On account of the novelty of the principles involved, we have entered somewhat more fully into the connection between wandering of the pole and transgression than the train of ideas of this book immediately required. What can we now conclude from these facts about the viscosity of the earth? The variations of level, which are produced by these transgressions and regressions, are of the order of magnitude of some hundreds of metres. Thus the crust of the earth may lie by this amount above its position of equilibrium in front of the pole; below it, behind the pole. All these transgressions have the character of shallow seas similar to the North Sea or the Baltic. But the equatorial radius of the earth is about 21 km. greater than the polar. Therefore the wandering of the pole between the Carboniferous and Quaternary, amounting to nearly 90° of arc, must, if the earth had behaved as a rigid body, have elevated Spitsbergen about 21 km. and depressed Central Africa a similar amount beneath the level of the sea. In place of this, as already said, we have only transitory elevations and submergences of some hundred metres. The earth has thus largely adjusted itself to this new position of its axis of rotation; the radius has become about 21 km. shorter beneath Spitsbergen, and 21 km. longer in Central Africa. This obviously can only take place because of flow.
But however clearly these facts testify to the viscosity of the earth, this is doubted by many geophy-
general depression of the surface of the ocean, and the melting will correspond to an elevation of the ocean. Since periods have been detected in the earth’s history where at one pole at least no ice-sheet existed (because it lay in the middle of the Pacific), there must have been on these grounds not insignificant fluctuations of sea-level. Nevertheless, all the great features in the variation of transgressions must be traced back directly to the wanderings of the poles.
