then. Thus the arid zone followed directly on the heels of the formation of coal. But the greatest salt and gypsum deposits first occur in the Permian, and indeed first in the Upper Permian, in which coals had already vanished, i.e. in Eastern Russia, North Germany, in the Southern Alps, and in the United States. Thus the formation of salt also advanced in this period of time from north to south, from Spitsbergen (in the Lower Carboniferous) to the Southern Alps (in the Upper Permian), and so followed after the formation of coal. Scarcely a doubt can therefore exist in this case that we are dealing with the northern arid zone.
In the above we have confined ourselves to the more important evidences of the climate of this period, and it must be allowed that, on the basis of the displacement theory, these can be presented with great logical consistency. It would carry us too far to deal here, completely, with the less important climatic evidences. As far as can be seen, the latter also fit themselves, without exception, into the picture. A few examples are given. The average size of the wings of insects in the Lower and Middle Carboniferous, according to Handlirsch, amounted to 51 mm.; in the Upper Carboniferous and Permian, however, only 20 to 17 mm. This is in good agreement with the fact that the equator had its most northerly position in the Lower Carboniferous, and that Europe fell into the northern arid zone in the Permian. In the Lower Carboniferous, coral reefs are not only known from Cantabria and the Carnic Alps, but also from Belgium, England and Ireland; from the Middle and Upper Carboniferous of North America (Middle Carboniferous: Indiana, Illinois, Alabama; Upper Carboniferous: Kansas to Texas).[1]
- ↑ Th. Arldt, Paläogeographie, 2. Leipzig, 1921.
