32 L. y. Pirsson — Crustal Wm'ping in Ontario. 



Summanj. — The ideas expressed in tliis paper may be now 

 hriefly siiimnarized. Tliat in tliis region there was first initi- 

 ated l)y torsional warping- in pre-glacial times a system of joint- 

 ing, fractnring, and structnral lines of rock weakness, and 

 possibly foliation, which has controlled the drainages. That 

 later, or continuing, warping has caused the beginning of a 

 broad synclinal fold with the production of the larger lakes 

 and other modilieations of drainage ; that this has taken j)lace 

 or contimxed into post-glacial times and may still be in pro- 

 gress, and that this is a minor feature of the uprise of the great 

 Ontarian shield. It is not intended to assert that this idea or 

 all parts of it are necessarily correct, or proven ; only that the 

 facts, so far as published and known, appear to point in this 

 direction. For the object of this paper is not so much to state 

 an hypothesis as to direct attention and to start an inquiry. 



Sheffield Scientific Scliool of Yale University, 

 New Haven, Conn. 



short synopsis the view is advanced that the Montreal Eiver in post-glacial 

 times has been diverted from a former northward direction and made to 

 jlow southward by an uprise of the land which gives a southward tilt to its 

 present course. This is in the region north of that covered by the map 

 accompanying this article. While the writer has not heard this pajaer, this 

 view, as tlius stated, appears to favor the general idea expressed in this arti- 

 cle and the southward flow of the river down the northern flank of the warp 

 to be a local feature of the more general problem here presented. 



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