. The liver cells (the
peculiar forms of which had been described by Purkinje,
Henle, and Dutrochet about 1838) have the power to
convert certain of the substances that come to them into
a starchlike compound called glycogen, and to store this
substance away till it is needed by the organism. This
capacity of the liver cells is quite independent of the
bile-making power of the same cells ; hence the discov-
ery of this glycogenic function showed that an organ
may have more than one pronounced and important
specific function. But its chief importance was in giv-
ing a clew to those intermediate processes between di-
gestion and final assimilation that are now known to
be of such vital significance in the economy of the or-
ganism.
In the forty-odd years that have elapsed since this
pioneer observation of Bernard, numerous facts have
come to light showing the extreme importance of such
intermediate alterations of food-supplies in the blood as
that performed by the liver. It has been shown that
the pancreas, the spleen, the thyroid gland, the supra-
renal capsules are absolutely essential, each in its own
way, to the health of the organism, through metabolic
changes which they alone seem capable of performing ;
and it is suspected that various other tissues, including
even the muscles themselves, have somewhat similar
metabolic capacities in addition to their recognized func-
tions. But so extremely intricate is the chemistry of
the substances involved that in no single case has the ex-
act nature of the metabolisms wrought by these organs
been fully made out. Each is in its way a chemical
laboratory indispensable to the right conduct of the
organism, but the precise nature of its operations re*
352
PROGRESS IX ANATOMY AND PHYSIOLOGY
mains inscrutable. The vast importance of the opera-
tions of these intermediate organs is unquestioned.
A consideration of the functions of that other set of
organs known collectively as the nervous system is re-
served for a later chapter.
CHAPTER XI
THE CENTURY'S PROGRESS IN SCIENTIFIC MEDICINE
ALTHOUGH Napoleon Bonaparte, First Consul, was not
lacking in self-appreciation, he probably did not realize
that in selecting a physician for his o\vn needs he was
markedly influencing the progress of medical science as
a whole. Yet so strangely are cause and effect ad-
justed in human affairs that this simple act of the First
Consul had that very unexpected effect. For the man
chosen was the envoy of a new method in medical prac-
tice, and the fame which came to him through being
physician to the First Consul, and subsequently to the
Emperor, enabled him to promulgate the method in a
way otherwise impracticable. Hence the indirect but
telling value to medical science of Napoleon's selection.
The physician in question was Jean Nicolas de Corvi-
sart. His novel method was nothing more startling
than the now familiar procedure of tapping the chest of
a patient to elicit sounds indicative of diseased tissues
within. Every one has seen this done commonly
enough in our day, but at the beginning of the century
Corvisart, and perhaps some of his pupils, were proba-
bly the only physicians in the world who resorted to
354
CENTURY'S PROGRESS IN SCIENTIFIC MEDICINE
this simple and useful procedure. Hence Napoleon's
surprise when, on calling in Corvisart, after becoming
somewhat dissatisfied with his other physicians, Pinel
and Portal, his physical condition was interrogated in
this strange manner. With characteristic shrewdness
Bonaparte saw the utility of the method, and the physi-
cian who thus attempted to substitute scientific method
for guess-work in the diagnosis of disease at once found
favor in his eyes, and was installed as his regular medi-
cal adviser.
For fifteen years before this Corvisart had practised
percussion, as the chest-tapping method is called, with-
out succeeding in convincing the profession of its value.
The method itself, it should be added, had not origi-
nated with Corvisart, nor did the French physician for a
moment claim it as his own. The true originator of the
practice was the German physician Avenbrugger, who
published a oook about it as early as 1761. This book
had even been translated into French, then the language
of international communication everywhere, by Roziere
de la Chassagne, of Montpellier, in 1770 ; but no one
other than Corvisart appears to have paid any attention
to either original or translation. It was far otherwise,
however, when Corvisart translated Avenbrngger's work
anew, with important additions of his own, in 1808. By
this time a reaction had set in against the metaphysical
methods in medicine that had previously been so allur-
ing; the scientific spirit of the time was making itself felt
in medical practice; and this, combined with Corvisart's
fame, brought the method of percussion into immediate
and well-deserved popularity. Thus was laid the foun-
dation for the method of so-called physical diagnosis,
which is one of the corner-stones of modern medicine.
355 ,r
THE STORY OF NINETEENTH-CENTURY SCIENCE
The method of physical diagnosis as practised in our
day was by no means completed, however, with the
work of Corvisart. Percussion alone tells much less
than half the story that may be elicited from the organs
of the chest by proper interrogation. The remainder of
the story can only be learned by applying the ear itself
to the chest, directly or indirectly. Simple as this
seems, no one thought of practising it for some years
after Corvisart had shown the value of percussion.
Then, in 1815, another Paris physician, Rene Theophile
Hyacinthe Laennec, discovered, almost by accident, that
the sound of the heart-beat could be heard surprisingly
through a cylinder of paper held to the ear and against
the patient's chest. Acting on the hint thus received,
Laennec substituted a hollow cylinder of wood for the
paper, and found himself provided with an instrument
through which not merely heart sounds, but murmurs
of the lungs in respiration, could be heard with almost
startling distinctness.
The possibility of associating the varying chest sounds
with diseased conditions of the organs within appealed
to the fertile mind of Laennec as opening new vistas in
therapeutics, which he determined to enter to the fullest
extent practicable. His connection with the hospitals of
Paris gave him full opportunity in this direction, and his
labors of the next few years served not merely to estab-
lish the value of the new method as an aid to diagnosis,
but laid the foundation also for the science of morbid
anatomy^ In 1819 Laennec published the results of his
labors in a work called Traite cT Auscultation M^diate^
a work which forms one of the landmarks of scientific
medicine. By mediate auscultation is meant of course
the interrogation of the chest with the aid of the little
356
LAKNNEC, INVENTOR OF THE STETHOSCOPE, AT THE NECKElt HOSPITAL,
PARIS
CENTURY'S PROGRESS IN SCIENTIFIC MEDICINE
instrument already referred to, an instrument which its
originator thought hardly worth naming until various
barbarous appellations were applied to it by others, after
which Laennec decided to call it the stethoscope, a name
which it has ever since retained.
In subsequent years the form of the stethoscope, as
usually employed, was modified, and its value augment-
ed by a binauricular attachment ; and in very recent
years a further improvement has been made through ap-
plication of the principle of the telephone ; but the es-
sentials of auscultation with the stethoscope were estab-
lished in much detail by Laennec, and the honor must
always be his of thus taking one of the longest single
steps by which practical medicine has in our century ac-
quired the right to be considered a rational science.
Laennec's efforts cost him his life, for he died in 1826
of a lung disease acquired in the course of his hospital
practice ; but even before this his fame was universal,
and the value of his method had been recognized all
over the world. Not long after, in 1828, yet another
French physician, Piorry, perfected the method of per-
cussion by introducing the custom of tapping, not the
chest directly, but the finger or a small metal or hard
rubber plate held against the chest — mediate percussion,
in short. This perfected the methods of physical diag-
nosis of diseases of the chest in all essentials ; and from
that day till this percussion and auscultation have held
an unquestioned place in the regular armamentarium of
the physician.
Coupled with the new method of physical diagnosis
in the effort to substitute knowledge for guess-work
came the studies of the experimental physiologists — in
particular, Marshall Hall in England, and Francois Ma-
339
THE STORY OF NINETEENTH-CENTURY SCIENCE
gendie in France ; and the joint efforts of these various
workers led presently to the abandonment of those se-
vere and often irrational depletive methods — blood-let-
ting and the like — that had previously dominated med-
ical practice. To this end also the " statistical method,"
introduced by Louis and his followers, largely contrib-
uted ; and by the close of the first third of our century
the idea was gaining ground that the province of thera-
peutics is to aid nature in combating disease, and that
this may often be better accomplished by simple means
than by the heroic measures hitherto thought necessary.
In a word, scientific empiricism was beginning to gain a
hearing in medicine, as against the metaphysical precon-
ceptions of the earlier generations.
ii
I have just adverted to the fact that Napoleon Bona-
parte, as First Consul and as Emperor, was the victim
of a malady which caused him to seek the advice of the
most distinguished physicians of Paris. It is a little
shocking to modern sensibilities to read that these
physicians, except Corvisart, diagnosed the distinguished
patient's malady as " gale repercutee " — that is to say,
in idiomatic English, the itch "struck in." It is hardly
necessary to say that no physician of to-day would
make so inconsiderate a diagnosis in the case of a royal
patient. If by any chance a distinguished patient were
afflicted with the itch, the sagacious physician would
carefully hide the fact behind circumlocutions, and pro-
ceed to eradicate the disease with all despatch. That
the physicians of Napoleon did otherwise is evidence
that at the beginning of the century the disease in ques-
360
CENTURY'S PROGRESS IN SCIENTIFIC MEDICINE
tion enjoyed a very different status. At that time, itch,
instead of being a most plebeian malady, was, so to say, a
court disease. It enjoyed a circulation, in high circles
and in low, that modern therapeutics has quite denied
it ; and the physicians of the time gave it a fictitious
added importance by ascribing to its influence the ex-
istence of almost any obscure malady that came under
their observation. Long after Napoleon's time, gale
continued to hold this proud distinction. For example,
the imaginative Dr. Hahnemann did not hesitate to af-
firm, as a positive maxim, that three-fourths of all the
ills that flesh is heir to were in reality nothing but va-
rious forms of " gale repercutee."
All of which goes to show how easy it may be for a
masked pretender to impose on credulous humanity ; for
nothing is more clearly established in modern knowl-
edge than the fact that " gale repercutee " was simply a
name to hide a profound ignorance ; no such disease ex-
ists, or ever did exist. Gale itself is a sufficiently tangi-
ble reality, to be sure ; but it is a purely local disease of
the skin, due to a perfectly definite cause, and the dire
internal conditions formerly ascribed to it have really no
causal connection with it whatever. This definite cause,
as every one nowadays knows, is nothing more or less
than a microscopic insect which has found lodgment on
the skin, and has burrowed and made itself at home
there. Kill that insect, and the disease is no more •
hence it has come to be an axiom with the modern
physician that the itch is one of the three or four dis-
eases that he positively is able to cure, and that very
speedily. But it was far otherwise with the physicians
of the first third of our century, because to them the
cause of the disease was an absolute mystery.
361
THE STORY OF NINETEENTH-CENTURY SCIENCE
It is true that here and there a physician had claimed
to find an insect lodged in the skin of a sufferer from
itch, and two or three times the claim had been made
that this was the cause of the malady, but such views
were quite ignored by the general profession, and in
1833 it was stated in an authoritative medical treatise
that the "cause of gale is absolutely unknown." But
even at this time, as it curiously happened, there were
certain ignorant laymen who had attained to a bit of
medical knowledge that was withheld from the inner
circles of the profession. As the peasantry of England
before Jenner had known of the curative value of cow-
pox over small-pox, so the peasant women of Poland
had learned that the annoying skin disease from which
they suffered was caused by an almost invisible insect,
and, furthermore, had acquired the trick of dislodging
the pestiferous little creature with the point of a needle.
From them a youth of the country, F. Renucci by
name, learned the open secret. He conveyed it to Paris
when he went there to study medicine, and in 1S3±
demonstrated it to his master, Alibert. This physician,
at first sceptical, soon was convinced, and gave out the
discovery to the medical world with an authority that
led to early acceptance.
Now the importance of all this, in the present con-
nection, is not at all that it gave the clew to the method
of cure of a single disease. What makes the discovery
epochal is the fact that it dropped a brand-new idea
into the medical ranks — an idea destined, in the long-
run, to prove itself a veritable bomb — the idea, namely,
that a minute and quite unsuspected animal parasite
may be the cause of a well-known, widely prevalent,
and important human disease. Of course the full force
362
CENTURY'S PROGRESS IN SCIENTIFIC MEDICINE
of this idea could only be appreciated in the light of
later knowledge ; but even at the time of its coming it
sufficed to give a great impetus to that new medical
knowledge, based on microscopical studies, which had
but recently been made accessible by the inventions
of the lens-makers. The new knowledge clarified one
very turbid medical pool, and pointed the way to the
clarification of many others.
Almost at the same time that the Polish medical stu-
dent was demonstrating the itch mite in Paris, it
chanced, curiously enough, that another medical stu-
dent, this time an Englishman, made an analogous dis-
covery, of perhaps even greater importance. Indeed,
this English discovery in its initial stages slightly ante-
dated the other, for it was in 1833 that the student in
question, James Paget, interne in Saint Bartholomew's
Hospital, London, while dissecting the muscular tissues
of a human subject, found little specks of extraneous
matter, which, when taken to the professor of compara-
tive anatomy, Richard Owen, were ascertained, with the
aid of the microscope, to be the cocoon of a minute and
hitherto unknown insect. Owen named the insect Tri-
china spiralis. After the discovery was published, it
transpired that similar specks had been observed by
several earlier investigators, but no one had previously
suspected, or, at any rate, demonstrated their nature.
Nor was the full story of the trichina made out for a
long time after Owen's discovery. It was not till 1847
that the American anatomist Dr. Joseph Leidy found
the cysts of trichina in the tissues of pork ; and another
decade or so elapsed after that before German workers,
chief among whom were Leuckart, Virchow, and Zen-
ker, proved that the parasite gets into the human sys-
363
THE STORY OF NINETEENTH-CENTURY SCIENCE
tern through ingestion of infected pork, and that it
causes a definite set of symptons of disease, which hith-
KUDOLF VIKCHOW
erto had been mistaken for rheumatism, typhoid fever,
and other maladies. Then the medical world was agog
for a time over the subject of trichinosis ; government in-
spection of pork was established in some parts of Ger-
364
CENTURY'S PROGRESS IN SCIENTIFiC MEDICINE
many ; American pork was excluded altogether from
France ; and the whole subject thus came prominently to
public attention. But important as the trichina parasite
proved on its own account in the end, its greatest im-
portance, after all, was in the share it played in direct-
ing attention at the time of its discovery in 1833 to the
subject of microscopic parasites in general.
The decade that followed that discovery was a time
of great activity in the study of microscopic organisms
and microscopic tissues, and such men as Ehrenberg and
Henle and Bory Saint Yincent and Kolliker and Roki-
tansky and Reraak and Dujardin were widening the
bounds of knowledge of this new subject with details
that cannot be more than referred to here. But the
crowning achievement of the period in this direction
was the discovery made by the German J. L. Schoen-
lein in 1839, that a very common and most distressing
disease of the scalp, known as favus, is really due to the
presence and growth on the scalp of a vegetable organ-
ism of microscopic size. Thus it was made clear that
not merely animal but also vegetable organisms of ob-
scure, microscopic species have causal relations to the
diseases with which mankind is afflicted. This knowl-
edge of the parasites was another long step in the direc-
tion of scientific medical knowledge; but the heights to
which this knowledge led were not to be scaled, or even
recognized, until another generation of workers had en-
tered the field.
in
Meantime, in quite another field of medicine, events
were developing which led presently to a revelation of
greater immediate importance to humanity than any
365
THE STORY OF NINETEENTH-CENTURY SCIENCE
other discovery that had come in the century, perhaps
in any field of science whatever. This was the discov-
ery of the pain-dispelling power of the vapor of sul-
phuric ether, inhaled by a patient undergoing a surgical
operation. This discovery come solely out of America,
and it stands curiously isolated, since apparently no
minds in any other country were trending towards it
even vaguely. Davy, in England, had indeed originated
the method of medication by inhalation, and carried out
some most interesting experiments fifty years earlier,
and it was doubtless his experiments with nitrous oxide
gas that gave the clew to one of the American investi-
gators; but this was the sole contribution of preceding
generations to the subject, and since the beginning of
the century, when Davy turned his attention to other
matters, no one had made the slightest advance along
the same line until an American dentist renewed the
investigation. Moreover, there had been nothing- in
Davy's experiments to show that a surgical operation
might be rendered painless in this way ; and, indeed,
the surgeons of Europe had acknowledged with one ac-
cord that all hope of finding a means to secure this
most desirable end must be utterly abandoned — that the
surgeon's knife must ever remain a synonym for slow
and indescribable torture. By an odd coincidence it
chanced that Sir Benjamin Brodie, the acknowledged
leader of English surgeons, had publicly expressed this
as his deliberate though regretted opinion at a time
when the quest which he considered futile had already
led to the most brilliant success in America, and while
the announcement of the discovery, which then had no
transatlantic cable to convey it, was actually on its way
to the Old World.
366
WILLIAM T. G. MO11TON
CENTURY'S PROGRESS IN SCIENTIFIC MEDICINE
The American dentist just referred to, who was, with
one exception to be noted presently, the first man in the
world to conceive that the administration of a definite
drug might render a surgical operation painless, and to
give the belief application, was Dr. Horace Wells, of
Hartford, Connecticut. The drug with which he experi-
mented was nitrous oxide; the operation which he ren-
dered painless was no more important than the extrac-
tion of a tooth — yet it sufficed to mark a principle ; the
year of the experiment was 1844.
The experiments of Dr. Wells, however, though im-
portant, were not sufficiently demonstrative to bring the
matter prominently to the attention of the medical
world. The drug with which he experimented proved
not always reliable, and he himself seems ultimately to
have given the matter up, or at least to have relaxed his
efforts. But meantime a friend, to whom he had com-
municated his belief and expectations, took the matter
up, and with unremitting zeal carried forward experi-
ments that were destined to lead to more tangible re-
sults. This friend was another dentist, Dr. W. T. G.
Morton, of Boston, then a young man, full of youthful
energy and enthusiasm. He seems to have felt that the
drug with which Wells had experimented was not the
most practicable one for the purpose, and so for several
months he experimented with other allied drugs, until
finally he hit upon sulphuric ether, and with this was
able to make experiments upon animals, and then upon
patients in the dental chair, that seemed to him abso-
lutely demonstrative.
Full of eager enthusiasm, and absolutely confident of his
results, he at once went to Dr. J. C. Warren, one of the
foremost surgeons of Boston, and asked permission to
2 A 369
THE .STORY OF NINETEENTH-CENTURY SCIENCE
test his discovery decisively on one of the patients at
the Boston Hospital during a severe operation. The re-
quest was granted ; the test was made on October 16, 1846,
in the presence of several of the foremost surgeons of
the city and of a body of medical students. The pa-
tient slept quietly while the surgeon's knife was plied,
and awoke to astonished comprehension that the ordeal
was over. The impossible, the miraculous, had been ac-
complished.
Swiftly as steam could carry it — slowly enough we
should think it to-day — the news was heralded to all the
world. It was received in Europe with incredulity,
which vanished before repeated experiments. Surgeons
were loath to believe that ether, a drug that had long
held a place in the subordinate armamentarium of the
physician, could accomplish such a miracle. " But scepti-
cism vanished before the tests which any surgeon might
make, and which surgeons all over the world did make
within the next few weeks. Then there came a linger-
ing outcry from a few surgeons, notably some of the
Parisians, that the shock of pain was beneficial to the
patient, hence that anesthesia — as Dr. Oliver Wendell
Holmes had christened the new method — was a proced-
ure not to be advised. Then, too, there came a hue-
and-cry from many a pulpit that pain was God-given,
and hence, on moral grounds, to be clung to rather than
renounced. But the outcry of the antediluvians of both
hospital and pulpit quickly received its quietus ; for soon
it was clear that the patient who did not suffer the
shock of pain during an operation rallied better than the
one who did so suffer, while all humanity outside the
pulpit cried shame to the spirit that would doom man-
kind to suffer needless agony. And so within a few
37(T
CRAWFOKD W. LONG
After a crayon portrait taken at the time of his discovery of the anaesthetic
properties of sulphuric ether .
CENTURY'S PROGRESS IN SCIENTIFIC MEDICINE
months after that initial operation at the Boston Hos-
pital in 18-i6, ether had made good its conquest of pain
throughout the civilized world. Only by the most ac-
tive use of the imagination can we of this present day
realize the full meaning of that victory.
It remains to be added that in the subsequent bicker-
ings over the discovery — such bickerings as follow every
great advance — two other names came into prominent
notice as sharers in the glory of the new method. Both
these were Americans — the one, Dr. Charles T. Jackson,
of Boston ; the other, Dr. Crawford W. Long, of Ala-
bama. As to Dr. Jackson, it is sufficient to say that he
seems to have had some vague inkling of the peculiar
properties of ether before Morton's discovery. He even
suggested the use of this drug to Morton, not knowing
that Morton had alread}^ tried it ; but this is the full
measure of his association with the discovery. Hence it
is clear that Jackson's claim to equal share with Mor-
ton in the discovery was unwarranted, not to say ab-
surd.
Dr. Long's association with the matter was far differ-
ent, and altogether honorable. By one of those coinci-
dences so common in the history of discovery, he was
experimenting with ether as a pain-destroyer simulta-
neously with Morton, though neither so much as knew
of the existence of the other. While a medical student
he had once inhaled ether for the intoxicant effects, as
other medical students were wont to do, and when par-
tially under influence of the drug he had noticed that a
chance blow to his shins was painless. This gave him
the idea that ether might be used in surgical operations;
and in subsequent years, in the course of his practice in
a small Georgia town, he put the idea into successful
373
THE STORY OF NINETEENTH-CENTURY SCIENCE
execution. There appears to be no doubt whatever that
he performed successful minor operations under ether
some two or three years before Morton's final demon-
stration ; hence that the merit of first using the drug,
or indeed any drug, in this way belongs to him. But
unfortunately Dr. Long did not quite trust the evidence
of his own experiments. Just at that time the medical
journals were full of accounts of experiments in which
painless operations were said to be performed through
practice of hypnotism, and Dr. Long feared that his own
success might be due to an incidental hypnotic influence
rather than to the drug. Hence he delayed announcing
his apparent discovery until he should have opportunity
for further tests — and opportunities did not come every
day to the country practitioner. And while he waited,
Morton anticipated him, and the discovery was made
known to the world without his aid. It was a true sci-
entific caution that actuated Dr. Long to this delay, but
the caution cost him the credit, which might otherwise
have been his, of giving to the world one of the greatest
blessings that science has ever conferred upon hu-
manity.
A few months after the use of ether became general,
the Scotch surgeon Sir J. Y. Simpson discovered that
another drug, chloroform, could be administered with
similar effects; that it would, indeed, in many cases pro-
duce anaesthesia more advantageously even than ether.
From that day till this surgeons have been more or less
divided in opinion as to the relative merits of the two
drugs ; but this fact, of course, has no bearing whatever
upon the merit of the first discovery of the method of
anaesthesia. Even had some other drug subsequently
quite banished ether, the honor of the discovery of the
374
CENTURY'S PROGRESS IN SCIENTIFIC MEDICINE
beneficent method of anaesthesia would have been in no
wise invalidated. And despite all cavillings, it is un-
equivocally established that the man who gave that
method to the world was William T. G. Morton.
iv
This discovery of the anaesthetic power of drugs was
destined presently, in addition to its direct beneficences,
to aid greatly in the progress of scientific medicine, by
facilitating those experimental studies of animals from
which, before the day of anaesthesia, many humane
physicians were withheld, and which in recent years have
led to discoveries of such inestimable value to humanity.
But for the moment this possibility was quite overshad-
owed by the direct benefits of anesthesia, and the long
strides that were taken in scientific medicine during the
first fifteen years after Morton's discovery were mainly
independent of such aid. These steps were taken, in-
deed, in a field that at first glance might seem to have
a very slight connection with medicine. Moreover, the
chief worker in the field was not himself a physician.
He was a chemist, and the work in which he was now
engaged was the study of alcoholic fermentation in vi-
nous liquors. Yet these studies paved the way for the
most important advances that medicine has made in any
century towards the plane of true science ; and to this
man more than to any other single individual — it might
almost be said more than to all other individuals — was
due this wonderful advance. It is almost superfluous to
add that the name of this marvellous chemist was Louis
Pasteur.
The studies of fermentation which Pasteur entered
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THE STORY OF NINETEENTH-CENTURY SCIENCE
upon in 1854 were aimed at the solution of a contro-
versy that had been waging in the scientific world with
varying degrees of activity for a quarter of a century.
Back in the thirties, in the day of the early enthusiasm over
the perfected microscope, there had arisen a new inter-
est in the minute forms of life which Leeuwenhoek and
some of the other early workers with the lens had first
described, and which now were shown to be of almost
universal prevalence. These minute organisms had been
studied more or less by a host of observers, but in par-
ticular by the Frenchman Cagniard Latour and the Ger-
man, of cell-theory fame, Theodor Schwann. These
men, working independently, had reached the conclu-
sion, about 1837, that the micro-organisms play a vastly
more important role in the economy of nature than any
one previously had supposed. They held, for example,
that the minute specks which largely make up the sub-
stance of yeast are living vegetable organisms, and that
the growth of these organisms is the cause of the im-
portant and familiar process of fermentation. They
even came to hold, at least tentatively, the opinion that
the somewhat similar micro-organisms to be found in all
putrefying matter, animal or vegetable, had a causal re-
lation to the process of putrefaction.
This view, particularly as to the nature of putrefac-
tion, was expressed even more outspokenly a little later
by the French botanist Turpin. Views so supported
naturally gained a following ; it was equally natural
that so radical an innovation should be antagonized. In
this case it chanced that one of the most dominating
scientific minds of the time, that of Liebig, took a firm
and aggressive stand against the new doctrine. In 1839
he promulgated his famous doctrine of fermentation, in
376
THEODOU SCIIWANN
CENTURY'S PROGRESS IN SCIENTIFIC MEDICINE
which he stood out firmly against any " vitalistic " ex-
planation of the phenomena, alleging that the presence
of micro-organisms in fermenting and putrefying sub-
stances was merely incidental, and in no sense causal.
This opinion of the great German chemist was in a
measure substantiated by experiments of his compatriot
Helmholtz, whose earlier experiments confirmed, but
later ones contradicted, the observations of Schwann,
and this combined authority gave the vitalistic concep-
tion a blow from which it had not rallied at the time
when Pasteur entered the field. Indeed, it was current-
ly regarded as settled that the early students of the
subject had vastly overestimated the importance of mi-
cro-organisms.
o
And so it came as a new revelation to the generality of
scientists of the time, when, in 1857 and the succeeding
half-decade, Pasteur published the results of his re-
searches, in which the question had been put to a series
of altogether new tests, and brought to unequivocal
demonstration.
He proved that the micro-organisms do all that his
most imaginative predecessors had suspected, and more.
Without them, he proved, there would be no fermenta-
tion, no putrefaction — no decay of any tissues, except by
the slow process of oxidation. It is the microscopic
yeast plant which, by seizing on certain atoms of the
molecule, liberates the remaining atoms in the form of
carbonic acid and alcohol, thus effecting fermentation;
it is another microscopic plant — a bacterium, asDevaine
had christened it — which in a similar way effects the
destruction of organic molecules, producing the condi-
tion which we call putrefaction. Pasteur showed, to
the amazement of biologists, that there are certain forms
379 .
THE STORY OF NINETEENTH-CENTURY SCIENCE
of these bacteria which secure the oxygen which all or-
ganic life requires, not from the air, but by breaking up
unstable molecules in which oxygen is combined ; that
putrefaction, in short, has its foundation in the activities
of these so-called anaerobic bacteria.
In a word, Pasteur showed that all the many familiar
processes of the decay of organic tissues are, in effect,
forms of fermentation, and would not take place at all
except for the presence of the living micro-organisms.
A piece of meat, for example, suspended in an atmos-
phere free from germs, will dry up gradually, without
the slightest sign of putrefaction, regardless of the tem-
perature or other conditions to which it may have been
subjected.
There was nothing in these studies bearing directly
upon the question of animal diseases, yet before they
were finished they had stimulated progress in more than
one field of pathology. At the very outset they sufficed
to start afresh the inquiry as to the role played by mi-
cro-organisms in disease. In particular, they led the
French physician Devaine to return to some interrupted
studies which he had made ten years before, in reference
to the animal disease called anthrax, or splenic fever, a
disease that cost the farmers of Europe millions of
francs annually through loss of sheep and cattle. In
1850, Devaine had seen multitudes of bacteria in the
blood of animals who had died of anthrax, but he did
not at that time think of them as having a causal rela-
tion to the disease. Now, however, in 1863, stimulated
by Pasteur's new revelations regarding the power of
bacteria, he returned to the subject, and soon became
convinced, through experiments by means of inocula-
tion, that the microscopic organisms he had discovered
380
CENTURY'S PROGRESS IN SCIENTIFIC MEDICINE
were the veritable and the sole cause of the infectious
disease anthrax.
The publication of this belief in 1863 aroused a furor
of controversy. That a microscopic vegetable could
cause a virulent systemic disease was an idea altogether
too startling to be accepted in a day, and the generality
of biologists and physicians demanded more convincing
proofs than Devaine as yet was able to offer.
Naturally a host of other investigators all over the
world entered the field. Foremost among these was the
German Dr. Robert Koch, who soon corroborated all
that Devaine had observed, and carried the experiments
further in the direction of the cultivation of successive
generations of the bacteria in artificial media, inocula-
tions being made from such pure cultures of the eighth
generation, with the astonishing result that animals thus
inoculated at once succumbed to the disease.
Such experiments seem demonstrative, yet the world
was unconvinced, and in 1876, while the controversy
was still at its height, Pasteur was prevailed upon to
take the matter in hand. The great chemist was be-
coming more and more exclusively a biologist as the
years passed, and in recent years his famous studies of
thesilk-worm diseases, which he proved due to bacterial in-
fection, and of theqnestion of spontaneous generation, had
given him unequalled resources in microscopical technique.
And so when, with the aid of his laboratory associates
Duclaux and Chamberland and Eoux, he took up the
mooted anthrax question, the scientific world awaited
the issue with bated breath. And when, in 1877, Pas-
teur was ready to report on his studies of anthrax, he
came forward with such a wealth of demonstrative ex-
periments— experiments the rigid accuracy of which no
381
THE STORY OF NINETEENTH-CENTURY SCIENCE
one would for a moment think of questioning — going to
prove the bacterial origin of anthrax, that scepticism
was at last quieted for all time to come.
Henceforth no one could doubt that the contagious
disease anthrax is due exclusively to the introduction
into an animal's system of a specific germ — a micro-
scopic plant — which develops there. And no logical
mind could have a reasonable doubt that what is proved
true of one infectious disease would some day be proved
true also of other, perhaps of all, forms of infectious
maladies.
Hitherto the cause of contagion, by which certain
maladies spread from individual to individual, had been
a total mystery, quite unillumined by the vague terms
"miasm," "humor," "virus," and the like cloaks of ig-
norance. Here and there a prophet of science, as Sch wann
and Henle, had guessed the secret; but guessing, in sci-
ence, is far enough from knowing. Now, for the first
time, the world knew, and medicine had taken another
gigantic stride towards the heights of exact science.
Meantime in a different, though allied, field of medi-
cine there had been a complementary growth that led
to immediate results of even more practical importance.
I mean the theory and practice of antisepsis in surgery.
This advance, like the other, came as a direct outgrowth
of Pasteur's fermentation studies of alcoholic beverages,
though not at the hands of Pasteur himself. Struck by
the boundless implications of Pasteur's revelations re-
garding the bacteria, Dr. Joseph Lister (the present
Lord Lister), then of Glasgow, set about as early as
382
SIK JOSEPH LISTER
CENTURY'S PROGRESS IN SCIENTIFIC MEDICINE
1860 to make a wonderful application of these ideas. If
putrefaction is always due to bacterial development, he
argued, this must apply as well to living as to dead tis-
sues ; hence the putrefactive changes which occur in
wounds and after operations on the human subject, from
which blood-poisoning so often follows, might be abso-
lutely prevented if the injured surfaces could be kept
free from access of the germs of decay.
In the hope of accomplishing this result, Lister began
experimenting with drugs that might kill the bacteria
without injury to the patient, and with means to pre-
vent further access of germs once a wound was freed
from them. How well he succeeded, all the world
knows ; how bitterly he was antagonized for about a
score of years, most of the world has already forgotten.
As early as 1867, Lister was able to publish results
pointing towards success in his great project ; yet so in-
credulous were surgeons in general that even some years
later the leading surgeons across the Channel had not
so much as heard of his efforts. In 1870 the soldiers of
Paris died, as of old, of hospital gangrene ; and when in
1871 the French surgeon Alphonse Guerin, stimulated
by Pasteur's studies, conceived the idea of dressing
wrounds with cotton in the hope of keeping germs from
entering them, he was quite unaware that a British con-
temporary had preceded him by a full decade in this ef-
fort at prevention, and had made long strides towards
complete success. Lister's priority, however, and the
superiority of his method, were freely admitted by the
French Academy of Science, which in 1881 officially
crowned his achievement, as the Royal Society of Lon-
don had done the year before. *
By this time, to be sure, as everybody knows, Lister's
SB 385
THE STORY OF NINETEENTH-CENTURY SCIENCE
new methods had made their way everywhere, revolu-
tionizing the practice of surgery, and practically banish-
ing from the earth maladies that hitherto had been the
terror of the surgeon and the opprobrium of his art.
And these bedside studies, conducted in the end by
thousands of men who had no knowledge of microscopy,
had a large share in establishing the general belief in
the causal relation that micro-organisms bear to disease,
which by about the year 1880 had taken possession of
the medical world. But they did more ; they brought
into equal prominence the idea that, the cause of a dis-
eased condition being known, it may be possible as
never before to grapple writh and eradicate that condi-
tion.
The controversy over spontaneous generation, which,
thanks to Pasteur and Tyndall, had just been brought
to a termination, made it clear that no bacterium need
be feared where an antecedent bacterium had not found
lodgment ; Listerism in surgery had now shown how
much might be accomplished towards preventing the
access of germs to abraded surfaces of the body, and
destroying those that already had found lodgment
there. As yet, however, there was no inkling of a way
in which a corresponding onslaught might be made upon
those other germs which find their way into the animal
organism by way of the mouth and the nostrils, and which,
as was now clear, are the cause of those contagious diseases
which, first and last, claim so large a proportion of man-
kind for their victims. How such means might be
found now became the anxious thought of every im-
aginative physician, of every working micro- biologist.
As it happened, the world was not kept long in sus-
pense. Almost before the proposition had taken shape
CENTURY'S PROGRESS IN SCIENTIFIC MEDICINE
in the minds of the other leaders, Pasteur had found a
solution. Guided by the empirical success of Jenner,
he, like many others, had long practised inoculation ex-
periments, and on the 9th of February, 1880, he an-
nounced to the French Academy of Science that he had
found a method of so reducing the virulence of a disease
germ that, when introduced into the system of a sus-
ceptible animal, it produced only a mild form of the dis-
ease, which, however, sufficed to protect against the
usual virulent form exactly as vaccinia protects against
small-pox. The particular disease experimented with
was that infectious malady of poultry known familiarly
as "chicken cholera." In October of the same year
Pasteur announced the method by which this "attenu-
ation of the virus," as he termed it, had been brought
about — by cultivation of the disease germs in artificial
media, exposed to the air; and he did not hesitate to
assert his belief that the method would prove " suscepti-
ble of generalization " — that is to say, of application to
other diseases than the particular one in question.
Within a few months he made good this prophecy,
for in February, 1881, he announced to the Academy
that, with the aid, as before, of his associates MM.
Chamberland and Roux, lie had produced an attenuated
virus of the anthrax microbe, by the use of which he
could protect sheep, and presumably cattle, against that
fatal malady.
This announcement was immediately challenged in
a way that brought it to the attention of the entire
world. The president of an agricultural society, real-
izing the enormous importance of the subject, proposed
to Pasteur that his alleged discovery should be submit-
ted to a decisive public test. He proposed to furnish a
387
THE STORY OF NINETEENTH-CENTURY SCIENCE
drove of fifty sheep, half of which were to be inoculated
with the attenuated virus by Pasteur. Subsequently all
the sheep were to be inoculated with virulent virus, all
being kept together in one pen, under precisely the same
conditions. The "protected" sheep were to remain
healthy ; the unprotected ones to die of anthrax ; so
read the terms of the proposition. Pasteur accepted
the challenge ; he even permitted a change in the pro-
gramme by which two goats were substituted for two
of the sheep, and ten cattle added ; stipulating, however,
that since his experiments had not yet been extended to
cattle, these should not be regarded as falling rigidly
within the terms of the test.
It was a test to try the soul of any man, for all the
world looked on askance, prepared to deride the maker
of so preposterous a claim as soon as his claim should be
proved baseless. Not even the fame of Pasteur could
make the public at large, lay or scientific, believe in the
possibility of what he proposed to accomplish. There
was time for all the world to be informed of the proced-
ure, for the first "preventive" inoculation, or vaccina-
tion, as Pasteur termed it, was made on the 5th of May,
the second on the 17th; and another interval of two
weeks must elapse before the final inoculations with the
unattenuated virus. Twenty-four sheep, one goat, and
five cattle were submitted to the preliminary vaccina-
tions. Then, on the 31st of May, all sixty of the ani-
mals were inoculated, a protected and an unprotected
one alternately, with an extremely virulent culture of
anthrax microbes that had been in Pasteur's laboratory
since 187T. This accomplished, the animals were left
together in one enclosure, to await the issue.
Two days later, the 2d of June, at the appointed hour
388
CENTURY'S PROGRESS IN SCIENTIFIC MEDICINE
of rendezvous, a vast crowd, composed of veterinary sur-
geons, newspaper correspondents, and farmers from far
and near, gathered to witness the closing scenes of this
scientific tourney. What they saw was one of the most
dramatic scenes in the history of peaceful science — a
scene which, as Pasteur declared afterwards, "amazed
the assembly." Scattered about the enclosure, dead,
dying, or manifestly sick unto death, lay the unprotected
animals, one and all; while each and every "protected"
animal stalked unconcernedly about with every appear-
ance of perfect health. Twenty of the sheep and the
one goat were already dead ; two other sheep expired
under the eyes of the spectators ; the remaining victims
lingered but a few hours longer. Thus in a manner
theatrical enough, not to say tragic, was proclaimed the
unequivocal victory of science. Naturally enough, the
unbelievers struck their colors and surrendered without
terms ; the principle of protective vaccination, with a
virus experimentally prepared in the laboratory, was es-
tablished beyond the reach of controversy.
That memorable scientific battle marked the begin-
ning of a new era in medicine. It was a foregone con-
clusion that the principle thus established would be still
further generalized ; that it would be applied to human
maladies; that, in all probability, it would grapple suc-
cessfully, sooner or later, with many infectious diseases.
That expectation has advanced rapidly towards realiza-
tion. Pasteur himself made the application to the hu-
man subject in the disease hydrophobia, in 1885, since
which time that hitherto most fatal of maladies has
largely lost its terrors. Thousands of persons, bitten
by mad dogs, have been snatched from the fatal conse-
quences of that mishap by this method, at the Pasteur
*389
THE STORY OF NINETEENTH-CENTURY SCIENCE
Institute in Paris, and at the similar institutes, built on
the model of this parent one, that have been established
all over the world, in regions as widely separated as
New York and Nha-Trang.
VI
In the production of the rabies vaccine Pasteur and
his associates developed a method of attenuation of a
virus quite different from that which had been employed
in the case of the vaccines of chicken cholera and of an-
thrax. The rabies virus was inoculated into the system
of guinea-pigs or rabbits, and, in effect, cultivated in the
systems of these animals. The spinal cord of these in-
fected animals was found to be rich in the virus, which
rapidly became attenuated when the cord was dried in
the air. The preventive virus, of varying strengths, was
made by maceration of these cords at varying stages of
desiccation. This cultivation of a virus within the ani-
mal organism, suggested, no doubt, by the familiar Jen-
nerian method of securing small-pox vaccine, was at the
same time a step in the direction of a new therapeutic
procedure which was destined presently to become of
all-absorbing importance — the method, namely, of so-
called serum-therapy, or the treatment of a disease with
the blood serum of an animal that has been subjected to
protective inoculation against that disease.
The possibility of such a method was suggested by
the familiar observation, made by Pasteur and numerous
other workers, that animals of different species differ
widely in their susceptibility to various maladies ; and
that the virus of a given disease may become more and
more virulent when passed through the systems of suc-
390
CENTURY'S PROGRESS IN SCIENTIFIC MEDICINE
cessive individuals of one species, and, contrariwise, less
and less virulent when passed through the systems of
successive individuals of another species. These facts
LOUIS PASTEUR
suggested the theory that the blood of resistant animals
might contain something directly antagonistic to the
virus, and the hope that this something might be trans-
ferred with curative effect to the blood of an infected
susceptible animal. Numerous experimenters all over
39}
THE STORY OF NINETEENTH-CENTURY SCIENCE
the world made investigations along the line of this al-
luring possibilit\r, the leaders perhaps being Drs. Behring
and Kitasato, closely followed by Dr. Koux and his as-
sociates of the Pasteur Institute of Paris. Definite re-
sults were announced by Behring in 1892 regarding two
important diseases — tetanus and diphtheria — but the
method did not come into general notice until 1894,
when Dr. Roux read an epoch-marking paper on the sub-
ject at the Congress of Hygiene at Buda-Pesth.
In this paper, Dr. Roux, after adverting to the labors
of Behring, Ehrlich, Boer, Kossel, and Wasserman, de-
scribed in detail the methods that had been developed
at the Pasteur Institute for the development of the cura-
tive serum, to which Behring had given the since familiar
name antitoxine. The method consists, first, of the cul-
tivation, for some months, of the diphtheria bacillus
(called the Klebs-Loeffler bacillus, in honor of its dis-
coverers) in an artificial bouillon, for the development
of a powerful toxine capable of giving the disease in a
virulent form.
This toxine, after certain details of mechanical treat-
ment, is injected in small but increasing doses into the
system of an animal, care being taken to graduate the
amount so that the animal does not succumb to the
disease. After a certain course of this treatment it is
found that a portion of blood serum of the animal so
treated will act in a curative way if injected into the
blood of another animal, or a human patient, suffering
with diphtheria. In other words, according to theory,
an antitoxine has been developed in the system of
the animal subjected to the progressive inoculations
of the diphtheria toxine. In Dr. Roux's experience
the animal best suited for the purpose is the horse,
392
CENTURY'S PROGRESS IN SCIENTIFIC MEDICINE
though almost any of the domesticated animals will
serve the purpose.
But Dr. Roux's paper did not stop with the description
of laboratory methods. It told also of the practical ap-
plication of the serum to the treatment of numerous cases
of diphtheria in the hospitals of Paris — applications that
had met with a gratifying measure of success. He made
it clear that a means had been found of coping success-
fully with what had been one of the most virulent and
intractable of the diseases of childhood. Hence it was
not strange that his paper made a sensation in all circles,
medical and lay alike.
Physicians from all over the world flocked to Paris to
learn the details of the open secret, and within a few
months the new serum-therapy had an acknowledged
standing with the medical profession everywhere. What
it had accomplished was regarded as but an earnest of
what the new method might accomplish presently when
applied to the other infectious diseases.
Efforts at such applications were immediately begun
in numberless directions — had, indeed, been under way
in many a laboratory for some years before. It is too
early yet to speak of the results in detail. But enough
has been done to show that this method also is suscep-
tible of the widest generalization. It is not easy at the
present stage to sift that which is tentative from that
which will be permanent ; but so great an authority as
Behring does not hesitate to affirm that to-day we pos-
sess, in addition to the diphtheria antitoxine, equally
specific antitoxines of tetanus, cholera, typhus -fever,
pneumonia, and tuberculosis — a set of diseases which in
the aggregate account for a startling proportion of the
general death-rate. Then it is known that Dr. Yersin,
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THE STORY OF NINETEENTH-CENTURY SCIENCE
with the collaboration of his former colleagues of the
Pasteur Institute, has developed, and has used with suc<
cess, an antitoxine from the microbe of the plague which
recently ravaged China.
Dr. Calmette, another graduate of the Pasteur Insti-
tute, has extended the range of the serum -therapy to
include the prevention and treatment of poisoning by
venoms, and has developed an antitoxine that has al-
ready given immunity from the lethal effects of snake
bites to thousands of persons in India and Australia.
Just how much of present promise is tentative ; just
what are the limits of the methods — these are questions
for the future to decide. But, in any event, there seems
little question that the serum treatment will stand as the
culminating achievement in therapeutics of our century.
It is the logical outgrowth of those experimental studies
with the microscope begun by our predecessors of the
thirties, and it represents the present culmination of the
rigidly experimental method which has brought medi-
cine from a level of fanciful empiricism to the plane of
a rational experimental science.
CHAPTER XII
THE CENTURY'S PROGRESS IN EXPERIMENTAL PSY-
CHOLOGY
I
A LITTLE over a hundred years ago a reform move-
ment was afoot in the world in the interests of the in-
sane. As was fitting, the movement showed itself first
in America, where these unfortunates were humanely
cared for at a time when their treatment elsewhere was
worse than brutal, but England and France quickly fell
into line. The leader on this side of the water was the
famous Philadelphian, Dr. Benjamin Rush, " the Syden-
ham of America" ; in England, Dr. William Tuke inau-
gurated the movement ; and in France, Dr. Philippe
Pinel, single-handed, led the way. Moved by a com-
mon spirit, though acting quite independently, these
men raised a revolt against the traditional custom
which, spurning the insane as demon-haunted outcasts,
had condemned these unfortunates to dungeons, chains,
and the lash. Hitherto few people had thought it other
than the natural course of events that the "maniac"
should be thrust into a dungeon, and perhaps chained
to the wall with the aid of an iron band riveted per-
manently about his neck or waist. Many an unfortu-
nate, thus manacled, was held to. the narrow limits of
his chain for years together in a cell to which full dav-
light never penetrated ; sometimes — iron being expen-
395
THE STORY OF NINETEENTII-CENTURY SCIENCE
sive — the chain was so short that the wretched victim
could not rise to the upright posture, or even shift his
position upon his squalid pallet of straw.
In America, indeed, there being no Middle Age prece-
dents to crystallize into established customs, the treat-
ment accorded the insane had seldom or never sunk to
this level. Partly for this reason, perhaps, the work of
Dr. Rush, at the Philadelphia Hospital, in 1784, by
means of which the insane came to be humanely treat-
ed, even to the extent of banishing the lash, has been
but little noted, while the work of the European lead-
ers, though belonging to later decades, has been made
famous. And perhaps this is not as unjust as it seems,
for the step which Rush took, from relatively bad to
good, was a far easier one to take than the leap from
atrocities to good treatment which the European re-
formers were obliged to compass. In Paris, for exam-
ple, Pinel was obliged to ask permission of the authori-
ties even to make the attempt at liberating the insane
from their chains, and notwithstanding his recognized
position as a leader of science, he gained but grudging
assent, and was regarded as being himself little better
than a lunatic for making so manifestly unwise and
hopeless an attempt. Once the attempt had been made,
however, and carried to a successful issue, the amelio-
ration wrought in the condition of the insane was so
patent that the fame of Pinel's work at the Bicetre and
the Salpetriere went abroad apace. It required, indeed,
many years to complete it in Paris, and a lifetime of
effort on the part of Pinel's pupil Esquirol and others
to extend the reform to the provinces ; but the epochal
turning-point had been reached with Pinel's labors of
the closing years of the eighteenth century.
396
PROGRESS IN EXPERIMENTAL PSYCHOLOGY
The significance of this -wise and humane reform, in
the present connection, is the fact that these studies of the
insane gave emphasis to the novel idea, which by-and-by
became accepted as beyond question, that " demoniacal
possession " is in reality no more than the outward ex-
pression of a diseased condition of the brain. This real-
ization made it clear, as never before, how intimately
the mind and the body are linked one to the other. And
so it chanced that in striking the shackles from the in-
sane, Pinel and his confreres struck a blow also, un-
wittingly, at time -honored philosophical traditions.
The liberation of the insane from their dungeons was
an augury of the liberation of psychology from the
musty recesses of metaphysics. Hitherto psychology,
in so far as it existed at all, was but the subjective
study of individual minds; in future it must become
objective as well, taking into account also the relations
which the mind bears to the body, and in particular to
the brain and nervous system.
The necessity for this collocation was advocated quite
as earnestly, and even more directly, by another worker
of this period, whose studies were allied to those of
alienists, and who, even more actively than they, focal-
ized his attention upon the brain and its functions. This
earliest of specialists in brain studies was a German by
birth, but Parisian by adoption, Dr. Franz Joseph Gall,
originator of the since notorious system of phrenology.
The merited disrepute into which this system has fallen
through the expositions of peripatetic charlatans should
not make us forget that Dr. Gall himself was appar-
ently a highly educated physician, a careful student
of the brain and mind according to the best light
of his time, and, withal, an earnest and honest be-
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THE STORY OF NINETEENTH -CENTURY SCIENCE
liever in the validity of the system he had originated.
The system itself, taken as a whole, was hopelessly
faulty, yet it was not without its latent germ of truth,
as later studies were to show. How firmly its author
himself believed in it is evidenced by the paper which
he contributed to the French Academy of Science in
1808. The paper itself was referred to a committee of
which Pinel and Cuvier were members. The verdict of
this committee was adverse, and justly so; yet the sys-
tem condemned had at least one merit which its de-
tractors failed to realize. It popularized the conception
that the brain is the organ of mind. Moreover, by
its insistence it rallied about it a band of scientific sup-
porters, chief of whom was Dr. Kaspar Spurzheim, a
man of no mean abilities, who became the propagandist
of phrenology in England and in America. Of course
such advocacy and popularity stimulated opposition as
well, and out of the disputations thus arising there grew
presently a general interest in the brain as the organ of
mind, quite aside from any preconceptions whatever as
to the doctrines of Gall and Spurzheim.
Prominent among the unprejudiced class of workers
who now appeared was the brilliant }'oung Frenchman,
Louis Antoine Desmoulins, who studied first under the
tutorage of the famous Magendie, and published jointly
with him a classical work on the nervous system of ver-
tebrates in 1825. Desmoulins made at least one discov-
ery of epochal importance. He observed that the brains
of persons dying in old age were lighter than the aver-
age, and gave visible evidence of atrophy, and he rea-
soned that such decay is a normal accompaniment of
senility. No one nowadays would question the accu-
racy of this observation, but the scientific world was
400
PROGRESS IN EXPERIMENTAL PSYCHOLOGY
not quite ready for it in 1825 ; for when Desmoulins an-
nounced his discovery to the French Academy, that
august and somewhat patriarchal body was moved to
quite unscientific wrath, and forbade the young icono-
clast the privilege of further hearings. From which it
is evident that the partially liberated spirit of the new
psychology had by no means freed itself altogether, at
the close of the first quarter of our century, from the
metaphysical cobwebs of its long incarceration.
ii
While studies of the brain were thus being inaugu-
rated, the nervous system, which is the channel of com-
munication between the brain and the outside world,
was being interrogated with even more tangible results.
The inaugural discovery was made in 1811 by Dr.
(afterwards Sir Charles) Bell, the famous English sur-
geon and experimental physiologist. It consisted of
the observation that the anterior roots of the spinal
nerves are given over to the function of conveying
motor impulses from the brain outward, whereas the
posterior roots convey solely sensory impulses to the
brain from without. Hitherto it had been supposed
that all nerves have a similar function, and the peculiar
distribution of the spinal nerves had been an unsolved
puzzle.
Bell's discovery was epochal; but its full significance
was not appreciated for a decade, nor, indeed, was its
validity at first admitted. In Paris, in particular, then
the court of final appeal in all matters scientific, the al-
leged discovery was looked at askance, or quite ignored.
But in 1823 the subject was taken up by the recognized
2c 401..
THE STORY OF NINETEENTH-CENTURY SCIENCE
leader of French physiology — Fran£ois Magendie — in
the course of his comprehensive experimental studies of
the nervous system, and Bell's conclusions were subject-
ed to the most rigid experimental tests, and found alto-
gether valid. Bell himself,
meanwhile, had turned his
attention to the cranial
nerves, and had proved
that these also are divisible
into two sets — sensor}7 and
motor. Sometimes, indeed,
the two sets of filaments
are combined into one nerve
cord, but, if traced to their
origin, these are found to
arise from different brain
centres. Thus it was clear
that a hitherto unrecog-
nized duality of function
pertains to the entire extra-
cranial nervous system.
Any impulse sent from the periphery to the brain must
be conveyed along a perfectly definite channel; the
response from the brain, sent out to the peripheral
muscles, must traverse an equally definite and altogether
different course. If either channel is interrupted — as by
the section of its particular nerve tract — the correspond-
ing message is denied transmission as effectually as an
electric current is stopped by the section of the trans-
mitting wire.
Experimenters ever}7 where soon confirmed the obser-
vations of Bell and Magendie ; and, as always happens
after a great discovery, a fresh impulse was given to in-
402
SIR CHARLES BELL
By permission of G. Bell and Sons, London
PROGRESS IN EXPERIMENTAL PSYCHOLOGY
vestigations in allied fields. Nevertheless, a full decade
elapsed before another discovery of comparable impor-
tance was made. Then MarshaU'Hall, the most famous
of English physicians of his day, made his classical ob-
servations on the phenomena that henceforth were to be
known as reflex action. In 1832, while experimenting
FRANCOIS MAGENDIE
one day with a decapitated newt, he observed that the
headless creature's limbs would contract in direct re-
sponse to certain stimuli. Such a response could no
longer be secured if the spinal nerves supplying a part
were severed. Hence it was clear that responsive cen-
tres exist in the spinal cord capable of receiving a sen-
sory message, and of transmitting a motor impulse in
reply — a function hitherto supposed to be reserved for
403
THE STORY OF NINETEENTH-CENTURY SCIENCE
the brain. Further studies went to show that such phe-
nomena of reflex action on the part of centres lying out-
side the range of consciousness, both in the spinal cord
and in the brain itself, are extremely common ; that, in
short, they enter constantly into the activities of every
living organism, and have a most important share in the
sum total of vital movements. Hence, Hall's discovery
must always stand as one of the great mile-stones of the
advance of neurological science.
All these considerations as to nerve currents and
nerve tracts becoming stock knowledge of science, it
was natural that interest should become stimulated as
to the exact character of these nerve tracts in them-
selves ; and all the more natural in that the perfected
microscope was just now claiming all fields for its own.
A troop of observers soon entered upon the study of the
nerves; and the leader here, as in so many other lines
of microscopical research, was no other than Theodor
Schwann. Through his efforts, and with the invaluable
aid of such other workers as Remak, Purkinje, Henle,
Miiller, and the rest, all the mystery as to the general
characteristics of nerve tracts was cleared away. It
came to be known that in its essentials a nerve tract is
a tenuous fibre or thread of protoplasm, stretching be-
tween two terminal points in the organism — one of such
termini being usually a cell of the brai'n or spinal cord ;
the other, a distribution point at or near the periphery —
for example, in a muscle or in the skin. Such a fibril may
have about it a protective covering, which is known as the
sheath of Schwann ; but the fibril itself is the essential
nerve tract ; and in many cases, as Remak presently dis-
covered, the sheath is dispensed with, particularly in
case of the nerves of the so-called sympathetic system.
404
PROGRESS IN EXPERIMENTAL PSYCHOLOGY
This sympathetic system of ganglia and nerves, by-
the-bye, had long been a puzzle to the physiologists. Its
ganglia, the seeming centres of the system, usually mi-
nute in size, and never very large, are found everywhere
through the organism, but in particular are gathered
into a long double chain which lies within the body cav-
ity, outside the spinal column, and represents the sole
nervous system of the non-vertebrated organisms. Fi-
brils from these ganglia were seen to join the cranial
and spinal nerve fibrils, and to accompany them every-
where, but what special function they subserved was
long a mere matter of conjecture, and led to many ab-
surd speculations. Fact was not substituted for conject-
ure until about the year 1851, when the great French-
man Claude Bernard conclusively proved that at least
one chief function of the sympathetic fibrils is to cause
contraction of the walls of the arterioles of the system,
thus regulating the blood-supply of any given part. Ten
years earlier Henle had demonstrated the existence of
annular bands of muscle fibres in the arterioles, hitherto
a much mooted question, and several tentative explana-
tions of the action of these fibres had been made, par-
ticularly by the brothers "Weber, by Stilling, who, as
early as 1840, had ventured to speak of "vaso-motor"
nerves, and by Schiff, who was hard upon the same
track at the time of Bernard's discovery. But a clear
light was not thrown on the subject until Bernard's ex-
periments were made in 1851. The experiments were
soon after confirmed and extended by Brown-Sequard,
Waller, Budge, and numerous others, and henceforth
phj'siologists felt that they understood how the blood-
supply of any given part is regulated by the nervous
system.
405
THE STORY OF NINETEENTH-CENTURY SCIENCE
In reality, however, they had learned only half the
story, as Bernard himself proved only a few years later
by opening up a new and quite unsuspected chapter.
While experimenting in 1858 he discovered that there
are certain nerves supplying the heart which, if stimu-
lated, cause that organ to relax and cease beating. As
the heart is essentially nothing more than an aggrega-
tion of muscles, this phenomenon was utterly puzzling
and without precedent in the experience of physi-
ologists. An impulse travelling along a motor nerve
had been supposed to be able to cause a muscular con-
traction and to do nothing else; yet here such an im-
pulse had exactly the opposite effect. The only tenable
explanation seemed to be that this particular impulse
must arrest or inhibit the action of the impulses that
ordinarily cause the heart muscles to contract. But the
idea of such inhibition of one impulse by another was
utterly novel, and at first difficult to comprehend.
Gradually, however, the idea took its place in the cur-
rent knowledge of nerve physiology, and in time it came
to be understood that what happens in the case of the
heart nerve-supply is only a particular case under a very
general, indeed universal, form of nervous action. Grow-
ing out of Bernard's initial discovery came the final un-
derstanding that the entire nervous system is a mechan-
ism of centres subordinate and centres superior, the
action of the one of which may be counteracted and
annulled in effect by the action of the other. This ap-
plies not merely to such physical processes as heart-
beats and arterial contraction and relaxing, but to the
most intricate functionings which have their counterpart
in psychical processes as well. Thus the observation of
the inhibition of the heart's action by a nervous impulse
406
PROGRESS IN EXPERIMENTAL PSYCHOLOGY
furnished the point of departure for studies that led to
a better understanding of the modus operand! of the
mind's activities than had ever previously been attained
bv the most subtle of psychologists.
m
The \vork of the nerve physiologists had thus an im-
portant bearing on questions of the mind. But there
was another company of workers of this period who
made an even more direct assault upon the " citadel of
thought." A remarkable school of workers had devel-
oped in Germany, the leaders being men who, having
more or less of innate metaphysical bias as a national
birthright, had also the instincts of the empirical scien-
tist, and whose educational equipment included a pro-
found knowledge not alone of physiology and psycholo-
gy, but of physics and mathematics as well. These men
undertook the novel task of interrogating the relations
of body and mind from the stand-point of physics.
They sought to apply the vernier and the balance, as far
as might be, to the intangible processes of mind.
The movement had its precursory stages in the early
part of the century, notably in the mathematical psy-
chology of Herbart, but its first definitiveoutputtoattract
general attention came from the master-hand of Hermann
Helmholtz in 1851. It consisted of the accurate measure-
ment of the speed of transit of a nervous impulse along
a nerve tract. To make such measurement had been re-
garded as impossible, it being supposed that the flight of
the nervous impulse was practically instantaneous. But
Helmholtz readily demonstrated the contrar}r, showing
that the nerve cord is a relatively sluggish message-
407
THE STORY OF NINETEENTH-CENTURY SCIENCE
bearer. According to his experiments, first performed
upon the frog, the nervous " current " travels less than
one hundred feet per second. Other experiments per-
formed soon afterward by Helmholtz himself, and by
EMIL DU BOIS HAYMOND
various followers, chief among whom was Du Bois-Re}T-
mond, modified somewhat the exact figures at first ob-
tained, but did not change the general bearings of the
early results. Thus the nervous impulse was shown to
be something far different, as regards speed of transit,
at any rate, from the electric current to which it had
408
PROGRESS IN EXPERIMENTAL PSYCHOLOGY
been so often likened. An electric current would flash
half-way round the globe while a nervous impulse could
travel the length of the human body — from a man's foot
to his brain.
The tendency to bridge the gulf that hitherto had
separated the physical from the psychical world was
further evidenced in the following decade by Helmholtz's
remarkable but highly technical study of the sensations
of sound and of color in connection with their physical
causes, in the course of which he revived the doctrine
of color vision which that other great physiologist and
physicist, Thomas Young, had advanced half a century
before. The same tendency was further evidenced by
the appearance, in 1852, of Dr. Hermann Lotze's famous
Medizinische Psychologic, oder Physiologic der Seele,
with its challenge of the old myth of a " vital force."
But the most definitive expression of the new movement
was signalized in 1860, when Gustav Fechner published
his classical work called Psychophysik. That title in-
troduced a new word into the vocabulary of science.
Fechner explained it by saying, "I mean by psycho-
physics an exact theory of the relation between spirit
and bod}% and, in a general way, between the physical
and the psychic worlds." The title became famous, and
the brunt of many a controversy. So also did another
phrase which Fechner introduced in the course of his
book — the phrase " physiological psychology." In mak-
ing that happy collocation of words Fechner virtually
christened a new science.
The chief purport of this classical book of the German
psycho-physiologist was the elaboration and explication
of experiments based on a method introduced more than
twenty years earlier by his countryman E. II. Weber, but
409
THE STORY OF NINETEENTH-CENTURY SCIENCE
which hitherto had failed to attract the attention it de-
served. The method consisted of the measurement and
analysis of the definite relation existing between exter-
nal stimuli of vary ing degrees of intensity (various sounds,
for example) and the mental states they induce. Weber's
experiments grew out of the familiar observation that the
nicety of our discriminations of various sounds, weights,
or visual images depends upon the magnitude of each
particular cause of a sensation in its relation with other
similar causes. Thus, for example, we cannot see the
stars in the daytime, though they shine as brightly then
as at night. Again, we seldom notice the ticking of a
clock in the daytime, though it may become almost pain-
fully audible in the silence of the night. Yet again, the
difference between an ounce weight and a two -ounce
weight is clearly enough appreciable when we lift the
two, but one cannot discriminate in the same way be-
tween a five-pound weight and a weight of one ounce
over five pounds.
This last example, and similar ones for the other senses,
gave Weber the clew to his novel experiments. TCeflec-
tion upoti every- day experiences made it clear to him
that whenever we consider two visual sensations, or two
auditory sensations, or two sensations of weight, in com-
parison one with another, there is always a limit to the
keenness of our discrimination, and that this degree of
keenness varies, as in the case of the weights just cited,
with the magnitude of the exciting cause.
Weber determined to see whether these common ex-
periences could be brought within the pale of a general
law. His method consisted of making long series of ex-
periments aimed at the determination, in each case, of
what came to be spoken of as the least observable dif-
410
PROGRESS IN EXPERIMENTAL PSYCHOLOGY
ference between the stimuli. Thus if one holds an ounce
weight in each hand, and has tiny weights added to one
of them, grain by grain, one does not at first perceive a
difference ; but presently, on the addition of a certain
grain, he does become aware of the difference. Noting
now how many grains have been added to produce
this effect, we have the weight which represents the
least appreciable difference when the standard is one
ounce.
Now repeat the experiment, but let the weights be
each of five pounds. Clearly in this case we shall be
obliged to add not grains, but drachms, before a differ-
ence between the two heavy weights is perceived. But
whatever the exact amount added, that amount repre-
sents the stimulus producing a just perceivable sensation
of difference when the standard is five pounds. And so
on for indefinite series of weights of varying magnitudes.
Now came Weber's curious discovery. Not only did he
find that in repeated experiments with the same pair of
weights the measure of "just perceivable difference" re-
mained approximately fixed, but he found, further, that
a remarkable fixed relation exists between the stimuli of
different magnitude. If, for example, he had found it
necessary, in the case of the ounce weights, to add one-
fiftieth of an ounce to the one before a difference was
detected, he found also, in the case of the five-pound
weights, that one-fiftieth of five pounds must be added
before producing the same result. And so of all other
weights ; the amount added to produce the stimulus of
"least appreciable difference" always bore the same
mathematical relation to the magnitude of the weight
used, be that magnitude great or small.
Weber found that the same thing holds good for the
411
THE STORY OF NINETEENTH-CENTURY SCIENCE
stimuli of the sensations of sight and of hearing, the dif-
ferential stimulus bearing always a fixed ratio to the
total magnitude of the stimuli. Here, then, was the law
he had sought.
Weber's results were definite enough, and striking
enough, yet they failed to attract any considerable meas-
ure of attention until they were revived and extended
by Fechner, and brought before the world in the famous
work on psycho-physics. Then they precipitated a veri-
table melee. Fechner had not alone verified the earlier
results (with certain limitations not essential to the pres-
ent consideration), but had invented new methods of
making similar tests, and had reduced the whole ques-
tion to mathematical treatment. He pronounced Weber's
discovery the fundamental law of psycho -physics. In
honor of the discoverer, he christened it Weber's Law.
He clothed the law in words and in mathematical for-
mulae, and, so to say, launched it full tilt at the heads
of the psychological world. It made a fine commotion,
be assured, for it was the first widely heralded bulletin
of the new psychology in its march upon the strongholds
of the time-honored metaphysics. The accomplishments
of the microscopists and the nerve physiologists had been
but preliminary — mere border skirmishes of uncertain
import. But here was proof that the iconoclastic move-
ment meant to invade the very heart of the sacred ter-
ritory of mind— a territory from which tangible objec-
tive fact had been supposed to be forever barred.
Hardly had the alarm been sounded, however, before
a new movement was made. While Fechner's book was
fresh from the press, steps were being taken to extend
the methods of the physicist in yet another way to the
intimate processes of the mind. As Helmholtz had shown
412
PROGRESS IN EXPERIMENTAL PSYCHOLOGY
the rate of nervous impulsion along the nerve tract to
be measurable, it was no\v sought to measure also the
time required for the central nervous mechanism to per-
form its work of receiving a message and sending out a
GUSTAV THBODOR FECHNKU
response. This was coming down to the very threshold
of mind. The attempt was first made by Professor
Bonders, in 1861, but definitive results were only ob-
tained after many years of experiment on the part of a
Irost of observers. The chief of these, and the man who
has stood in the forefront of the new movement, and
413
THE STORY OF NINETEENTH CENTURY SCIENCE
has been its recognized leader throughout the remainder
of the century, is Dr. Wilhelm Wundt, of Leipzig.
The task was not easy, but, in the long run, it was
accomplished. Not alone was it shown that the nerve
centre requires a measurable time for its operations, but
much was learned as to conditions that modify this
time. Thus it was found that different persons vary in
the rate of their central nervous activity — which ex-
plained the "personal equation" that the astronomer
Bessel had noted a half-century before. It was found,
too, that the rate of activity varies also for the same
person under different conditions, becoming retarded,
for example, under influence of fatigue, or in case of
certain diseases of the brain. All details aside, the es-
sential fact emerges, as an experimental demonstration,
that the intellectual processes — sensation, apperception,
volition — are linked irrevocably with the activities of
the central nervous tissues, and that these activities, like
all other physical processes, have a time element. To
that old school of psychologists, who scarcely cared
more for the human head than for the heels — being in-
terested only in the mind — such a linking of mind and
body as was thus demonstrated was naturally disquiet-
ing. But whatever the inferences, there was no escap-
ing the facts.
Of course this new movement has not been confined
to Germany. Indeed, it had long had exponents else-
where. Thus in England, a full century earlier, Dr.
Hartley had championed the theory of the close and in-
dissoluble dependence of mind upon the brain, and
formulated a famous vibration theory of association that
still merits careful consideration. Then, too, in France,
at the beginning of the century, there was Dr. Cabanis
414
HIOUUESS IN EXPERIMENTAL PSYCHOLOGY
with his tangible, if crudely phrased, doctrine that the
brain digests impressions and secretes thought as the
stomach digests food and the liver secretes bile. More-
over, Herbert Spencer's Principles of Psychology, with
its avowed co-ordination of mind and body and its vital-
izing theory of evolution, appeared in 1855, half a decade
before the work of Fechner. But these influences,
though of vast educational value, were theoretical rather
than demonstrative, and the fact remains that the experi-
mental work which first attempted to gauge mental opera-
tions by physical principles was mainly done in Germany.
Wundt's Physiological Psychology, with its full pre-
liminary descriptions of the anatomy of the nervous sys-
tem, gave tangible expression to the growth of the new
movement in 1874; and four years later, with the open-
ing of his laboratory of Physiological Psychology at the
University of Leipzig, the new psychology may be said
to have gained a permanent foothold, and to have.forced
itself into official recognition. From then on its con-
quest of the world was but a matter of time.
It should be noted, however, that there is one other
method of strictly experimental examination of the men-
tal field, latterly much in vogue, which had a different
origin. This is the scientific investigation of the phe-
nomena of hypnotism. This subject was rescued from
the hands of charlatans, rechristened, and subjected to
accurate investigation by Dr. James Braid, of Manches-
ter, as early as 1841. But his results, after attracting
momentary attention, fell from view, and, despite desul-
tory efforts, the subject was not again accorded a gen-
eral hearing from the scientific world until 1878, when
Dr. Charcot took it up at the Salpetriere in Paris, fol-
lowed soon afterwards by Dr. Rudolf Heidenhain, of
415
THE STORY OF NINETEENTH-CENTURY SCIENCE
Breslau, and a host of other experimenters. The value
of the method in the study of mental states was soon
apparent. Most of Braid's experiments were repeated,
and in the main his results were confirmed. His expla-
nation of hypnotism, or artificial somnambulism, as a
JEAN MARTIN CIIARCOT
self-induced state, independent of any occult or super-
sensible influence, soon gained general credence. His
belief that the initial stages are due to fatigue of ner-
vous centres, usually from excessive stimulation, has not
been supplanted, though supplemented by notions grow-
416 .
PROGRESS IN EXPERIMENTAL PSYCHOLOGY
ing out of the new knowledge as to subconscious men-
tality in general, and the inhibitory influence of one
centre over another in the central nervous mechanism.
rv
These studies of the psychologists and pathologists
bring the relations of mind and body into sharp relief.
But even more definite in this regard was the work of
the brain physiologists. Chief of these, during the mid-
dle period of the century, was the man who is some-
times spoken of as the " father of brain physiology,"
Marie Jean Pierre Flourens, of the Jardin des Plantes
of Paris, the pupil and worthy successor of Magendie.
His experiments in nerve physiology were begun in the
first quarter of the century, but his local experiments
upon the brain itself were not culminated until about
1842. At this time the old dispute over phrenology had
broken out afresh, and the studies of Flourens were
aimed, in part at least, at the strictly scientific investi-
gation of this troublesome topic.
In the course of these studies Flourens discovered that
in the medulla olblongata, the part of the brain which
connects that organ with tne spinal cord, there is a cen-
tre of minute size which cannot be injured in the least
without causing the instant death of the animal oper-
ated upon. It may be added that it is this spot which
is reached by the needle of the garroter in Spanish exe-
cutions, and that the same centre also is destroyed when
a criminal is "successfully" hanged, this time by the
forced intrusion of a process of the second cervical ver-
tebra. Flourens named this spot the "vital knot." Its
extreme importance, as is now understood, is due to the
So 417
THE STORY OF NINETEENTH-CENTURY SCIENCE
fact that it is the centre of nerves that supply the
heart ; but this simple explanation, annulling the con-
ception of a specific " life centre," was not at once ap-
parent.
Other experiments of Flourens seemed to show that
the cerebellum is the seat of the centres that co-ordinate
muscular activities, and that the higher intellectual fac-
ulties are relegated to the cerebrum. But beyond this,
as regards localization, experiment faltered. Negative
results, as regards specific faculties, were obtained from
all localized irritations of the cerebrum, and Flourens
was forced to conclude that the cerebral lobe, while
being undoubtedly the seat of higher intellection, per-
forms its functions with its entire structure. This con-
clusion, which incidentally gave a quietus to phrenology,
was accepted generally, and became the stock doctrine
of cerebral physiolog}r for a generation.
It will be seen, however, that these studies of Flourens
had a double bearing. They denied localization of
cerebral functions, but they demonstrated the localiza-
tion of certain nervous processes in other portions of the
brain. On the whole, then, they spoke positively for
the principle of localization of function in the brain, for
which a certain number of students contended ; while
their evidence against cerebral localization was only
negative. There was here and there an observer who
felt that this negative testimony was not conclusive. In
particular, the German anatomist Meynert, who had
studied the disposition of nerve tracts in the cerebrum,
was led to believe that the anterior portions of the cere-
brum must have motor functions in preponderance ; the
posterior portions, sensory functions. Somewhat simi-
lar conclusions were reached also by Dr. Hughlings-
418
PROGRESS INT EXPERIMENTAL PSYCHOLOGY
Jackson, in England, from his studies of epilepsy. But
no positive evidence was forth-coming until 1861, when
Dr. Paul Broca brought before the Academy of Medi-
cine in Paris a case of brain lesion which he regarded as
having most important bearings on the question of cere-
bral localization.
The case was that of a patient at the Bicetre, who for
twenty years had been deprived of the power of speech,
seemingly through loss of memory of words. In 1861
this patient died, and an autopsy revealed that a certain
convolution of the left frontal lobe of his cerebrum had
been totally destroyed by disease, the remainder of his
brain being intact. Broca felt that this observation
pointed strongly to a localization of the memorj' of
words in a definite area of the brain. Moreover, it
transpired that the case was not without precedent. As
long ago as 1825 Dr. Boillard had been led, through
pathological studies, to locate definitely a centre for the
articulation of words in the frontal lobe, and here and
there other observers had made tentatives in the same
direction. Boillard had even followed the matter up
with pertinacity, but the world was not ready to listen
to him. Now, however, in the half -decade that fol-
lowed Broca's announcements, interest rose to fever-
heat, and through the efforts of Broca, Boillard, and
numerous others it was proved that a veritable centre
having a strange domination over the memory of articu-
late words has its seat in the third convolution of the
frontal lobe of the cerebrum, usually in the left hemi-
sphere. That part of the brain has since been known to
the English-speaking world as the convolution of Broca,
a name which, strangely enough, the discoverer's com-
patriots have been slow to accept.
419 ,'
THE STORY OF NINETEENTH-CENTURY SCIENCE
This discovery very naturally reopened the entire
subject of brain localization. It was but a short step to
the inference that there must be other definite centres
worth the seeking, and various observers set about
searching for them. In 1867 a clew was gained by Eck-
hard, who, repeating a forgotten experiment of Haller
and Zinn of the previous century, removed portions of
the brain cortex of animals, with the result of producing
convulsions. But the really vital departure was made
in 1870 by the German investigators Fritsch and Hitzig,
who, by stimulating. definite areas of the cortex of ani-
mals with a galvanic current, produced contraction of
definite sets of muscles of the opposite side of the body.
These most important experiments, received at first with
incredulity, were repeated and extended in 1873 by Dr.
David Ferrier, of London, and soon afterwards by a
small army of independent workers everywhere, prom-
inent among whom were Franck and Pitres in France,
Munck and Goltz in Germany, and Horsley and Schafer
in England. The detailed results, naturally enough,
were not at first all in harmony. Some observers, as
Goltz, even denied the validity of the conclusions in toto.
But a consensus of opinion, based on multitudes of ex-
periments, soon placed the broad general facts for which
Fritsch and Hitzig contended beyond controversy. It
was found, indeed, that the cerebral centres of motor
activities have not quite the finality at first ascribed to
them by some observers, since it may often happen that
after the destruction of a centre, with attending loss of
function, there may be a gradual restoration of the lost
function, proving that other centres have acquired the
capacity to take the place of the one destroyed. There
are limits to this capacity for substitution, however, and
420
PROGRESS IN EXPERIMENTAL PSYCHOLOGY
with this qualification the definiteness of the localization
of motor functions in the cerebral cortex has become an
accepted part of brain physiology.
PAUL BROCA
Nor is such localization confined to motor centres.
Later experiments, particularly of Ferrier and of Munck,
proved that the centres of vision are equally restricted
in their location, this time in the posterior lobes of the
421
THE STORY OF NINETEENTH-CENTURY SCIENCE
brain, and that hearing has likewise its local habitation.
Indeed, there is every reason to believe that each form
of primary sensation is based on impressions which main-
ly come to a definitely localized goal in the brain. But
all this, be it understood, has no reference to the higher
forms of intellection. All experiment has proved futile
to localize these functions, except indeed to the extent
of corroborating the familiar fact of their dependence
upon the brain, and, somewhat problematically, upon
the anterior lobes of the cerebrum in particular. But
this is precisely what should be expected, for the clearer
insight into the nature of mental processes makes it plain
that in the main these alleged " faculties " are not in
themselves localized. Thus, for example, the " faculty"
of language is associated irrevocably with centres of
vision, of hearing, and of muscular activity, to go no
further, and only becomes possible through the associa-
tion of these widely separated centres. The destruction
of Broca's centre, as was early discovered, does not alto-
gether deprive a patient of his knowledge of language.
He may be totally unable to speak (though as to this
there are all degrees of variation), and yet may compre-
hend what is said to. him, and be able to read, think, and
even write correctly. Thus it appears that Broca's cen-
tre is peculiarly bound up with the capacity for articu-
late speech, but is far enough from being the seat of the
faculty of language in its entirety.
In a similar way, most of the supposed isolated " fac-
ulties" of higher intellection appear, upon clearer anal-
ysis as complex aggregations of primary sensations, and
hence necessarily dependent upon numerous and scattered
centres. Some " faculties," as memory and volition, may
be said in a sense to be primordial endowments of every
433
PROGRESS IN EXPERIMENTAL PSYCHOLOGY
nerve cell — even of every body cell. Indeed, an ultimate
analysis relegates all intellection, in its primordial adum-
brations, to every particle of living matter. But such
refinements of analysis, after all, cannot hide the fact
that certain forms of higher intellection involve a pretty
definite collocation and elaboration of special sensations.
Such specialization, indeed, seems a necessary accompani-
ment of mental evolution. That every such specialized
function has its localized centres of co-ordination, of some
such significance as the demonstrated centres of articu-
late speech, can hardly be in doubt — though this, be it
understood, is an induction, not as yet a demonstration.
In other words, there is every reason to believe that nu-
merous "centres," in this restricted sense, exist in the
brain that have as yet eluded the investigator. Indeed,
the current conception regards the entire cerebral cortex
as chiefly composed of centres of ultimate co-ordination
of impressions, which in their cruder form are received
by more primitive nervous tissues — the basal ganglia,
the cerebellum, and medulla, and the spinal cord. This
of course is equivalent to postulating the cerebral cortex
as the exclusive seat of higher intellection. This prop-
osition, however, to which a safe induction seems to lead,
is far afield from the substantiation of the old conception
of brain localization, which was based on faulty psy-
chology, and equally faulty inductions from few premises.
The details of Gall's system, as propounded by genera-
tions of his mostly unworthy followers, lie quite beyond
the pale of scien ti fie d iscussion . Yet, as I have said, a germ
of truth was there — the idea of specialization of cerebral
functions — and modern investigators have rescued that
central conception from the phrenological rubbish heap
in which its discoverer unfortunately left it buried.
433
THE STORY OF NINETEENTH-CENTURY SCIENCE
The common ground of all these various lines of in-
vestigations of pathologist, anatomist, physiologist, phys-
icist, and psychologist is, clearly, the central nervous
system — the spinal cord and the brain. The importance
of these structures as the foci of nervous and mental ac-
tivities has been recognized more and more with each
new accretion of knowledge, and the efforts to fathom
the secrets of their intimate structure has been unceas-
ing. For the earlier students, only the crude methods
of gross dissections and microscopical inspection were
available. These could reveal something, but of course
the inner secrets were for the keener insight of the mi-
croscopist alone. And even for him the task of investi-
gation was far from facile, for the central nervous tissues
are the most delicate and fragile, and on many accounts
the most difficult of manipulation of any in the body.
Special methods, therefore, were needed for this essay,
and brain histology has progressed by fitful impulses,
each forward jet marking the introduction of some in-
genious improvement of mechanical technique, which
placed a new weapon in the hands of the investigators.
The very beginning was made in 1824 by Rolando,
who first thought of cutting chemically hardened pieces
of brain tissues into thin sections for microscopical ex-
amination— the basal structure upon which almost all
the later advances have been conducted. Miiller pres-
ently discovered that bichromate of potassium in solu-
tion makes the best of fluids for the preliminary preser-
vation and hardening of the tissues. Stilling, in 1842,
perfected the method by introducing the custom of cut-
ting a series of consecutive sections of the same tissue,
424
PROGRESS IN EXPERIMENTAL PSYCHOLOGY
in order to trace nerve tracts and establish spacial rela-
tions. Then from time to time mechanical ingenuity
added fresh details of improvement. It was found that
pieces of hardened tissue of extreme delicacy can be
made better subject to manipulation by being impreg-
nated with collodion or celloidine, and embedded in par-
affine. Latterly it has become usual to cut sections also
from fresh tissues, unchanged by chemicals, by freezing
them suddenly with vaporized ether, or, better, carbonic
acid. By these methods, and with the aid of perfected
microtomes, the worker of recent periods avails himself
of sections of brain tissues of a tenuousness which the
early investigators could not approach.
But more important even than the cutting of thin sec-
tions is the process of making the different parts of the
section visible, one tissue differentiated from another.
The thin section, as the early workers examined it, was
practically colorless, and even the crudest details of its
structure were made out with extreme difficult}^. Remak
did, indeed, manage to discover that the brain tissue is
cellular, as early as 1833, and Ehrenberg in the same
year saw that it is also fibrillar, but beyond this no great
advance was made until 1858, when a sudden impulse
was received from a new process introduced by Gerlach.
The process itself was most simple, consisting essentially
of nothing more than the treatment of a microscopical
section with a solution of carmine. But the result was
wonderful, for when such a section was placed under
the lens, it no longer appeared homogeneous. Sprinkled
through its substance were seen irregular bodies that had
taken on a beautiful color, while the matrix in which they
were embedded remained unstained. In a word, the cen-
tral nerve cell had sprung suddenly into clear view.
425
THE STORY OF NINETEENTH-CENTURY SCIENCE
A most interesting body it proved, this nerve cell, or
ganglion cell, as it came to be called. It was seen to be
exceedingly minute in size, requiring high powers of the
microscope to make it visible. It exists in almost infi-
nite numbers, not, however, scattered at random through
the brain and spinal cord. On the contrary, it is confined
to those portions of the central nervous masses which to
the naked eye appear gray in color, being altogether
wanting in the white substance which makes up the chief
mass of the brain. Even in the gray matter, though
sometimes thickly distributed, the ganglion cells are
never in actual contact one with another; they always
lie embedded in intercellular tissues, which came to be
known, following Virchow, as the neuroglia.
Each ganglion cell was seen to be irregular in con-
tour, and to have jutting out from it two sets of mi-
nute fibres, one set relatively short, indefinitely numer-
ous, and branching in every direction ; the other set
limited in number, sometimes even single, and starting
out directly from the cell as if bent on a longer journey.
The numerous filaments came to be known as proto-
plasmic processes; the other fibre was named, after its
discoverer, the axis cylinder of Deiters. It was a natural
inference, though not clearly demonstrable in the sec-
tions, that these filamentous processes are the connect-
ing links between the different nerve cells, and also the
channels of communication between nerve cells and the
periphery of the body. The white substance of brain
and cord, apparently, is made up of such connecting
fibres, thus bringing the different ganglion cells every-
where into communication one with another.
In the attempt to trace the connecting nerve tracts
through this white substance by either macroscopical or
436
PROGRESS IN EXPERIMENTAL PSYCHOLOGY
microscopical methods, most important aid is given by
a method originated by Waller in 1852. Earlier than
that, in 1839, Nasse had discovered that a severed nerve
cord degenerates in its peripheral portions. "Waller dis-
covered that every nerve fibre, sensory or motor, has a
nerve cell to or from which it leads, which dominates
its nutrition, so that it can only retain its vitality while
its connection with that cell is intact. Such cells he
named trophic centres. Certain cells of the anterior
part of the spinal cord, for example, are the trophic
centres of the spinal motor nerves. Other trophic cen-
tres, governing nerve tracts in the spinal cord itself, are
in the various regions of the brain. It occurred to
Waller that by destroying such centres, or by severing
the connection at various regions between a nervous
tract and its trophic centre, sharply defined tracts could
be made to degenerate, and their location could subse-
quently be accurately defined, as the degenerated tis-
sues take on a changed aspect, both to macroscopical
and microscopical observation. Recognition of this
principle thus gave the experimenter a new weapon of
great efficiency in tracing nervous connections. More-
over, the same principle has wide application in case of
the human subject in disease, such as the lesion of nerve
tracts or the destruction of centres by localized tumors,
by embolisms, or by traumatisms.
All these various methods of anatomical examination
combine to make the conclusion almost unavoidable
that the central ganglion cells are the veritable "cen-
tres " of nervous activity to which so many other lines
of research have pointed. The conclusion was strength-
ened by experiments of the students of motor localiza-
tion, which showed that the veritable centres of their
427
THE STORY OF NINETEENTH-CENTURY SCIENCE
discovery lie, deraonstrably, in the gray cortex of the
brain, not in the white matter. But the full proof came
from pathology. At the hands of a multitude of ob-
servers it was shown that in certain well-known diseases
of the spinal cord, with resulting paralysis, it is the
ganglion cells themselves that are found to be destroyed.
Similarly, in the case of sufferers from chronic insani-
ties, with marked dementia, the ganglion cells of the
cortex of the brain are found to have undergone degen-
eration. The brains of paretics in particular show such
degeneration, in striking correspondence with their men-
tal decadence. The position of the ganglion cell as the
ultimate centre of nervous activities was thus placed be-
yond dispute.
Meantime, general acceptance being given the histo-
logical scheme of Gerlach, according to which the mass
of the white substance of the brain is a mesh-work of
intercellular fibrils, a proximal idea seemed attainable of
the way in which the ganglion ic activities are corre-
lated, and, through association, built up, so to speak,
into the higher mental processes. Such a conception ac-
corded beautifully with the ideas of the association ists,
who had now become dominant in psychology. But
one standing puzzle attended this otherwise satisfactory
correlation of anatomical observations and psychic anal-
yses. It was this: Since, according to the histologist,
the intercellular fibres, along which impulses are con-
veyed, connect each brain cell, directly or indirectly,
with every other brain cell in an endless mesh-work,
how is it possible that various sets of cells may at times
be shut off from one another? Such isolation must
take place, for all normal ideation depends for its integ-
rity quite as much upon the shutting out of the givnt
428
PROGRESS IN EXPERIMENTAL PSYCHOLOGY
mass of associations as upon the inclusion of certain
other associations. For example, a student in solving a
mathematical problem must for the moment become
quite oblivious to the special associations that have to
do with geography, natural history, and the like. But
does histology give any clew to the way in which such
isolation may be effected ?
Attempts were made to find an answer through con-
sideration of the very peculiar character of the blood-
supply in the brain. Here, as nowhere else, the ter-
minal twigs of the arteries are arranged in closed sys-
tems, not anastomosing freely with neighboring systems.
Clearly, then, a restricted area of the brain may, through
the controlling influence of the vaso-motor nerves, be
flushed with arterial blood, while neighboring parts re-
main relatively anaemic. And since vital activities un-
questionably depend in part upon the supply of arterial
blood, this peculiar arrangement of the vascular mech-
anism may very properly be supposed to aid in the
localized activities of the central nervous ganglia. But
this explanation left much to be desired— in particular
when it is recalled that all higher intellection must in
all probability involve multitudes of widely scattered
centres.
No better explanation was forth-coming, however,
until the year 1889, when of a sudden the mystery was
cleared away by a fresh discovery. Not long before
this the Italian histologist, Dr. Camille Golgi, had dis-
covered a method of impregnating hardened brain tis-
sues with a solution of nitrate of silver, with the result
of staining the nerve cells and their processes almost in-
finitely better than was possible by the method of Ger-
lach, or by any of the multiform methods that other
429
THE STOKY OF NINETEENTH-CENTURY SCIENCE
workers had introduced. Now for the first time it be-
came possible to trace the cellular prolongations definite-
ly to their termini, for the finer fibrils had not been
rendered visible by any previous method of treatment.
Golgi himself proved that the set of fibrils known as
protoplasmic prolongations terminate by free extremi-
ties, and have no direct connection with any cell save
the one from which they spring. He showed also that
the axis cylinders give off multitudes of lateral branches
not hitherto suspected. But here he paused, missing
the real import of the discovery of which he was hard
on the track. It remained for the Spanish histologist,
Dr. S. Ramon y Cajal, to follow up the investigation by
means of an improved application of Golgi's method of
staining, and to demonstrate that the axis cylinders, to-
gether with all their collateral branches, though some-
times extending to a great distance, yet finally termi-
nate, like the other cell prolongations, in arborescent
fibrils having free extremities. In a word, it was shown
that each central nerve cell, with its fibrillar offshoots,
is an isolated entity. Instead of being in physical con-
nection with a multitude of other nerve cells, it has no
direct physical connection with any other nerve cell
whatever.
When Dr. Cajal announced his discovery, in 1889, his
revolutionary claims not unnaturally amazed the mass
of histologists. There were some few of them, however,
who were not quite unprepared for the revelation ; in
particular His, who had half suspected the independence
of the cells, because they seemed to develop from disso-
ciated centres ; and Forel, who based a similar suspicion
on the fact that he had never been able actually to
trace a fibre from one cell to another. These observers
430
PROGRESS IN EXPERIMENTAL PSYCHOLOGY
then came readily to repeat Cajal's experiments. So
also did the veteran histologist Kolliker, and soon after-
wards all the leaders everywhere. The result was a
practically unanimous confirmation of the Spanish his-
tologist's claims, and within a few months after his an-
nouncements the old theory of union of nerve cells into
an endless mesh-work was completely discarded, and
the theory of isolated nerve elements — the theory of
neurons, as it came to be called — was fully established
in its place.
As to how these isolated- nerve cells functionate, Dr.
Cajal gave the clew from the very first, and his expla-
nation has met with universal approval.
In the modified view, the nerve cell retains its old
position as the storehouse of nervous energy. Each of
the filaments jutting out from the cell is held, as before,
to be indeed a transmitter of impulses, but a transmit-
ter that operates intermittently, like a telephone wire
that is not always " connected," and, like that wire, the
nerve fibril operates by contact and not by continuity.
Under proper stimulation the ends of the fibrils reach
out, come in contact with other end fibrils of other cells,
and conduct their destined impulse. Again they re-
tract, and communication ceases for the time between
those particular cells. Meantime, by a different ar-
rangement of the various conductors, different sets of
cells are placed in communication, different associations
of nervous impulses induced, different trains of thought
engendered. Each fibril when retracted becomes a non-
conductor, but when extended and in contact with an-
other fibril, or with the body of another cell, it conducts
its message as readily as a continuous filament could do
—precisely as in the case of an electric wire.
431
T11E STOUY OF NINETEENTH-CENTURY SCIENCE
This conception, founded on a most tangible anatom-
ical basis, enables us to answer the question as to ho\v
ideas are isolated, and also, as Dr. Cajal points out,
throws new light on many other mental processes. One
can imagine, for example, by keeping in mind the flexi-
ble nerve prolongations, how new trains of thought may
be engendered through novel associations of cells ; how
facility of thought or of action in certain directions is
*/
acquired through the habitual making of certain nerve
cell connections; how certain bits of knowledge may
escape our memory, and refuse to be found for a time,
because of a temporary incapacity of the nerve cells to
make the proper connections; and so on indefinitely.
If one likens each nerve cell to a central telephone-
office, each of its filamentous prolongations to a tele-
phone wire, he can imagine a striking analogy between
the modus operand! of nervous processes and of the tel-
ephone system. The utility of new connections at the
central office, the uselessness of the mechanism when
the connections cannot be made, the "wires in use"
that retard your message, perhaps even the crossing of
wires, bringing you a jangle of sounds far different from
what you desire — all these and a multiplicity of other
things that will suggest themselves to every user of the
telephone may be imagined as being almost ludicrously
paralleled in the operations of the nervous mechanism.
Arid that parallel, startling as it may seem, is not a mere
futile imagining. It is sustained and rendered plausible
by a sound substratum of knowledge of the anatomical
conditions under which the central nervous mechanism
exists, and in default of which, as pathology demonstrates
with no less certitude, its functionings are futile to pro-
duce the normal manifestations of higher intellection.
432
CHAPTER XIII
SOME UNSOLVED SCIENTIFIC PROBLEMS
IN the preceding chapters I have endeavored to out-
line the story of the achievements of our century in
the various fields of pure science. In so broad an at-
tempt, within such spacial limits, it has of course been
impossible to dwell upon details, or even to hint at
every minor discovery. At best one could but sum-
marize the broad sweep of progress somewhat as a bat-
tle might be described by a distant eye-witness, telling
of the general direction of action, of the movements
of large masses, the names of leaders of brigades and
divisions, but necessarily ignoring the lesser fluctuations
of advance or recession and the individual gallantry of
the rank and file. In particular, interest has centred
upon the storming of the various special strongholds of
ignorant or prejudiced opposition, which at last have
been triumphantly occupied by the band of progress.
In each case where such a stronghold has fallen, the
victory has been achieved solely through the destructive
agency of newly discovered or newly marshalled facts
—the only weapons which the warrior of science seeks
or cares for. Facts must be marshalled, of course,
about the guidon of a hypothesis, but that guidon can
only lead on to victory if the facts themselves support
2E 433
THE STORY OF NINETEENTH-CENTURY SCIENCE
it. Once planted victoriously on the conquered ram-
parts, the hypothesis becomes a theory — a generaliza-
tion of science — marking a fresh coign of vantage, which
can never be successfully assailed unless by a new host
of antagonistic facts. Such generalizations, with the
events leading directly up to them, have chiefly occu-
pied our attention.
But a moment's reflection makes it clear that the bat-
tle of science, thus considered, is ever shifting ground
and never ended. Thus at any given period there are
many unsettled skirmishes under way ; many hypoth-
eses are yet only struggling towards the strongholds of
theory, perhaps never to attain it ; in many directions
the hosts of antagonistic facts seem so evenly matched
that the hazard of war appears uncertain ; or, again, so
few facts are available that as yet no attack worthy the
name is possible. Such unsettled controversies as these
have, for the most part, been ignored in our survey of
the field. But it would not be fair to conclude our
story without adverting to them, at least in brief ; for
some of them have to do with the most comprehensive
and important questions with which science deals, and
the aggregate number of facts involved in these unfin-
ished battles is often great, even though as yet the
marshalling has not led to final victory for any faction.
In some cases, doubtless, the right hypothesis is actually
in the field, but its supremacy not yet conclusively
proved — perhaps not to be proved for many years or
decades to come. Some of the chief scientific results of
our century have been but the gaining of supremacy for
hypotheses that were mere forlorn hopes, looked on
with general contempt, if at all heeded, when the eigh-
teenth centur}' came to a close — witness the doctrines of
434
SOME UNSOLVED SCIENTIFIC PROBLEMS
the great age of the earth, of the immateriality of heat,
of the undulatorj' character of light, of chemical atom-
icy, of organic evolution. Contrariwise, the opposite
ideas to all of these had seemingly a safe supremacy
until the new facts drove them from the field. Who
shall say, then, what forlorn hope of to-day's science
may not be the conquering host of to-morrow ? All
that one dare attempt is to cite the pretensions of a few
hypotheses that are struggling over the still contested
ground.
SOLAK AND TELLURIC PROBLEMS
Our sun being only a minor atom of the stellar peb-
ble, solar problems in general are of course stellar prob-
lems also. But there are certain special questions re-
garding which we are able to interrogate the sun because
of his proximity, and which have, furthermore, a pecul-
iar interest for the residents of our little globe because
of our dependence upon this particular star. One of the
most far-reaching of these is as to where the sun gets
the heat that he gives off in such liberal quantities. We
have already seen that Dr. Mayer, of conservation-of-
energy fame, was the first to ask this question. As soon
as the doctrine of the persistence and convertibilit}' of
energy was grasped, about the middle of the century, it
became clear that this was one of the most puzzling of
questions. It did not at all suffice to answer that the
sun is a ball of fire, for computation showed that, at the
present rate of heat-giving, if the sun were a solid mass
of coal, he would be totally consumed in about five thou-
sand years. As no such decrease in size as this implies
435^
T11E STORY OF NINETEENTH-CENTURY SCIENCE
had taken place within historic times, it was clear that
some other explanation must be sought.
Dr. Mayer himself hit upon what seemed a tenable
solution at the very outset. Starting from the observed
fact that myriads of tiny meteorites are hurled into the
earth's atmosphere daily, he argued that the sun must
receive these visitants in really enormous quantities —
sufficient, probably, to maintain his temperature at the
observed limits. There was nothing at all unreasonable
about this assumption, for the amount of energy in a
swiftly moving body capable of being transformed into
heat if the body be arrested is relatively enormous. Thus
it is calculated that a pound of coal dropped into the sun
from the mathematician's favorite starting-point, infin-
ity, would produce some six thousand times the heat it
could engender if merely burned at the sun's surface.
In other words, if a little over two pounds of material
from infinity were to fall into each square }Tard of the
sun's surface each hour, his observed heat would be ac-
counted for; whereas almost seven tons per square yard
of stationary fuel would be required each hour to produce
the same effect.
In view of the pelting which our little earth receives,
it seemed not an excessive requisition upon the meteoric
supply to suppose that the requisite amount of matter
may fall into the sun, and for a time this explanation of
his incandescence was pretty generally accepted. But
soon astronomers began to make calculations as to the
amount of matter which this assumption added to our
solar system, particularly as it aggregated near the sun
in the converging radii, and then it was clear that no
such mass of matter could be there without interfering
demonstrably with the observed course of the interior
436
SOME UNSOLVED SCIENTIFIC PROBLEMS
planets. So another source of the sun's energy had to
be sought. It was found forthwith by that other great
German, Helmholtz, who pointed out that the falling
matter through which heat may be generated might just
as well be within the substance of the sun as without ;
in other words, that contraction of the sun's heated body
is quite sufficient to account for a long-sustained heat-
supply which the mere burning of any Known substance
could not approach. Moreover, the amount of matter
thus falling towards the sun's centre being enormous —
namely, the total substance of the sun — a relatively small
amount of contraction would be theoretically sufficient
to keep the sun's furnace at par, so to speak.
At first sight this explanation seemed a little puzzling
to many laymen and some experts, for it seemed to im-
ply, as Lord Kelvin pointed out, that the sun contracts
because it is getting cooler, and gains heat because it
contracts. But this feat is not really as paradoxical as
it seems, for it is not implied that there is any real gain
of heat in the sun's mass as a whole, but quite the reverse.
All that is sought is an explanation of a maintenance of
heat-giving capacity relatively unchanged for a long, but
not an interminable, period. Indeed, exactly here comes
in the novel and startling feature of LTelmholtz's calcu-
lation. According to Mayer's meteoric hypothesis, there
were no data at hand for any estimate whatever as to the
sun's permanency, since no one could surmise what might
be the limits of the meteoric supply. But Helmholtz's
estimate implied an incandescent body cooling — keeping
up a somewhat equable temperature through contraction
for a time, but for a limited time only ; destined ulti-
matety to become liquid, solid ; to cool below the tem-
perature of incandescence — to die. Not only so, but it
437
THE STORY OF NINETEENTH-CENTURY SCIENCE
became possible to calculate the limits of time within
which this culmination would probably occur. It was
only necessary to calculate the total amount of heat
which could be generated by the total mass of our solar
system in falling together to the sun's centre from " in-
finity " to find the total heat-supply to be drawn upon.
Assuming, then, that the present observed rate of heat-
giving has been the average maintained in the past, a
simple division gives the number of years for which the
original supply is adequate. The supply will be ex-
hausted, it will be observed, when the mass comes into
stable equilibrium as a solid body, no longer subject to
contraction, about the sun's centre — such a body, in
short, as our earth is at present.
This calculation was made by Lord Kelvin, Professor
Tait, and others, and the result was one of the most truly
dynamitic surprises of the century. For it transpired
that, according to mathematics, the entire limit of the
sun's heat-giving life could not exceed something like
twenty-five millions of years. The publication of that
estimate, with the appearance of authority, brought a
veritable storm about the heads of the physicists. The
entire geological and biological worlds were up in arms
in a trice. Two or three generations before, they hurled
brickbats at any one who even hinted that the solar sys-
tem might be more than six thousand years old ; now
they jeered in derision at the attempt to limit the life-
bearing period of our globe to a paltry fifteen or twenty
millions.
The controversy as to solar time thus raised proved
one of the most curious and interesting scientific dispu-
tations of the century. The scene soon shifted from the
sun to the earth ; for a little reflection made it clear
438
SOME UNSOLVED SCIENTIFIC PROBLEMS
that the data regarding the sun alone were not suffi-
ciently definite. Thus Dr. Croll contended that if the
parent bodies of the sun had chanced to be " flying
stars " before collision, a vastly greater supply of heat
would have been engendered than if the matter merely
fell together. Again, it could not be overlooked that a
host of meteors are falling into the sun, and that this
source of energv, though not in itself sufficient to ac-
o*. 2 o
count for all the heat in question, might be sufficient to
vitiate utterly any exact calculations. Yet again, Pro-
fessor Lockyer called attention to another source of
variation, in the fact that the chemical combination of
elements hitherto existing separately must produce large
quantities of heat, it being even suggested that this source
alone might possibly account for all the present output.
On the whole, then, it became clear that the contraction
theory of the sun's heat must itself await the demonstra-
tion of observed shrinkage of the solar disc, as viewed by
future generations of observers, before taking rank as an
incontestable theory, and that computations as to time
based solely on this hypothesis must in the meantime be
viewed askance.
But, the time controversy having taken root, new
methods were naturally found for testing it. The ge-
ologists sought to estimate the period of time that must
have been required for the deposit of the sedimentary
rocks now observed to make up the outer crust of the
earth. The amount of sediment carried through the
mouth of a great river furnishes a clew to the rate of
denudation of the area drained by that river. Thus the
studies of Messrs. Humphreys and Abbot, made for a
different purpose, show that the average level of the
territory drained by the Mississippi is being reduced by
439
THE STORY OF NINETEENTH-CENTURY SCIENCE
about one foot in six thousand years. The sediment is,
of course, being piled up out in the Gulf at a proportion-
ate rate. If, then, this be assumed to be an average rate
of denudation and deposit in the past, and if the total
thickness of sedimentary deposits of past ages were
known, a simple calculation would show the age of the
earth's crust since the first continents were formed.
But unfortunately these "ifs" stand mountain-high
here, all the essential factors being indeterminate.
Nevertheless, the geologists contended that they could
easily make out a case proving that the constructive
and destructive work still in evidence, to say nothing
of anterior revolutions, could not have been accom-
plished in less than from twenty-five to fifty millions of
years.
This computation would have carried little weight
with the physicists had it not chanced that another com-
putation of their own was soon made which had even
more startling results. This computation, made by Lord
Kelvin, was based on the rate of loss of heat by the
earth. It thus resembled the previous solar estimate in
method. But the result was very different, for the new
estimate seemed to prove that since the final crust of
the earth formed a period of from one hundred to two
hundred millions of years has efapsed.
With this all controversy ceased, for the most grasp-
ing geologist or biologist would content himself with a
fraction of that time. What is more to the point, how-
ever, is the fact, which these varying estimates have
made patent, that computations of the age of the earth
based on any data at hand are little better than rough
guesses. Long before the definite estimates were under-
taken, geologists had proved that the earth is venT, very
440
SOME UNSOLVED SCIENTIFIC PROBLEMS
old, and it can hardly be said that the attempted com-
putations have added much of definiteness to that propo-
sition. They have, indeed, proved that the period of
time to be drawn upon is not infinite; but the nebular
hypothesis, to say nothing of common-sense, carried us
as far as that long ago.
If the computations in question have failed of their
direct purpose, however, they have been by no means
lacking in important collateral results. To mention but
one of these, Lord Kelvin was led by this controversy
over the earth's age to make his famous computation in
which he proved that the telluric structure, as a whole,
must have at least the rigidity of steel in order to resist
the moon's tidal pull as it does. Hopkins had, indeed,
made a somewhat similar estimate as early as 1839,
proving that the earth's crust must be at least eight
hundred or a thousand miles in thickness; but geologists
had utterly ignored this computation, and the idea of a
thin crust on a fluid interior had continued to be the
orthodox geological doctrine. Since Lord Kelvin's
estimate was made, his claim that the final crust of the
earth could not have formed until the mass was solid
throughout, or at least until a honeycomb of solid matter
had been bridged up from centre to circumference, has
gained pretty general acceptance. It still remains an
open question, however, as to what proportion the lacunas
of molten matter bear at the present day to the solidified
portions, and therefore to what extent the earth will be
subject to further shrinkage and attendant surface
contortions. That some such lacuna? do exist is demon-
strated daily by the phenomena of volcanoes. So, after
all, the crust theory has been supplanted by a compro-
mise theory rather than completely overthrown, and
441
THE STORY OF NINETEENTH-CENTURY SCIENCE
our knowledge of the condition of the telluric depths is
still far from definite.
If so much uncertainty attends these fundamental
questions as to the earth's past and present, it is not
strange that open problems as to her future are still
more numerous. We have seen how, according to Pro-
fessor Darwin's computations, the moon threatens to
come back to earth with destructive force some day.
Yet Professor Darwin himself urges that there are ele-
ments of fallibility in the data involved that rob the
computation of all certainty. Much the same thing is
true of perhaps all the estimates that have been made
as to the earth's ultimate fate. Thus it has been sug-
gested that, even should the sun's heat not forsake us,
our day will become month-long, and then year-long;
that all the water of the globe must ultimately filter
into its depths, and all the air fly off into space, leaving
our earth as dry and as devoid of atmosphere as the
moon ; and, finally, that ether-friction, if it exist, or, in
default of that, meteoric friction, must ultimately bring
the earth back to the sun. But in all these prognosti-
cations there are possible compensating factors that
vitiate the estimates and leave the exact results in
doubt. The last word of the cosmic science of our
century is a prophecy of evil — if annihilation be an evil.
But it is left for the science of another generation to
point out more clearly the exact terms in which the
prophecy is most likely to be fulfilled.
SOME UNSOLVED SCIENTIFIC PROBLEMS
ii
PHYSICAL PROBLEMS
In regard to all these cosmic and telluric problems,
it will be seen, there is always the same appeal to one
central rule of action — the law of gravitation. When
we turn from macrocosm to microcosm it would appear
as if new forces of interaction were introduced in the
powers of cohesion and of chemical action of molecules
and atoms. But Lord Kelvin has argued that it is pos-
sible to form such a conception of the forms and space
relations of the ultimate particles of matter that their
mutual attractions may be explained by invoking that
same law of gravitation which holds the stars and plan-
ets in their course. What, then, is this all-compassing
power of gravitation which occupies so central a position
in the scheme of mechanical things?
The simple answer is that no man knows. The wisest
physicist of to-day will assure you that he knows abso-
lutely nothing of the why of gravitation — that he can
no more explain why a stone tossed into the air falls
back to earth than can the boy who tosses the stone.
But while this statement puts in a nutshell the scientific
status of explanations of gravitation, yet it is not in
human nature that speculative scientists should refrain
from the effort to explain it. Such efforts have been
made ; yet, on the whole, they are surprisingly few in
number ; indeed, there are but two that need claim our
attention here, and one of these has hardly more than
historical interest. One of these is the so-called ultra-
mundane-corpuscle hypothesis of Le Sage; the other is
based on the vortex theory of matter.
443
THE STORY OF NINETEENTH-CENTURY SCIENCE
The theory of Le Sage assumes that the entire uni-
verse is filled with infinitely minute particles flying in
right lines in every direction with inconceivable rapidity.
Every mass of tangible matter in the universe is inces-
santly bombarded by these particles, but any two non-
contiguous masses (whether separated by an infinitesi-
mal space or by the limits of the universe) are mutually
shielded by one another from a certain number of the
particles, and thus impelled towards one another by the
excess of bombardment on their opposite sides. What
applies to two masses applies also, of course, to any
number of masses — in short, to all the matter in the
universe. To make the hypothesis workable, so to say,
it is necessary to assume that the k' ultra-mundane " par-
ticles are possessed of absolute elasticity, so that they
rebound from one another on collision without loss of
speed. It is also necessary to assume that all tangible
matter has to an almost unthinkable degree a sieve-like
texture, so that the vast proportion of the coercive par-
ticles pass entirely through the body of any mass they
encounter — a star or world, for example — without really
touching any part of its actual substance. This assump-
tion is necessary because gravitation takes no account
of mere corporeal bulk, but only of mass or ultimate
solidarity. Thus a very bulky object may be so loosely
meshed that it retards relatively few of the corpuscles,
and hence gravitates with relative feebleness — or, to
adopt a more familiar mode of expression, is light in
weight.
This is certainly heaping hypotheses together in a
reckless way, and it is perhaps not surprising that Le
Sage's conception did not at first arouse any very great
amount of interest. It was put forward about a century
444
SOME UNSOLVED SCIENTIFIC PROBLEMS
ago, but for two or three generations remained prac-
tically unnoticed. The philosophers of the first half of
our century seem to have despaired of explaining gravi-
tation, though Faraday long experimented in the hope
of establishing a relation between gravitation and elec-
tricity or magnetism. But not long after the middle of
the century, when a new science of dynamics was claim-
ing paramount importance, and physicists were striving
to express all tangible phenomena in terms of matter in
motion, the theory of Le Sage was revived and given a
large measure of attention. It had at least the merit of
explaining the facts without conflicting with any known
mechanical law, which was more than could be said of
any other guess at the question that had ever been
made.
More recently, however, another explanation has been
found which also meets this condition. It is a concep-
tion based, like most other physical speculations of the
last generation, upon the hypothesis of the vortex atom,
and was suggested, no doubt, by those speculations which
consider electricity and magnetism to be conditions of
strain or twist in the substance of the universal ether.
In a word, it supposes that gravitation also is a form of
strain in this ether — a strain that may be likened to a
suction which the vortex atom is supposed to exert on
the ether in which it lies. According to this view, gravi-
tation is not a push from without, but a pull from within ;
not due to exterior influences, but an inherent and indis-
soluble property of matter itself. The conception has
the further merit of correlating gravitation with elec-
tricity, magnetism, and light, as a condition of that
strange ethereal ocean of which modern physics takes
so much account. But here, again, clearly, we are but
445
THE STORY OF NINETEENTH-CENTURY SCIENCE
heaping hypothesis upon hypothesis, as before. Still, a
hypothesis that violates no known law and has the war-
rant of philosophical probability is always worthy of a
hearing. Only we must not forget that it is hypothesis
only, not conclusive theory.
The same caution applies, manifestly, to all the other
speculations which have the vortex atom, so to say, for
their foundation-stone. Thus Professors Stewart and
Tait's inferences as to the destructibility of matter, based
on the supposition that the ether is not quite frictionless,
Professor Dolbear's suggestions as to the creation of
matter through the development of new ether ripples,
and the same thinker's speculations as to an upper limit
of temperature, based on the mechanical conception of
a limit to the possible vibrations of a vortex ring, not
to mention other more or less fascinating speculations
based on the vortex hypothesis, must be regarded, what-
ever their intrinsic interest, as insecurely grounded, until
such time as new experimental methods shall give them
another footing. Lord Kelvin himself holds all such
speculations utterly in abeyance. "The vortex theory."
he says, " is only a dream. Itself unproven, it can prove
nothing, and any speculations founded upon it are mere
dreams about a dream."
That certainly must be considered an unduly modest
pronouncement regarding the only workable hypothe-
sis of the constitution of matter that has ever been
imagined; yet the fact certainly holds that the vortex
theory, the great contribution of our century towards
the solution of a world-old problem, has not been car-
ried beyond the stage of hypothesis, and must be passed
on, with its burden of interesting corollaries, to another
generation for the experimental evidence that will lead
446
SOME UNSOLVED SCIENTIFIC PROBLEMS
to its acceptance or its refutation. Our century has
given experimental proof of the existence of the atom,
but has not been able to fathom in the same way the
exact form or nature of this ultimate particle of matter.
Equally in the dark are \ve as to the explanation of
that strange affinity for its neighbors which every atom
manifests in some degree. If we assume that the power
which holds one atom to another is the same which in.
case of larger bodies we term gravitation, that answer
carries us but a little way, since, as we have seen, gravi-
tation itself is the greatest of mysteries. But again, how
chances it that different atoms attract one another in such
varying degrees, so that, for example, fluorine unites
with everything it touches, argon with nothing? And
how is it that different kinds of atoms can hold to them-
selves such varying numbers of fellow-atoms — oxygen
one, hydrogen two. and so on ? These are questions for
the future. The wisest chemist does not know why the
simplest chemical experiment results as it does. Take,
for example, a water-like solution of nitrate of silver,
and let fall into it a few drops of another water-like solu-
tion of hydrochloric acid; a white insoluble precipitate
of chloride of silver is formed. Any tyro in chemistry
could have predicted the result with absolute^ certainty.
But the prediction would have been based purely upon
previous empirical knowledge — solely upon the fact that
the thing had been done before over and over, always
with the same result. AVhy the silver forsook the ni-
trogen atom, and grappled the atom of oxygen, no one
knows. Nor can any one as yet explain just why it is
that the new compound is an insoluble, colored, opaque
substance, whereas the antecedent ones were soluble,
colorless, and transparent. More than that, no one can
447
TI1E STORY OF NINETEENTH-CENTURY SCIENCE
explain with certainty just what is meant by the famil-
iar word soluble itself. That is to say, no one knows
just what happens when one drops a lump of salt or
sugar into a bowl of water. We may believe with Pro-
fessor Ostwald and his followers, that the molecules of
sugar merely glide everywhere between the molecules of
water, without chemical action ; or, on the other hand,
dismissing this mechanical explanation, we may say
with Mendeleef that the process of solution is the most
active of chemical phenomena, involving that incessant
interplay of atoms known as dissociation. But these
two explanations are mutually exclusive, and no one can
say positively which one, if either one, is right. Nor is
either theory at best more than a half-explanation, for
the why of the strange mechanical or chemical activi-
ties postulated is quite ignored. How is it, for example,
that the molecules of water are able to loosen the inter-
molecular bonds of the sugar particles, enabling them to
scamper apart?
But, for that matter, what is the nature of these in-
termolecular bonds in any case ? And why, at the same
temperature, are some substances held together with
such enormous rigidity, others so loosely ? Why does
not a lump of iron dissolve as readily as the lump of
sugar in our bowl of water? Guesses may be made to-
day at these riddles, to be sure, but anything like tena-
ble solutions will only be possible when we know much
more than at present of the nature of intermolecular
forces, and of the mechanism of molecular structures.
As to this last, studies are under way that are full of
promise. For the past ten or fifteen years Professor
Yan 't Hoof of Amsterdam (now of Berlin), with a com-
pany of followers, has made the space relations of atoms
_ 448
SOME UNSOLVED SCIENTIFIC PROBLEMS
a special study, with the result that so-called stereo-
chemistry has attained a firm position. A truly amaz-
ing insight has been gained into the space relations of
the molecules of carbon compounds in particular, and
other compounds are under investigation. But these re-
sults, wonderful though they seem when the intricacy
of the subject is considered, are, after all, only tenta-
tive. It is demonstrated that some molecules have their
atoms arranged in perfectly definite and unalterable
schemes, but just how these systems are to be mechani-
cally pictured — whether as miniature planetary systems
or what not — remains for the investigators of the future
to determine.
It appears, then, that whichever way one turns in the
realm of the atom and molecule, one finds it a land of
mysteries. In no field of science have more startling
discoveries been made in our century than here ; yet
nowhere else do there seem to lie wider realms yet un-
fathomed.
in
, LIFE PROBLEMS
In the life history of at least one of the myriad star
systems there has come a time when, on the surface of
one of the minor members of the group, atoms of mat-
ter have been aggregated into such associations as to
constitute what is called living matter. A question
that at once suggests itself to any one who conceives
even vaguely the relative uniformity of conditions in
the different star groups is as to whether other worlds
than ours have also their complement of living forms.
The question has interested speculative science more
2v 449
THE STORY OF NINETEENTH-CENTURY SCIENCE
perhaps in our century than ever before, but it can
hardly be said that much progress has been made tow-
ards a definite answer. At first blush the demonstration
that all the worlds known to us are composed of the
same matter, subject to the same general laws, and
probably passing through kindred stages of evolution
and decay, would seem to carry with it the reasonable
presumption that to all primary planets, such as ours, a
similar life-bearing stage must come. But a moment's
reflection shows that scientific probabilities do not carry
one safely so far as this. Living matter, as we know it,
notwithstanding its capacity for variation, is condi-
tioned within very narrow limits as to physical sur-
roundings. Xow it is easily to be conceived that these
peculiar conditions have never been duplicated on any
other of all the myriad worlds. If not, then those more
complex aggregations of atoms which we must suppose
to have been built up in some degree on all cooling
globes must be of a character so different from what we
term living matter that we should not recognize them as
such. Some of them may be infinitely more complex,
more diversified in their capacities, more widely re-
sponsive to the influences about them, than any living
thing on our earth, and yet not respond at all to the
conditions which we apply as tests of the existence of
life.
This is but another way of saying that the peculiar
limitations of specialized aggregations of matter which
characterize what we term living matter may be mere
incidental details ot the evolution of our particular star
group, our particular planet even — having some such
relative magnitude in the cosmic order as, for example,
the exact detail of outline of some particular leaf of a
450
SOME UNSOLVED SCIENTIFIC PROBLEMS
tree bears to the entire subject of vegetable life. But,
on the other hand, it is also conceivable that the condi-
tions on all planets comparable in position to ours,
though never absolutely identical, yet pass at some stage
through so similar an epoch that on each and every one
of them there is developed something measurably com-
parable, in human terms, to what \ve here know as liv-
ing matter; differing widely, perhaps, from any partic-
ular form of living being here, yet still conforming
broadly to a definition of living things. In that case
the life-bearing stage of a planet must be considered as
having far more general significance; perhaps even as
constituting the time of fruitage of the cosmic orsran-
<~J O O
ism, though nothing but human egotism gives warrant to
this particular presumption.
Between these two opposing views every one is free
to choose according to his preconceptions, for as yet
science is unable to give a deciding vote. Equally open
to discussion is that other question, as to whether the
evolution of universal atoms into a "vital" association
occurred but once on our globe, forming the primitive
mass from which all the diversified forms evolved, or
whether such shifting from the so-called non-vital to the
vital was many times repeated — perhaps still goes on in-
cessantly. It is quite true that the testimony of our
century, so far as it goes, is all against the idea of
" spontaneous generation " under existing conditions. It
has been clearly enough demonstrated that the bacteria
and other low forms of familiar life which formerly were
supposed to originate "spontaneously" had a quite dif-
ferent origin. But the solution of this special case leaves
the general problem still far from solved. Who knows
what are the conditions necessary to the evolution of the
451
THE STORY OF NINETEENTH-CENTURY SCIENCE
ever-present atoms into " vital " associations ? Perhaps
extreme pressure may be one of these conditions ; and,
for aught any man knows to the contrary, the "spon-
taneous generation " of living protoplasm may be taking
place incessantly at the bottom of every ocean of the
globe.
This of course is a mere bald statement of possibilities.
It may be met by another statement of possibilities, to
the effect that perhaps the conditions necessary to the
evolution of living matter here may IUIVQ been fulfilled
but once, since which time the entire current of life on
our globe has been a diversified stream from that one
source. Observe, please, that this assumption does not
fall within that category which I mention above as con-
traband of science in speaking of the origin of worlds.
The existence of life on our globe is only an incident
limited to a relatively insignificant period of time, and
whether the exact conditions necessary to its evolution
pertained but one second or a hundred million years does
not in the least matter in a philosophical analysis. It is
merely a question of fact, just as the particular temper-
ature of the earth's surface at any given epoch is a ques-
tion of fact, the one condition, like the other, being tem-
porary and incidental. But, as I have said, the question
of fact as to the exact time of origin of life on our globe
is a question science as yet cannot answer.
But, in any event, what is vastly more important than
this question as to the duration of time in which living
matter was evolved is a comprehension of the philosophi-
cal status of this evolution from the "non-vital" to the
" vital." If one assumes that this evolution was brought
about by an interruption of the play of forces hitherto
working in the universe — that the correlation of forces
453
SOME UNSOLVED SCIENTIFIC PROBLEMS
involved was unique, acting then and then only — by that
assumption he removes the question of the origin of life
utterly from the domain of science — exactly as the as-
sumption of an initial push would remove the question
of the origin of worlds from the domain of science. But
the science of to-day most emphatically demurs to any
such assumption. Every scientist with a wide grasp of
facts, who can think clearly and without prejudice over
the field of what is known of cosmic evolution, must be
driven to believe that the alleged wide gap between
vital and non-vital matter is largely a figment of prej-
udiced human understanding. In the broader view there
seem no gaps in the scheme of cosmic evolution — no
break in the incessant reciprocity of atomic actions,
whether those atoms be floating as a "fire mist" out in
one part of space, or aggregated into the brain of a man
in another part. And it seems well within the range of
scientific expectation that the laboratory worker of the
future will learn how so to duplicate telluric conditions
that the play of universal forces will build living matter
out of the inorganic in the laboratory, as they have done,
and perhaps still are doing, in the terrestrial oceans.
To the timid reasoner that assumption of possibilities
may seem startling. But assuredly it is no more so than
seemed, a century ago, the assumption that man has
evolved, through the agency of "natural laws" only,
from the lowest organism. Yet the timidity of that
elder day has been obliged by the progress of our cen-
tury to adapt its conceptions to that assured sequence
of events. And some day, in all probability, the timid-
ity of to-day will be obliged to take that final logical
step which to-day's knowledge foreshadows as a future
if not a present necessity.
453
THE STORY OF NINETEENTH-CENTURY SCIENCE
Whatever future science may be able to accomplish in
•this direction, however, it must be admitted that present
science finds its hands quite full, without going farther
afield than to observe the succession of generations
among existing forms of life. Since the establishment
of the doctrine of organic evolution, questions of hered-
ity, always sufficiently interesting, have been at the very
focus of attention of the biological world. These ques-
tions, under modern treatment, have resolved them-
selves, since the mechanism of such transmission has
been proximately understood, into problems of cellular
activity. And much as has been learned about the cell
of late, that interesting microcosm still offers a multi-
tude of intricacies for solution.
Thus, at the very threshold, some of the most element-
ary principles of mechanical construction of the cell are
still matters of controversy. On the one hand, it is held
by Professor O. Biitschli and his followers that the sub-
stance of the typical cell is essentially alveolar, or foam-
like, comparable to an emulsion, and that the observed
reticular structure of the cell is due to the intersections
of the walls of the minute ultimate globules. But an-
other equally authoritative school of workers holds to
the view, first expressed by Frommann and Arnold,
that the reticulum is really a system of threads, which
constitute the most important basis of the cell structure.
It is even held that these fibres penetrate the cell Avails
and connect adjoining cells, so that the entire body is a
reticulum. For the moment there is no final decision
between these opposing views. Professor Wilson of
Columbia has suggested that both may contain a meas-
ure of the truth.
Again, it is a question whether the finer granules seen
454
SOME UNSOLVED SCIENTIFIC PROBLEMS
within the cell are or are not typical structures, "capa-
ble of assimilation, growth, and division, and hence to
be regarded as elementary units of structure standing
between the cell and the ultimate molecules of living
matter." The more philosophical thinkers, like Spencer,
Darwin, Haeckel, Michael Foster, August Weismann,
and many others, believe that such "intermediate units
must exist, whether or not the microscope reveals them
to view. Weismann, who has most fully elaborated a
hypothetical scheme of the relations of the intracellular
units, identifies the larger of these units not with the
ordinary granules of the cell, but with a remarkable
structure called chromatin, which becomes aggregated
within the cell nucleus at the time of cellular division —
a structure which divides into definite parts, and goes
through some most suggestive manoeuvres in the
process of cell multiplication. All these are puzzling
structures; and there is another minute body within
the cell, called the centrosome, that is quite as much
so. This structure, discovered by Van Beneden. has
been regarded as essential to cell division, yet some
7 »/
recent botanical studies seem to show that sometimes
it is altogether wanting in a dividing cell.
In a word, the architecture of the cell has been shown
by modern researches to be wonderfully complicated, but
the accumulating researches are just at a point where
much is obscure about many of the observed phenomena.
The immediate future seems full of promise of advances
upon present understanding of cell processes. But for
the moment it remains for us, as for preceding genera-
tions, about the most incomprehensible, scientifically
speaking, of observed phenomena, that a single micro-
scopic egg cell should contain within its substance all
455
THE STORY OF NINETEENTH-CENTURY SCIENCE
the potentialities of a highly differentiated adult being.
The fact that it does contain such potentialities is the
most familiar of e very-day biological observations, but
not even a proximal explanation of the fact is as yet
attainable.
Turning from the cell as an individual to the mature
organism which the cell composes when aggregated
with its fellows, one finds the usual complement of open
questions, of greater or less significance, focalizing the
attention of working biologists. Thus the evolutionist,
secure as is his general position, is yet in doubt when
it comes to tracing the exact lineage of various forms.
He does not know, for example, exactly which order
of invertebrates contains the type from which verte-
brates sprang, though several hotly contested opin-
ions, each exclusive of the rest, are in the field. Again,
there is like uncertaint}7 and difference of opinion
as to just which order of lower vertebrates formed
the direct ancestry of the mammals. Among the mam-
mals themselves there are several orders, such as the
whales, the elephants, and even man himself, whose ex-
act lines of more immediate ancestry are not as fully
revealed by present paleontology as is to be fully
desired.
All these, however, are details that hardly take rank
with the general problems that we are noticing. There
are other questions, however, concerning the history
and present evolution of man himself, that are of wider
scope, or at least of seeming!}7 greater importance from
a human stand-point, which within recent decades have
come for the first time within the scope of truly induc-
tive science. These are the problems of anthropology
— a science of such wide scope, such far-reaching col-
456
SOME UNSOLVED SCIENTIFIC PROBLEMS
lateral implications, that as yet its specific field and
functions are not as clearly defined or as generally rec-
ognized as they are probably destined to be in. the near
future. The province of this new science is to correlate
the discoveries of a wide range of collateral sciences —
paleontology, biology, medicine, and so on — from the
point of view of human history and human welfare.
To this end all observable races of men are studied as
to their physical characteristics, their mental and moral
traits, their manners, customs, languages, and religions.
A mass of data is already at hand, and in process of
sorting and correlating. Out of this effort will probably
come all manner of useful generalizations, perhaps in
time bringing sociologj7, or the study of human social
relations, to the rank of a veritable science. But great
as is the promise of anthropology, it can hardly be de-
nied that the broader questions with which it has to
deal — questions of race, of government, of social evolu-
tion— are still this side the fixed plane of assured gener-
alization. No small part of its interest and importance
depends upon the fact that the great problems that
engage it are as yet unsolved problems. In a word,
anthropology is perhaps the most important science in
the hierarchy to-day exactly because it is an immature
science. Its position to-day is perhaps not unlike that
of paleontology at the close of the eighteenth century.
May its promise find as full fruition !
INDEX
ADAMS, JOHN, his determination of
the exact location of Neptune, 48 ;
corrects Laplace in reference to the
moon's acceleration, 51.
Adams, Professor, his investigation
of meteor showers, 59.
Aerial currents, their classification
and the laws governing them, 182-
191.
Aerolites, study of their origin and
character, 157-162.
Agassiz, Jean Louis Rodolphe, his
belief in the special-creation hy-
pothesis, 105 ; his advocacy and es-
tablishment of the glacial theory,
134-136; on the reception of sci-
entific truth, 153.
Alibert, Jean Louis, makes known
the cause and cure of the itch, 362.
Alpha Centauri, its comparative dis-
tance from the earth, 66.
Amici, Giovanni Battista, his inven-
tion of the reflecting microscope,
327, 328.
Ampere, Andre Marie, establishes the
connection of magnetism and elec-
tricity, 207 ; confirms the atomic
theory of Avogadro, 258 ; discovers
the properties of ammonium, 267.
Anaesthesia, discovery of the method
of, 365-375.
Anatomy, eighteenth - century prog-
ress in the science, 36. See Anat-
omy and physiology.
Anatomy and physiology, their prog-
ress in the nineteenth century,
321-353; Cuvier's classification of
the animal kingdom and his " law
of co-ordination," 321, 322; Bi-
chat's generalization of the animal
organs, 322, 323 ; and his division
of all animal structures into tis-
sues, 324 ; improvements in micro-
scopes and lenses, and the inven-
tion of the compound microscope,
324-328 ; rise of histology and its
triumphs, 328-336 ; establishment
and development of the cell theory,
336-346 ; investigations of the proc-
esses of digestion and respiration
and of the functions of the human
organs, 346-353.
Anthrax, discovery of its cause and
remedy, 380, 381, 387-389.
Anthropology, its far-reaching pos-
sibilities and its unsolved prob-
lems, 456, 457.
Anti-cyclone, description of, 190.
Antisepsis, the theory and practice
of, 382-386.
Antitoxine, its discovery and appli-
cation, 390-392.
Anti-trade-winds, their cause and
effects, 178, 185, 186.
Arago, Dominique Fran9ois, his pio-
neer work in celestial photography,
76 ; champions Fresnel's undulatory
theory of light and the feud which
his advocacy engendered, 202-204,
225 ; discovers that magnets may be
produced by electrical induction, 208.
Arcturus, its comparative brightness,
69.
Asteroids, their discovery and theo-
ries regarding, 44-48.
Astronomy, its development during
the eighteenth century, 5-17; the
"nebular hypothesis," its amplifi-
cation and completion, 13-17; prog-
ress of the science during the
459
INDEX
nineteenth century, 44-87 ; dis-
covery of Ceres, by Piazzi, 44 ; of
Pallas and Vesta, by Olbers, 44,
47 ; and of Juno, by Harding, 47 ;
Hencke's discovery of a fifth as-
teroid is followed by a thorougli
investigation of the asteroidal sys
tern, 47 ; how the asteroids are
accounted for, 47, 48 ; discovery of
Neptune, predicated by Bessel and
Leverrier, is accomplished by Dr.
Galle, 48, 49 ; Leverrier's predica-
tion of a trans-Neptunian planet,
49 ; discovery of the moons of
Mars by Professor Hall, 49 ; dis-
covery of Saturn's crape ring, 49,
50; Saturn's rings discussed and
their nature determined, 50 ; theo-
ries regarding the acceleration of
the moon, and how it is accounted
for, 50-53 ; speculations regarding
comets and the discovery of their
nature and constituents, 53-60 ; the
study of double stars by William
and John Herschel and others,
63-65 ; star distance determined,
65-69 ; and star motion, mass, and
brightness reckoned, 69, 70 ; solar
and sidereal investigations bv
means of the spectroscope, 70—76 ;
discovery of "invisible" or dark
stars, 74-76 ; triumphs of celestial
photography, 76-83, 285, 286;
Lockyer's "meteoric hypothesis,"
83-86 ; speculations as to the po-
tentialities of the stellar universe,
86, 87 ; some unsolved solar and
telluric problems, 435-442.
Atomic theory, discovery and devel-
opment of, "252-262.
Atom?, Boscovich's speculations re-
garding, 241 ; their combining
weights determined and the method
of expressing them invented, 254,
255, 259, 260; law" of the specific
heat of, 260-262 ; establishment of
the law of valency, 269-275 ; their
character and properties investi-
gated, 275-278 ; Front's theory of
the atomic weights and compound
nature of the elements, 278-280,
283-287; some unsolved problems
regarding, 447-449.
Auenbrugger von Auenbrog, his in-
vention of the percussion method
for studying disease, 355.
Aurora, the, speculations regarding
cause of, 162-167.
Auscultation, its discovery and de-
velopment as an aid to diagnosis,
356, 359.
Avogadro, Amadeo, his hypothesis as
to the numbers of ultimate par-
ticles in volumes of gases, and his
invention of the term " molecule "
as the unit of physical structure,
258, 269.
BACTKRIA, investigations relating to,
379-386.
Baer, Karl Ernst von, his anatomi-
cal researches, 337.
Bary, Heinrich Anton de, his dis-
covery of the identity of the ani-
mal and vegetable cell, 340.
Bastian, Henry Charlton, revives
Pouchet's theory of " spontaneous
generation," 320.
Beaumont, Elie de, his contention as
to the origin of mountains, 130, 145.
Behring, Dr., his discoveries in serum-
therapy, 392.
Bell, Sir Charles, his epochal psy-
chological discovery, 401, 402.
Bernard, Claude, his study of the
pancreas, 347 ; his discovery of the
glycogenic function of the liver,
351, 352; his discoveries relating
to the nervous system, 405, 406.
Bernoulli, Daniel, originator of the
kinetic theory of gases, 242, 243.
Berthollet, Claude Louis, aid* in
the development of a new chemistry,
32 ; his theory of chemical com-
bination, 255.
Berzelius, Johan Jacob, confirms
and advocates Dalton's atomic the-
ory, 256, 259; his extension of the
binarv theory and establishment of
theoretical chemistry, 264, 265, 267,
268.
Bessel, Friedrich Wilhelm, predicts
the existence of a trans-Urani.-ui
planet, 48 ; his successful measure-
ment of the parallax of a star, 66 ;
his discovery of " invisible" stars, 71 .
460
Bichat, Marie Frar^ois Xavier, his
generalization of the animal organs,
322, 323; liis classification of all
animal structures into tissues, 324.
Biela, Wilhelm von, his discovery of
the comet bearing his name, 58;
and its after career and destruc-
tion, 58, 59.
Bii:ary composition of all chemical
compounds, theory of, 262-265.
Biology, the great advances in the
science made possible through
eighteenth-century explorations, 35,
36; its progress during the nine-
teenth century, 288-320; eighteenth-
century theories of organic evolu-
tion, 288-293 ; Lamarck's theory
of the transmutation of species,
293-297 ; Cuvier's theory of special
creation ;ind fixity of species, 297-
302 ; Oken's theory of " sponta-
neous generation " and of evolution
of species, 298, 320; Darwin's
theory of the origin of species by
natural selection, or the "survival
of the fittest," 302-310; triumph
of Darwin's theory and how it was
effected, 310-317; theories regard-
ing the "origin of the fittest,"
317-319 ; consideration of the next
step in organic evolution, 320.
Biot, Jean Baptiste, his investigation
of the L'Aigle aerolite, 158 ; op-
poses the undulatory theory of light,
203, 223. .
Black, Joseph, discoverer of latent
heat, 34, 171.
Blood, the, discoveries relating to,
329, 349, 350.
Boerhaave, Hermann, his theory of
the respiratory function, 39.
Boillard, Dr., his researches in cere-
bral physiology, 419.
Bois-Reymond, Emil du, his psycho-
physiological researches, 408.
Bond, William C., his discovery of
Saturn's inner ring, 49.
Boscovich, Ruggiero Giuseppe, his
speculation as to the ultimate con-
stitution of matter, 241.
Braid, James, his investigation of
hypnotism, 415.
Brain, the, Cabanis's conception of
the action and functions of, 414,
415. See Psychology.
Bredichin's cometary theory, 54, 55.
Brewster, Sir David, refuses to accept
the theory of the conservation of
energy, 218; his suggested im-
provement of lenses, 325, 326.
Broca, Paul, his discovery of cerebral
localization, 419, 422.
Brodie, Sir Benjamin, his untimely pre-
diction regarding anaesthetics, 366.
Brongniart, Alexandre, how lie ac-
counted for the bowlders on the
Jura, 131; his study of strata
around Paris, 138.
Brontotheridce, or 7'if another ex, their
line of descent, 121.
Brown, Robert, his discovery of the 1111-
cleu.- of the vegetable cell, 330, 331.
Brown-Sequard, Charles Edouard, his
investigations of the nervous sys-
.tem, 405.
Bruno, Giordano, believed some of
the planets inhabited, 12; burned
at, the stake for teaching that our
earth is not the centre of the uni-
verse, 16.
Buch, Leopold von, his conception of
the origin of mountains and of the
erratic bowlders on the Jura, 130;
dissents from the doctrine of special
creation, 301.
Buckhmd, William, his discovery of
fossil bones at Kirkdale, Yorkshire,
and his deductions therefrom, 95 ;
how he accounted for the bowlders
on the Jura, 131 ; adopts the glacial
theory, 135.
Buffon, Comte de (Georges Louis Le-
clerc), his early advocacy of the
theory of transmutation of species,
291, 292, 318.
Bunsen, Robert Wilhelm, with the
assistance of Kirchhoff, perfects the
spectroscope, 70, 283.
Burnham, S. W., his enthusiastic
search for double stars, 65.
Biitschli, Professor, his theory of cell
formation, 454.
CABANIS, PIERRE JKAX GEORGE, his
conception of the action and func-
tions of the brain, 414, 415.
461
INDEX
Carnot, Sadi, discovers that heat and
mechanical work are mutually con-
vertible, 213.
Carpenter, William Benjamin, his
theory of oceanic circulation, 180;
his advocacy of Baer's anatomical
theories, 337.
Catastrophisin, discussions regarding
the theory of, 97-99, 126, 130.
Cavendish, Henry, discovers hydrogen
gas and the composition of water,
31, 34, 253.
Cell theory, the, its conception and
development, 330-346 ; some of its
unsolved problems, 454-456.
Chambers, Robert, his anonymous
argument for the theory of trans-
mutation of species, 300, 301.
Charcot, Jean Martin, his revival of
hypnotism, 415.
Charpentier, Jean de, first ridicules
and then becomes an enthusiastic
advocate of the glacial theory,
134.
Chemistry, the contest it gave rise to
and its advances in the eighteenth
century, 29-35 ; the phlogiston
theory, 29-31 ; discovery of hydro-
gen gas, 31 ; discovery of oxygen,
which led to the development of the
"new chemistry," 31-35; solving
the mysteries of respiration, 39-41 ;
progress of the science during the
nineteenth century, 252-287 ; dis-
covery and development of the
atomic theory, 252-255; discovery of
the laws of atomic weights, the spe-
cific heat of atoms, and of isomor-
phism, 255-262; study of the theory
of the binary composition of chemi-
cal compounds and the establish-
ment of theoretical chemistry, 262-
265 ; discoveries in organic chemis-
try and the establishment of the law
of molecular structure, 265-269 ;
discovery of the law of valency,
and the establishment and develop-
ment of isomerism, 269-275 ; de-
termination of the character and
properties of atoms and molecules,
275-278 ; discovery of the law of
atomic weights and of the "law of
octaves " lead to an investigation
of the probable compound nature
of the elements, 278-287.
Chladni, Ernst F. F., his theory of
meteorites, 159, 160, 161, 162.
Chloroform, discovery of its anaes-
thetic properties, 374.
Christol, M., his discovery of human
fossils in the south of France, 111.
Christy, Henry, his important find in
the caves of Dordogne, 113.
Clark, Alvan, Jr., his discovery of a
"dark star," the companion of
Sirius, 75.
Clausius, Rudolph Julius Emanuel,
aids in establishing the doctrine of
the conservation of energy, 223-
226 ; investigates the kinetic theory
of gases, 242-244 ; points out the
way to measure the size of mole-
cules, 244 ; measures the energy of
a molecule of gas, 245.
Climate, and the study of the influ-
ences which affect it, 172-182 ;
how that of northern India is af-
fected by the monsoons, 191.
Clouds, classification of, and their
formation, 169-172.
Comets, theories regarding, and the
determination of their character
and origin, 53-60; photographed,
79.
Conservation of energy, discovery of
the law of, 209-221.
Contagion, its cause discovered, 380—
382.
Co-ordination, Cuvier's law of, 322.
Cope, Edward Drinker, his important
discoveries in the Rocky Mountain
region, and the story they tell, 114-
121 ; advocates Lamarck's theory of
the origin of favored species, 318,
319.
Corpuscles, red blood, discovery of,
349, 350,
Corvisart, Jean Nicholas de, intro-
duces the percussion method into
medical practice, 354-356.
Couper, A. S., his investigations of
the affinities of different elements,
271.
Croll, James, his " pre-nebular the-
ory," 86 ; contends for many lee
ages, 136; his estimate of the
462
INDEX
weight of the ice-sheet over New
England, 150; his theory of the
Gulf Stream, 180, 181, 182; his
theory of solar heat, 439.
Crookes, William, his ultra-gaseous
theory of matter, 247; advocates
the Proutian theory of the com-
pound nature of the so-called ele-
ments, 287.
Cuvier, Georges, his doctrine of the
correlation of parts, 36 ; his study
and investigation of fossil bones,
which lead to the establishment of
vertebrate paleontology, 91-94, 96 ;
his belief in catastrophism, 98,
131 ; his disbelief in the authen-
ticity of human fossils, 111; his
investigation of strata near Paris,
138; his theory of special creation
and fixity of species, 297, 299-302 ;
his classification of the animal
kingdom, 321 ; his law of co-ordi-
nation, 322; opposes Gall's phre-
nological system, 400.
Cyclone, description of, 186.
DAGUEIIRE, Louis JACQUKS MANDE,
his perfection of photography, 284.
Dalton, John, his solution of the
problem of evaporation and pre-
cipitation, 168, 169, 171, 172, 252,
253 ; his explanation of the trade-
winds, 178, 182; his conception of
the chemical atom and his atomic
theory, 253-255, 259, 260, 262.
Darwin, Charles Robert, and his
Origin of Species, 105-108, 302-
810; cited by Lyell to prove a
change of level in continental
areas, 126 ; his theory of latent
heat, 171 ; his construction and
establishment of the theory of the
origin of species by natural selec-
tion, 302-317.
Darwin, Erasmus, how he accounted
for the aurora, ]63; his prophetic
conception of the transmutation of
species, 290, 291, 296.
Darwin, Professor G. H., his determi-
nations as to the comparative mo-
tion of the earth and moon, 51, 52.
Davy, Humphry, his experiments in
photography, 2 ; endorses Thomp-
son's theory of heat, 27 ; experi-
ments on respiration, 40; his sug-
gestion to account for the molten
condition of the earth, 125 ; dis-
covers that the cause of chemical
and of electrical attraction are
identical, 206; proves the trans-
formation of labor into heat, 210 ;
melts ice by friction, 225; his the-
ory of the properties of particles of
matter (or atoms), 241, 242; non-
committal as to Dalton's atomic
theory, 259 ; his remarkable dis-
coveries which led to the theory of
the binary composition of chemical
compounds, 262-265 ; originates the
method of medication by inhala-
tion, 366.
Dawes, Rev. W. R., his discovery of
a new ring around Saturn, 49, 50.
Dawson, Sir William, his study of the
Laurentian system of Canada, 139.
Deluc, Guillaume Antoine, his theory
of evaporation, 168, 170.
Desmoulins, Louis Antoine, his psy-
chological researches, 400.
Devaine, a French physician, discov-
ers the cause of the infectious dis-
ease anthrax, 380, 381.
Deville, Sainte Claire, his investiga-
tion of the chemical process known
as dissociation, 273.
Dew, the problem of its formation
solved, 167-172.
Digestion, investigation of its proc-
esses, 39, 347-352.
Diphtheria, the serum treatment for,
392, 393.
Dissociation of molecules and atoms,
investigated by Deville, 273 ; an
unsolved problem, 447, 448.
Donati, Giovanni Battista, spectro-
scopic researches of, 70.
Donders,FransCornelis, makes the first
attempt to time nervous action, 413.
Dove, Ileinrich Wilhelm, his study of
the winds, 182, 183.
Draper, Henry, successfully photo-
graphs a nebula, 79.
Draper, John William, his pioneer
work in celestial photography, 76 ;
his application of photography to
spectrum analysis, 285.
463
INDEX
Dubois, Eugene, his find of the ape-
man fossil in the island of Java,
120.
Dujardin, Felix, his histological re
searches, 339.
Dulong and Petit's discovery of the
specific heat of atoms, 260, 261.
Dumas, Jean Baptiste Andre, his
work in organic chemistry, 266,
268, 279, 280, 346, 347.
Dunn, Sergeant, bis principal work in
weather observation, 190.
Dutrocliet, Rene Joachim Henri, his
study of the processes of digestion,
352.
EARTH, the, Thomson's estimate of its
longevity, 74, 154; some unsolved
problems regarding, 435-442.
Ehrenberg, Christian Gottfried, dis-
putes Mohl's cell theory, 343 ; dis-
covers the fibril lar character of
brain tissue, 425.
Electricity, conception of, in the
eighteenth century, 24 ; how af-
fected by the discovery of Volta,
28, 29 ; its relationship to galvan-
ism demonstrated, 204, 205 ; the
cause of chemical and electrical
action demonstrated to be identi-
cal, and the science of magneto-
electricity established, 206-209 ;
its first use in signalling, 207.
Electro-chemistry, its accidental dis-
covery through the experiments of
Nicholson and Carlyle, 28 ; Davy's
theory of, 206.
Electro - magnetism, Helmholtz and
Hertz's study and development of,
227, 228.
Encke, Johann Franz, determines the
orbital movement of comets, 57.
Espy, James Pollard, his theory of
wind storms, 190.
Ether, sulphuric, discovery of its
anaesthetic properties, 369-374.
Ether, the, and ponderable matter,
its displacement of the " imponder-
ables," 228, 229 ; its discovery, and
speculations as to its constitution
and properties, 230-236 ; experi-
ments of Helmholtz and Thomson
to prove the vortex theory of atoms,
236-240 ; theories as to the distri-
bution, mutual relations, properties,
and dimensions of molecules, 241-
245 ; also as to their outline, ac-
tion, temperature, and energy, 245-
251 ; the hypothesis that the vor-
tex whirl is the essence of matter
itself, 251. See Chemistry.
Euler, Leonhard,his extraordinary con-
clusion as to the midnight temper-
ature at the equator, 175.
Evans, John, aids Prestwich in mak-
ing report on the paleolithic im-
. plements found at Abbeville, 109.
Evaporation and precipitation, the-
ories regarding, and the determina-
tion of their causes, 167-172.
Evolution, theories of, 288-297, 302-
310, 317-320 ; some unsolved prob-
lems regarding, 454—456.
FALCONER, HCGH, verifies the paleo-
lithic find of Perthes at Abbeville,
109.
Faraday, Michael, attributes the aurora
to magnetism, 164; establishes and
develops the science of magneto-
electricity, 208, 209, 226 ; refuses
to accept the doctrine of the con-
servation of energy, 218; his con-
ception of an invisible, all-pervad-
ing plenum, 234 ; liquefies carbonie-
acid gas, 249 ; confirms Berzelius's
theory of binary combinations, 2t>5.
Favus, its cause discovered, 365.
Fechner, Gustav Theodor, his re-
searches in the new science of
" physiological psychology," 409-
412."
Fermentation and putrefaction, inves-
tigation of the processes of, 375-
380.
Ferrel, William, his rediscovery of
the cause of atmospheric circula-
tion, 183, 184.
Ferrier, David, his experiment* in
brain localization, 420, 421.
Fizeau, Hippolyte L., his experiments
on light, 222 ; his experiments on
ether, 234.
Flourens. Marie Jean Pierre, his ex-
periments in nerve phvsiologv,
417, 418.
464
INDEX
Forbes, James David, proves that
radiant heat and light conform to
the same laws, 223, 225.
Forster, George, his remarkable cli-
matic observations, 176.
Forster, Thomas, his theory of aero-
lites, 161.
Foucault, Leon, his experiments to
prove the undulatorv nature of
light, 222.
Fourcroy, Antoine Fran9ois, aids La-
voisier in the development of a
new chemistry, 32.
Frankland, Edward, discovers the
difference in combining power of
different atoms, which leads to the
law of valency, 271.
Franklin, Benjamin, tries to account
for evaporation, 168.
Fraunhofer, Joseph, perfects the re-
fracting telescope and invents the
heliometer, 65 ; suggests the im-
provement of the spectro?cope, 70.
Fresnel, Augustin Jean, his investi-
gations of the phenomena of light,
200-204, 225.
Fritsch, Gustav, his researches relat-
ing to brain localization, 420.
Frommann, Professor, his theory of
cell formation, 454.
Fuhlrott, Dr., his discovery of the
Neanderthal skull, 110.
GALL, FRANZ JOSEPH, originates the
system of phrenology, 399, 400, 423.
Galle, Johann Gottfried, directed by
Leverrier, discovers Neptune, 49.
Galvani, Luigi, and the invention and
application of the galvanic battery,
27, 28.
Gulvanic battery, the far-reaching
effects of its invention, 27-29.
Galvanism, its discovery and far-reach-
ing effects, 27-29; its kinship to
electricity demonstrated, 204-206.
Gauss, Karl Friedrick, his first test
of the electric telegraph, 207.
Gay-Lussac, Joseph Louis, his experi-
ments with gases, which lead to the
discovery of the molecule, 256-
258 ; his discovery of cvanogen,
266, 267. '
Geology, its ghostly character in the
eighteenth century, 17-19; Hutton
labors to systematize the science,
but his Theory of the Earth is pro-
nounced heretical, 19-23 ; William
Smith's first geological map of
England, 90 ; progress of the sci-
ence during the nineteenth century,
123-156; controversy between the
Neptunists and the Plutonists re-
garding terrestrial phenomena, and
the establishment of the theory of
the latter, 123-125; discussion re-
garding the changes in land sur-
faces, whether cataclysmic or
gradual, 125-130; establishment
of the glacial theory, 130-136;
study of the earth's strata, and
their classification, 136-145; con-
sideration, of the evidence which
shows the age and growth of moun-
tains and continents, 145-150 ; evi-
dences of the .glacial epoch, 150,
153; reasons for believing in the
gradual diminution of changes in
the surface of the earth owing to
its refrigeration, 153-156.
Gerhardt, Charles FiedeVic, working in
the field of organic chemistry, 266-
268 ; revives Avogadro's law, 269.
Gerlach's histological scheme of the
brain, 428.
Germ theory, Pasteur's and Tyndall's
advocacy of, 320, 386.
Gill, David, photographs a comet, 79.
Glacial theory, the establishment of,
130-136 ; the work of the ice-sheet
in New England, 150.
Goethe, Johann Wolfgang von, his
doctrine of the metamorphoses of
parts, 36, 102, 288-291.
Golgi, Camille, .his method of stain-
ing nerve cells and their processes,
429, 430.
Gravitation, its cause an unsolved
problem, 443-446.
Gray, Asa, an ardent propagandist of
the Darwinian theory, 313.
Gulf Stream, the, speculations as to
its effect on climate, 178-131, 182.
t.EY, JOHN, his explanation of the
trade-winds, 178.
Haeckel, Ernst Heinrich, an enthusi-
2G
465
INDEX
astic advocate of the Darwinian
theory, 313, 414 ; favors the La-
marckian theory of the origin of
favored species, 318.
Hahnemann, Christian Samuel Fried-
rich, his belief in the prevalence
of the itch, 361.
Hall, Asaph, his discovery of the
moons of Mars, 49.
Hall, Marshall, his services in the
practice of medicine, 359, 360 ; his
important psychological discovery,
403, 404.
Haller, Albrecht von, his idea of the
function of respiration, 39.
Harding, of Lilienthal, his discovery
of Juno, 47.
Hartley, David, his associational the-
ory of psychology, 414.
Heat, how regarded in the eighteenth
century, 24 ; Thompson's vibratory
theory of, 26, 27 ; the investigation
of, helps to solve the problem of
evaporation and precipitation, 171 ;
Humboldt's study of its distribu-
tion on the surface of the globe,
175-177; discovery of its nature
and properties, 222-224 ; the source
of animal heat discovered, 349.
Heidenhain, Rudolf, his experi-
ments in hypnotism, 415, 416.
Helmholtz, Hermann Ludwig Ferdi-
nand von, his theory as to the dis-
crepancy between the motion of
the earth and the jnoon, 51 ; his
theory of solar energy, 74, 437 ;
his share in the discovery of the
doctrine of the conservation of
energy, 214, 217, 221, 225, 437;
his electro-magnetic theory of light,
227, 228 ; his calculations to prove
the vortex theory of atoms, 238;
opposes the vitalistic conception of
fermentation, 379 ; his researches
and discoveries in psycho-physics,
407-409.
Hencke, an amateur astronomer, dis-
covers a fifth asteroid, 47.
Henderson, Thomas, Astronomer Roy-
al of Scotland, the first to success-
fully measure a star's parallax, 66.
Henle, Friedrich Gustav Jakob, his
anatomical researches, 332 336,
352 ; his study of the nervous sys-
tem, 404.
Herbart, Johann Friedrich, founder
of mathematical psychology, 407.
Herschel, Caroline, aiding William in
his investigations, 6, 7.
Herschel, Sir John, his study of
double stars, 63, 64, 65 ; refuses to
accept the doctrine of the conserva-
tion of energy, 218; his improve-
ment of the microscope, 326, 327.
Herschel, Sir William, his improve-
ment of the telescope and his
astronomical discoveries, 5 — 12,
226 ; his nebular hypothesis, 13-
16 ; his theory of the asteroids, 47 ;
his study of double stars and dis-
covery of their relative change of
positions, 63, 65 ; his unsuccessful
efforts to solve the problem of star
distance, 65 ; his study of sun-
spots, 166.
Hertz, Heinrich, confirms Helmholtz's
electro- magnetic theory of light,
227, 228.
Hinrichs, Gustav, his investigations
confirm the " law of octaves," 280.
Histology. See Anatomy and Physi-
ology ; Psychology.
Hooke, Robert, his happy guess as to
the nature of light, 198.
Hooker, Sir Joseph Dalton, his aid
sought by Darwin in the publi-
cation of his Origin of Species,
307, 809, 310; becomes his con-
vert and disciple, 313.
Howard, Edward, his conclusion as to
aerolites, 158.
Howard, Luke, his classification of
clouds and his theory of their for-
mation, 169. 170; his theory of dew
formation, 170.
Huggins, William, his spectroscopic
researches, 70, 80.
Humboldt, Alexander von, his discov-
eries in terrestrial magnetism, 167;
his study of heat distribution and
its climatic effects, 175-177.
Hunter, John, discovers the processes
of digestion, 39, 347.
Hutton, James, his geological inves-
tigations and his Tlieory of the
Earth, 19-23, 123, 129, 153; gen-
466
INDEX
eral acceptance of his proposition
that "time is long," 97, 102; his
followers known as Plutonists, 123 ;
and their final success in proving
the igneous origin of rocks, 125;
his theory of rain, 169, 172.
Huxley, Thomas Henry, the lesson he
draws from the evidence of paleon-
tology, 117, 118; his estimate of
Darwin, 317.
Huygens, Christian, originator of the
undulatory theory of light, 198;
conceives the existence of the true
ether, 231.
Hyatt, A., advocates the theory of
Lamarck as to the origin of favored
species, 318.
Hydrogen gas, discovery of, 31.
Hydrophobia, discovery of its cure
by protective vaccination, 389, 890.
Hypnotism, investigation of its phe-
nomena, 415-417.
ICEBERG THKORY, the, discussion re-
garding, 130-136; Ihe effects of
the ice-sheet in New England, 150.
"Imponderables," the, eighteenth-
century controversy regarding the
nature, of, 24-27 ; the study of, in
the nineteenth century, 192-228;
their abolishment, 228^ 229.
Inhalation originated by Davy as a
method of medication, 366.
Insane, the, reform in treatment of,
395-401.
Isomerism, discovery of, 274.
Isomorphism, discovery of, 261.
Itch ("gale repercutee''), its cause
and cure discovered, 360-363.
JACKSON, CHARLES T., his claims to
the discovery of the anaesthetic
properties of ether, 373.
Jenner, Edward, anil his discovery of
vaccination, 42, 43.
Joule, James Prescott, discovers the
law of the mechanical equivalent
of heat, the corner-stone of the law
of the conservation of energy, 213,
214, 217, 218, 221, 223, 225.'
KANT, IMMANUEL, conceives the idea of
the transmutation of species, 291.
Keeler, Professor, his conclusions as
to the character of nebulae, 83.
Kekule, A., his investigations lead to
the establishment of the law of
valency, 271.
Kelvin, Lord. See Thomson, William.
Kinetic theory of gases inrestigated
by Clausius and Maxwell, 242-245.
Kirchhoff, Gustav Robert, with Bun-
sen, perfects the spectroscope and
invents the method of spectrum
analysis, 70, 283.
Kirkdale, Yorkshire, England, dis-
covery of fossil bones in cave at,
95.
Kirwan, Richard, calculates empiri-
cally the temperatures of all lati-
tudes, 175.
Kitasato, Dr., a leader in the develop-
ment of serum-therapy, 392.
Koch, Robert, his bacterial investi-
gations, 381.
Kolliker, Rudolf Albert, confirms the
theory of isolated nerve cells, 431.
LAENNEC, RENE THEOPHILE HYACINTHE,
discovers and practises the auscul-
tation method in diagnosing dis-
eases of the heart and lungs, 356,
359.
Lagrange, Joseph Louis, systematizes
Newton's hypothesis of universal
gravitation, 15; accounts for the
accelerated motion of the moon, 50.
Lamarck, Jean Baptiste, opposes the
theory of special creation, 103; his
theory of the transmutation of
species, 293-297 ; his selection of
the word "biology " to express the
science of living things, 298.
Langley, Samuel Pierpont, spectro-
scopic researches of, 70.
Laplace, Pierre Simon de, solves the
problems of universal gravitation,
15; completes Herschel's nebular
hypothesis, 15, 16; his theory of
Saturn's rings, 50 ; how he ac-
counted for the moon's acceleration,
50 ; how he accounted for aerolites,
158; opposes Fresnel's undulatory
theory of light, 203.
Lartet, Edouard, his important find in
the caves of Dordogne, 113.
467
INDEX
Latour, Cagniard, discoverer of pep-
sin, 347 ; his microscopical re-
searches, 376.
Laurent, Augustus, his work in or-
ganic chemistry, 266, 268.
of the compound microscope, 327,
328 ; his discovery of the true form
of red blood corpuscles, 329 ; liis
discovery and development of anti-
sepsis in surgery, 382-386.
Lavoisier, Antoine Laurent, his chem- ! Lockyer, J. Norman, his "meteoric
ical experiments and discoveries,
26, 31-33; his tragic fate and the
triumph of his doctrines, 33-35 ;
his experiments on respiration, 40.
" Law of octaves," the, its discovery
and development, 280, 283.
Leeuwenhoek, Antonius von, his mi-
croscopical researches, 329, 376.
Leidy, Joseph, his discoveries of the
hypothesis," 83-86 ; his endorse-
ment of the theory that our so-
called elements have a compound
nature, 286, 287 ; his theory of
solar heat, 439.
Lodge, J. Oliver, his theory of two
ethers, 235.
Logan, William I., his geological in-
vestigations in Canada, 139.
Tertiary period in the Rocky Moun- Long, Crawford W., his investiga-
tain region and the truth they teach, tions of the anaesthetic properties of
114-121; his investigation of the! ether, 373. 374.
Trichina spiralis, 363. j Lotze, Rudolf Hermann, his advocacy
Lenz, Professor, first proposer of j of psycho-physiology, 409.
gravitation as the cause of oceanic Louis, Pierre Charles Alexandre, his
circulation, 180.
Le Sage's hypothesis of the cause of
gravitation, 443-445.
Leuckart, Karl Georg Friedrich Ru-
dolf,
his investigations of
stpiralis, 363, 364.
the
Leverrier, Urbain Jean Joseph, his
calculations lead to the discovery
of Neptune, 48, 49 ; his further cal-
culations as to the location of a
hypothetical planet known as Vul-
can, 49.
Liebig, Justus von, foremost among
the workers in organic chemistry,
266, 268, 274 ; his important chem-
ical researches, 346, 347 ; discovers
the source of animal heat, 349 ;
opposes Pasteur's doctrine of fer-
mentation, 376, 379.
Life, some unsolved problems of cos-
mic and telluric, 449-453.
Light, how regarded in the eighteenth
century, 24 ; establishment of the
undulatory theory of, 192-204, 223;
Helmholtz's electro-magnetic the-
ory of, 227, 228.
Liquefaction of air, of carbonic-acid
gas, hydrogen, and of other perma-
nent gases, 249 ; the question as to
the liquefaction of air in our outer
atmosphere, 250.
Lister, Sir Joseph, his improvement
468
introduction of the " statistical
method " into the practice of med-
icine, 360.
Lubbock, Sir John William, advocates
the Darwinian theory of natural
selection, 313.
Lyell. Charles, the apostle of uniform-
"itarianism, 99-102, 125, 126, 130;
convinced by Darwin, endorses the
transmutation theory, 107, 108,
313 ; his advocacy of the glacial
theory, 131, 132; his citation of a
fact from Playfair which is undis-
puted, 153; his aid sought by
Darwin in the publication of his
Origin, of Species, 307, 309.
MAGKNDIE, FRANCOIS, his services in
the rational practice of medicine,
359, 360; his studies of the ner-
vous system, 400, 402.
Magnetism, its relations to electricity
discovered, and the science of mag-
neto-electricity founded, 207-209.
Magneto-electricity, Faraday estab-
lishes and develops the science of.
208, 209.
Malthas, Thomas Robert, how his
Population aided Darwin
in formulating his theory of the
origin of species by natural selec-
tion, 305, 306.
INDEX
Marais, M., his description of a nine-
teen tli-century miracle, 157.
Mars, discovery of its seven moons,
49.
Marsh, Othniel Charles, his discovery
of new Tertiary species in the
Rocky Mountain region, and what
they signify, 114-121.
Mastodon, the Warren, description of,
119.
Maury, Matthew Fontaine, his the-
ory of the Gulf Stream, 178-180.
Maxwell, James Clerk, determines the
character of Saturn's rings, 50; his
theories in reference to electricity
and magnetism, and to light and
electro-magnetism, 227 ; his testi-
mony as to the existence of an all-
pervading plenum, 230, 234 ; his
investigation of the kinetic theory
of gases, 242-244.
Mayer, Julius Robert von, his share
in establishing the doctrine of the
conservation of energy, 214, 215-
217, 221, 225, 435, 436.
Medical science : Jenner's eighteenth-
century discovery of the method of
preventing small-pox, 42, 43 ; prog-
ress of the science during the nine-
teenth century, 354-394 ; discov-
ery and development of percussion
and auscultation in the diagnosing
of disease, 354-359 ; introduction of
the "statistical method," 360;
causes of '' gale re percutee " (itch),
of trichinosis, and of favus dis-
covered, 360-365 ; discovery of
anaesthesia, 365-375 ; processes of
fermentation and putrefaction in-
vestigated, 375 - 380 ; cause of
contagion discovered, 380-382 ;
discovery and establishment of
antisepsis in surgery, 382-386;
discovery and development of pro-
tective vaccination by virus pre-
pared in the laboratory 386-390 ;
discovery and development of the
serum-therapy method of curing
disease, 390-394.
Meldrum, Mr., on the effects of sun-
spots, 166.
Mendeleeff, Dmitri, confirms the " law
of octaves " under the title of
" periodic law," 280, 283 ; his dis-
sociation theory of atoms, 448.
" Meteoric hypothesis," the, of J.
Norman Loekyer, 83-86.
Meteorites. See Aerolites.
Meteorology, its eighteenth- century
students' views of the imponder-
ables, 25, 26 ; its triumphs and
failures in the nineteenth century,
15V-191 ; study and determination
of the origin and nature of aero-
lites, 157-162; speculations regard-
ing the aurora 162-167; problem
of dew formation solved, and of
clouds, rain, snow, and hoar-frost,
167-172; study of climatic con-
ditions, and speculations as to the
influences which affect them, 172-
182, 191 ; aerial currents investi-
gated, and their laws determined,
182-191 ; the greatest triumph of
practical meteorology, 191.
Meteors, determination of their origin
and character, 59, 60.
Meyer, Lothar, his confirmation of
the " law of octaves," 280.
Microscope, nineteenth - century im-
provements in, 324-328 ; the inven-
tion of the compound microscope,
327, 328.
Miller, William Allen, his spectro-
scopic investigations, 70.
Mitscherlidi, Eilhard, his discovery of
isomorphism, 261.
Mohl, Hugo von, his discovery of
protoplasm, 338, 339 ; his theory
of cell formation, 343, 344.
Mohr, Karl Friedrich, his share in the
discovery of the doctrine of the
conservation of energy, 214, 215,
221, 225.
Molecules, theories as to their dis-
tribution, properties, dimensions,
etc., 242-251, 275-278; their iso-
morphous property, 261 ; establish-
ment of the law of molecular struct-
ure, 265-269, 272-275 ; some un-
solved problems regarding, 448, 449.
Moon, the, how its acceleration is ac-
counted for, 50-53.
Morton, William, T. G., demonstrates
tlie practicability and benefit of
anaesthesia, 369, 370, 375.
469
INDEX
Morveau, Guyton de, and the new
chemistry, 32.
Miiller, Johannes, his discovery of
the resemblance between animal
and vegetable cells, 331, 332, 337;
his study of the nervous system,
404 ; his discovery of the means of
hardening and preserving brain
tissues, 424.'
Murchison, Roderick Impey, combats
the uniformitarianism of Lyell, 130;
his classification of transition rocks
into chronological groups, 138.
NAPOLEON BONAPARTE, how his choice
of a physician influenced the prog-
ress of medical science, 354, 355,
360.
Neanderthal skull, its discovery and
description, 110.
Nebulae, investigation of, and theories
concerning, 13-17, 79-87.
" Nebular hypothesis," the, its con-
ception and completion, -13-1 7, 84.
Neptune, how it was discovered, 48,
49.
Neptunists, theory of the, 123-125.
Nervous system, the, discoveries re-
lating to, 401-407.
Neurons, the theory of, 430, 431.
New photography, the, 2, 5, 284-286.
Newburg, New York, description of
the mastodon found there, 119.
Newlands. John A. R., discovers the
" law of octaves," 280.
Newton, Professor, determines the
true character of meteor showers,
59.
Newton, Sir Isaac, his hypothesis of
universal gravitation, systematized
by Laplace and Lagrange, 15 ; pro-
nounced impious and heretical in
1700, 16; his blow at the super-
natural character of comets, 54.
OCEAN CURRENTS, speculations as to
their effects on climate, 178-182.
Oersted, Hans Christian, his discovery
of the deflection of the magnetic
needle by electric currents, 207.
Oken, Lorenz, his extension of the
theory of metamorphoses of parts
to the animal kingdom, 289 ; his
theory of spontaneous generation
and of the evolution of species, 298.
Olbers, Heinrich Wilhelm Matthias,
his discovery of Pallas, 44, 47 ; his
explosion theory of the asteroids,
and the objections to it, 47 ; hi.-*
discovery of Vesta, 47 ; teaches the
true character of the comet's tail,
54 ; his theory of aerolites, 158.
Olmsttd, Denison, determines the cos-
mical origin of shooting-stars, 161.
Origin of species by natural selection,
theory of, 302-310.
" Origin of the fittest," speculations
regarding, 317-319.
Owen, Sir Richard, sustains Lyell 's
hypothesis of special creation, 105;
his discovery of the Trichina spi-
ralis, 363.
PALEONTOLOGY, the work of its eigh-
teenth-century devotees, 23 ; the
story of its progress during the
nineteenth century, 88-122; the
true character of fossils first recog-
nized by Da Vinci, 88; William
Smith's early paleontological discov-
eries and his deductions therefrom,
89-91 ; Cuvier's studies and inves-
tigations, which result in the estab-
lishment of vertebrate paleontology,
91-94, 96; Buckland's Kirkdale
discovery and the contention re-
garding it, 95 ; other fossil discover-
ies, and the general acceptance of
Hutton's proposition that " time is
long," 95-97; the theory of catas-
trophism overthrown and the doc-
trine of unifonnitarianism es-
tablished, 97-102 ; controversy
regarding the theory of special
creation, 102-105 ; Darwin's Origin
of Specie*, and the general accept-
ance of his transmutation theory,
105-109 ; fossil discoveries of Fal-
coner, Fuhlrott, Schmerling, and
others, which demonstrate the ex-
istence of paleolithic man, 109-
114; discovery of new Tertiary
species in the Rocky Mountain
region, and of vertebrate fossils
elsewhere, which prove the truth
of evolution, 114-121.
470
INDEX
Pappenheim, Gottfried Heinrich, his
discovery of the function of the
pancreas, 347.
Pasteur, Louis, his services in the
cause of organic chemistry, 266,
274, 375; refutes Pouchet's theory
of spontaneous generation, 320,
386 ; his study of fermentation and
putrefaction, 375-380 ; his discov-
ery and establishment of protective
vaccination, 387-390.
Peirce, Benjamin, disproves Laplace's
theory of Saturn's rings, 50.
Penn, Granville, how he accounted
for the fossil discoveries at Kirk-
dale, 95.
Pepsin, its discovery, 347.
Percussion, its discovery and develop-
ment as a method of diagnosing
disease, 354-356, 359.
Perraudin, a chamois-hunter of the
Alps, conceives the glacial theory,
132-134.
Perthes, M. Boucher des, his paleo-
lithic discoveries at Abbeville, 109.
Phlogiston, the eighteenth-century
theory of, 29-32.
Photography, experiments in, by Davy
and Wedgwood, 2 ; its services in
spectrum analysis, 284-286 ; per-
fected by Daguerre and Draper,
284, 285.
Phrenology, origin of the system,
399.
Physics, advances made in the science
during the eighteenth century, 23-
29 ; controversy over the nature of
the " imponderables," 24-27 ; dis-
covery of the galvanic battery and
its far-reaching results, 27-29;
progress made in the science dur-
ing the nineteenth century, 192—
229; study of light and colors, and
the establishment of the undula-
tory theory, 192-204; identity of
galvanic and electrical action de-
monstrated, 204-206; the link be-
tween magnetism and electricity
discovered, and the science of mag-
neto-electricity founded, 207-209 ;
discovery of the law of the conser-
vation of energy, 209-221 ; discov-
ery of the nature and properties of
heat, and the establishment of the
science of thermo-dynamics, 222-
224; Helmholtz's electro-magnetic
theory of light, 227, 228 ; displace-
ment of the imponderables in favor
of an all-pervading ether, 228, 229;
some unsolved problems, 443-449.
Physiology, its eighteenth - century
triumphs, 39-41 ; discoveries in
brain physiology, 417-423. See
Anatomy and physiology; Medical
science.
Piazzi, Giuseppe, his discovery of
Ceres, 44.
Pickering, Edward Charles, his spec-
troscopic researches, 70, 73.
Pinel, Philippe, his anatomical inves-
tigations, 324; inaugurates in
France a reform in the treatment
of the insane, 395—399 ; opposes
the system of phrenology, 400.
PitJiecanthropus erectus, the ape-man
fossil from the island of Java, 120.
Playfair, John, his advocacy of the
Huttonian theory of the earth, 123,
126.
Pleiades, the, facts concerning, 64,
80.
Plutonists, theory of the, 123-125.
Poisson, Simeon Denis, discovers the
cause of the atmospheric circula-
tion, 184; opposes the undulatory
theory of light, 203.
Pouchet, M. F. A., his theory of
" spontaneous generation," 320.
Prestwich, Joseph, investigates the
Abbeville find and makes report
thereon, 109.
Priestley, Joseph, his discovery of
oxygen, 31 ; his inexplicable oppo-
sition to the doctrines of Lavoisier,
34, 35 ; his experiments on respi-
ration, 40.
Protoplasm, its discovery by Molil
and Dujardin, 338-340.
Proust, Louis Joseph, his theory of
the combination of chemical ele-
ments, 255, 256.
Front, William, his theory of the
compound nature of the so-called
elements, 278-287 ; his discovery
of hydrochloric acid in the gastric
juice, 347.
471
INDEX
Psychology, experimental, its advances
during the present century, 395
-432 ; the reform in the treatment
of the insane, 395-401 ; discov-
eries regarding the nervous sys-
tem, 401-407 ; establishment and
development of psycho- physics,
407-417 ; discoveries in brain phys-
iology, 417-423 ; establishment
and development of brain histol-
ogy, 423-432.
Psycho-physics, discoveries relating
to, 407-417.
Putrefaction and fermentation, their
processes investigated, 375-380.
RAIN, theories regarding, and the de-
termination of its causes, 167-172.
Ramon y Cajal, S., his discoveries re-
lating to nerve cells, 430, 431, 432.
Ramsay, Andrew Crombie, how he
accounted for many of the lake
basins, 153.
Rankine, William John Macquorn,
his researches prove the law of the
conservation of energy, 223, 224,
225.
Remak, Professor, his microscopical
researches of the brain and nervous
system, 404, 425.
Respiration, its processes investigated,
39-41, 349, 350.
Rontgen, Professor, and the X ray,
1, 2, 228.
Rosse, Lord, his studies of nebula)
through his six-foot reflector, 80.
Roux, Dr., his services in the cause
of serum-therapy, 392, 393.
Rum ford, Count, see Thompson, Ben-
jamin.
Rush, Benjamin, his reform in the
treatment of the insane, 395, 396.
Rutherford, Daniel, his discovery of
nitrogen, 34.
Ruthorford, Lewis Morris, his spec-
troscopic researches, 70, 72.
SAlNT-HlLAIRE, GEOFFROY, his
cacy of the transmutation theory,
104 ; opposes Cuvier's special-cre-
ation hypothesis, and partially en-
dorses the Lamarckian theory, 300,
318.
Saturn, discoveries relating to, 49, 69.
Savary, M., accounts for the elliptical
orbits of double stars by the laws
of gravitation, 64.
Scheele, Karl Wilhelm, his discovery
of oxygen, 31 ; his physiological ex-
periments, 40.
Schiaparelli, Giovanni Virginio, his
establishment of the cometary
origin of meteors, 59.
Schleiden, Matthias Jakob, his dis-
covery of the function of the cell
nucleus, 331, 332, 345; his discov-
ery of so-called free-cell formation,
343.
Schmerling, Anton von, his impor-
tant discoveries at Engis, Westpha-
lia, 111.
Schoenlein, J. L., discovers the cause
of favus, 365.
Schultze, Max Johann Sigismund, dis-
covers the identical character of
vegetable and animal cells, 340.
Schwann, Theodor, his cell theory,
331-336, 337, 338, 343, 345; his
discovery of pepsin, 347 ; his mi-
croscopical researches, 376, 404.
Scientific problems, some unsolved,
433-457 ; regarding the sun and
earth, 435-442; in physics, 443—
449 ; of life and the evolution of
living matter, 444-456 ; of anthro-
pology, 456, 457.
Scrope, G. Poulett, his work account-
ing for the origin of volcanoes, liM.
Secchi, Father Angelo, his researches
in spectrum analysis, 70, 72.
Sedgwick, Adam, his classification of
transition rocks into chronological
groups, 138.
Serum-therapy, discovery and devel-
opment of the system of, 390-
394.
Shooting-stars, determination of their
origin, 59, 60.
Simpson, Sir J. Y., his discovery of
chloroform as an anaesthetic, 374.
Sirius and its " invisible " companion,
74, 75.
Six, Mr., his theory of dew formation,
171.
Small-pox, Jenner's discovery of the
means of its prevention, 42, 43.
473
INDEX
Smith, William, " the father of Eng-
lish geology," his paleontological
discoveries and his deductions
therefrom, 89-91 ; his study of
strata as a kev to the earth's chro-
nology, 137, 138.
South, James, aids John Herschel in
his investigation of double stars, 64.
Spallanzani, Abbe, discovers the proc-
esses of digestion, 39, 347 ; his ex-
periments on respiration, 40.
Special creation, discussions relating
to the hypothesis of, 91-97, 104,
105, 297-302.
Spectroscope, its perfection by Kirch-
hoff and Bunsen, and its solar and
sidereal analyses, 70-76, 283, 284 ;
its necromantic po\ver, 76; its
application to nebula;, 80.
Spectrum analysis, its remarkable dis-
closures, 70-76, 283-287.
Spencer, Herbert, advocates the Dar-
winian theory, 313, 316 ; favors the
Lamarckian conception of the ori-
gin of favored species, 318; his
theoretical study of psychology, 415.
Spontaneous generation, Pouchet's
hypothesis of, 320.
Spurzheim, Kaspar, advocates phre-
nology, 400.
Stars, double or multiple stars, and
stiir clusters, the investigations of
the nineteenth century relating to,
60-76.
•' Statistical method," the, its intro-
duction into medical practice, 360.
Stethoscope, its invention and improve-
ment, 356, 359.
Storm-centre, description of, 186, 189.
Struve, F. G. W., his discovery of
double stars, 64 ; solves the prob-
lem of star distance, 66.
Sun, the, its elements discovered by
spectrum analysis, 70-72 ; Helm-
holtz's theory of solar energy, 74 ;
some unsolved problems regarding,
435-442; estimate as to its heat-
giving life, 438.
Sun-spots, effects of, 166.
TAIT, PETER GPTHRIE, his measure-
ment of the free path of molecules,
247.
Talbot, William Henry Fox, his ser-
vices in the perfection of photog-
raphy, 285.
Temperature, the, absolute zero of,
250.
Tetanus, the serum treatment for, 392.
Theory of the Earth, James Hut-
ton's, 20-23.
Thermo-dynamics, and how the sci-
ence originated, 223, 224.
Thompson, Benjamin (Count Rum-
ford), his vibratory theory of heat,
26, 27 ; he proves the transforma-
tion of labor into heat, 210.
Thomson, Thomas, advocates Dalton's
atomic theory, 259.
Thomson, William (Lord Kelvin), his
estimate of the earth's longevity,
74, 154, 441 ; aids Joule in estab-
lishing the doctrine of the conser-
vation of energy, 218-223, 225;
his doctrine of the dissipation of
energy, 223, 224 ; his studies in
thermo-dynamics, 223, 224, 227;
his calculation of the probable den-
sity and rigidity of ether, 235 ; his
conception of the vortex theory of
atoms, and his verifying experi-
ments, 238-240; calculates the
dimensions of a molecule, 244,
245 ; refuses to recognize any re-
pulsive power in molecules, 246 ;
his estimate of the heat-giving life
of the sun, 438.
Titanotheres, or Erontotheridce, evolu-
tion of, 121.
Tournal, M., his discovery of human
fossils in the south of France, 111.
Toxine and antitoxine, their discovery
and introduction, 390-394.
Trade-winds, study of their origin
and effects, 177/178, 182.
Transmutation of species, doctrine of,
105-108, 293-297, 302-310, 317-
320.
Treviranus, Gottfried Reinhold, his
theory of the transmutation of
species published the same year in
which Lamarck's first appeared,
398 ; foreshadows the cell theory,
336.
Ti-i<-hina spiralis, its discovery, 363-
365.
473
INDEX
Trichinosis, character of the disease
and its cause discovered, 363-365.
Tuke, William, inaugurates reform in
treatment of the insane, 395.
Tyndall, John, his advocacy of May-
er's doctrine of the conservation of
energy, 221, 223; and of Darwin's
theory of natural selection, 313;
his endorsement of the germ the-
ory, 320, 386.
ULTRA-GASEOUS or fourth state of
matter, theory of, 247.
Undulatory theory of light, establish-
ment of, 192-204.
Uniformitarianism, Sir Charles Ly-
ell's advocacy of the doctrine of,
99-102, 127, 131.
VACCINATION, its discovery as a means
of preventing small-pox, 42 ; its
application as a preventative of
other diseases by virus prepared in
the laboratory, 386-390.
Valency, development of the law of,
269/275.
Valentin, Gabriel Gustav, his study
of pancreas, 347.
Van 't Hoof, Professor, his establish-
ment of stereo-chemistry, 448, 44S.
Venetz, M., an early believer in and
advocate of the glacial theory, 134.
Vertebrate paleontology, establish-
ment of, 91-97.
Vinci, Leonardo da, his early recog-
nition of the true character of fos-
sils, 88.
Virchow, Rudolf, his demonstration
of Schwann's cell theory, 344, 345 ;
his researches which lead to the
discovery of trichinosis, 363, 364.
Volta, Count Alessandro, his inven-
tion of the voltaic pile, 27, 28.
Vortex theory of atoms, the, experi-
ments to prove, 236-240 ; an un-
solved problem, 446, 447.
Vulcan, a hypothetical planet located
by Leverrier, 49.
WALLACE, ALFRED RUSSELL, his re-
markable conception of the theory
of natural selection contemporane-
ously with Darwin, 307-310.
Waller, Professor, his discovery of
" trophic centres," 427.
Warren, John C., mounted, described,
and gave name to the mastodon
found at Newburg, N. Y., 119.
Water, its com position discovered, 31,
34, 253.
Weather bureaus, their principal oc-
cupation, 186, 191.
Weber, Ernst Heinrich, his experi-
ments and discovery in psycho-
physics, 409-412.
Weber, Wilhelm Eduard, makes a
practical test of the electric tele-
graph, 207 ; his study of the ner-
vous system, 405.
Wedgwood, Josiah, invents the py-
rometer, 24.
Wedgwood, Thomas, his experiments
in photography, 2, 5.
Weismann, August, opposes La-
marck's theory of acquired vari-
ations in the origin of favored
species, 318; elaborates a hypo-
thetical scheme of the relations of
intracellular units, 455.
Wells, C. W., his solution of the
problem of dew formal ion and of
the precipitation of \vatery vapor
in any form, 170-172.
Wells, Horace, the first to administer
an anaesthetic in a surgical opera-
ation, 369.
Werner, Abraham Gottlob, the pro-
pounder of the Neptunian theory,
his belief in the aqueous origin
of the solids of the earth's crust,
123; his belief in the uniformity of
strata over thewhole earth, 136, 137.
Wilson, Patrick, his theory of dew
formation, 171.
Winds. See Aerial currents.
Wohler, Friedrich, his synthesization
of urea, 265, 266 ; his investigation
substantiates the binary theory of
Berzelius, 268 ; his discovery of
isomerism, 274 ; his important ser-
vices to physiology, 346, 347
Wolff, Kaspar Friedrich, founder of
the science of embryology, 36 ;
foreshadows the cell theory, 336.
Wollaston, William Hyde, discovers
the identity of galvanism and elec-
474
INDEX
tricky, 205 ; his observation of
chemical combinations confirms
Datum's atomic theory, 256, 259;
his improvement of lenses, 325,
326, 327. ,
Wortrnan, J. L., his fossil lineage of
the edentates, 121.
Wundt, Wilhelm Max, his psycholog-
ical discoveries, 414, 415.
" X RAY," its discovery, 1, 2, 228.
YOUNG, CHARLES AUGUSTUS, his spec-
troscopic researches, 70.
Young, Thomas, his establishment of
the undulatory theory of light, 27,
192-204, 225; confirms the identity
of galvanism and electricity, 205;
practising medicine and studying
Egyptian hieroglyphics, 206 ; the
real discoverer of the ether 231,
232.
Z6LLNER, JOHANN KARL FRIEDRICH,
his cometary theory, 54, 55; his in-
terpretation of the diversities in the
spectra of stars, 73.
'^
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