Page:The origin of continents and oceans - Wegener, tr. Skerl - 1924.djvu/146



the compilation in the foregoing chapters of the chief arguments in favour of the displacement theory, we will henceforth assume them to be correct, and on this supposition we will deal with a series of problems which are linked so closely with the subject-matter of the displacement theory that a discussion of them seems to be desirable. A new light will thus be shed on many an old problem, and many things will be spoken of, in which can be seen a further confirmation of the displacement theory, even if they are not so convincing as the earlier proofs.

The question as to whether, and if so in how far, the earth is to be considered as a viscous or as a rigid body is now being much discussed by the geophysicists. We will consider the grounds of both views in turn, beginning with those of viscosity. They are especially the phenomena of isostasy, the continental displacements, the movement of the poles, and the flattening of the earth near the poles.

It is a well-known fact that isostasy, the equilibrium of adjoining portions of the earth's crust, is universally satisfied on a large scale. Just as indubitable is the occurrence of vertical movements of compensation tending to the restoration of isostasy wherever it has been disturbed over a great area. We have already