:356 A. KEITH OUTLINES OF APPALACHIAN STRUCTURE 



motion on planes of any such angle as are contemplated in the theory, 

 Avhile at depths there can not fail to be an increase with the load, what- 

 ■ever may be the modifications of the principle. The difficulty raised by 

 friction is more important in the case of the F. B. Taylor theory, because 

 the assumed plane of motion must pass deep into the more rigid parts of 

 the crust. 



The space relations of the F. B. Taylor theory are in reality a chief 

 obstacle to its acceptance, although its author states that it is founded on 

 the trend lines of mountain systems and their space relations, just as was 

 the theory of Suess. The diagram presented by Tajdor to show these 

 :S23ace relations was drawn on the Mercator projection, which renders it 

 easy to think of unlimited areas north of the continents. From such 

 areas the crust of the earth is indicated in the diagram as having moved 

 southward. In his map of the polar regions, however, drawn on the 

 nearly true scale, this unlimited northern area is seen to be a small affair 

 in comparison with the areas of the continents surrounding it. It is, in 

 "fact, hardly larger than the area directly inclosed in only one of the 

 Tertiary mountain loops — that of the East Indies. Since the thickness 

 of the moving crust increases southward, the mass which moved in the 

 East Indies must have been enormously greater than the mass of equal 

 area near the poles. Even assuming that it was no greater, and sub- 

 tracting from the polar area the mass inclosed in the East Indian loops, 

 nothing is left to satisfy the enormous motions which are postulated for 

 the rest of the world; no source would remain from which such motion 

 -could emanate. Granting, for the sake of argument, that the motion did 

 start radially from the poles, a very few miles of motion of all the north- 

 ern continents would create such a hole in the polar region that the 

 gravity relations would be totally reversed and motion back toward the 

 pole would be compulsory. 



While the theory appears to receive strong support from the mountain 

 trend lines, the hypothesis of southward creep of the continents is not 

 the only conclusion that can be drawn from them, Hobbs, on the con- 

 trary, concludes precisely the opposite — that is, that the mass of Asia 

 remained stationar}', while the suboceanic mass pressed northward 

 against it and was thrust beneath it, raisino- the mountains around its 



:margin. Taylor states that the crust of the earth moved like a field of 

 ice, crushing against obstacles, such as the Indian Plateau, and flowing 

 past them in sweeping curves. This, however, is only an illustration, 

 and the conditions of the two operations were so different as to leave it 

 little value as an argument. In ice and rock the melting points and 



