24 THE CANADIAN NATURALIST. [Vol. vi. 



My interpretation of the phenomena would differ from that of 

 Dr. Newberry in the following particulars — (1) I would refer the 

 continental elevation and the deep erosion to the Pliocene period, 

 before the advent of the glacial epoch. (2) I would refer the 

 glaciated surfaces and the lower part of the Erie clay to the time 

 of the Canadian Boulder-clay, and would regard it as an evidence 

 of subsidence and an ice-laden sea, with the arctic current passing 

 over the continent from the North-East. (3) I would regard the 

 upper part of the Erie clay as equivalent to the Leda clay. (4) 

 I would place the upper and confessedly water-borne drift as the 

 equivalent of the Saxicava sand, and as belonging to the period 

 of elevation. 



It is a difficulty, both in Dr. Newberry's view and mine, that 

 marine shells are not found in the Erie clay and surface drift. 

 The following considerations, however, diminish this. (1) The 

 greater part of the Leda clay is very poor in fossils, even near the 

 ocean, and so is the boulder clay. (2) The submergence of a 

 vast continental area under cold water misrht have continued for 

 a long time before the marine animals could widely spread them- 

 selves over it, especially under the unfavourable circumstances of 

 ice erosion. (3) The few and scattered marine remains to be 

 expected in these deposits may have escaped observation. The 

 occurrence of much drift-wood in the Erie clay is also, in my 

 judgment, inconsistent with the occurrence of a general glacier 

 immediately previous to the deposition of the clay. 



We may now consider the several members of the Post-pliocene 

 in succession, bes-inninir with the oldest. 



GENERAL DESCRIPTION. 



1. TJie Boulder-Clwj, 



Throughout a great part of Canada there is a true " Till," 

 consisting of hard gray clay, filled with stones and thickly packed 

 with boulders. In some places, however, the clay becomes sandy, 

 and in some portions of the carboniferous areas, the paste is an in- 

 coherent sand. The mass is usually destitute of any stratification 

 or subordinate lamination ; but sometimes in thick beds horizon- 

 tal lines of different texture or colour can be perceived, and occa- 

 sionally the clay intervening between the stones becomes laminated, 

 or at least shows such a structure when disintegrated by frost. 

 The Boulder-clay usually rests directly on striated rock surfaces ; 



