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.