Page:The origin of continents and oceans - Wegener, tr. Skerl - 1924.djvu/55

Rh a single frequency-maximum somewhere in the region of the mean sphere level (−2,450 m.). Instead of this we see two maxima, both of which have a curve with a course similar to that of the law of errors. From this it must be concluded that there are already two undisturbed original levels, and from this the step seems inevitable, that in the continents and the floors of the oceans we have two different layers of the body of the earth, which—expressed in a somewhat exaggerated form—act as water does between great sheets of ice. This step seems so easy and obvious that the next generation will certainly wonder that we should have hesitated such a long time over taking it.

In Fig. 6 a diagrammatic vertical section is given across the margin of a continent according to this new conception.

It is at once necessary to exercise caution against any exaggeration of this new conception of the nature of the oceanic floors. In our comparison with the tabular icebergs we must certainly also consider the fact that the upper surface of the sea between them can be again covered with newer ice, and further also, that smaller fragments of the iceberg which have become detached from its upper margin, or have risen from its foot, deeply submerged as it is under-water, could cover the surface of the water. In a similar manner this will occur at many places on the ocean floors. Islands are always larger pieces of continent, which, with their substructure, reach 50 to 70 km. under the floor of the ocean, as is shown by gravity measurements. They are comparable to the non-tabular icebergs.

Although this argument of the double