In several earlier papers the writer has presented brief studies of certain of the greater features of the earth’s surface—mountain ranges, foredeeps, etcetera—in an effort to explain their origin. The details of those studies and of the conclusions reached are contained in the seven papers listed below and can not be restated here.2 Condensed into one short paragraph, the main conclusions reached may be stated as follows: Beginning rather abruptly in the latter part of the Cretaceous period and continuing down to the present time, the northern continents—Europe, Asia, and North America—began to slide very slowly in southernly directions. At the same time the southern continents—South America and Australia—began moving in northerly directions. Hence, abstractly, the moving continents slid from high latitudes toward lower latitudes in both hemispheres. Greenland and Africa, with Arabia and India, and probably with Antarctica, remained unmoved in this . . .