EMERSON— RECURRENT TETRAHEDRAL DEFORMATIONS. 455 



itself may have been raised abnormally like Angara Land to form 

 the similar slope down which the northward sliding occurred. 



The three intercontinental seas are not all alike, but the true 

 Mediterranean is contrasted with the Caribbean and East Indian 

 areas. 



The two latter are placed on the borders of the Pacific at the 

 points where the old and new equators intersect near the Galapagos 

 Islands and Sumatra (see the map), and the former where the 

 equators are most widely separated. In the two the east-west tor- 

 sions have moved the continental segments most apart, so that moun- 

 tain curves could flow north toward the equatorial depths to form 

 their curved mountain boundaries, and their three deep depressions. 



The classical Mediterranean has mountain chains which have 

 moved not toward oceanic depths but toward the continental center, 

 and it is placed directly opposite to the center of the Pacific, while 

 the other two are where both equators intersect the volcanic border 

 of the Pacific. By an unexplained coincidence it has three deeps 

 like the others. 



The Mediterranean has been the center of civilization. The 

 other two have been rather the opposite, more centers of seismic and 

 of cyclone activity and the United States has unfortunately acquired 

 foothold in both. 



The Mediterranean zone has always been a more continuous 

 ocean (the Tethys of Suess) in transgression periods than in tetra- 

 hedral periods, therefore it has been many times built up and de- 

 stroyed. Therefore its being maintained as equator till the Tertiary 

 has made these cycles possible. 



The Migration of the Poles 



This transfer of the pole and equator to the new position, in 

 whole or in part, in the late Tertiary agrees with the independent 

 suggestions of many botanists and zoologists in explanation of the 

 Tertiary and modern distribution of plants and animals. 



Arldt rejects this Tertiary deformation and places the transfer 

 of the pole in the Archaean, because it would, he believes, have been 

 attended by more enormous mass movements even than those of the 

 Tertiary. He is discussing the matter from the standpoint of the 



