Page:South African Geology - Schwarz - 1912.djvu/16

12 enough, and the method of reasoning in the end will be found to be as accurate as that employed in the physical sciences, although the geologist cannot support his findings by mathematics.

South African geology differs from European or American geology, which is the subject-matter of most textbooks of the science, in that South Africa is a fragment of a southern world-segment which, in many respects, is different from the continents which are found in the northern hemisphere. The differences in the rocks themselves we shall deal with in the special part, but in the general part also there will be found considerable divergence from the usual treatment. This is necessary because the conditions in South Africa are not the same as those in Europe and America. South Africa is a young country, geologically speaking; there are no navigable rivers; the action of frost is negligible, while desert conditions are frequent; on one side the influence of the tropics is apparent on the coast, while on the other the currents from the Antarctic make themselves felt; the land borders the sea with an almost straight coast line, there are no inlets of any size, and the central plateaux lie far removed from the influence of the sea—these and other differences are reflected in the character of the face of the earth revealed in South Africa, and a textbook to be of use in this country must deal with facts as they exist. It is not, of course, that the fundamental laws as worked out in Europe and America have no application here, but the features that occur so rarely in these countries, that they require no mention in textbooks, are prominent here, and vice versa.

The Cosmical Aspects of Geology.—Underlying most geological reasoning is the conception of the origin of