Reviews and Notices of Boohs, 22 



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at the close of the Drift period, a vast fresh-water sea extended 

 over the greater portion of Western Canada, and at a level of at 

 least 500 feet above the present surface of Lake Ontario." 



Prof. Chapman does not enter into the question of the relative 

 age of the Drift deposits of Upper Canada, as compared with the 

 marine Pleistocene beds of Lower Canada described in this Jour- 

 nal by Mr. Billing?, Dr. Dawson, and Mr. Bell. Our present belief 

 is that the upper member describe 1 by Prof. Chapman must 

 correspond with the Saxicava sand and the lower member with 

 the Leda clay. Dr. Dawson has shown* that at Pakenham on the 

 Ottawa, and also toward Lake Champlain, the Saxicava sand, or 

 its equivalent, is rich in fresh-water shells, while it contains very 

 few that are marine, and these principally Tellina groenlandica. 

 Mr. Bell has in his late paper largely added to facts of this class. 

 On the other hand, such cases have not occurred in the eastern 

 part of Lower Canada. 'J'his points, as Mr. Bell infers, to a pas- 

 sage into estiiarine and fresh water conditions toward Upper Ca- 

 nada, and we need not be surprised that these actually occur 

 there. The Saxicava sand also, like the upper deposit in Upper 

 Canada, often contains Laurentian stones and boulders. With 

 respect to the equivalency of the Leda clay to the lower member 

 of Prof. Chapman's series, we may remark that the mineral 

 character of the two deposits corresponds. Further, the Leda 

 clay holds few boulders and except in its upper part very few 

 fossils. Indeed many parts of it are quite destitute of these, 

 especially where the upper layer has been removed by denudation 

 before the deposition of the sand or gravel. This may possibly 

 be its general condition in Upper Canada, 



Should these views prove correct, it will not be necessary to 

 suppose that the enormous lakes indicated by the fresh water 

 deposits of Upper Canada emptied themselves into the Mississippi ; 

 since the character of the Saxicava sand in its upper parts im- 

 plies the influx of much fresh water from the west. Still the 

 occurrence of marine shells in Lower Canada at heights of more 

 than 400 feet above the sea, points to entire submergence of the 

 country around Lake Ontario ; and it may well be that the an- 

 cient extension of the lake was only one of the phases of the pro- 

 cess of elevation in the period indicated by our Saxicava sand. 

 It still requires however the discovery of marine shells in the 



Canad. Nat. Vol. iv. p. 16, Vol. y, p. 194. 



