igoS.J 



THE PHYSICS OF THE EARTH. 



241 



(for in neither case would the arch support itself), but by .mashing together 

 and in thickening and crumpling of the strata and an upswelling of the whole 

 mass along the line of greatest yielding. That this is the immediate or 

 proximate cause of the origin or elevation of mountains is plainly shown by 

 their structure. As to the ultimate cause — /. c., the cause of the enormous, 

 lateral pressure— this lies still in the field of discussion. We shall discuss 

 it briefly in its proper place" (pp. 261-2). 



Again, on page 264, we find this account : 



"Proof of Elevation by Lateral Pressure alone: i. Folding. — It is evi- 

 dent that foldings such as those represented in all the above figures, and 

 which occur in nearly all mountains, cannot be produced except by lateral 

 pressure, and are therefore proof of such pressure. But, moreover, it can 

 be shown that, when we take into consideration the immense thickness of 

 mountain strata and the degree of folding, lateral pressure is sufficient to 

 account for the whole elevation, without calling in the aid of any upward 

 pushing from beneath. For example, the Coast range of California (Fig. 

 228) is composed of at least five anticlines and corresponding synclines. If 



Fig. 14. Section of a Portion of the Alps. 



its folded strata were spread out horizontally in the position of the original 

 sediments, they would undoubtedly cover double the space. Now, supposing 

 the strata here are only 10,000 feet thick — a very moderate estimate — in 

 mashing to one half the extent, they would be thickened to 20,000 feet, 

 which would be a clear elevation of 10,000 feet if they were not subsequently 

 eroded. According to Renevier, a section of the Alps reveals seven anticlines 

 and corresponding synclines, and some of them are complete overfolds (Fig. 

 230). We are safe in saying that Alpine strata have been mashed horizontally 

 into one half their original extent. Supposing these were originally 30,000 

 feet thick (they were really much thicker), this would make a clear eleva- 

 tion of 30,000 feet. Of course, most of this has been cut away by erosion. 

 In the Appalachian range, according to Claypole, the foldings are so extreme 

 that in one place 95 miles of original extent have been mashed into 16 miles, 

 or six into one, and yet the Appalachian strata are estimated as 40,000 feet 

 thick. Cases of still greater doubling of strata upon themselves occur. In 



