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, 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.
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
- Hutton's Theory of the Earth.