138 Prof. J. D. Dana on some Results of 



solidified, and left in high ridges, but over the eastern the final 

 disturbances were local and slight. 



There were hence two parallel series, contemporaneous in 

 steps of progress, situated on opposite borders of the Great 

 Basin, a coast series and a mountain series, each having its 

 highest member toward the basin — the coast series the grandest 

 in its three parts and leaving evidences of the profoundest dis- 

 turbance and the greatest amount of metamorphism. The 

 Wahsatch range is nearly as high as the Sierra ; but probably 

 a fourth of its height is due to the final elevation of the Rocky- 

 Mountain region. 



The last bendings were more local than the preceding, be- 

 cause the crust had become stiffened by its plicated and solidified 

 and partly crystallized coatings, as well as by thickening beneath; 

 and, therefore, while the Tertiary movements were in progress 

 the part of the force not expended in producing them carried 

 forward an upward bend, or geanticlinal, of the vast Rocky- 

 Mountain region as a whole. For the same reason profound 

 breakings took place where bending was not possible, and 

 thereby immense floods of liquid rock were poured out over the 

 surface. (Most of the great mountains of the globe were lifted 

 about this time — that is, in the course of the Tertiary era™ and 

 many of the great volcanoes were made.) 



There were irregularities, or exceptional courses, in connexion 

 with this system of movements and their effects. But these 

 show only that in the same area the lateral pressure at work 

 was not alike either in amount or in direction in different lati- 

 tudes, nor was the resistance before it the same. 



The results correspond with the well-understood effects of 

 lateral pressure. Suppose a long beam, having an even texture, 

 except that a portion toward the middle (say a sixth of the 

 whole length) is stouter than the rest, to be subjected at its 

 extremities to direct pressure. The first yielding and fracture 

 would take place toward the stouter portion on either side. If 

 this break were mended by splicing and cementing until firmer 

 than before, the next region of yielding would be just outside of 

 the former. In brief, the fracturing would be in each case 

 near the stouter portion of the beam. Moreover the extent of 

 the yielding and fracture on each side would have some relation 

 to the amount of pressure against that side. Just so has it 

 been with the earth's crust under the action of lateral pressure. 

 The facts further illustrate the truth, before announced, that 

 the force from the ocean side had in some way the advantage, 

 and in fact was the greater. But the full difference is not in* 

 dicated by the difference in the results of disturbance, since the 

 shoving force on the side of greatest pressure would not be 



