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PKOCEEDINGS OF THE GEOLOGICAL SOCIETY. [June 19, 



would be destroyed, the large "blocks would bcome imbedded in true 

 marine sands, with shells of mollusks now inhabiting our western 

 shores, either entire or in broken pieces, bones of cetaceans, fishes, 

 and remains of plants occurring between. 



The land rising again, the drainage- channels cut through the 

 marine deposits, would offer sections of a very curious structure ; 

 and there is no doubt that in many instances the conclusion arrived 

 at would be, that these extensive beds were of glacial origin, de- 

 posited by icebergs, and that the fossil flora and fauna imbedded in 

 them belonged to a much colder climate than that which existed in 

 reality when these beds were deposited. 



It struck me at the same time that many beds in the northern 

 hemisphere which are called glacial, are probably similar beds re- 

 arranged ; and that many apparent difficulties will disappear if such 

 a process is taken into consideration. Furthermore may we not 

 assume that at least some of these beds in older formations, in 

 which similar rounded and sharp-edged blocks are associated toge- 

 ther, have a similar origin ? 



In any case the formation of these recent marine beds from the 

 destruction of Postpliocene accumulations is highly suggestive to 

 the physical geologist; and deductions drawn from such observa- 

 tions may claim some consideration at the hands of those who are 

 attempting to account for the various characteristic features of the 

 glacial beds in the northern hemisphere. 



If we examine the structure of the large moraines under consi- 

 deration, and the lithological character of the rocks imbedded in the 

 debris, some important facts are revealed to us, to which I beg to 

 draw your special attention. 



In my short explanation of the structure of the Southern Alps, I 

 have pointed out that their very summit consists of dioritic sand- 

 stones, cherts, &c., and that towards the west they are imme- 

 diately underlain by the newer gneissic schists, below which follow 

 mica-schists &c., until the gneiss -granites which form the base of 

 the Southern Alps are reached. 



This peculiarly regular succession of the strata according to age 

 and metamorphic change, from east to west, assists us, when we 

 examine the debris of which the huge Postpliocene moraines con- 

 sist, to obtain a clear conception of the extent, breadth, and other 

 conditions of the huge glaciers to which they owe their existence. 

 Thus we observe, as there is no debris of truly metamorphic rocks 

 amongst the component parts of these enormous deposits, but only 

 cliorite-sandstones, felstones, true clay-slates, and other similar rocks 

 which form the summit of the central Alps of the present day, that 

 the height of land was the same in the glacial epoch as it is now. 

 In fact, the present huge glaciers on the eastern slopes of the central 

 chain are covered with debris of the same lithological character as 

 that of which the Postpliocene moraines along the west coast are 

 composed. The total absence of true mica- and chlorite-schists, 

 gneiss, and gneissic granite, which form the western foot of the 

 ranges under consideration, as well as of the granite and sericite- 



