Page:The origin of continents and oceans - Wegener, tr. Skerl - 1924.djvu/38

14 we should, that radium only occurs in the uppermost crust of the earth, is still uncertain, but it is evident in any case that a noteworthy contraction of the earth from loss of heat by radiation cannot be seriously maintained. We know, indeed, no way of avoiding the conclusion that the heat-content of the earth is on the increase.

But even if, in spite of all this, such a contraction did take place, we should be forced to the fatal assumption, made, for example, by Heim, that the shrinkage of a complete great circle takes effect only at one single point upon it. This involves the impossible assumption of a transference of pressure within the earth’s crust over an arc of 180 degrees. Numerous authors, as Ampferer, Reyer, Rudzki, Andrée, among others, have objected to this and have demanded that the contraction must affect the whole surface of the earth in a manner similar to that of the puckering shown by the drying apple. Recently Koszmat, in particular, has repeatedly emphasized the fact that an explanation of mountain building must take into account immense tangential crustal movements, which do not fit in with the notion of a simple contraction theory. Thus doubt after doubt is experienced, so that the standpoint of geology has for some time been summarized in the statement: “The contraction theory has long ceased to be completely accepted, and