290 THE CANADIAN NATURALIST. [Vol. X. 



by sub aerial agencies, which removed the upper surfaces of the 

 narrow spur of rocks separating this glen and Glen Webster from 

 the canon of the Dundas valley. 



It seems impossible that in the region of the lakes any great 

 moving glacier did exist, which measured from a depth of what is 

 now 500 feet below the sea to a height sufficiently great to push 

 forward the debris from that depth to an elevation of from 1000 

 to 2000 feet or more over the highlands of New York, Pennsyl- 

 vania and Ohio. The configuration of the region would not 

 ftivor such a condition of ice — for the mountains of Labrador, 

 of Quebec, and of New England, assisted by those of New York 

 and Pennsylvania, together with the highlands of Ohio, would 

 have necessarily cut off the moisture and prevented the precipi- 

 tation on the interior of the continent, as we to day see in Hall's 

 basin and the Polar sea in the far north. 



Origin of Boulder Clay. — Boulder clay may be produced 

 by floating ice as well as by glaciers. Prof. H. Y. Hind 

 has observed its formation at the present time on the coast of 

 Labrador, by the action of pan ice. In Arctic regions the con- 

 tortion of submarine mud by the jamming of stranding masses 

 of the thick ice of the polar seas, has been observed to produce 

 such effects as are often attributed to glaciers, and could quite as 

 easily by pushing along the softened mud produce the so-called 

 ground moraine, as a glacier. 



Thickness of. Drift. — Throughout the Province of Ontario, the 

 average thickness of the Post Pliocene deposits is less than 50 

 feet, excepting in buried channels and along certain ridges. As 

 exhibited in many sections exposed to the bed rock and in many 

 bore holes, it seems that the drift is nearly everywhere stratified, 

 and the unstratified drift is the exception outside of buried 

 channels. 



Glacicd Lake {Hypothetical). — According to the glacial the- 

 ory, after the recession of the glacier-ice which scooped out and 

 filled the great lake basins, and moved over the hills (from 1500 

 to 2500 feet above their deepest beds) to the south, there was 

 produced a great glacial lake by the closing of the outlets with 

 ice, and in this lake the stratified drift was deposited. We have 

 already shown that the lakes are not of glacier origin. If it had 

 been possible for the ice to have been pushed up and over the 

 great elevations referred to, yet it seems highly improbable, that 

 a remnant of floating ice could have dammed up not only the 



