Carboniferous. The Devonian coals at Neunkirchen in the Eifel consequently belong to the equatorial zone of rains, and the Devonian coral reefs in England, Belgium, Southern France, North-west Germany, Silesia and the Alps fit in very well with this view. The greatest part of Africa (Lower Nubian Sandstone) and Brazil lay in the southern arid zone. However, we cannot go into any further details here, it being sufficient to have shown that when the positions of the poles have been found for the Carboniferous and Permian a connection with those of the Devonian is not lacking.
The whole of these evidences of the climate of the Permo-Carboniferous period give such a convincing picture of the climatic zone prevailing then that I do not see how this conception of the position and direction of movement of the poles can be dismissed. In this way these evidences become a strong proof of the accuracy of the displacement theory.
The Carboniferous period has been deliberately chosen for the foregoing discussion, since it shows most clearly the simplification produced by the displacement theory. It is now clear that the rôle of this theory becomes greater the further we go back into the earth’s history, since at the same time the displacements of the continents become greater and greater in comparison with their present position. Also the Carboniferous is the most ancient period in which the displacement theory has been yet worked out. On account of this also, the criteria for the displacement theory which we have obtained from the study of the position of the poles for the later periods are of gradually decreasing importance. If we would completely test the state of affairs, we must also determine the position of the climatic belts for the succeeding periods up to the Quaternary with the same thoroughness as for the Permo-Carboniferous, and in each case attempt to
