[A] In this article I have attempted to give only the development
of geological thought.
Geology is one of the youngest of the sciences. It may almost be said
to have been born of the present century. It is true that knowledge
concerning the structure of the earth had been accumulating ever since
the time of the Greeks and Romans; it is true that these materials
became more abundant and were better organized in the eighteenth
century; but this knowledge had not yet taken form as a distinct
branch of science until about the end of that century. There are two
distinctive marks of scientific as compared with popular knowledge:
First, that its fundamental idea is clearly conceived; and, second,
that its method is distinctly inductive.
1. FUNDAMENTAL IDEA.--The fundamental idea underlying geological
thought is the history of the earth. Now, until the beginning of the
present century the earth was not supposed to have any history. It was
supposed to have been made at once, out of hand, about six thousand
years ago, and to have remained substantially unchanged ever since as
the necessary theater of human history. Changes were known to have
taken place and in less degree to be still taking place, but these
were not supposed to follow any law such as is necessary to constitute
a history, and thus to constitute a science distinct from geography.
Buffon, about the middle of the last century, did indeed bring out
dimly the idea of an abyss of time, preceding the advent of man, in
which the earth was inhabited by animals and plants wholly different
from those of the present day, but he was compelled by the priests of
the Sorbonne to retract these supposed irreligious views. So tardily
was the fundamental idea of geology clearly conceived that Comte, the
great originator of scientific philosophy, in his classification of
the sciences in 1820, denied a place to geology because, according
to him, it was not a distinct science at all, but only a field for
the application of all the sciences. It is evident that he did not
perceive the fundamental idea underlying geology and distinguishing
it from geography--viz., a life history of the earth through all
time. The claim of geology to a place in a scheme of classification
is exactly the same as that of astronomy. As astronomy is a field for
the application of mathematics, mechanics, physics, and, recently,
chemistry, but is distinguished from them all by its characteristic
fundamental idea of illimitable space, so geology is a field for the
application of all other lower sciences, but is distinguished from
them all by her characteristic fundamental idea of illimitable time.
As all other sciences are terrestrial, but astronomy alone celestial,
so all other sciences belong to the present--the “_now_”--but geology
alone belongs to the illimitable past. The fundamental idea of the one
is infinite _space_, of the other infinite, in sense of inconceivable,
_time_. All other sciences, including astronomy, are but a flash-light
view of Nature. Geology alone is a view of Nature in continuous
movement, a life history--an evolution of Nature. This mode of thought
began to dawn only in the closing years of the last and the opening
years of the present century. It seems to have been first clearly
conceived by the mind of Hutton in the last part of the eighteenth
century.
2. INDUCTIVE METHOD APPLIED.--When the true idea underlying geology
was clearly conceived and geology thus distinctly separated from other
departments of science, geology may be said to have been born. But
it was still in helpless infancy, its growth irregular, and even its
continuous life uncertain, because a solid basis of inductive method
was not yet laid. That basis was laid mainly by Hutton in 1795,[B] and
still more clearly by Charles Lyell in 1830, in the principle that
the study of _causes now in operation_ is the only true foundation of
geology.
[B] Hutton’s Theory of the Earth.
Geological changes, of course, belong to the irrevocable past, and are
therefore hopelessly removed from _direct_ observation. Their causes
and process must be reconstructed by the skillful use of the scientific
imagination. Until Lyell, more or less probable hypotheses seemed all
that was possible. What a field was here for the conflict of opposite
extreme views! But Lyell showed that “causes now in operation” are
producing similar effects under our eyes, if we will only observe. From
that moment geology became a truly inductive science and its indefinite
progress assured.
These two events, then--viz., the conception of geology as a distinct
science, and the introduction of a true scientific method--are the
greatest epochs in the history of geological science. Some dim
adumbrations of these appear before this century, especially the former
in the mind of Buffon, and the latter somewhat fully in the mind of
Hutton, but they were not generally accepted and had not become working
principles until the beginning and even some time after the beginning
of the nineteenth century. These must be borne in mind in all we have
further to say of the progress of geology through the century.
When the century opened, the war between the Neptunists and the
Plutonists, between the Wernerites and the Huttonites, was still
going on, but was approaching the usual result in such cases of
dispute--viz., the recognition of the fact that there was truth on
both sides, and they must be combined into a more comprehensive view.
The chief difference of opinion still remaining was as to the relative
importance of the two agencies, aqueous and igneous. Two great advances
took place about the beginning of this century: William Smith, by
patient, painstaking field observation and mapping, laid the foundation
of stratigraphy; and Cuvier, by his profound and brilliant studies of
the wonderful discoveries of extinct mammals in the Eocene basin of
Paris, laid the foundations of paleontology. These researches placed
in clearer light than ever before the existence of other time-worlds
before the present one. William Smith published his tabular view of the
British Strata in 1790, but his map was not completed and published
until 1815. Cuvier’s great work on the Organic Remains of the Paris
Basin was published in 1808.
Thus, early in the century the two bases of our science were laid by
Smith and Cuvier. We now proceed to touch lightly only the main steps
of subsequent growth through the century.
As, in the previous century and the early part of this, the discussion
was between the opposite schools of Neptunists and Plutonists, with
the final result of reconciliation in a more scientific view which
combined these two surface views into a stereoscopic reality, so now
the discussions began between catastrophism and uniformitarianism, and
ended with a similar final result. Geologists, in the early part of the
century, before the study of causes and processes now in operation was
generally acknowledged as the only rational basis of a true scientific
geology, seeing the frequent unconformities in the geological series
and the apparently sudden changes of life forms associated with these
unconformities, were naturally led to the conclusion that the whole
history of the earth consisted of a series of sudden and violent
catastrophes by which the bed of the ocean was suddenly raised and
its waters precipitated on the land as a great wave of translation,
carrying universal ruin and extermination of all life in its course.
Such catastrophes were supposed to be followed by periods of quiet,
during which the new earth was repeopled, by direct act of creation,
with new forms of life adapted to the new conditions.
This view was in perfect accord with the then accepted doctrine of
the supernatural origin and the permanence of species. Species were
supposed to have been created at once, out of hand, without natural
process, in some place (center of specific origin), spread in all
directions as far as physical conditions would allow, but remained
unchanged and unchangeable as long as they continued to live or until
another universal exterminating catastrophe. Species are “medals of
creation.” They are successive individuals struck from the same die,
until the die is worn out or broken. Then a new die is made, and the
process of coinage of identical individuals is renewed.
Thus the whole history of the earth was supposed to consist of
a succession of alternate supernatural and natural events. The
catastrophes were supernatural; the times of quiet were natural. The
creation of new dies or creation of first individuals was supernatural;
the coinage of individuals of successive generations was natural. But
on the whole the successive conditions of physical geography and the
successive faunas and floras were higher and more complex according to
a preordained plan. The great apostles of catastrophism were Cuvier
in France and Buckland in England. According to Buckland, the last
of these great catastrophes was the Quaternary or drift period, and
this period was, by him and by many others since, associated with the
Noachian Deluge.
Lyell opposed this view with all his power. According to him we can not
judge of geological causes and processes except by study of causes and
processes now in operation and producing effects under our eyes. The
slow operation of similar causes and processes is sufficient--given
time enough--to account for all the phenomena in geological history.
Thus arose the extreme opposite doctrine of _uniformitarianism_. Things
have gone on from the beginning and throughout all time much as they
are going on now. This view, of course, required illimitable time, and
was of great service in enforcing this idea. But, in revulsion from the
previous idea of catastrophism, it undoubtedly was pushed much too far.
Meanwhile the theory of evolution was incubating in the mind of Darwin.
Even Lyell, while he established the doctrine of slow uniform changes
so far as inorganic Nature was concerned, was still compelled to admit
supernatural catastrophic changes in organic Nature. Species, even for
Lyell, were still immutable--still there were supernatural creation of
first individuals, and continuance of similar individuals by natural
process of generation. On the publication of Darwin’s Origin of Species
by Descent with Modification, Lyell at once embraced the new view
as a completion of his principle of causes now in operation and his
doctrine of uniformitarianism. In a certain superficial sense evolution
is certainly confirmatory of the doctrine of uniformity of causes and
processes in the past and the present, but in a deeper sense it is
quite contrary in its spirit. Uniformitarians of the Lyell school look
upon geology as a chronicle of events--evolutionists as a life history
of the earth. The one regards the slow changes as irregular, uncertain,
without progress or purpose or goal; the other as an evolution to
higher and higher conditions, as a gradual movement onward toward the
present condition and toward man as its goal. The recognition of this
is only now approaching clearness. If geology is the history of the
evolution of the earth from primal chaos until now, then the conditions
have changed at every step, and absolute uniformity is impossible.
Extreme uniformitarianism is therefore untenable. Catastrophism and
uniformitarianism are opposite extremes which must be combined and
reconciled. This reconciliation is only now being completed, and we
therefore put off its discussion for the present. Suffice it to say
now that geologic thought in this regard has passed through three
stages--catastrophism, uniformitarianism, and evolutionism. And this
latter is the final stage, because (1) it is a complete reconciliation
between the other two, and (2) because it is plastic and indefinitely
modifiable and progressive, while the other two are equally rigid and
unchangeable by their mutual antagonism.
With these fundamental principles in mind, we proceed to touch briefly
the most important advances during the century.