50 THE TIDAL PROBLEM. 



much' less an elevated girdle accidented by cross-folds, or knots, or con- 

 torted protuberances; nor do I find evidences of the truncated remains of 

 these. Since the rotation-period of 15.63 hours, 40 miles of shortening 

 should have been added to all that preceded, and 15 miles of this should 

 have been added since the 19.77-hour period. Even if these were remote 

 in 5'ears, they should have served to perpetuate a phenomenon that in its 

 nature must have been dominant from the beginning, for it is difficult to 

 assign any other agency of deformation that should have overmastered 

 this, if it had this degree of efficiency. On the contrary, other agencies of 

 deformation should, according to an accepted generalization derived from 

 observation, have reenforced the deformation assigned to this cause, for 

 old lines of yielding usually determine new ones. 



As a matter of fact the depressions below sea level on the line of the 

 equator are fully as great as the amount normal to a great circle; about 

 three-fourths of the equatorial zone is submerged and one-fourth emergent. 

 The oceans crossed are normally deep; the mountains of the tract are 

 scarcely normal in height or massiveness, the Andes of Ecuador being the 

 only conspicuous range within the equatorial tract. The mountains which 

 cross the equatorial tract show no special signs of limitation to it, as they 

 should if they were essentially dependent on the agencies involved in the 

 retardational hypothesis. 



If we take into consideration the whole compressional belt from 35^* 

 north to 35° south, it is found to embrace but little more than the average 

 amount of land; indeed, the emergent surface within it is less, in proportion 

 to the submerged area, than in the region north of it, though it is more 

 than in the region south of it. 



If we turn to the tensional areas that should, under the hypothesis of 

 reduced rotation, lie between 35° north and south and the poles, the inspec- 

 tion is unembarrassed by any doubt about the effect of the stress upon 

 the density of the rock, for appreciable stretching can not be assigned to 

 rocks, except as it expresses itself by Assuring and equivalent modes, 

 which leave an appropriate record. It is to be observed here again that, 

 while the larger part of this tension was brought to bear in the early stages, 

 it was, according to the hypothesis, continuous throughout the whole 

 history. The results naturally assignable to this progressive tension would 

 be a persistent Assuring and gaping radial from the poles, somewhat as 

 implied by fig. 6. This must have run through all geological time, except as 

 counteracted by some other agency. The cooling of the earth, or its shrink- 

 age from internal molecular change or from any similar pervasive agency, 

 would antagonize this, and if equal to it might prevent the actual opening 

 of the fissures. But, to be consistent, this shrinkage must be applied gen- 

 erally and such appHcation would intensify the difiiculties in the equatorial 

 belt in proportion as it reheved those of the polar caps. Simply to counter- 

 act the 495 miles of stretching required by the hypothesis in the rotational 

 reduction from a period of 3.82 hours to the present, leaving out of con- 

 sideration its special distribution, would require about 78 miles of vertical 

 shrinkage in the polar regions and of 1,600 miles in the equatorial belt. 

 But there is a special difficulty of distribution. The stretching required by 



