120 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [DeC. 6, 



glaciers choking their mouths. But, as I know of no evidence that 

 such glaciers ever existed, I must look elsewhere for an explanation ; 

 and that which occurs to me is, that such deposits would be best 

 preserved in valleys occupied by still water. In a rough sea of 

 which the level was gradually falling, the waves would under- 

 mine and wash away such loose deposits, and spread them over the 

 base of the valley, in a less regular form. If this view be correct, it 

 will agree with the fact that the sheltered inner valleys of the Alps 

 have terraces up to very high elevations ; while the outer valleys, 

 into which the seas on the north and south of the chain must have 

 beaten with violence, have terraces only in their lower and more 

 sheltered portions ; and that some valleys on the south of the Alps, 

 of which the east and west direction would be a cause of shelter, are 

 also studded with terraces, as the Valtelline, Val Insernone, Val 

 Isone, Val Misocco, &c. 



Whether this explanation be accepted or not, I still think the 

 uniformity of level observed in valleys on the opposite sides of the 

 mountains must outweigh all other considerations, in favour of the 

 conclusion that such terraces were formed in the same sea. 



Another difficulty will doubtless be found in our not having dis- 

 covered any organic remains in the terraces of alluvium. But this 

 meets us equally if we suppose the terraces to have been formed in 

 lakes. The almost entire absence of organic remains in the drift- 

 deposits of Europe is a most remarkable fact, which has not yet re- 

 ceived a plausible explanation ; it is so general, that we must look for a 

 wide- spread cause, and, until that is discovered, the fact itself must 

 not be allowed to weigh against conclusions which can be safely 

 derived from evidence of another nature*. 



* After this memoir was read to the Society I received the following note from 

 Mr. James Smith, of Jordan Hill, which leads me to hope that marine shells may 

 be found in the alluvial deposits of Switzerland : — 



Athenaeum, Dec. 14, 1855. 

 My Dear Sir, — A summer's examination of the superficial beds of gravel in 

 Switzerland led me to the conclusion that some of them must have been deposited 

 under the sea, for the following reasons : — 



1. They are stratified and exhibit no appearance of disturbances, hence the 

 configuration of the country must have been the same as at present. 



2, They are at an elevation which does not admit the supposition that they are 

 lacustrine. 



I did not discover marine remains in situ, but the following indications of the 

 existence of pleistocene shells may perhaps lead to their discovery and set an 

 important question at rest. 



In the Museum at Geneva I found in a drawer marked '* Swiss fossils " Mya 

 Udevallensis, a most characteristic and abundant species in the Clyde beds. 



In the Museum at Berne I observed several shells with the locality " Court" 

 attached to them : they had all the appearance of pleistocene shells ; I inquired for 

 the curator of the Museum, but as it was during the vacation of the University he 

 was absent. It is ten years since, and at this distance of time I do not recollect 

 whether I could identify any of the species. 



Yours truly, 



James Smith. 

 Daniel Sharpe, Esq. 



