222 Reviews and Notices of Booh. 



in addition to the localities mentioned in this paper — prove in- 

 contestibly the former expansion and union of our lakes, or, in 

 other words, the presence in this part of Western America, of a 

 widely extended fresh-water sea, covering an enormous area. A 

 curious circumstance, and one of great significance in its bearings 

 on this question, is the fact that all the inclined layers of modi- 

 fied Drift (to the east, at least, of Lake Superior) appear to slope 

 towards the west or south. A remarkable instance of this, 

 hitherto, it is believed, unnoticed, may be seen near the mouth 

 of the Niagara river, at Lewiston. At this spot, oblique layers 

 of modified Drift, in beds made up of coarse gravel and pebbles, 

 point nearly due south, and thus bear witness to the fact, that 

 the current, which occasioned the inclined stratification, must 

 have set directly up the gorge, or against the direction of the pre- 

 sent stream, 



" The assumption of an immense fresh-water lake of this char- 

 acter, gradually falling from a high level, necessarily involves the 

 additional assumption of an eastern barrier, extending at one 

 period between the lake-waters and the Atlantic. This view was 

 maintained by some of the earlier investigators of our geology, 

 and, notably, by Mr, Roy, in his much-discussed paper on the 

 terraces of Lake Ontario, communicated to the Geoloo-ical So- 

 ciety of London, in 1837.* The diflSculty of finding a satis- 

 factory location for a barrier of this kind, led Sir Charles Lyell, 

 however, to reject the idea of an original lake extension, and to 

 refer the formation of our terraces entirelv to the action of the 

 sea, during the slow uprise of the land at the commencement of 

 the present epoch. In this, he has been followed by all Geolo- 

 gists who have subsequently examined these terraces. The diffi- 

 culty may perhaps be surmounted, by assuming the earher and 

 greater elevation of that portion of the country lying to the east 

 of the gneissoid belt which connects our northern Laurentian dis- 

 trict with the Adirondack Mountains of New York. The subse- 

 quent depression of this region would open an eastern outlet to 

 the lake-waters, and gradually lower these to their present levels. 

 But whatever the explanation, the undoubted fact remains, that, 



* See likewise the paper already referred to, by Sanford Fleming, 

 C.E., on the physical characters of the Nottawasaga Valley. — Can. 

 Journ. First Series, Vol. i. Mr. Roy's paper, I believe, was never 

 printed. 



