286 J. W. Dawson on the Drift. 
temporaneous with, or immediately following, the supposed gla- 
cier period. In my former papers on the Post-pliocene of the St. 
Lawrence, I have shown that the change of climate involved is 
no greater than that which may have been due to the subsidence 
of land and change of course of the Arctic current, actually 
northeastern America, strong reasons against the existence of 
any such period of extreme glaciation, as supposed by many 
geologists; and that if we can otherwise explain the rock-stria- 
tion and polishing, and the formation of fiords and lake basins, 
the strong points With these theorists, we can dispense altogether 
with the portentous changes in physical geography involved in 
their views, and which are not necessary to explain any of the 
other phenomena, 
It is on these points, more especially, that the Report of the 
Geological Survey throws new light; though Sir William, with 
his usual caution, has not committed himself to theoretical con- 
clusions; and in one or two local eases he seems to favor the 
glacier theory. It has long been known to geologists, that m 
northeastern America, two main directions of striation of roe! 
surfaces occur, from northeast to southwest, and from northwest 
to southeast; and that locally the directions vary from these to 
north and south, and east and west. Various attempts have 
been made, but without much success, to account for these direc- 
tions of striation by the motion of glaciers; and while it is quite 
easy for any one prepossessed with this view to account in this 
way for the striation in a particular valley or part of a valley, 8° 
may exceptional facts occur as to throw doubt on the explana 
tion, except in the case of a few of the smaller and steeper 
mountain gorges, 
In the Report of the Survey of Canada, a valuable table of 
