52 THE TIDAL PROBLEM. 



The distribution of folded mountains appears to be quite indifferent 

 to the latitudinal distinction which the hypothesis of rotational reduction 

 involves. The great Cordilleran belt of the Americas begins far within 

 the southern tensional area, is strong where it crosses the southern neutral 

 belt, is also strong in the southern half of the equatorial belt, becomes weak, 

 scattered, and tortuous in the northern half of this belt, attains strength 

 and broadens as it crosses the northern neutral zone, and reaches great 

 breadth and aggregate mass in the lower part of the north tensional area. 

 About 30° within that zone, still strong, it swings about toward the Asian 

 continent. The great tangled mass of mountains of central Asia lies chiefly 

 in the northern tensional area. According to Suess, the thrust movement 

 was generally from the northwest; that is, from the more highly tensional 

 to the less highly tensional area. The great east-westerly range of southern 

 Europe and Asia lies chiefly in the lower tensional and neutral zones and 

 only at the east passes obliquely into the equatorial belt. A thrust from the 

 compressional zone toward the tensional zone is indicated in the western 

 portion and the opposite in the eastern portion. If, neglecting the latter, 

 we fasten upon the former as dynamically probable under the hypothesis, 

 it is to be noted that, with tension increasing in the direction of the thrust, 

 it is not apparent whence came the resistance that was necessary to the 

 intricate folding and distorting of the east-west ranges. Rather should 

 we expect yielding in the direction of the tensional area and lateral crowd- 

 ing of the shell as it was pushed from the periphery toward the center of 

 the tensional cap, wdth short meridional ranges as the result. Without 

 reviewing the multitude of minor mountains, it may be sufficient to note 

 that the Urals, the ranges of Scandinavia and of the British Isles, the 

 Appalachians, and the mountains of Greenland testify to the dominance 

 of thrust phenomena in the northern zone of tension. Statistically con- 

 sidered, the facts now known give this northern zone precedence over all 

 others in thrust phenomena. The great Archean tracts of Canada, Green- 

 land, Scandinavia, and Finland carry the dominance of this thrust phenom- 

 ena back to the earliest known ages. Taking the facts as we now know 

 them, there seems to be no observational support for the compressional- 

 tensional distribution which the hypothesis of great tidal retardation 

 involves. 



In the discussion thus far, agencies of compression and tension, other 

 than rotational, have largely been ignored for the sake of following out, 

 consecutively and uninterruptedly, the consequences of the hypothesis 

 of rotational reduction and comparing them with observed facts. It is 

 proper now to consider whether the intercurrence of other agencies of 

 deformation would mask the results of tidal retardation, if these were of 

 the order of magnitude implied by the fission theory of the origin of the 

 moon, or even the close approximation of the moon to the earth in its 

 early history under the planetesimal hypothesis. The existence of other 

 causes of crustal deformation is of course fully recognized. To bring these 

 under consideration in connection with the hypothetical tidal effects, it 

 is necessary to note first their qualitative relations and second their relative 

 values. y - 



