274 THE CANADIAN NATURALIST. [Vol. X. 



off rough surfaces. I have frequently seen, myself, in northern 

 regions, high boulders transported by the ice to which they were 

 trozen in the margin of small lakes. 



From what has been written, it seems to the writer that the 

 glacial ctrigin of Lake Ontario does not rest on a single basis 

 further than that ice scratchings (producible by either glaciers 

 or icebergs, neither of which need be great erosive agents) are 

 fseen at various places about Lake Ontario, both above and below 

 the water level. The remarks applied to Lake Ontario hold 

 good for the other lakes. The description of their topography 

 strengtheus the proofs that their origin cannot be accounted for 

 by glaciers, because we find the islands at the western end of 

 Lake Erie, or northern end of Lake HuroD, polished and stri- 

 ated. 



One thing is certain, the valley of Lake Ontario is one of erosion 

 — not of glacier-erosion — in operation, during much of the time 

 that has elapsed since, at least, the close of the Palaeozoic times, 

 olosed partly by drift, but also apparently by great geological up- 

 lifts, either along the Mowhawk-Hudson valley, or else the 

 inconspicuous broad valley of the upper portion of the St. Law- 

 rence river, formed a continuation of the Ontario plane, which 

 in its north-eastern urea became elevated, and now constitutes 

 the shallow floor of the lake and the adjacent low uplands. 



Age of Niagara Rivtr. — That the Niagara river is Post-glacial, 

 at least from the Whirlpool to Queenston, is apparent. It is 

 known that the Niagara river formerly left its present course 

 near the Whirlpool and flowed down the valley of St. David, 

 which is now filled with drift. This valley (through the lime- 

 stone escarpment) is not so great as the present canon. This 

 buried valley of St. David could only have been produced after 

 the closing of the Dundas valley outlet of the Erie basin, for 

 until then the waters flowed at a very much lower level. There- 

 ibre, it seems necessary to regard this channel (not of very great 

 magnitude) as an inter-glacial outlet for Lake Erie. 



The geologists of the Western States point to the Forrest bed 

 as a period of high elevation, preceded by the Erie clay (strati- 

 fied) and succeeded by the yellow stratified clays or loam, cor- 

 responding to the Brown Saugeen clay of Canada, which is 

 unconformable to the underlying Erie clays (or Boulder clays in 

 the upper portion of the Dunday valley). So, for the present, 

 we look upon the old course of the Niagara river as the channel 

 excavated during this warm interglacial period. 



