FUNDAMENTAL PRINCIPLES OF GEOLOGY. Geo logical work is so slow, and the evidence of vast changes in the past so clear, that, so long as it was held that the age of the earth was to be reckoned in a period of a few thousand years, no other conclusion was possible than that the changes observed had been rapidly made as a result of stupendous catastrophes. Thus the early literature of geology deals largely with imagined deluges, sudden upliftings of the crust to form mountains, destructive invasions of the land by ocean water, and similar catastrophes. When, however, it was made clear by Hutton and his successors that the recorded facts indicated slow changes, it began to appear possible that the age of the earth was great. The promulga tion of the doctrine of evolution, and the in creased knowledge of past life, as recorded by the fossils, brought further evidence of the great age of the earth. In consequence of these ad
vances in science, the interpretation of the former history of the earth by modern geology rests upon two principles that may be considered es tablished: one that the age of the earth is very great; the other, that in the processes in opera tion at present, we may look for illustrations of most of the changes of the past. These two principles were formulated in the doctrine of uni formitarianism (q.v.) which was proposed as a substitute for the older theory of catastrophism (q.v.). By this doctrine the past may be investigated in the light of the present. Given time enough, even the slow processes operating at present, which produce no perceptible change in one's surroundings in a lifetime, will accom plish the stupendous results so clearly proved by geological study.