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.