an opinion, the amount and orientation of the polar flattening are in agreement with its rotation, a state of affairs which can only be attained by flow. But we can examine this question geologically by comparing the alternate advance (transgression) and withdrawal (regression) of the sea with the wandering of the poles. That a simple connection exists between these phenomena has already been suspected by numerous authors as, for example, Reibisch, Kreichgauer, Semper, Heil, Köppen, amongst others.
_-_figure_21.jpg)
Fig. 21.—Transgressions and regressions caused by the wandering of the poles.
Fig. 21 explains this. If during a wandering of the poles the earth lags behind in the alteration of its shape whilst the ocean adjusts itself immediately, then regression must prevail, in front of the wandering pole and transgression behind it. The reconstructed map of the displacement theory places us in a position to verify this already long-asserted, but never proved, law. We select for this the period from the Devonian to the Permian, because the poles during this time wandered rapidly,[1] as was shown in Chapter VI. If we introduce into our Carboniferous map of the earth the coast-lines of the Lower Devonian and Lower Carboniferous according to the customary
- ↑ The similarly very rapid polar wandering in the Tertiary is less suitable for the purpose, because then the continents had already emerged to a greater extent; the area of continental shelf has become so small that the alterations of its boundary are not so striking as in more ancient periods, when much greater portions of the continental blocks lay beneath the water.
