The sufficient justification of the demand that has now arisen for explanation and correlation in the study of land forms is found in the repeated experience that until an explanatory description of a region can be given, one may be sure that some of its significant elements pass unnoticed; and until the controls that it exerts on living forms are studied, one may be confident that its geographical value is but half measured. A sentence from Guyot’s Earth and Man may here be taken as a guide: “To describe, without rising to the causes, or descending to the consequences, is no more science than merely and simply to relate a fact of which one has been a witness.” There could hardly be devised a more concise and searching test of good work than this quotation suggests. The causes, in so far as the physical geography of the lands is concerned, have been learned chiefly through the study of geology; yet it does not by any means follow that all geologists are possessed of such knowledge of these causes as will constitute them geographers. The consequences have been learned through the study of evolutionary biology; yet a distinct addition to the usual discipline of biology is required in order to apprehend its geographical correlations. The limited space allowed to this article will require that further consideration of the consequences be excluded, in order to give due consideration to the causes. One of the preparatory steps in the century’s advance was taken by the German geographer, Ritter, who, near the beginning of the century, advocated a new principle that may be illustrated by the change in the definition of geography from “the description of the earth and its inhabitants” to “the study of the earth in relation to its inhabitants;” but advance beyond this beginning was for a long time obstructed by certain ancient beliefs. Theological preconceptions as to the age of the earth and the associated geological doctrine of catastrophism, although attacked by the rising school of uniformitarianism, were then dominant. They gave to the geographer a ready-made earth, on which the existing processes of change were unimportant. Furthermore, the belief in the separate creation of every organic species led to the doctrine of teleology, which maintained the predetermined fitness of the earth for its inhabitants, and of its inhabitants for their lifework. All this had to be outgrown before geographers could understand the slow development of land forms and the progressive adaptation of all living beings to their environments. Yet the beginning that Ritter made was of great importance, and it would have led further had it not happened that for many decades professors of geography in Europe brought chiefly a historical training to their chairs, to the almost entire neglect of physical geography. In the last thirty years there has been a reaction from this condition in Germany and France, but Italy, with many professors of geography in her