to a polar one immediately suggests a displacement of the poles and of the equator, and therefore of the whole zonal system of climates. This view finds at once its confirmation in the fact that Central Africa, lying 90° of latitude south of Spitsbergen, underwent just such an enormous but exactly reverse change of climate in the same period of time. In the Carboniferous it was buried under a covering of land-ice; to-day it is in the region of equatorial rains. But 90° east of Central Africa, in the Sunda Archipelago, no variation of climate occurred; from the Tertiary at least this region had the same climate as to-day, which is shown in the unchanged preservation of numerous ancient plants and animals, as, for example, of the sago-palm or of the tapir. The northern part of South America was also in the same position as now, for, among other examples, the tapir has been preserved, whilst it is only found fossil in North America, Europe and Asia, except Further India, where it survives; it is not found at all in Africa.
Therefore it is not to be wondered at that in attempts to ascertain the rationale of former climatic changes, recourse was early and increasingly had to changes in the position of the poles. The parallel hypothesis of a sliding of the whole earth’s crust over its lower portions, adopted to comply with the necessity of keeping the axis of the earth unaltered in relation to the main mass, we can treat as identical with that of the shifting of the earth’s axis, as we have no means of deciding between them. We shall, therefore, for all purposes, understand by the wandering of the poles, a displacement of the poles on the earth’s surface, without reference to whether this was produced by a movement of the crust, or by a displacement of the axis in the interior of the earth, or by both together. Herder has already suggested such an explanation of
