MOUNTAIN ORIGIN AND STRUCTURE. 259 



feet more of thickness was added, and the aggregate thickness became 

 40,000 feet. Of course, it is impossible that such thickness could ac- 

 cumulate on the same spot without pari passu subsidence of the sea- 

 floor. In fact, we have abundant evidence of comparatively shallow 

 water at every step of the process — evidence sometimes in the character 

 of the fossils, sometimes in the form of shore-marks of all kinds, some- 

 times in the form of seams of coal, showing even swamp-land condi- 

 tions. Again, of course, the sediments were thickest and coarsest near 

 the shore-line, and thinned out and became finer toward the open sea, 

 i. e., westward. Finally, after 40,000 feet of sediments had accumulated 

 along this line the earth-crust in this region gave way to the lateral 

 pressure, and the sediments were mashed together and folded and 

 swollen up into the Appalachian range. Subsequent erosion has 

 sculptured it into the forms of scenic beauty which we find there 

 to-day. 



2. Sierra. — This was apparently the first-lorn of the Cordilleran 

 family. Its history is as follows : During the whole Palaeozoic and 

 earlier part of the Mesozoic, there was in the Basin region a land-mass, 

 whose form and dimensions we yet imperfectly know, but whose Pacific 

 shore-line was east of the Sierra. The Sierra region was therefore at 

 that time the marginal bottom of the Pacific Ocean. Probably the 

 position of this shore-line changed considerably at the end of the 

 Palaeozoic. The extent of this change we will discuss hereafter. 

 Suffice it to say now that, during the whole of this time, the Sierra 

 region received sediments from this land-mass until an enormous 

 thickness (how much we do not know, because the foldings are too 

 complex to allow of estimate) was accumulated. At last, at the end of 

 the Jurassic, the sea-floor gave way to the increasing lateral pressure 

 along the line of thickest sediments, and these latter were crushed to- 

 gether with complex foldings and swollen up into the Sierra. An 

 almost inconceivable subsequent erosion has sculptured it into the 

 forms of beauty and grandeur which characterize its magnificent scenery. 



3. Coast Range. — The birth of the Sierra transferred the Pacific 

 shore-line westward, and the waves now washed against the western 

 foot of that range, or possibly even farther westward in the region of 

 the Sacramento and San Joaquin plains. At this time, therefore, the 

 region of the Coast Range was the marginal bottom of the Pacific Ocean. 

 During the whole Cretaceous, Eocene, and Miocene, this region re- 

 ceived abundant sediments from the now greatly enlarged continental 

 mass to the eastward ; until finally, at the end of the Miocene, when 

 30,000 feet of sediments had accumulated along this line, the sea-floor 

 yielded to the lateral pressure, and the Coast Range was born ; and the 

 coast-line transferred to near its present position. 



4. Wahsatch. — The physical geography of the region to the east of 



