242 SEE— FURTHER RESEARCHES ON [April 24, 



the Highlands of Scotland the strata by lateral thrust were broken and 

 slidden one over another for ten miles. In the Canadian Rocky Mountains 

 there is an overthrust of seven miles, by which the Cambrian is made to 

 override the Cretaceous, and 50 miles of strata are mashed into 25 miles 

 (McConnell). In the Appalachians of Georgia the Rome fault is an over- 

 thrust which brings the Cambrian in contact with the Carboniferous and the 

 fault under different names may be traced northward for 275 miles; and in 

 the Cartersville thrust-fault there is an overriding of 11 miles (Hayes). The 

 manner in which this is done is illustrated on a previous page (Fig. 209). 

 Evidently, then, the whole height of the mountains mentioned above is due 

 to lateral crushing alone." 



If Professor Leconte had been familiar with the folding pro- 

 duced in the sea trenches he could have completed the theory of 

 mountain formation developed in this paper. As geologists have 

 for centuries recognized the fossils found in mountains as having 

 been deposited in the sea, it is remarkable that the suggestion seems 

 never to have occurred to them that the folding was done in the sea 

 before the land was lifted above the water, and by earthquake proc- 

 esses due to the sea itself. Leconte, however, came very near this 

 view, as the following will show (p. 267 et seq.) : 



"Mountains are made out of lines of thick sediments. — But the question 

 occurs, What determines the place of a mountain-range? The answer is, 

 A mountain-range while in preparation — before it became a range — was a 

 line of very thick sediments. This is a very important point in the theory 

 of mountain origin, and therefore must be proved. The strata of all moun- 

 tains, where it is possible to measure them, are found to be of enormous 

 thickness. The strata involved in the folded structure of the Appalachian, 

 according to Hall, are 40,000 feet thick, the strata exposed in the structure 

 of the Wahsatch, according to King, are more than 50,000 feet thick ; the 

 Cretaceous strata of the Coast Range, near the Bay of San Francisco, 

 according to Whitney, are 20,000 feet thick; and if we add to this 10,000 

 feet for the Eocene and Miocene strata, the whole thickness is probably not 

 less than 30,000 feet, while the Cretaceous alone in Northern California, 

 according to Diller, is 30,000 feet. The Alpine geologists estimate the 

 thickness of the strata involved in the intricate structure of the Alps as 

 50,000 feet. The strata of Uintah, according to Powell, are 32,000 feet 

 thick. 



" Now, it must not be imagined that these numbers merely represent 

 the general thickness of the stratified crust; only that in these places the 

 strata are turned up and their edges exposed by erosion, and thus their 

 thickness revealed. On the contrary, it may be shown that the same strata 

 arc much thinner elsewhere. The same strata which along the Appalachian 

 range arc 40,000 feet thick, when traced westward thin out to 4,000 feet at 

 the Mississippi River. The same strata which along the line of the Wah- 



