Page:The origin of continents and oceans - Wegener, tr. Skerl - 1924.djvu/228

 can be explained by the agency of the attraction of the sun and of the moon on the viscous earth.

But Schweydar holds the view that the deviations of the earth’s figure from the ellipsoid of rotation, as shown by the gravity measurements, give rise to flow-movements within the sima, and can thereby also cause displacement of the continents. “One may also, however, suspect a flow of the sima, at least in the earlier epochs. In his latest work Helmert infers, from the distribution of the force of gravity on the earth’s surface, that the earth is a triaxial ellipsoid; the equator forms an ellipse. The difference of the axes of this ellipse amounts to only 230 m.; the long axis cuts the surface of the earth at longitude 17° west (Atlantic Ocean), the short at 73° east (Indian Ocean). According to the theories of Laplace and Clairaut, from which in geodesy we have not departed, the earth is to be considered as constructed like a liquid, that is, the pressure in the solid earth (apart from the crust) is assumed to be of the nature of hydrostatic pressure. Helmert’s results are unintelligible from this point of view. The hydrostatically constructed earth with its oblateness and its velocity of rotation cannot be a triaxial ellipsoid. It might now be assumed that the deviation from an ellipsoid of rotation will be brought about by the continents. But this is not the case. I have made the calculation on the supposition that the continents are floating and have the thickness adduced above (200 km.; difference in density between sial and sima 0.034, water = 1), and found that the distribution of continents and seas produces a deviation of the mathematical shape of the earth from an ellipsoid of rotation which is considerably smaller than that found by Helmert. The axes of the equatorial ellipse are absolutely different from Helmert’s, the long axis