THK PLEISTOCENE. 7 



Lower and Upper boulder drift, and corresponding to tlic inter-glacial 

 beds of the interior of America. 



Tlie general conditions of the period are thus summarized in a 

 recent paper : — * 



" In this district and the eastern part of North America generally, 

 it is, I think, universally admitted that the later Pliocene period was 

 one of continental elevation, and probably of temperate climate. The 

 evidence of this is too well known to require re-statement here. It is 

 also evident, from the raised beaches holding marine shells, extending 

 to elevations of 600 feet, and from boulder drift reaching to a far 

 greater height, that extensive submergence occurred in the middle 

 and later Pleistocene. This was the age of the marine Leda clays 

 and Saxicava sands found at heights of 600 feet above the sea in the 

 St Lawrence valley nearly as far west as Lake Ontario. 



" It is reasonable to conclude that the till or boulder clay under the 

 Leda clay belongs to the intervening period of probably gradual sub- 

 sidence, accompanied with a severe climate and with snow and glaciers 

 on all the higher grounds, sending glaciated stones into the sea. This 

 deduction agrees with the marine shells, bryozoa, and cirripedes found 

 in the boulder deposits on the lower St Lawrence, with the unoxidized 

 character of the mass, which proves subaquatic deposition, witli the 

 fact that it contains soft boulders, which would have crumbled if ex- 

 posed to the air, with its limitation to the lower levels and absence on 

 the hill-sides, and with the prevalent direction of striation and boulder 

 drift from the north-east.j 



" All these indications coincide with the conditions of the modern 

 boulder drift on the lower St Lawi-ence and in the Arctic regions, 

 where the great belts and ridges of boulders accumulated by the 

 coast ice would, if the coast were sinking, climb upward and be filled 

 in with mud, forming a continuous sheet of boulder deposit similar to 

 that which has accumulated and is accumulating on the shores of 

 Smith's Sound and elsewhere in the Arctic, and which, like the 

 older boulder clay, is known to contain both marine shells and di'ift- 

 wood.J 



" The conditions of the deposit of till diminished in intensity as the 

 subsidence continued. The gathering ground of local glaciers was 

 lessened, the ice was no longer limited to narrow sounds, but had a 

 wider scope as well as a freer drift to the southward, and the climate 



* The Pleistocene Flora of Canada, Bulletin of Geol. Society of America, 1889. 



f Notes on the Post-Pliocene: Canadian Naturalist, op. cit. ; also Pajier hy the 

 autlior on i'ouldcr Drift at Metis, Canadian Record of Science, vol. ii., 188<i, p. 3G, 

 et seq. 



X For references see Koyal Society's Arctic Manual, Loudon, 1875, op. cit. 



