lii PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



marine shells *. To explain the origin of such a succession of pebbly- 

 strata, we are naturally referred, by Studer, Escher, Sir K . jMurchison, 

 and others, to a long-continued depression along the whole external 

 northern face of the Alps. Numerous torrents are supposed to have 

 issued from the islands which then occupied the site of the loftiest 

 portions of the chain, and the continuity of the strata is explained by 

 imagining them to have accumulated on a shelying shore like that 

 of the present maritime Alps. At first the materials must have 

 been arranged in beds which sloped away from their parent rocks of 

 the Alps ; yet after sinking successively to enormous depths, they 

 have been brought up again, so as to dip towards the older rocks, 

 as if they passed under them. 



The first part of this grand subsidence of the sea-bottom was doubt- 

 less analogous to that now in progress on part of the coast of Green- 

 land. But if the adjoining land participated in the same downward 

 movement, it is difficult to conceive how it escaped being submerged, 

 or how it could continue to retain its size and altitude so as to continue 

 to be the source of such an inexhaustible supply of pebbles. We can 

 scarcely avoid speculatmg on a contemporaneous slow upheaval of the 

 mountains. There may have been an ascending movement in one re- 

 gion, and a descending one in a contiguous parallel zone of country, 

 as the northern part of Scandinavia is now rising while the southern 

 portion in Scania is sinking, or at least has sunk within the historical 

 period. Perhaps the not uncommon occurrence, of deep sea in the 

 immediate vicinity of bold coasts and mountain-chains, may be con- 

 nected with extensive lines of fault, parallel to the shores, on the op- 

 posite sides of which, vertical movements may be taking place in con- 

 trary directions, or one side may be motionless, while the other is 

 subsiding. In no other way does it seem possible to account for the 

 proximity, throughout a long series of ages, of high land, and of a 

 sea-bottom always going down so gradually as to remain for a long 

 time the receptacle of annual tributes of rolled pebbles, and acquiring 

 in the end a thickness of -5000 and 8000 feet. In regard to faults 

 which have shifted rocks several thousand feet in a vertical direction, 

 it is often too hastily assumed that they must have been produced 

 suddenly ; whereas the reverse is indicated by the fact that the walls 

 of such faults are rubbed, pohshed and striated, as if they had been 

 * Murchison, ibid. p. 229. 



