30 CHARLES DARWIN
have been led to adopt the views promulgated
in this remarkable paper. He had himself
witnessed a severe earthquake, and could
speak from personal knowledge of its effects
in a region which had often been convulsed
by similar events. He had found that one
of these effects was a marked uplift of some
parts of the coast-line. He had beheld with
his own eyes the simultaneous and violent
activity of two of the great volcanoes of
the Cordillera 33 . Pondering on these mighty
manifestations of terrestrial energy, and re-
membering what a long succession of volcanic
periods he had detected in the framework
of the continent, he conceived not only that
earthquakes and volcanoes are intimately
related to each other, as was then generally
believed, but that they both proceed from
movements in the internal molten material
of the globe. Although the origin of these
movements was shrouded from him, he be-
came convinced, to use his own impressive
words, that "the configuration of the fluid
surface of the earth's nucleus is subject to
AS GEOLOGIST 31
some change its cause completely unknown,
its action slow, intermittent, but irresistible 34 ."
These theoretical views seemed at the time
to be warranted by all the evidence which
had then been obtained on the subject, and
more especially by the large body of proof
which the author himself had gathered to-
gether. But the extended researches of later
years in seismology and mountain-building
have brought to light much information which
he did not possess. We now know that there
is no such general and intimate relation, as
was then assumed, between earthquakes and
volcanoes; for many gigantic earthquakes
have taken their origin at a distance from
active volcanoes, while vigorous volcanic
energy is not always accompanied with earth-
quakes or with permanent alterations in the
relative levels of sea and land. Since his
time, too, the complicated structure of
mountain-chains has been elucidated in much
detail. We have learnt how intensely, along
these tracts of elevated ground, the terrestrial
crust has been folded, crumpled, fractured
! BERK ELEVEN
LIBRARY
JNIVERSITY OF 1
CALIFORNIA I
I/BRA/?'-
THE LIBRARY
OF
THE UNIVERSITY
OF CALIFORNIA
PRESENTED BY
PROF. CHARLES A. KOFOID AND
MRS. PRUDENCE W. KOFOID
CHARLES DARWIN
AS GEOLOGIST
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All rights reserved
CHARLES DARWIN
AS GEOLOGIST
THE REDE LECTURE
GIVEN AT THE DARWIN CENTENNIAL COMMEMORATION
ON 24 JUNE 1909
BY
SIR ARCHIBALD GEIKIE, K.C.B.
D.Sc., D.C.L."(OxoN.)
PRESIDENT OF THE ROYAL SOCIETY
Cambridge :
at the University Press
1909
Cambridge i
PRINTED BY JOHN CLAY, M.A
AT THE UNIVERSITY PRESS
CHARLES DARWIN AS GEOLOGIST
When the Vice-Chancellor honoured me
with his invitation to give the Rede Lecture
this year, he informed me that it would be
included in the proceedings of the present
Celebration. Although he left me free in the
choice of a subject, it was obvious that the
lecturer could hardly hesitate to select a
theme which would have reference, more or
less direct, to the illustrious Naturalist whose
Centenary the University had resolved to
commemorate. The nature and extent of
Charles Darwin's contributions to biological
science have been so often and so fully
described, and his influence on almost all
departments of human thought has been so
amply recognised, that for the present, little
more may seem to remain to be said on the
subject until, in the course of time, a fresh
G. 1
CHARLES DARWIN
review of his relations to the history of
intellectual development may be called for.
Nevertheless, I venture to think that there is
one branch of his scientific labours, the value
and significance of which have scarcely
perhaps received the notice and appreciation
to which they are entitled. It is- apt to be
forgotten that Darwin began his active scien-
tific career as a geologist, that it was mainly
to geological problems that the earlier years
of his life were devoted, and that it was in no
small measure from the side of geology that
he was led into those evolutional studies
which have given him so just a title to our
admiration and gratitude, and have placed
him so high among the immortals. I have
therefore decided to ask your attention to-day
to an outline of what he accomplished in
geology, and of the relation of his studies iu
that science to the great problems of evolu-
tion with which his name is indissolubly
associated.
In Darwin's younger days geology had
hardly as yet completely vindicated for itself
AS GEOLOGIST
an acknowledged and assured place in the
circle of the natural sciences. Those who
then cultivated it could not agree among
themselves upon its fundamental principles.
They were divided into three distinct and
antagonistic schools, between whom a long
and sometimes acrimonious controversy was
waged. /On the one side, the Neptunists, or
Champions of Water, maintained, as the prime
article of their creed, that our planet was
once enveloped in an universal ocean, from
which the various rocks now to be seen in
its crust were deposited as chemical and
mechanical precipitates. They ridiculed the
notion that the globe had a heated interior,
and they regarded volcanoes as a late appear-
ance in the earth's history, due to the spon-
taneous combustion of subterraneous beds of
coal 1 *. On the other side the Vulcanists, or
Plutonists, with Fire as their watchword,
vehemently insisted on the important part
which they believed had been taken by the
globe's internal heat, whether in the form of
* The figures in the text refer to the Notes at the end.
12
CHARLES DARWIN
volcanoes or by the subterranean intrusion of
molten material into the solid crust 2 . But
this school was split into two parties who
opposed each other with hardly less vigour
than they both showed towards the Neptunists.
The one section proclaimed that the pheno-
mena revealed by geology bear witness to a
far greater intensity of action in former ages
than now, and especially to the occurrence
from time to time of gigantic cataclysms
whereby the face of the planet was changed,
whole tribes of plants and animals were
destroyed, and place was made for the crea-
tion of new faunas and floras. Those who
belonged to this division were known as the
Catastrophic or Convulsionist school 3 . The
other section received the name of Uniformi-
tarian, inasmuch as they held that Nature's
operations have always been carried on much
as they are now, that instead of being marked
by periodical frenzies of eftergy, her action
has been generally uniform, and that thus the
Present may be taken as the Key to the
Past 4 . / It is interesting to find that Darwin
AS GEOLOGIST
in his youth had personal relations with
some of the leaders in each of these three
camps.
When as a lad of sixteen he went to the
University of Edinburgh he found himself
at the headquarters of the Neptunists in this
country. The Professor of Natural History
there, Robert Jameson, had been trained at
Freiberg under Werner, the great law-giver
of the Neptunist cult, and for more than
twenty years had been carrying on an active
propagandism of Wernerian doctrines, which
have long since been abandoned as illogical
and absurd. Darwin has recorded that he
found the lectures " incredibly dull." He
particularly refers to an excursion to Salis-
bury Craigs, near Edinburgh, where, with
volcanic rocks all around, he heard the pro-
fessor actually declare that "a trap-dyke, with
amygdaloidal margins and the strata in-
durated on each side, was a fissure filled with
sediment from above, adding with a sneer
that there were men who maintained that it
had been injected from beneath in a molten
CHARLES DARWIN
condition." The young student had sharp
enough eyes to see the true state of the case
and sufficient independence to follow his own
judgment in the matter. Well might he long
afterwards remark, "When I think of this
lecture I do not wonder that I determined
never to attend to Geology 5 ."
But fortunately for the science this deter-
mination disappeared when a few years
afterwards he discovered that the Wernerism
which he had been taught at Edinburgh by
no means represented the real character and
aim of geological studies. He tells us that
during the last of the three years which he
spent at Cambridge he read Humboldt's
Personal Narrative and Herschel's Prelimi-
nary Discourse on the Study of Natural
Philosophy, and he adds that "no one or a
dozen other books influenced him nearly so
much as these two 6 ." Herschel's admirable
little volume with its logical presentation of
scientific method, and Humboldt's glowing
pictures of tropical scenery and wide outlook
into all domains of science might well kindle
AS GEOLOGIST
in him a keen desire to follow in the paths of
scientific travel.
It was in the spring of the year 1831, when
these influences were at work on Darwin's
mind, that he was persuaded by his sagacious
and accomplished tutor, John Stevens Hen-
slow, " to begin the study of geology." His
first essays in field-work appear to have been
made in the summer of that year when, to
use his own words, he " worked like a tiger "
among the geological sections around Shrews-
bury, trying to fill in geological details upon a
map of that district a task which proved less
easy than he expected?. Henslow introduced
him to Adam Sedgwick, the distinguished
Woodwardian Professor at Cambridge, with
whom he made a geological excursion that
autumn through a part of North Wales.
Doubtless practical lessons from so accom-
plished and inspiring a leader were of no
little service to Darwin in fostering his
growing geological enthusiasm and teaching
him the methods of observation in the field.
We may be sure, too, that he was privileged
CHARLES DARWIN
to listen to much instructive and vigorous
discourse, not only on the local geology, but
on many of the wider bearings of the science.
Sedgwick was a stout champion of the con-
vulsionist creed, which he no doubt inculcated
on his pupil as the true faith. That Darwin
at first had himself some predilections in
the same direction may perhaps be inferred
from one of his letters to Henslow, in which,
speaking of his geological doings in Shrop-
shire before the excursion into North Wales,
he said that he had " only indulged in hypo-
theses, but they are such powerful ones that,
I suppose, if they were put into action but
for one day, the world would come to an end 8 ."
The first volume of Lyell's immortal
Principles of Geology was published in the
month of January 1830 9 . Although this work
was eventually to have so profound an in-
fluence on the progress of geological science,
it was received at first with doubt and oppo-
sition. In spite of its singularly luminous
presentation of the whole connected system
of natural operations that modiiy the surface
AS GEOLOGIST
of the globe, alike in the organic and in-
organic kingdoms, notwithstanding its over-
whelming array of evidence drawn from all
quarters of the earth and the clear and
eloquent language in which the logical
deductions from this evidence were enforced,
the whole spirit and aim of the book ran so
directly counter to the tenets of the prevalent
convulsionist school that it seemed for a time
to reawaken the fires of controversy which
had for years been gradually waxing dim.
Its uniformitarianism, carried even to further
lengths than Hutton and Playfair had ven-
tured to go, was denounced with character-
istic vigour by Sedgwick from the chair of the
Geological Society 4 . Even so judicious and
impartial a counsellor as Henslow, when he
advised Darwin to procure and study Lyell's
treatise, w r arned him "on no account to accept
the views therein advocated 10 ." The young
geologist followed the advice of his tutor,
but not the proviso with which it was accom-
panied. He took the book with him on the
voyage of the Beagle and studied it with
10 CHARLES DARWIN
enthusiasm, and with a result the very reverse
of what Henslow desired. In recording,
among the Cape de Verde Islands, the first
observations made by him on foreign soil, he
affirms that "they convinced me of the infinite
superiority of Lyell's views over those advo-
cated in any other work known to me 11 ." In
this way began that life-long indebtedness to
Lyell which he sincerely felt, and never ceased
to express.
In reviewing the nature and value of
Darwin's geological work on the voyage of
the Beagle, we must bear in mind the con-
ditions under which it was undertaken. In
the first place, he had only begun, a few
months before, to turn his attention to the
study of geology, and although he had doubt-
less worked hard at the subject during that
brief interval, his knowledge and practical
experience in it could hardly be other than
limited. Further, it should be remembered
that as the vessel was continually cruising
from place to place, never remaining more
than a short time at anchor, he had scant
AS GEOLOGIST 11
opportunity of completing a detailed study
of any locality. His observations had often
to be made under the pressure of a limitation
in the number of days, or sometimes even
of hours, that were available. In the most
favourable circumstances, little more than a
first broad sketch of the geology of each
place could reasonably be expected. But
Charles Darwin was no ordinary observer.
From the very beginning of the voyage he
displayed a zeal and aptitude for geological
work which in a short time enabled him to
gather together an astonishing amount of
valuable detail, while at the same time he
rapidly gained experience in noting the wider
bearing of the facts that came under his eye,
and in drawing far-reaching and suggestive
conclusions from them.
The enthusiasm with which he pursued
his geological enquiries on the voyage is
charmingly revealed in his letters and his
Journal. The very first land at which the
Beagle touched on her outward voyage
gave him the opportunity of beginning his
12 CHARLES DARWIN
field-work on the old volcanic ground of
St Jago, one of the Cape de Verde Islands.
Wandering over its mouldering lava-streams
and fired with fresh zeal from his eager
perusal of the first volume of the Principles
of Geology he realised, as he wrote in later
years, "the wonderful superiority of Lyell's
manner of treating geology, compared with
that of any other author whose works I had
with me or ever afterwards read 12 ." It was
there under the spell of this great teacher
that, as he has recorded, " it first dawned on
me that I might perhaps write a book on the
geology of the various countries visited, and
this made me thrill with delight 13 ." This
geological ardour lasted undimmed through-
out the whole of the five years of the
Beagle's voyage. When after his first cross-
ing of the Atlantic he began his explora-
tions on South American soil, he wrote of
his voyage and its incidents : " Geology carries
the day; it is like the pleasure of gambling.
Speculating on arriving what the rocks may
be, I often mentally cry out ' 3 to 1 Tertiary
AS GEOLOGIST 13
against Primitive'; but the latter have
hitherto won all the bets 14 ." In sending home
his collections from Brazil he wrote to Hen-
slow that "the box contains a good many
geological specimens; I am well aware that
the greater number are too small. But I
maintain that no person has a right to accuse
me till he has tried carrying rocks under a
tropical sun. I have endeavoured to get
specimens of every rock, and have written
notes upon all 15 ." After two years of con-
tinuous work along the American shores he
could still tell the same sympathetic cor-
respondent: "I am quite charmed with
geology, but like the wise animal between
two bundles of hay, I do not know which to
like best the old crystalline group of rocks
or the softer and fossiliferous beds. When
puzzling about stratification etc. I feel in-
clined to cry, ' a fig for your big oysters and
your bigger megatheriums.' But when dig-
ging out some fine bones, I wonder how any
man can tire his arms with hammering
granite 16 ."
14 CHARLES DARWIN
How thoroughly he grew to be a field-
geologist, never to be caught without his
hammer, even when on botanical or zoological
quests, is amusingly illustrated by his account
of a visit to the island of San Pedro, north
of the Chonos Archipelago off the southern
part of the coast of Chile. Two of the
officers of the ship had landed to take some
bearings with the theodolite, while Darwin,
hammer in hand, was rambling by himself.
In the course of his perambulations, as he
has told, "a fox (Canis fulvipes) of a kind
said to be peculiar to the island and very
rare in it, and which is a new species, was
sitting on the rocks. He was so intently
absorbed in watching the work of the officers
that I was able by quietly walking up behind
to knock him on the head with my geological
hammer. This fox, more curious or more
scientific, but less wise, than the generality
of his brethren is now mounted in the Museum
of the Zoological Society 17 ."
While from time to time he was able to
send home the collections that were accumu-
AS GEOLOGIST 15
lating in the Beagle, his notes of specimens
and field-observations continued to grow in
bulk. By the middle of the voyage, as he
informed Henslow, they already filled some
600 quarto pages of manuscript, of which
about the half related to geology 18 . The
perusal of the second and third volumes of
the Principles of Geology, which had now
been published and were sent out to him,
increased his devotion to Lyellian views. He
even remarks that he was inclined to carry
some parts of the doctrine to a further length
than the master himself 19 .
It is not possible within the limits of a
lecture to offer more than a mere sketch of
the geological work which was accomplished
by Darwin during the voyage. In four
distinct departments he enriched the science
with new and valuable material. In the first
place he added to our knowledge of the
volcanic history of the globe by many
detailed observations extending over a vast
geographical region. In the second place,
he brought forward a body of striking evidence
16 CHARLES DARWIN
as to upward and downward movements
of the terrestrial crust, and drew from this
evidence some of the most impressive de-
ductions to be found in the whole range of
geological literature. In the third place, he
made important observations on the geology
of South America, from the crystalline cores
of Brazil and the Andes to the Tertiary
and Post-tertiary deposits of Patagonia. In
the fourth place, he furnished new and inter-
esting illustrations of the potent part taken
by the denuding agents of nature in effecting
the decay and degradation of the land.
I. As we follow Darwin in his rambles
over the volcanic tracts that were visited
during the voyage of the Beagle, we cannot
but be struck with the way in which he
always seeks to unravel the sequence of
events in the history of each centre of
eruption. While the details of rock-structure
and composition do not escape his notice,
their interest for him was obviously much
less than that of the chronicle of geological
changes which the rocks revealed. How
AS GEOLOGIST 17
delighted he seems always to have been to
trace in a volcanic island the successive
phases from the early submarine eruptions
to the completed subaerial volcano ! With
what zeal he observes and records the occur-
rence of layers of sea-shells and nests of salt
and gypsum, intercalated between the more
ancient lavas, as proofs of the uprise of the
sea-floor! The pursuance of the later history
of the volcano was a further source of keen
pleasure to him, as he noted the positions of the
earlier vents and the evidence of long intervals
of quiescence between the successive out-
bursts, when the mouldering lavas were
hollowed out by running water into valleys
and ravines, which eventually became the
channels wherein the youngest streams of
molten rock found their way to the sea. It
was always these broader questions of geo-
logical history that more especially appealed
to his imagination and awakened his active
interest.
Throughout those years of travel he was
ever on the outlook for fresh records of former
18 CHARLES DARWIN
igneous action. As the result of his continued
observations he was able at last to sketch an
impressive picture of the part which that
form of geological agency has played in the
construction of the framework of the South
American continent. In his traverses of the
Andes, under an atmosphere resplendently
clear, and among steep mountain-sides rising
up absolutely bare of vegetation, he could
detect and follow the several great rock-groups
out of which the giant chain of the Cordillera
has been built. At the base he found a vast
succession of andesitic lavas and conglome-
rates, estimated by him to be some 7000 or
8000 feet thick, which from the fossils he
found associated with them, he assigned to
the age of the early part of the Cretaceous
period. Later in date came another copious
volcanic series in which the lower lavas were
believed by him to have been poured out
under the sea, while the later eruptions were
certainly subaerial, for he found a group of
erect silicifled coniferous trees enclosed
among the hardened volcanic ashes and
AS GEOLOGIST 19
surmounted by a massive canopy of basalt,
1000 feet in thickness 20 . Younger still were
the huge basaltic sheets which he traced
among the Upper Tertiary formations of the
Santa Cruz river, and last of all came the
existing still active volcanoes of the Andes,
which brought the long record of eruptions
down to the present day.
We may well believe that this marvellous
chronicle of volcanic activity deeply impressed
itself on Darwin's mind. It could not but
give him a more vivid conviction of the
potency of this branch of geological dynamics
than most geologists have an opportunity of
acquiring. Nevertheless it did not turn him
into a convulsionist. Nor while his imagina-
tion dwelt upon the grand succession of
events which revealed itself to him step by
step as the years went on, did he neglect the
less exciting but not less necessary observa-
tions of the lithological and other details that
characterised the volcanic rocks. He was
a diligent and judicious collector of rock-
specimens, as his collections, still extant,
22
20 CHARLES DARWIN
abundantly testify, and he studied them with
such appliances as were then available for
petrographical research. Besides the elabo-
rate notes which he made of their characters
in the field, he examined them with the blow-
pipe, the goniometer, and the microscope,
besides taking their specific gravity and
applying to them the simpler chemical tests.
His account of the bombs and the banded
trachytes and obsidians of the island of
Ascension has long taken its place as one of
the classic descriptions of modern petro-
graphy 21 . Still more remarkable was his
prescient inference as to the separation of
the basic from the acid constituents in large
bosses of granite a suggestion which, after
having been for many years lost sight of,
has now been established as true 22 . His
sagacious reflections upon the relations be-
tween the cleavage and foliation of altered
rocks were likewise far in advance of his
time 23 .
II. The long series of observations and
deductions made by Darwin on the move-
AS GEOLOGIST 21
ments of the crust of the earth, both in an
upward and downward direction, have long
held an honoured place in the literature of
physical geology. He was the first observer
who could devote himself to this department
of investigation by personal research and
comparison over a vast area of the surface of
the globe, and could thus generalise in it upon
a basis of his own experience in the field.
During the very first halt of the Beagle at
the Cape de Verde Islands, his attention was
drawn to this subject of enquiry by the
evidence of upheaval which he met with at
St Jago. All through the successive years
of the voyage he continued to accumulate
facts, until they grew into such an array of
evidence as no previous geologist had ever
been able to amass. Especially important
were the proofs which he collected of the
rise of the southern part of South America.
From the shores of Brazil and Uruguay, where
the youngest marks of uplift are found only
a few feet above sea-level, he traced a mag-
nificent succession of terraces that spread
22 CHARLES DARWIN
over the broad tract of lowland between the
mountains and the Atlantic, and stretch
southwards for hundreds of miles to the
southern bounds of Patagonia. At least
eight of these terraces were noted by him,
each flanked with a bold line of winding
escarpment that fronted the coast-line and
slowly mounted as they were followed south-
wards, one above another, up to heights of
950 or even 1200 feet. The occurrence of
recent marine shells on at least the lower
platforms led him to the conclusion that the
uplift of this part of the continent must have
been a comparatively late geological event.
From the step-like series of terraces he in-
ferred that the elevation took place inter-
mittently, with long pauses of rest, during
which the sea cut back the successive fronts
of these ancient inland-cliffs, as it is doing
still along the present coast-line. From the
greater height of the terraces in southern
Patagonia, he drew the deduction that the
uprise of the continent has been greatest
towards the south, and has gradually and
AS GEOLOGIST 23
imperceptibly diminished in a northerly
direction 24 .
Similar evidence of the recent uprise of
the continent was obtained by Darwin on
the western coast at various places between
lat. 4635' and 12S. a distance of more than
2000 geographical miles. The nearness of
the mountain chain to the Pacific Ocean has
not allowed the formation of any such display
of broad platforms at successive levels, as in
Patagonia. But he gathered conclusive proofs
of uplift, not only in raised beaches with
recent marine shells, but in abundant marks
of old sea-margins at different levels, such
as sea-worn caves, barnacle-crusted rocks,
pholades still in their positions of growth,
and successive gravel-terraces. The greatest
height at which he was able to detect recent
species of marine organisms was 1300 feet
above the sea at Valparaiso 25 .
As his acquaintance grew with the records
of the geological history of South America,
Darwin became more and more impressed
by the proofs he obtained of the remarkable
24 CHARLES DARWIN
oscillations of level which the continent has
undergone from the earliest times down to
our own day. Reflecting on what he had
seen on his traverses of the Cordillera and in
Patagonia, he made this deliberate state-
ment : " Daily it is forced home on the mind
of the geologist that nothing, not even the
wind that blows, is so unstable as the crust of
the earth 26 ."
It so happened that Darwin was ashore at
Valdivia on the day of the great earthquake
in February 1835, and felt the shock. A few
days later the Beagle entered the harbour of
Concepcion where, amidst a city of ruins, he
came upon what he describes as "the most
awful yet interesting spectacle he had ever
beheld." He has recorded that from a
geological point of view, "the most remark-
able effect of this earthquake was the per-
manent elevation of the land," but he adds
that instead of saying the effect, "it would
probably be far more correct to speak of it
as the cause 27 ." He was satisfied that the
land around the bay had been upraised two
A8 GEOLOGIST 25
or three feet, while on an island about thirty
miles off, Captain Fitzroy had found putrid
mussel-shells still adhering to the rocks ten
feet above high-water mark, where the in-
habitants had previously dived at low-water
spring-tides for these shells. He connected
this result of the earthquake with the general
rise of the whole continent, regarding it as a
kind of sample of the process whereby the
uplift had been brought about. As he re-
marked in his Journal : " it is hardly possible
to doubt that this great elevation has been
effected by successive small upliftings, such
as that which accompanied or caused the
earthquake of this year, and likewise by an
insensibly slow rise, which is certainly in
progress on some parts of this coast 28 ." As
his generalisation on the whole subject, he
held that " thousands of miles of both coasts
of South America have been upraised within
the recent period by a slow, long-continued,
intermittent, movement 29 ."
This impressive conclusion, as the final
outcome of his long years of investigation,
26 CHARLES DARWIN
was accepted by geologists and was incor-
porated by them into their common stock of
ascertained knowledge. Some years ago,
however, its validity was called in question.
The illustrious president of the Vienna
Academy of Sciences, Professor Suess, in the
series of striking pictures which he has drawn
of the changes which the surface of the earth
has undergone, and of the causes to which
these revolutions are to be ascribed, has
referred to Darwin's observations, which he
has somewhat summarily rejected as inad-
missible. He has been led, I think, by his
strong theoretical prepossessions against any
kind of evidence for the secular elevation of
continental areas of land, to minimise and
explain away the proofs adduced by Darwin.
He has availed himself of any expression of
doubt or denial made by one or two later
writers, which he accepts as well-founded.
The testimony alleged to be borne by the
terraces to the uprise of the land he briefly
sets aside, with the suggestion that they may
often be relics of the action of rivers or
AS GEOLOGIST 27
lakes. The recent marine shells found inland
he looks upon as having been carried by
the inhabitants and to be counterparts of
the familiar kitchen-middens of European
coasts 30 .
Charles Darwin was not a careless or casual
observer, nor one who rapidly jumped to a
conclusion from a limited basis of proof. He
was in the constant habit of repeating his
observations and checking his deductions,
and he had ample opportunities of doing so
in the geological field during the years that
he spent in South America. He was surely
competent to discriminate between platforms
extending for hundreds of miles parallel to
the coast-line, and terraces limited to each
river-system or to lakes. He was perfectly
familiar with the custom of the natives to
transport edible shell-fish for long distances
into the interior, and actually alludes to this
habit when describing deposits which he
believed to be true raised beaches 31 . He
was consequently on his guard against being
deceived by artificial accumulations of shells,
28 CHARLES DARWIN
and he gives the criteria by which he dis-
criminated between them and natural deposits
criteria which any field-geologist would
accept as sufficient.
Until therefore the evidence has been
sifted on the ground by a witness as capable
and as unbiassed as Darwin himself, I shall
continue to retain my belief in the trustworthi-
ness and importance of the observations and
conclusions of the great naturalist as to the
upheaval of those parts of South America
which he had himself the opportunity of ex-
amining. His contributions to this subject
have long been prized by geologists for their
fullness and clearness, and for their interest
and value in relation to the great problem
of the secular elevation of land. He himself
had no doubt that they were solid additions
to geological science, and such, I venture to
anticipate, will be the judgment of posterity.
After the close of the voyage of the
Beagle, when Darwin had found time to
study his collections and to reflect upon his
varied experiences of geological phenomena
AS GEOLOGIST 29
during five busy years, he put in writing the
matured opinions which he had formed on
the forces concerned in continental elevation.
His ample discussion of this subject, com-
municated to the Geological Society on
March 7th, 1838, forms one of the most
brilliant and suggestive essays which that
Society ever published 32 . Although the pro-
gress of investigation has not sustained some
important parts of his theoretical opinions
on this subject, it is impossible to read his
memoir without a high admiration for the
genius of its author. Marshalling all the
evidence then available, he arranges it in
logical sequence and deduces from it con-
clusions of profound interest in regard to
some of the obscurest problems in the history
of our globe. It was the first attempt to
treat this subject not as a mere matter of
idle speculation, but on a basis of personal
observation in the field. And thus, as a
pioneering effort it is worthy of lasting re-
cognition.
We can readily understand how he should
30 CHARLES DARWIN
have been led to adopt the views promulgated
in this remarkable paper. He had himself
witnessed a severe earthquake, and could
speak from personal knowledge of its effects
in a region which had often been convulsed
by similar events. He had found that one
of these effects was a marked uplift of some
parts of the coast-line. He had beheld with
his own eyes the simultaneous and violent
activity of two of the great volcanoes of
the Cordillera 33 . Pondering on these mighty
manifestations of terrestrial energy, and re-
membering what a long succession of volcanic
periods he had detected in the framework
of the continent, he conceived not only that
earthquakes and volcanoes are intimately
related to each other, as was then generally
believed, but that they both proceed from
movements in the internal molten material
of the globe. Although the origin of these
movements was shrouded from him, he be-
came convinced, to use his own impressive
words, that "the configuration of the fluid
surface of the earth's nucleus is subject to
AS GEOLOGIST 31
some change its cause completely unknown,
its action slow, intermittent, but irresistible 34 ."
These theoretical views seemed at the time
to be warranted by all the evidence which
had then been obtained on the subject, and
more especially by the large body of proof
which the author himself had gathered to-
gether. But the extended researches of later
years in seismology and mountain-building
have brought to light much information which
he did not possess. We now know that there
is no such general and intimate relation, as
was then assumed, between earthquakes and
volcanoes; for many gigantic earthquakes
have taken their origin at a distance from
active volcanoes, while vigorous volcanic
energy is not always accompanied with earth-
quakes or with permanent alterations in the
relative levels of sea and land. Since his
time, too, the complicated structure of
mountain-chains has been elucidated in much
detail. We have learnt how intensely, along
these tracts of elevated ground, the terrestrial
crust has been folded, crumpled, fractured
32 CHARLES DARWIN
and piled upon itself, without any sign of con-
comitant and co-operating volcanic agency.
But in regard to the cause of the secular up-
lift of continental land, we are still as ignorant
as Darwin confessed himself to be. It is
quite conceivable that for this phenomenon
his suggestion respecting movements of the
molten nucleus of the planet may, in some
form, come to be eventually established.
Besides meditating on the evidence in
favour of the elevation of land, Darwin during
his life in the Beagle had occasion to
consider terrestrial movements of an opposite
kind. It was during those eventful years
that he thought out his famous theory of
coral-reefs which gave to the world the most
original and impressive picture ever drawn
of the slow disappearance of an ancient land-
surface beneath the sea. The origin of these
singular islands, rising out of the profound
depths of mid-ocean, had long been a subject
of discussion, and several explanations of
them had been proposed, more or less plausi-
ble, but not free from objections. Darwin
A8 GEOLOGIST 33
offered a new suggestion which appeared to re-
move all the difficulties that were then known.
He showed how on the simple hypothesis of
a slow subsidence of the bed of the ocean,
fringing-reefs of coral along a coast-line could
be converted into barrier-reefs with a lagoon-
channel between them and the shore, and
further, how, where the land was insular and
continued to sink along with the surrounding
sea-floor, while at the same time the polypifers,
in their accumulation of calcareous material,
kept pace with the downward movement, the
barrier-reef would become an atoll or ring
of coral-rock enclosing a lagoon beneath which
the last peak of land might in the end dis-
appear. With admirable clearness he worked
out the application of this theory to all the
facts that were then known about the struc-
ture and distribution of coral-reefs, and he
came to the conclusion that over vast spaces
of the Pacific and Indian Oceans former tracts
of land have slowly sunk beneath the water,
and that the sites of the submerged peaks
G. 3
34 CHARLES DARWIN
are to be recognised in the countless groups
and archipelagoes of coral-islands 35 .
The remarkable simplicity of this expla-
nation of phenomena that had so long been
matters of dispute, together with the grandeur
of the vista which the theory opened up of a
stupendous geographical revolution that had
been in progress since a remote antiquity,
assured Darwin's views of close attention
and led to their general acceptance. First
brought briefly before the Geological Society
in 1837, and expounded more fully five years
later in his well-known volume on coral-reefs,
the theory held its place unchallenged for
many years. Louis Agassiz had indeed in-
sisted that it could not be applied to the
coral-reefs of Florida, but not until 1863 were
serious doubts thrown on its general appli-
cability, when Professor Semper brought
forward evidence of elevation among the
Pelew Islands. In a second edition of his
book, which appeared in 1874, Darwin briefly
referred to this new evidence, but did not
regard it as incompatible with his views. In
AS GEOLOGIST 35
later years, however, the observations which
have multiplied over many widely distributed
parts of the Pacific and Indian Oceans, as
well as in the warmer waters of the Western
Atlantic, have supplied a large body of proof
that in many groups of coral-islands the
movement of the sea-bottom has been up-
ward, the amount of elevation amounting in
some cases to more than 1000 feet. The
conclusion reached by such observers as Sir
John Murray, Professor Alexander Agassiz,
Dr H. B. Guppy and others is that true
atolls may be formed without subsidence,
by the outward growth of the coral upon a
talus of debris torn from the face of the reefs
by the force of the breakers. These writers,
who have carefully studied the subject on
the ground, have come to the conclusion that
Darwin's explanation cannot be maintained
as of universal application. After the fullest
consideration I have been compelled to
admit that this conclusion is well founded.
There can, I think, be no doubt that Darwin's
simple and striking explanation would per-
32
36 CHARLES DARWIN
fectly account for the origin of a great many
atolls. It remains to be seen whether, and
how far, it may be possible eventually to dis-
criminate between those which are to be thus
understood from those where the coral-site
has remained stationary or has been upraised.
But the mere existence of an atoll can no
longer be regarded as in itself a proof of
subsidence. It has been to myself and to
many other geologists a matter of keen regret
that this brilliant generalisation of the great
naturalist has been deprived of the wide
application which for many years we attri-
buted to it. But while we bow to the results
of later investigation, we must still be allowed
to regard it as a monument of his genius,
which did good service by lifting geological
speculation to a higher plane, and filling our
minds with a more vivid conception of the
gigantic scale on which the movements of
the terrestrial crust may have been effected.
III. An important part of the solid
work accomplished by Darwin during his
life in the Beagle is to be found in his
A8 GEOLOGIST 37
numerous contributions to the elucidation
of South American geology. It would be
out of place to attempt to enumerate on
this occasion these various additions to our
knowledge of the subject. I have already
alluded to his studies of the older crystalline
rocks of that continent, to his sagacious con-
clusions regarding the connection between
cleavage and foliation which he drew from
these rocks, and to his far-sighted remarks
on the segregation of the more basic from
the acid constituents of eruptive bosses of
granite which he traced in Brazil. His tra-
verses of the chain of the Andes enabled him
to furnish an interesting sketch of the general
architecture of that great range of mountains.
He fixed, from the evidence of associated
fossils, the geological age of the vast igneous
protrusions which form the core of the Cor-
dillera. His researches in Patagonia led the
way in the investigation of the great Tertiary
series in that extensive territory. To his
enthusiastic labours we owe the important
palaeontological discoveries which for the first
38 CHARLES DARWIN
time revealed the extraordinary abundance
and variety of the extinct vertebrate remains
in the youngest deposits of that region. Owen
in the Preface to his Memoir descriptive of
the series of fossils exhumed by Darwin,
speaks of the collection having been made
by one individual from a comparatively small
part of South America, and remarks that
"the future traveller may fairly hope for
similar success, if he bring to the search
the same zeal and tact which distinguish the
gentleman to whom Oryctological Science is
indebted for such novel and valuable ac-
cessions 36 ."
IV. The voyage of the Beagle, with its
ample opportunities on land as well as on
sea, gave Darwin many occasions to study
the great system of agencies which are cease-
lessly at work in sculpturing the face of
the land. He probably gained such a vivid
personal acquaintance with this subject as
few, if any, of the geologists of his day had
an opportunity of acquiring. This first-hand
knowledge stood him in good stead when in
A8 GEOLOGIST 39
later years he had to deal with questions of
geological time. It enabled him also to lend
a powerful support to the views of Lyell and
the cause of uniformitarianism against cata-
strophism.
The deep impression made on his mind
by the examples of stupendous denudation
which came before him in South America,
finds frequent mention in his writings. In
this regard, the chain of the Cordillera more
particularly roused his enthusiastic appre-
ciation. "This grand range," he remarks,
"has suffered both the most violent disloca-
tions and slow, though grand, upward and
downward movements in mass. I know not
whether the spectacle of its immense valleys
with mountain masses of once-liquefied and
intrusive rocks, now bared and intersected,
or whether the view of those plains, composed
of shingle and sediment hence derived, which
stretch to the borders of the Atlantic Ocean,
is best adapted to excite our astonishment
at the amount of wear and tear which these
mountains have undergone 37 ."
40 CHARLES DARWIN
In the earlier part of his geological career,
like his great teacher Lyell, he was disposed
to credit the sea with a larger share than is
now generally believed to be its due in the
sculpture of the land. Nor need this be, in
his case, matter of surprise, for he had made
intimate personal acquaintance with the sea
alike in calm and in storm. He had seen
many striking instances of the efficacy of
breakers in the erosion of coast-clifls. When
he visited St Helena and gazed on its range
of precipices rising here and there 1000 or
even 2000 feet above the waves that burst
into foam at their base, he felt that "the
swell of the Atlantic Ocean has obviously
been the active power in forming these cliffs."
Again as he sailed along the coast of Pata-
gonia and traced its successive escarpments
that front the sea, one above another, for so
many hundreds of miles, he could not but be
impressed with the efficacy of marine action
in the denudation of that wide region. When
he found himself among the deep and wide
valleys of the Blue Mountains in New South
AS GEOLOGIST 41
Wales, with their surrounding escarpment-
cliffs, it was to the action of the sea that his
thoughts naturally adverted as the cause of
such a magnificent series of excavations.
Like most of the geologists of the day he was
convinced that " to attribute these hollows to
alluvial action would be preposterous 39 ."
Yet he was far from insensible to the
results of the long-continued operation of sub-
aerial agents in changing the face of the land.
In his Journal he has recorded in graphic
language the lesson on the erosive power
of rivers which was graven on his memory by
what he saw when he crossed the Andes by
the Portillo Pass. As he watched the
torrents, brown with mud, rushing headlong
down the valleys and sweeping onwards the
stones on their channels with a roar which
could be heard at a distance, like the tumult
of the sea in a storm, he realised how "the
sound spoke eloquently to the geologist ; the
thousands and thousands of stones which,
striking against each other, made the one
dull uniform sound, were all hurrying in one
42 CHARLES DARWIN
direction. It was like thinking on time, where
the minute that now glides past is irrecover-
able. So was it with these stones; the ocean
is their eternity, and each note of that wild
music told of one more step towards their
destiny. It is not possible," he continues,
"for the mind to comprehend except by a
slow process, any effect produced by a cause
repeated so often that the multiplier itself
conveys an idea not more definite than the
savage implies when he points to the hairs of
his head. As often as I have seen beds of
mud, sand and shingle, accumulated to the
thickness of many thousand feet, I have felt
inclined to exclaim that causes such as the
present rivers and the present beaches could
never have ground down and produced such
masses. But, on the other hand, when listen-
ing to the rattling noise of these torrents, and
calling to mind that whole races of animals
have passed away from the face of the earth,
and that during this whole period, night and
day, these stones have gone rattling onward
on their course, I have thought to myself can
A8 GEOLOGIST 43
any mountains, any continent withstand such
waste 40 ."
After an absence of almost five years the
Beagle came back to England in October,
1836. That in spite of all the biological
questions which during the voyage had
shaped themselves before him and had en-
gaged his keenest interest, Darwin still
retained his early enthusiasm for geology is
well shown in his records of the vessel's
homeward journey which filled the fifth year
of the expedition. It was during that year
that he saw Tahiti, and touched at New
Zealand, Sydney and Tasmania, everywhere
adding fresh geological material to his note-
books. It was then, too, that he crossed the
Indian Ocean and had an opportunity of
making his study of coral-reefs which led to
his generalisation about oceanic subsidence.
On the same section of the voyage he again
traversed the Atlantic twice, halting at St
Helena and Ascension on the way, and once
more landing at the Cape de Verde Islands as
44 CHARLES DARWIN
the vessel finally shaped her course towards
home. His letters show how eagerly, as each
chance presented itself, to use his own words,
he "set to work with a good will at my old
work of geology 41 ." From St Helena he
wrote to Henslow that he was " very anxious
to belong to the Geological Society 42 ." This
desire was speedily fulfilled. His work on
the Beagle had become widely known by the
publication of excerpts from his letters to
Henslow. His scientific reputation had con-
sequently been so well established that not
only was he elected into the Society at the
beginning of the session in November, a few
weeks after his return, but in the following
February he was chosen as one of the Council,
and a year later (1838) was persuaded to
accept one of the two secretaryships an
office which he held for three years.
He was now at the very centre of geo-
logical activity, surrounded with colleagues
whose names and work have given to that
heroic age of geology in this country an
imperishable lustre. To be associated with
AS GEOLOGIST 45
such leaders as Lyell, Sedgwick, Murchison,
Greenough, Buckland, Fitton, De la Beche,
Whewell and Owen could hardly fail to fan
the flame of Darwin's geological proclivities.
That he was appreciated and welcomed by
these magnates in the science is testified in
a hearty way by Lyell who wrote to Sedgwick
(21st April, 1837): "It is rare even in one's
own pursuits to meet with congenial souls;
and Darwin is a glorious addition to my
society of geologists, and is working hard
and making way both in his book and in our
discussions. I really never saw that bore -
so successfully silenced, or such a bucket of
cold water so dexterously poured down his
back as when Darwin answered some imper-
tinent and irrelevant questions about South
America 43 ."
For some years most of Darwin's time
was necessarily occupied in working up and
publishing the voluminous material accu-
mulated during his travels. Some of this
material he prepared in the form of papers
communicated to the Geological Society,
46 CHARLES DARWIN
notably the great memoir, already alluded to,
on the Connection of Volcanoes and Earth-
quakes. But he found time also for some
fresh geological work in this country, more
particularly in regard to certain later phases
in the evolution of the present features
of the surface of the land. Thus in one of
these enquiries he was led to visit the Parallel
Roads of Glen Roy and to write a memoir
upon them wherein he advocated their marine
origin 44 . Somewhat later he made an excur-
sion into the district of North Wales over
which Sedgwick had taken him eleven years
before. But in the interval the attention
of British geologists had been roused by
Agassiz to the proofs that their own country,
at a comparatively late geological period,
was buried under snow and ice. Darwin may
have been led to return to Caernarvonshire
by some vague recollection of topographical
features in that region which were not
specially noted by him at the time. He has
recorded that neither Sedgwick nor he " saw
a trace of the wonderful glacial phenomena
A8 GEOLOGIST 47
all around us. Yet these are so conspicuous
that a house burnt down by fire did not tell
its story more plainly than did this valley.
If it had been still filled by a glacier, the
phenomena would have been less distinct
than they now are 45 ." The paper in which
he described his observations in this Welsh
valley was one of the earliest in the volumi-
nous literature that has now gathered round
the subject of the glaciation of the British
Isles 46 .
For some twenty years after his return
from the voyage of the Beagle Darwin con-
tinued to write occasional geological papers,
especially in relation to glacial matters, the
last of them being published so late as 1855 47 .
Of all these contributions to geology the
most original and important was a brief
paper on the formation of vegetable soil,
which he communicated to the Geological
Society in the autumn of 183T 48 . The
youngest or surface layer of the earth's crust
had for many years been strangely neglected
by geologists. They had lost sight of the
48 CHARLES DARWIN
pregnant reference to it made at the begin-
ning of last century by Playfair. That
far-seeing writer, following up the earlier
ideas of Hutton, had pointed out how con-
tinually the surface soil is washed off the
land and how it is as constantly renewed by
the decay of organic and inorganic materials.
But though he clearly recognised the reality
and importance of this process of waste and
renewal, he did not perceive the operation of
perhaps the most important agency con-
cerned in its efficiency. This discovery was
first made known by Charles Darwin 49 .
In the course of one of his visits to Maer
Hall, his uncle, Josiah Wedgwood, called
Darwin's attention to the curious way in which
layers of cinders, burnt marl or lime, spread
on the surface of pasture lands, eventually dis-
appear under the grass, and at the same time
suggested that this disappearance appeared to
be due to the action of earth-worms in bring-
ing up the finer particles of earth from below
and leaving them on the surface. Darwin
was naturally much interested in a subject so
A8 GEOLOGIST 49
obviously both geological and biological.
With his characteristic patience and care he
made a series of diggings, and soon satisfied
himself as to the facts to be accounted for.
He found that in one case a layer of marl,
spread over a field of pasture, had in about
80 years sunk some twelve or fourteen inches
beneath the surface. He came to the con-
clusion that this apparent subsidence had
undoubtedly been due to the continued
action of the worms, which after swallowing
and digesting the finer portions of the soil,
carry it up to the surface and void it there in
their castings. He drew the striking deduc-
tion that "every particle of earth forming the
bed from which the turf in old pasture-lands
springs has passed through the intestines of
worms."
Trifling as the topic may seem, and brief
as was the announcement of it (for the paper
filled only some four pages), the observations
published by Darwin were eventually seen to
possess a high importance in reference to
the problems of land-sculpture. But these
o.
50 CHARLES DARWIN
problems did not at that time, nor for many
years afterwards, engage much attention. It
was only when they began to be seriously
discussed, and when the evidence was accumu-
lating that the carving out of the face of the
land had not been in great measure the work
of the sea, as was so long believed, but was
mainly due to subaerial agencies, as Hutton
and Playfair had maintained, that the wide
significance of Darwin's little paper was per-
ceived. It was then realised that even grass-
covered lands, screened as they seemed
effectually to be by their vegetable covering,
were nevertheless not exempt from the general
process of degradation, for it was manifest
that by the work of worms an appreciable
quantity of soil, brought up to the surface
every year, was there exposed to be washed
off by rain or to be dried and blown away by
wind. Thus level prairies and verdurous
slopes were seen to be no exception to the
operation of the universal ablation of the
land.
Although Darwin's original observations
AS GEOLOGIST 51
on this curious and important subject re-
mained, as it were, buried in the publications
of a scientific Society, he never lost his
interest in it. As he wrote to Professor
Carus, "it had been to him a hobby-horse."
He was accustomed to keep worms in pots,
for the purpose of studying their habits, and
eventually he was led to renew and extend
the observations contained in his early paper.
He attacked the problem in much greater
detail than before, including, as part of his
labour, minute investigations of the habits
and mode of action of the worms. He like-
wise obtained more precise data by carefully
measuring and weighing all the worm-castings
thrown up within a given time in a measured
space. The results of these patient enquiries
were comprised in his well-known volume on
Vegetable Mould 50 .
It is interesting to remember that in this,
his last published work, he returned once
more to geological studies. But he now
brought to their prosecution a wealth of
biological experience and an ingeniously
42
52 CHARLES DARWIN
devised system of measurement which gave
to his results a precision not always attain-
able in experimental geology. His volume
thus holds an altogether unique place among
modern contributions to the problems of
denudation. It shows no lessening in his
marvellous patience, his scrupulous aim at
accuracy and his masterly power of rising
from the minutest details into the broadest
generalisations. Geologists may well regard
this final volume as a legacy and example
to them.
I now come to consider in the last place
the geological side of Darwin's masterpiece
The Origin of Species. This great work, the
outcome of his life-long researches and re-
flections, could not but contain frequent
reference to geological evidence which he
had himself gathered from so wide a field,
which he had pondered over so deeply, and
which was so intertwined with all his other
scientific work. We may compare his volume
to a great symphony in which the chords
AS GEOLOGIST 53
from the various departments of biology are
blended into one vast harmony, but where
the deep under-tones of geology seldom fail
to be audible.
From the days of Buffon the problems
presented by the question of the geographical
distribution of plants and animals have
engaged the thoughts of many naturalists and
travellers. But not until the appearance of
Lyell's Principles were the geological aspects
of the subject systematically discussed. The
chapters in the second volume of that work,
wherein the phenomena of geographical dis-
tribution were shown to have so close a
connection with geological changes, must have
been diligently perused by Darwin on the
voyage of the Beagle. We may believe, in-
deed, that it was in no small measure from
their broad philosophical treatment and their
suggestiveness to him in his own researches,
that he conceived that deep respect and admi-
ration for Lyell, to whom he was always proud
to acknowledge his indebtedness. Darwin's
two chapters on Geographical Distribution
54 CHARLES DARWIN
bear the characteristic impress of that wide
biological and geological experience which
gave him so firm a mastery of the points to
be discussed. They display his candid fair-
ness in stating difficulties, together with his
earnest desire not to minimise or ignore them,
his caution and even diffidence in offering his
own suggestions for their solution, and his
power of luminous presentation wherewith he
could place the whole complicated subject in
coherent, intelligible arid interesting form.
The progress of geology since Lyell's early
days enabled him to trace more definitely the
effects of geographical changes for which there
is reasonable evidence. Thus he attached
much importance to the direct and indirect
influence of the Glacial Period in reference
to the dispersal of plants and animals. His
treatment of this subject fills some of the
most striking pages of his volume. The reader
is made to realise, as he may never have done
before, that each species has had a long
geological history, which in many cases throws
light on the geographical revolutions that
AS GEOLOGIST 55
preceded or accompanied the advent of
man.
But with his cautious temperament he
could find no favour for the bold hypotheses
of some naturalists who, in default of other
means of accounting for the present distribu-
tion of living organisms, have not scrupled to
invoke the most gigantic changes in the
disposition of sea and land, for which, how-
ever, no geological evidence can be adduced.
" I do not believe," he affirmed, " that it will
ever be proved that within the recent period
most of our continents, which now stand quite
separate, have been continuously, or almost
continuously, united with each other and
with the many existing oceanic islands 51 ."
He was content with less heroic methods of
interpretation, and relied on such means of
dispersal as can be seen to be effective in the
present geographical condition of our globe.
The two specially geological chapters in
the Origin of Species have always seemed to
me to form Darwin's most momentous con-
tribution to the philosophy of geology. I
56 CHARLES DARWIN
well remember the effect which, when they
first appeared, they produced on at least the
younger geologists of the day. The fact that
the Geological Record is far from complete
was, of course, familiar knowledge. But until
these two chapters revealed it with such full-
ness of detail and such force of argument,
I do not believe that any one of us had the
remotest conception that the extent of its
imperfection was so infinitely greater than
we had ever imagined. The idea of pro-
gressive organic development was then in
general disfavour, and so long as that was
the case, the blanks in the Geological Record
lost much of their interest and importance
as indications of chronometric intervals.
Lyell, from the appearance of the first edition
of his Principles of Geology had consistently
maintained his determined opposition to all
doctrines involving the mutability of species.
In his ninth edition which, in an "entirely
revised" form, appeared in 1853, he could
still write: "the views which I proposed in
the first edition of this work, January 1830,
AS GEOLOGIST 57
in opposition to the theory of progressive
development do not seem to me to require
material modification, notwithstanding the
large additions since made to our know-
ledge of fossil remains 52 ." What he had been
inculcating for nearly a quarter of a century
had become the accepted belief of the great
body of geologists in this country, even of
those who dissented most strongly from his
uniformitarianism.
Yet there were some among them who
found it hard to follow their great leader in
this part of his teaching. He seemed to
them to undervalue the evidence that ap-
peared so plainly to indicate that there has
been an ordered upward succession in the
appearance of the several divisions of the
animal and vegetable worlds. When he
declared that the occurrence of the remains
of fishes in the groups of strata below the
Coal formation " entirely destroys the theory
of the precedence of the simplest forms of
animals 53 ;" when he suggested that the non-
occurrence of mammalian remains among the
58 CHARLES DARWIN
older rocks might be merely due to the
imperfect state of our information 54 , and when,
in explanation of the poverty of the records
of the floras and faunas of the past, he offered
the consolation "that it has evidently been
no part of the plan of Nature to hand down
to us a complete or systematic record of the
former history of the animate world," an un-
easy conviction grew up that the testimony
of the rocks could not thus be set aside.
Vehemently insisting on "the doctrine of
absolute uniformity" in geological causation 55 ,
Lyell could account for the extinction of the
thousands of species of organisms that once
lived on the earth by reference to the normal
laws of nature, as seen in the operation of
the various causes that are still at work.
But when he contemplated the thousands of
new species which have successively replaced
those that died out or were destroyed, he
had recourse to a special act of creation for
each of them, thus appealing to an agency
whose working, while it might be in conson-
ance with natural law, lies outside of human
AS GEOLOGIST 59
experience. His deliberate judgment was
formulated in the following words: "Each
species may have had its origin in a single
pair, or individual where an individual was
sufficient, and species may have been created
in succession at such times and in such
places as to enable them to multiply and
endure for an appointed period, and occupy
an appointed space on the globe 56 ."
It is well to recall these aspects of geo-
logical thought in the middle of last century,
and to remember what a dead weight of
opinion, or, if we choose to call it prejudice,
was opposed to the reception of Darwin's
views. We must bear in mind also that the
leader of this school of thought was none
other than his own revered master Lyell, at
whose feet he had sat for so many years and
to whom he felt that he owed more inspira-
tion than to any other man. Lyell, who had
all his life opposed the idea of the mutation
of species, was slow to be completely con-
vinced of the truth of the conclusions at
which his friend and follower had arrived.
60 CHARLES DARWIN
In the volume on the Antiquity of Man which
he published four years after the appearance
of the Origin of Species he hesitatingly and
v only partially accepted them 57 . In the course
of a few years more his conversion was com-
plete, as he announced in the tenth and last
edition of his Principles of Geology.
Lyell's courageous abandonment of opin-
ions which he had stoutly proclaimed through
a long life was a noble example of self-
abnegation in the cause of truth. It did
good service in helping forward the general
acceptance of the newer creed, and it was
especially appreciated by the younger geolo-
gists. Among their number were not a few
who felt when they read the Origin of Species,
that truly the scales had now fallen from
their eyes. There had been with them a
conviction that the grand progression of
organic life, from the earliest time until now,
must somehow have been governed by normal
biological law, though no satisfactory ex-
planation had been offered of the manner
in which this continuous upward progress
AS GEOLOGIST 61
had been achieved. Darwin's treatment of
the subject fascinated them by the genius
with which his long and varied experience
abroad and at home, alike in the geological
and biological domains, was brought to bear
on the elucidation of the great problem of
evolution for which he had so amply prepared
himself. Especially were they struck with his
mastery of the whole range of stratigraphy.
Into that department of geology he threw
a flood of new light, as for example when he
so cogently urged that complete conforma-
bility, or absence of visible break, may be no
proof of continuous deposition, but may con-
ceal protracted periods of time unrepresented
by strata. Yet even where his arguments
were most forcible and convincing, they were
stated without the least show of dogmatism,
but with a quiet restraint that was apt to
conceal their strength. As we read them
now, they seem to be so obvious that it may
be wondered why they were not pressed long
before. Not only did he convince us of the
unsuspected degree of imperfection in the
.
62 CHARLES DARWIN
Geological Record, but he revealed a new
method of interpreting it by showing that, on
the theory of descent with modification, fossils
possess a high chronometric value as in-
dicative of the relative importance of strati-
graphical horizons and likewise a new sugges-
tiveness in regard to geographical changes of
which no other memorial may have survived.
The light thrown by Darwin upon the
fossiliferous formations of the earth's crust
led to clearer conceptions of the principles
that must be applied to the interpretation
of the facts of stratigraphy. The sudden
appearance of whole groups of new species
upon a special stratigraphical platform, had
once been confidently appealed to as evidence
of a fresh creation of plants and animals to
replace those which were destroyed by a catas-
trophe that convulsed the world. This opinion,
though no longer expressed in the crude
shape in which such writers as Cuvier had
announced it 58 , still in a modified form in-
fluenced many naturalists and geologists who,
though not convulsionists, were opposed to
AS GEOLOGIST 63
the idea of the transmutation of species.
Darwin's cogent reasoning may be said to
have finally set it aside, by showing how such
breaks in the succession of organic remains
may be completely explained by regarding
them as marking enormous chronological
gaps in the records of what was neverthe-
less a continuous organic evolution. How
soon these fertile ideas in the Origin of
Species bore fruit was shown a few years
after the publication of that work, when
Kamsay gave his two brilliant addresses to
the Geological Society on breaks in the
succession of strata in Britain 59 .
When the history of the progress of
science in the nineteenth century comes to be
written the views expressed in the geological
chapters of Darwin's great work, whether novel
or enforcing with new emphasis what had been
more or less clearly perceived before, will
be seen to mark a notable epoch in modern
geology. They have thoroughly permeated
the recent literature of the science, insomuch
that there is sometimes a risk that the student
64 CHARLES DARWIN AS GEOLOGIST
who finds them so intimately incorporated
may lose sight of the source to which he
owes them. As one of the survivors of the
time when the Origin of Species appeared I
am glad to be privileged with this public
opportunity of acknowledging the deep debt
which the science of geology, in many of its
departments and in the whole spirit by which
it is now informed, owes to the life-long
labour of the author of that work. Geologists
are proud to claim him as one of themselves
and as one of the great masters by whom
their favourite science has been advanced.
In their name, therefore, I beg to offer at
this centennial celebration our tribute of
gratitude and admiration to the memory
of Charles Darwin.
NOTES
1 The best account of the Neptunist doctrines is to be
found in Robert Jameson's Treatise on Geognosy (1808),
which forms the third volume of his System of Mineralogy.
Owing in large measure to the eloquence and personal
influence of Abraham Gottlob Werner, the great apostle of
this creed at the mining school of Freiberg in Saxony, these
doctrines (often known as Wernerian or Wernerism) enjoyed
a great vogue all over Europe in the later decades of the
eighteenth and the earlier of the nineteenth century. But
their prevalence rapidly diminished after his death in 1817,
especially when some of his more distinguished pupils, such
as L. von Buch and A. von Humboldt, abandoned them.
Jameson, however, who had studied under Werner,
remained longer unconvinced of the untenability of his
master's opinions. In 1804 he had become Professor of
Natural History at the University of Edinburgh. Four
years later (as if in rivalry to the Geological Society of
London, which was started in the previous year) he founded
the Wernerian Society, one main object of which was to
support and propagate the teaching of Freiberg. Even so
late as 1826, when Darwin attended his lectures, he was
still inculcating to his students the then discredited notions
of Werner as to the aqueous origin of igneous rocks. He
66 CHARLES DARWIN
afterwards at a meeting of the Royal Society of Edinburgh
frankly acknowledged that he had been compelled to abandon
the distinctive tenets of Wernerism. It has not been
possible to recover the precise date of this recantation,
though both the late Sir Robert Christison and Professor
J. H. Balfour assured me that they had been present when
it was made. It must have taken place between the years
1826 and 1838, for in the latter year Hay Cunningham
published his Plutonist description of Salisbury Craigs,
which he said was " nearly that which the Professor now
delivers to his pupils" (Essay on the Geology of the
Lothians, 1838, p. 56, footnote).
2 It was in this country that the Vulcanist or Plutonist
creed was first clearly proclaimed by Button in his Theory of
the Earth, of which the first sketch was laid before the Royal
Society of Edinburgh in 1785, and the enlarged form in
two octavo volumes ten years later. The general principles
expressed in this work were after Button's death expounded
and enforced with admirable force and elegance by John
Playfair in his flliistrations of the Huttonian Theory (1802).
These two authors may be said to have laid the foundations
of the physical side of modern geology. While fully
Plutonist in their teaching they yet recognised, more vividly
than had ever been done before, the potent influence of the
aqueous and atmospheric influences which have ceaselessly
modified the surface of the globe.
In this country the controversy between the two schools
of the Neptunists or "Wernerians and the Plutonists
(Vulcanists) or Huttonians was prosecuted with much
vigour, while it lasted, but it had practically died out some
time before the middle of last century. One of the most
curious signs of its decay is to be found in the last volumes
AS GEOLOGIST 67
of the Memoirs of the Wernerian Society, which are as frankly
Plutonist as the previous volumes had been exclusively
Neptunist. One cause of the cessation of the warfare is
undoubtedly to be recognised in the ultimate influence of
the Geological Society, which was founded in 1807 for the
purpose of investigating the facts of geology rather than the
advocacy of any theory regarding them. The continual
advance of the doctrines taught by Hutton and Playfair is
well indicated by the successive appearance of memoirs in
scientific journals and also independent treatises which
stand out as landmarks in the progress of geology, culmi-
nating in 1830 when the first volume of Lyell's Principles
of Geology made its appearance. It is interesting to
remember that in his relations to geological science Charles
Darwin lived through this transition period. He had
actually been a pupil of Jameson, the high priest of
Wernerism in Britain, and he became one of the earliest
and most effective followers of Lyell, the great prophet of
Uniformitarianism.
3 It was natural that the phenomena of geology, appeal-
ing powerfully to the imagination in their striking memorials
of terrestrial revolutions, should favour the rise of the
Catastrophist school. They seemed to require the operation
of stupendous convulsions, and to be wholly inexplicable by
the action of any forces now visible to human observation.
It was only by degrees, and after Lyell's able advocacy, that
the efficacy of apparently feeble causes, acting through long
periods of time, came to be recognised. Among the
champions of this school none was more eloquent and out-
spoken than Adam Sedgwick, the illustrious Woodwardian
Professor at Cambridge. In the address which he gave to
the Geological Society on quitting the presidential chair on
52
68 CHARLES DARWIN
February 18, 1831, he vigorously criticised the uniformi-
tarian doctrines which had been in the previous year
advocated with so much persuasive power by Lyell in the
first volume of his Principles. The following passages
may be quoted from this address.
" Though we have not found the certain traces of any
great diluvian catastrophe which we can affirm to be within
the human period ; we have, at least, shown that paroxysms
of internal energy, accompanied by the elevation of moun-
tain-chains, and followed by mighty waves desolating whole
regions of the earth, were a part of the mechanism of nature."
11 Volcanic action is necessarily paroxysmal ; yet Mr Lyell
will admit no greater paroxysms than we ourselves have
witnessed no periods of feverish spasmodic energy, during
which the very framework of nature has been convulsed and
torn asunder. The utmost movements that he allows are a
slight quivering of her muscular integuments." Proc. Geol.
Soc., Vol. I, pp. 307, 314.
4 The uniformitarian doctrines in geology were clearly
enunciated in Button's Theory of the Earth (see especially
Vol. II, pp. 205, 328, 467, 510, 547), and were admirably
expounded in Playfair's Hlmtrations of the Huttonian
Theory, wherein a large body of evidence was brought
forward in support of them. Twenty years later Karl E. A.
von Hoff began to publish his laborious chronicle of all the
geological changes recorded by man within the times of
human history (Geschichte der durch tlberlieferung nachge-
wiesenen naturlichen Verdnderungen der Erdoberflache,
Vol. I, 1822 ; n, 1824 ; in, 1834 ; iv, 1840 ; v, 1841).
There could not have been gathered together a more impos-
ing array of proof of the nature and importance of the
vicissitudes of the earth's surface now in progress than is
A8 GEOLOGIST 69
contained within these meritorious volumes. But the
cumulative effect of such changes, prolonged through vast
periods of time, was not for some time realised by the general
body of geologists. It was reserved for Lyell to point out
the deductions that might logically be drawn from the large
accumulation of evidence by his time available, and thus
to place geology on a more solid foundation with a rightful
claim to a higher rank than it had hitherto held among the
observational sciences. Darwin, who had known something
of its state in earlier days, never wavered in his conviction
that Lyell had revolutionised the science of geology.
5 The Life and Letters of Charles Darwin, including an
Autobiographical Chapter, edited by his son, Francis
Darwin. Three vols. London, 1887. Vol. i, pp. 41, 42.
See also my Founders of Geology, 2nd edn., p. 329, for an
account of another excursion to Salisbury Craigs, where the
Plutonist notions were contemptuously rejected by one of
the Wernerian faith.
6 Life and Letters, Vol. I, p. 55.
7 Ibid., pp. 56, 189.
8 Ibid., p. 189.
9 The title of this work is Principles of Geology, being
an Attempt to explain the Former Changes of the Earth's
Surface, by reference to Causes now in Operation. The first
volume which, as stated in the text, appeared in January,
1830, was followed by the second in January, 1832, while
the third and concluding volume was issued in May, 1833.
10 Life and Letters, I, p. 72.
11 Ibid., I, p. 73.
12 Ibid., I, p. 62.
13 Ibid., I, p. 66.
14 Ibid., I, p. 233.
70 CHARLES DARWIN
15 More Letters of Charles Darwin, a Record of his
Work in a series of hitherto unpublished Letters, edited by
Francis Darwin (1903), Vol. I, p. 9.
16 Life and Letters, I, p. 249.
17 Journal of Researches into the Natural History and
Geology of the Countries visited during the wyage of
H.M.S. "Beagle" round the World, Chap, xiii., p. 280. The
first edition of this work was published in 1839 as Vol. m
of The Narrative of the Surveying Voyages of Her Majesty's
Ships "Adventure" and "Beagle" between the years 1826 and
1836. The citations in these Notes are made from the
second edition, published 1845 in Murray's Colonial and
Home Library.
The Museum of the Zoological Society was dispersed
many years ago, but the important parts of its contents
were placed in the Natural History galleries of the British
Museum. In answer to an application which I made to
Mr S. F. Harmer, F.R.S., Keeper of Zoology in the Natural
History Museum, Cromwell Road, for information as to
Darwin's specimen, he has been so good as to send me the
following particulars : " The fox to which you refer as
having been killed by Charles Darwin with a geological
hammer is in our collection. It is represented by a skin
and a skull, and it is the type of Canis fulvipes, "Water-
house."
18 More Letters, Vol. I, p. 14.
19 Life and Letters, Vol. I, p. 263.
20 Geological Observations on South America, being the
Third Part of the Geology of the Voyage of the "Beagle"
during the years 1832 to 1836. 1846. Pp. 175, 202, 232,
241, 247.
21 Geological Observations on the Volcanic Islands,
AS GEOLOGIST 71
visited during the Voyage of H.M.S. " Beagle? together
with some brief notes on the Geology of Australia and the
Cape of Good Hope, being the Second Part of the Geology of
the Voyage of the "Beagle" 1844. Chap. iii.
22 One of the most striking conclusions contained in
Darwin's volume on " Volcanic Islands " is to be found in
his account of the great granitic masses of South America.
He not only perceived that there might be a " sinking of
crystals through a viscid substance like molten rock "
(p. 118) by virtue of their specific gravity being greater
than that of the base, but he inferred that in large plutonic
masses " a certain amount of separation of their constituent
parts has often taken place." He goes on to remark, "I
suspect this from having observed how frequently dykes of
greenstone and basalt intersect widely extended formations
of granite and the allied metamorphic rocks " (p. 123). He
had never examined a district in an extensive granitic region
without discovering such dykes. He thinks it probable
" that these dykes have been formed by fissures penetrating
into partially-cooled rocks of the granitic and metamorphic
series, and by their more fluid parts, consisting chiefly of
hornblende [or augite] oozing out, and being sucked into
such fissures/' "We may admit, in the case of a great
body of plutonic rock being impelled by repeated movements
into the axis of a mountain-chain, that its more liquid
constituent parts might drain into deep and unseen abysses ;
afterwards, perhaps, to be brought to the surface under the
form, either of injected masses of greenstone and augitic
porphyry, or of basaltic eruptions. Much of the difficulty
which geologists have experienced when they have compared
the composition of volcanic with plutonic formations, will,
I think, be removed, if we may believe that most plutonic
72 CHARLES DARWIN
masses have been, to a certain extent, drained of those
comparatively weighty and easily liquefied elements, which
compose the trappean and basaltic series of rocks " (p. 124).
For two examples of the segregation of a basic periphery in
granitic bosses see Messrs Dakyns and Teall, Quart. Journ.
Geol Soc., XLVIH (1892), p. 104 ; and Mr A. Harker, op.
cit., L (1894), p. 311 ; LI (1895), p. 125.
23 Darwin made a special study of this subject wherever
he had an opportunity of examining slates and schists in
South America, and his observations and conclusions have
been confirmed by later observers. " I cannot doubt," he
says, " that in most cases foliation and cleavage are parts
of the same process : in cleavage there being only an in-
cipient separation of the constituent minerals : in foliation,
a much more complete separation and crystallisation"
(Geol. Obs. on South America, p. 166). This is doubtless
true in regard to such rocks as clay-slate, phyllite, &c.,
where the successive stages from uncleaved, through
cleaved into foliated rocks and perfect schists can be
traced. Darwin also conceived that "the planes of
cleavage and foliation are intimately connected with the
planes of different tension to which the area was long
subjected before the cessation of the molecular movement "
(p. 168). He saw that the direction of these planes was
always parallel to the principal axes of elevation (p. 169).
24 Geological Observations on South America, Chap. i.
25 Op. cit., p. 32.
26 Journal of Researches, Chap. xv. p. 321.
27 Op. cit., Chap. xiv. p. 310.
28 Ibid.
29 Geological Observations on South America, p. 135.
He believed that "the excessively disturbed condition of
AS GEOLOGIST 73
the strata in the Cordillera, so far from indicating single
periods of extreme violence, presents insuperable difficulties,
except on the admission that the masses of once liquefied
rocks of the axes were repeatedly injected, with intervals
sufficiently long for their successive cooling and consolida-
tion " (p. 248).
30 The passages in which Professor Suess controverts
Darwin's views will be found in the first and second
volumes of his Antlitz der Erde (Vol. I, pp. 95 105 and
Vol. n, pp. 522 534 of the English translation of his
work which has recently appeared under the title of The
Face of the Earth, edited by Prof. Sollas). One particular
observation has been especially singled out for criticism.
Darwin has recorded that on the island of San Lorenzo,
at a height of 85 feet above the sea, he found a bed
two feet thick of recent marine shells, some of them with
their insides incrusted with barnacles and serpulae. From
this bed, amongst light corallines, horny ovule-cases of
mollusca and roots of sea-weeds, he extracted some bones
of birds, heads of Indian corn, a piece of woven rushes,
and another piece of nearly decayed cotton string. He
regarded these relics of human workmanship to have been
contemporaneously embedded with the shells, and inferred
that the land had here been upraised 85 feet since Indian
man inhabited Peru (Geol. Obs. on South America, p. 49,
and Journal of Researches, Chap. xvi. p. 370).
The same locality was visited a few years later by
Prof. J. D. Dana, who published the following comment upon
Darwin's deductions. "The argument [for an elevation
of this coast] is urged with force and discrimination by
Mr Darwin. My own observations have been confined
to so small a part of the coast, that any opinion here
74 CHARLES DARWIN
expressed is entitled to but little weight, especially as I
am unable to draw comparisons with the beds in other
portions of the western coast alleged as similar in character.
I may, however, frankly confess that the evidence does not
seem to me to place the question beyond doubt." He then
proceeds to state his "sources of doubt." These are (1)
the occurrence of the shells in an irregular unstratified
bed, just beneath or in the soil ; (2) the absence of an
inner cliff at the place. He thinks it more likely that the
shells together with the relics of human occupation were
accumulated by the Peruvians themselves, and he goes
on to refer to the habits of the Patagonians and New
Zealanders in transporting shell-fish from the sea-coast
inland. He suggests that possibly a rush of waters over
the land, such as is occasionally produced by an earth-
quake, might have been concerned in the spreading out
of these remains, though without further examination, he
does not feel ready to attribute the effects to this cause
(Report of United States Exploring Expedition (1838
1842) under C. Wilkes, Vol. X. Geology (1849), p. 591).
Professor Suess assumes that what Darwin observed
was merely one of the "kitchen middens" which occur
at many localities along the margin of the coast. He
remarks: "When Darwin visited these coasts in 1835
little was known as to the wide distribution of such
remains. It must therefore have filled him with the
greatest astonishment to meet with a thread, pieces of
wicker-work and other traces of human activity in a
deposit of sea-shells on the island of San Lorenzo, near
Callao, at a height of 85 feet above the sea, and he may
well, according to the state of knowledge at that time,
have regarded it as a proof of recent elevation. Dana,
AS GEOLOGIST 75
who visited the place some years later, has already ex-
plained the circumstance." He cites in a footnote the
passage from Dana's work above quoted. I leave any
impartial reader to judge whether the extremely guarded
statement of the American geologist " explains the circum-
stance" or justifies the summary rejection of Darwin's
observation.
When Darwin read the passages in Dana's volume,
which was published in 1849, he was naturally somewhat
indignant. Thus in writing to Lyell in December of that
year about the volume, he referred to Dana as " disputing
my conclusions without condescending to allude to my
reasons. Thus, regarding S. Lorenzo elevation, he is
pleased to speak of my ' characteristic accuracy,' and then
gives difficulties (as if his own) when they are stated by
me, and I believe explained by me" (More Letters of
Charles Darwin, Vol. n, p. 226).
In the passage above quoted Prof. Suess expresses
his opinion that at the time of Darwin's exploration in
South America little was known of the wide distribution
of sea-shells in the interior of the country by the in-
habitants. But he has omitted to notice the references
to this mode of transport which are made by Darwin
himself, who positively says that he was " well aware from
what he had seen at Chiloe and in Tierra del Fuego, that
vast quantities of shells are carried during successive ages,
far inland, where the inhabitants chiefly subsist on these
productions" (Geol. Obs. on South America, p. 33).
One of the grounds on which Darwin convinced himself
that he was dealing not with kitchen-middens but with
natural deposits of marine origin, was derived from an
examination of the comminuted organic debris found filling
76 CHARLES DARWIN
the shells and diffused through the enclosing earth. This
material " was in considerable part composed of minute
fragments of the spines, mouth-bones and shells of echini,
and of minute fragments of chiefly very young Patellae,
Mytili and other species " (Ibid}. Not until he returned
home and had an opportunity of unpacking and studying
his collections, did he realise how fully this accumulation
of comminuted organisms confirmed his conclusion as to
"the marine origin of the earth in which many of the
shells are packed. Considering these facts," he adds, "I
do not feel a shadow of doubt that the shells, at the height
of 1300 feet, have been upraised by natural causes into
their present position " (Ibid, footnote).
The endeavour to account for all the shelly deposits of
the coast of Chili as mere human refuse has been extended
to the eastern side of the continent by various writers.
The most recent author who has treated of this subject,
Dr H. von Ihering, Director of the Museum of Sao
Paulo, Brazil, in a detailed memoir entitled Les Mollusques
Fossiles du Tertiaire et du Cretace Sup&rieur de I Argen-
tine^ which forms the whole of Vol. vn of the third series
of the Anales del Museo National, Buenos Aires (1907),
refers to the abundant evidence of a former sea-margin,
30 to 40 metres above the present level of the sea, along
the coast of Brazil and Argentina. He alludes to vast
accumulations of shells in southern Brazil, called by the
natives sambaquis, which sometimes form hills that rise
10 or 15 metres above the low marshy land, while in other
places the equivalent deposits consist only of more or less
clayey soil through which oysters and other shells are
scattered. These sambaquis are sometimes formed entirely
of valves of Anamalocardia, in other places exclusively of
AS GEOLOGIST 77
oysters or of valves of Corbula mactroides prisca. Layers
of one or other of the shells may be seen to alternate in
some of the mounds. "Some authors," says the writer,
"compare these deposits to the kitchen-middens of Denmark,
but the conditions are quite distinct, since the shells are
never found mingled with bones of animals of the chase,
of fish, of wood charcoal, of fragments of pottery or other
human relics. The archaeological objects which are met
with in these deposits are only associated with the skeletons
which have there been buried " (p. 430). Dr von Ihering adds
that he need not enter into the details of this matter, as he
has already fully discussed it in several communications,
of which he subjoins a list. Dr Florentino Ameghino, so
well known for his numerous contributions to the geology
and vertebrate palaeontology of Argentina, has pointed out
the distinction between true kitchen-middens and natural
deposits of shells on the Patagonian coast (p. 432).
31 Geological Observations on South America, p. 33.
32 The title of this Memoir is "On the Connexion of
certain Volcanic phenomena and on the Formation of
Mountain-chains and the effects of Continental elevations"
(Trans. Geol Soc., 2nd Ser., v, 1840, pp. 601632). In this
paper the author expresses the opinion that the earthquakes
of South America are " caused by the interjection of liquefied
rock between strata " (p. 615). He supposes that " the train
of connected volcanoes in Chili and the tract of coast upraised,
extending together for a length of more than 800 geographical
miles rest on a sheet of fluid matter " (p. 630). He believes
that "mountain-chains are only subsidiary and attendant
phenomena on continental elevations " (p. 623). He argues
that while " mountain-chains are the effects of continental
elevations, continental elevations and the eruptive force of
78 CHARLES DARWIN
volcanoes are due to one great motive power now in pro-
gressive action ; therefore the formation of mountain-chains
is likewise in progress and at a rate which may be judged
of by either phenomenon, but most nearly by the growth of
volcanoes " (p. 629). He thinks this subterranean " power,
now in action, and which has been in action with the same
average intensity (volcanic eruptions being the index) since
the remotest periods, not only sufficient to produce, but
which almost inevitably must have produced, unequal
elevation on the lines of fracture " (pp. 624, 625).
33 Journal of Researches, pp. 275, 291, 310.
34 Trans. Geol Soc., 2nd Ser., v (1840), p. 631.
35 Darwin first published his theory of coral reefs in a
brief statement read to the Geological Society in 1837
(Vol. H of the Society's Proceedings, 1838, pp. 552554),
with the title " On certain Areas of Elevation and Subsidence
in the Pacific and Indian oceans, as deduced from the study
of Coral-formations." The first edition of his book on the
subject appeared in 1842 as the First Part of the Geology
of the Beagle, with the title, The Structure and Distribution
of Coral Reefs.
The first note of objection to the general applicability of
Darwin's explanation appears to have been raised by
Professor Louis Agassiz in 1851 (Bull. Mm. Comp. Zool.,
Vol. i), who from his investigation of the Florida reefs came
to the conclusion that they furnished no evidence of
subsidence an inference which was subsequently sup-
ported by the more detailed investigations of his son,
Prof. Alexander Agassiz, in a paper on the Tortugas and
Florida Reefs (Trans. Amer. Acad., xi, 1883). More
important evidence in the same direction was published
by Prof. Carl Semper from the Pelew Islands in 1863
AS GEOLOGIST 79
(ZeitscL Wissensch. Zoologie, xin, 1863, p. 558 ; Verhandl.
Physik-med. Geselkch. Wwrzburg, 1868, and Die Philippinen
und ihre Bewohner, 1869), and by Dr J. J. Rein from
Bermuda (Bericht. SencTcenberg. Naturforsch. Gesellsch.,
1869 70, p. 157). These writers insisted on evidence of
uplift where, according to Darwin's view, there ought to
have been depression.
In 1874 Darwin published a second edition of his volume
on Coral-reefs, revised and in some parts almost re-written.
It contained some additional matter, and took notice of
Semper's criticism, but without attaching to it any great
importance as necessitating a modification of the theory
originally promulgated. He was well aware that in many
places coral-reefs have been upheaved, and he cites examples
of them. He contemplated the association of elevation
with volcanic action, and the absence of active volcanoes
over vast regions where coral-islands are numerous seemed
to him a corroboration of his view that these areas are
sinking.
But he was at this time in the full tide of the biological
researches which engrossed his attention during the years
that followed the publication of the Origin of Species, and
it was hardly possible for him to keep in touch with the
progress of geological enquiry. In the preface to the second
edition of his Coral Islands he says that he might have
greatly improved his map of the distribution of coral-reefs
if he " had been better situated during the last thirty years,
for hearing of recent discoveries in the Pacific, and for con-
sulting charts published in other countries." He was
probably unaware of the early objections of Louis Agassiz
and of those made in later years by Dr Rein. It is doubt-
ful also whether or not he became aware of the large body
80 CHARLES DARWIN
of evidence which, after the publication of his second
edition, came from many widely separated localities with
constantly increasing force in opposition to his theory.
But even if this fresh information reached him, he was
content to let the matter rest where he had left it. A third
edition of his book was issued after his death under the
care of Professor Bonney in 1889.
In 1880, after the great voyage of the Challenger had
been carried out, Sir John Murray published a theoretical
explanation of the origin of coral-islands without the aid of
subsidence. Pointing out, as Darwin had already done (see
Note 51), that the oceanic islands are almost all of volcanic
origin and thus that no evidence from continental rocks can
be adduced in favour of the former existence of land now
submerged, he argued that the submarine ridges and peaks
which rise to various distances from the surface are pro-
bably due to the protrusion of volcanic materials. These
platforms, he conceived, might be brought in two ways
to the proper level at which reef-building polypifers could
live and grow. Those which rose above the sea-level could
be worn away by breakers and currents until they were
reduced to the lower limit of wave-action, while those
which lay at greater depths could be brought up to the
requisite level by the deposit upon them of the remains
of the calcareous pelagic organisms which swarm in the
upper waters of tropical seas. Thus, partly by erosion and
partly by the accumulation of organic debris, fitting building-
places could be furnished for the growth of corals. The
chief reef-builders flourish most vigorously on the outer
margin, amidst the play of the waves which are always
bringing them food. By the force of the breakers huge
blocks of the coral-rock are torn off the face of the reef.
A8 GEOLOGIST 81
These form a steep talus below, and on the top of this talus
the reef continues to grow outward (J. Murray, Proc. Roy.
Soc. Edin., x, 187980, p. 505 ; xvn, 1889, p. 79. In the
Proceedings of the Royal Physical Society of Edinburgh,
Vol. vni, p. 1, 1 gave an account of the state of the question
up to the year 1884).
Strong support to these views has been given by
Professor Alexander Agassiz, who in his numerous and
extensive cruises has acquired a more extended and inti-
mate knowledge of coral-reefs than any living naturalist.
His various published Reports afford an ample picture of
the structure and growth of these reefs all over the Pacific
Ocean as well as in the warmer waters of the western
Atlantic. The reader will find an index to the more
important contributions to the literature of coral-reefs on
p. 614 of the first volume of my Text-book of Geology. The
latest work of note is the voluminous Report on the borings
carried out on the Atoll of Funafuti, published by the
Royal Society (The Atoll of Funafuti Borings into a
Coral Reef and the Results ; Being the Report of the Coral
Reef Committee of the Royal Society y 1904. See also
A. Agassiz, Mem. Mus. Comp. ZooL, Harvard, Vol. xxvin
(1903), p. 212). The cores extracted from a bore sunk
on the reef of this atoll down to a depth of 1114 feet were
carefully studied by the most competent naturalists and
yielded reef-building genera from top to bottom. The base of
the calcareous mass was not reached, but its total thickness
was proved to be more than 1100 feet. If it could be
certainly shown that this mass consists of coral-rock in
its original position of growth this particular atoll would
demonstrate subsidence of the sea-floor, and could thus be
cited in support of Darwin's view. But if the mass is made
G. 6
82 CHARLES DARWIN
up of material broken by the waves from the face of the
reef during its slow seaward extension, or if it consists in
part of Tertiary limestone, it would not give any certain
proof of change of level.
If however we turn to the abundant and striking evi-
dence of uprise among the coral islands of the Pacific and
Indian Oceans and the reefs in the western part of the
Atlantic, which has been brought to light in recent years
by A. Agassiz, H. B. Guppy and others, it is, I think,
impossible any longer to insist on the vast area of subsi-
dence in these oceans which Darwin's theory required. He
undoubtedly pointed out a vera causa in subsidence, which
under the requisite conditions would give rise to the suc-
cession of different types of reef ending in true atolls. But
it must be admitted that the later explanation, while quite
compatible with the existence of local subsidence in different
areas, is in harmony with overwhelming evidence in favour
of elevation rather than depression among many oceanic
islands.
36 Zoology of the Voyage of H.M.S. Beagle, Vol. I,
Fossil Mammalia described by Richard Owen, with a Geo-
logical Introduction by Charles Darwin, 1838. The hope
here expressed by the great comparative anatomist has
been abundantly fulfilled by the successful labours of later
investigators, especially those of the Argentine Republic
and of the expedition to Patagonia sent out from Princeton
University.
37 Geological Observations on South America, p. 247.
See also pp. 136, 185187.
38 Volcanic Islands, p. 91.
39 Ibid., p. 136.
40 Journal of Researches, Chap, xv., pp. 316, 317.
AS GEOLOGIST 83
41 Life and Letters, Vol. i, p. 265.
42 Ibid., Vol. i, p. 267.
43 Life and Letters of the Reverend Adam Sedgwick, by
John Willis Clark and Thomas McKenny Hughes, 1890,
Vol. i, p. 484.
44 "Observations on the Parallel Roads of Glen Roy
and of other parts of Lochaber in Scotland, with an attempt
to prove that they are of marine origin" (Phil. Trans.,
1839, pp. 39 82). In this paper Darwin had in his mind
that the only conceivable barriers of the supposed lake or
lakes must have consisted of rock or of detritus, and he
rightly refused to believe the supposition that barriers of
these materials could be admitted. The idea of barriers of
ice had not then been suggested, and the only waters that
seemed capable of accounting for the terraces were those of
the sea. In the following year, however, Agassiz showed
that Scotland must have been deeply buried in ice, and
suggested that the Parallel Roads marked the levels of
lakes that had been ponded back by glaciers (Proc. Geol.
Soc., in, p. 327 ; Edin. New Phil Jowrn., xxxra, p. 217 ;
Atlantic Monthly for June, 1864). "When Mr Jameson's
paper was published in which this view was completely
demonstrated (Quart. Journ. Geol. Soc., Vol. xix, p. 235),
Darwin frankly admitted his own explanation to have been
erroneous (More Letters, Vol. n, pp. 188193).
45 Life and Letters, i, p. 58. The same simile was
used in the Origin of Species, p. 330. The references in
these Notes are to the sixth edition of the work.
46 This paper bears the title "Notes on the effects
produced by the Ancient Glaciers of Caernarvonshire, and
on the Boulders transported by Floating Ice " (Phil. Mag.,
Vol. xxi, 1842, p. 180). It is an interesting example of A
84 CHARLES DARWIN
characteristic phase in the evolution of opinion regarding
the phenomena of the Ice-Age. At first the so-called
" Drift," also scattered boulders and striated rock-surfaces,
were all attributed to powerful debacles produced by earth-
quake shocks whereby the sea was violently launched across
the surface of the land. When the idea gained ground that
ice had in some way helped in these operations, the super-
ficial accumulations were still regarded as having been
deposited in the sea, over which icebergs and floes trans-
ported materials from the land. Even when the presence
of former glaciers among the mountains of Britain was
admitted, the general distribution of ice-borne boulders over
the face of the country was still attributed to the sea. In
this paper of Darwin's (which followed a previous communi-
cation by Buckland " On the Diluvio-glacial Phenomena in
Snowdonia and the adjacent parts of North Wales"), while
the moraines with their boulders and the ice-worn domes
of rock are recognised as manifestly due to valley-glaciers,
the boulders lying scattered over the surrounding district
and the till underneath them are spoken of as having been
transported by floating ice when the mountains formed islets
in the sea. In like manner, in his paper on the Parallel
Roads he took for granted that the boulders in the Lochaber
district had been distributed by floating ice. It was long
before the efficacy of land-ice as an agent in the transport
of erratics was adequately acknowledged.
47 This was an article " On the power of Icebergs to
make rectilinear, uniformly-directed Grooves across a sub-
marine undulatory surface" (Phil. Mag., x, 1855, p. 96).
A growing disposition was then showing itself to doubt
whether floating ice could mould itself upon an irregular
rock-surface. The way in which on glaciated rocks the
AS GEOLOGIST 85
striae mount over the protuberances and descend into the
hollows of such surfaces was gradually coming to be recog-
nised as the work of land-ice. Darwin still clung to the
older faith. He thought that icebergs can mould them-
selves more perfectly than glaciers on the rocks over which
they are driven, and "can slide straight onwards over
considerable inequalities, scratching and grooving the un-
dulatory surface in long straight lines."
48 " On the formation of Mould," Proc. Geol Soc., n
(1838), pp. 574576 ; Trans. Geol. 8oc., 2nd Ser., v (1840),
pp. 505510.
49 Button was the first geologist who grasped the
general principle that although a layer of soil remains as a
covering on the land, its component particles are con-
tinually being washed off the surface while, in compensation,
fresh materials are added to it from the slow disintegration
of the rocks underneath (Theory of the Earth, Vol. I,
pp. 205, 210 ; H, pp. 93, 94, 95, 96, 184, 196, 202, 242,
244). The question was stated with characteristic clear-
ness and precision by Playfair. "It is interesting to
observe," he remarks, " how skilfully nature has balanced
the action of all the minute causes of waste, and rendered
them conducive to the general good. Of this we have a
most remarkable instance in the provision made for pre-
serving the soil, or the coat of vegetable mould, spread out
over the surface of the earth." He points out that although
its materials are easily and continually washed away by the
rains and carried down by the rivers into the sea, it still
remains as a covering on the land, being augmented from
other causes. " This augmentation evidently can proceed
from nothing but the constant and slow disintegration of
the rocks. In the permanence, therefore, of a coat of
6-3
86 CHARLES DARWIN
vegetable mould on the surface of the earth, we have a
demonstrative proof of the continual destruction of the
rocks ; and cannot but admire the skill with which the
powers of the many chemical and mechanical agents, em-
ployed in this complicated work, are so adjusted as to make
the supply and the waste of the soil exactly equal to one
another " (Illustrations of the Huttonian Theory, 103).
These conclusions, so vital for an intelligent compre-
hension of how a land-surface, even when covered with
vegetation, does not wholly escape from degradation, were
for many years ignored by later writers. It is true that
Lyell, in commenting upon the passage above quoted from
Playfair's treatise, supports its main contention, though he
adds that it did not take into account the organic material
supplied from the atmosphere (Principles of Geology,
first edit., Vol. n, p. 188). How little importance was
generally attached to the Huttonian view of this matter
may be gauged from the language used by Sedgwick from
the chair of the Geological Society, when he vehemently
opposed the uniformitarianism maintained in the then
recently published first volume of LyelPs Principles. "The
destructive powers of nature," he said, "act only upon
lines, while some of the grand principles of conservation
act upon the whole surface of the land. By the processes
of vegetable life, an incalculable mass of solid matter is
absorbed, year after year, from the elastic and non-elastic
fluids circulating round the earth, and is then thrown
down upon its surface. In this single operation there is a
vast counterpoise to all the agents of destruction " (Proc.
Geol Soc., i, 1831, p. 303. This portion of Sedgwick's
address was made the subject of some caustic remarks by
Lyell in the second volume of his Principles, p. 197).
AS GEOLOGIST 87
But the most absolute negation of the Huttonian
doctrine is to be found in the lectures given at the
College de France by filie de Beaumont, the most dis-
tinguished French geologist of his day. He devoted a
special discourse to the subject, wherein he entered upon
a detailed endeavour to prove that neither the soil, nor the
general surface of the land, nor the beds of rivers, have
undergone any perceptible modification during the time of
human history. He came to the conclusion that while
there are many places on the surface of the globe where
degradation is continual and plainly visible, this waste is
appreciable precisely because elsewhere the vegetable soil
preserves its integrity almost intact during immense periods
of time. "The surface of the ground, covered with vegeta-
tion, remains without sensible alteration for thousands of
years. It is a fixed point, a zero from which the phenomena
can be measured, which advance with rapidity " (Lemons de
Geologie Pratique, tome I, 1845, p. 182). Many years ago
I pointed out the fallacy in this reasoning (Trans. Geol.
Soc. Glasgow, Vol. m, 1868, p. 170).
]j!lie de Beaumont made no reference to Hutton or
Playfair, nor to Darwin's paper, which had been published
three years before he lectured on the subject. That the
views of the English naturalist met with little favour among
geologists was shown when, in reviewing the progress of
geology, D'Archiac summarised with approval the observa-
tions and conclusions of ]5lie de Beaumont, but referred to
Darwin's views as a "singulidre thebrie." "We fear," he
added, "that the learned English traveller has been too
much prepossessed by the importance of an organic influence,
which could have no effect save in low and damp meadows.
Cultivated lands, woods, high-lying meadows, afford no
88 CHARLES DARWIN
support to this view. The formation of the vegetable soil
results from the simultaneous co-operation of mechanical
and chemical agents, often helped by human industry "
(Histoire des Progrts de la Geblogie, tome I, 1847, p. 224).
Darwin in his volume on Vegetable Mould took notice of
both these French writers. He remarks that D'Archiac
" must have argued from inner consciousness and not from
observation, for worms abound to an extraordinary degree
in kitchen gardens, where the soil is continually worked "
(p. 4).
50 The Formation of Vegetable Mould through the Action
of Worms, with Observations on their Habits, 1881. The
popularity of this volume was immediate. We learn from
Life and Letters, Vol. in, p. 218, "that in the three years
following its publication, 8500 copies were sold," a sale
relatively greater than that of the Origin of Species.
51 Origin of Species, Chap, xii., pp. 324, 347. He
adduces his reasons for this belief, one of the most important
being the geological argument that the almost universally
volcanic composition of oceanic islands does not favour the
admission " that they are the wrecks of sunken continents.
If they had originally existed as continental mountain-
ranges, some at least of the islands would have been formed,
like other mountain summits, of granite, inetainorphic
schists, old .fossiliferous and other rocks, instead of con-
sisting of mere piles of volcanic matter." His opinion was
in favour of the view that the present continents and
oceans have long remained in nearly the same relative
positions (Chap, x., p. 288).
52 Principles of Geology, ninth edit., 1853, p. 146.
On the same page he affirms " No satisfactory proof has
yet been discovered of the gradual passage of the earth
AS GEOLOGIST 89
from a chaotic to a more habitable state, nor of any law of
progressive development governing the extinction and
renovation of species, and causing the fauna and flora to
pass from an embryonic to a more perfect condition, from a
simple to a more complex organisation." It may have been
allowable to say that no " law of progressive development "
had been discovered, but of the fact that a striking pro-
gressive advancement had taken place there could no
longer be any doubt.
53 Op. cit., first edition, Chap, ix., p. 148.
54 Op. cit., ninth edition, Chap, ix., pp. 134 et seq.
55 It is not always quite clear what "uniformity"
implied in the creed of the uniformitarians. Lyell dis-
claimed that he " contended for the absolute uniformity
throughout all time of the succession of sublunary events "
(Principles, ninth edit., p. 149). He insisted that "the
order of nature has from the earliest periods been uniform
in the same sense in which we believe it to be uniform at
present, and expect it to remain so in future " (Ibid.}. But
human experience embraced a mere fraction of geological
time, and gave but a limited basis on which to determine
what "the order of nature" is. It was this limitation
which so roused the indignation of the Catastrophists.
Lyell's own inclination evidently was against an admission
that geological energy had ever been manifested on a more
vigorous scale than has been witnessed by man. As he
described himself, he was " a staunch advocate for absolute
uniformity in the order of Nature" (Life, Letters and
Journals of Sir Charles Lyell, Vol. I, p. 260).
56 Principles of Geology, first edit., Vol. I, p. 124. This
statement was repeated up to and including the ninth
edition of the work.
90 CHARLES DARWIN
57 Lyell's Geological Evidences of the Antiquity of Man,
with remarks on Theories of the Origin of Species by Vari-
ation was published in 1863. It greatly disappointed
Darwin with its halting language, when from their inter-
course and discussions on the subject he had expected more
decided support (Life and Letters, Vol. in, pp. 8 et seq).
The tenth edition of the Principles of Geology appeared in
two volumes, the first in 1867 and the second in 1868. The
latter contained the author's full acceptance of Darwin's
views. As Mr "Wallace truly remarked, "the history of
science hardly presents so striking an instance of youthful-
ness of mind in advanced life as is shown by this abandon-
ment of opinions so long held and so powerfully advocated "
(Quarterly Review, April, 1869).
58 This thesis was maintained by Cuvier in his Theory
of the Earth a work which went through many editions,
and of which an English translation appeared under the
editorship of Robert Jameson. Cuvier's great contemporary,
Lamarck, on the other hand, disbelieved in the occasional
catastrophes and re-creations which the former so confidently
asserted. On the contrary, he looked on the succession of
life as having probably been unbroken from the beginning,
and he believed the existing faunas and floras of the globe
to be the lineal descendants and representatives of other
forms which have preceded them, and the remains of some
of which have been preserved among the stratified rocks of
the earth's crust.
59 During his presidency of the Geological Society A. C.
Ramsay gave from the chair two addresses (in 1863 and
1864), wherein he discussed the character and meaning of
what he called " breaks in succession " among the stratified
formations of Britain, whether these interruptions are
AS GEOLOGIST 91
marked by unconformabilities or by abrupt changes in fossil
contents. These brilliant addresses, printed in the Quarterly
Journal of the Society, contained the first detailed and
serious attempt to show the relative chronometric^ value of
"breaks in succession," and gave strong support to the
arguments maintained in the geological chapters of the
Origin of Species.
CAMBRIDGE : PRINTED BY JOHN CLAY, M.A. AT THE UNIVERSITY PRESS.
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