i8o Transactions of the Canadian Institute. [Vol. VII. 



there are many exposures in the valleys of creeks and rivers, and in a 

 few places along the shore. It is thus known that there is no extensive 

 discordant deepening for forty miles east of Burlington Heights. The 

 lowest part of this section, with reference to the present lake level, is 

 situated on Lorraine shales and sandstones. The surface is lightly 

 rolling, but the average elevation toward the escarpment is about one 

 foot per mile. At right angles to the lake shore it varies to about 

 fifteen feet per mile. 



Between the Rouge and Whitb}- (thirteen miles), there is no known 

 rock exposure. At Whitby and near Bowmanville the Utica shales 

 come to the surface; between these two points there is possibly a valley 

 twelve miles in breadth, but probably of no great depth. For twenty 

 miles east of Bowmanville, to Gull Island (three miles east of Port 

 Hope) the rock, Trenton limestone, is again concealed. From Gull 

 Island to Presqu' Isle (twenty miles), there are a number of exposures 

 of Trenton limestone. East of Presqu' Isle the rock is continuous to 

 below Kingston. 



Between the Rouge and Presqu' Isle the upper edge of the lowest 

 till sheet seldom sinks below the water line. Were there any very deep 

 or canon-like depression of the rock surface the till might reasonably be 

 expected to give some indication of the existence of such depression, 

 for in every case within the area, where such depressions are known to 

 occur, the till sheets above would give ample evidence by their accord- 

 ant depressions. 



Along the Georgian Bay unsubmerged portions of the old valleys 

 are in some cases over i,ooo feet below the escarpment, and are graded 

 with reference to a level still lower. So far as is at present known 

 there is no evidence of discordant deepening due to the movement of 

 the ice along the front of the escarpment in a direction different from 

 that of the general movement ; if such deepening has taken place it is 

 not located on the soft Medina strata, but on the Lorraine, which are 

 known to form escarpments, or upon the Trenton. In no case, so far as 

 the writer is aware, has drift from a higher geological horizon been 

 found overlying a lower horizon, well out on the lowland, a result 

 which must obtain if there has been significant lateral motion of the ice 

 from the Georgian Bay region. 



Sinnniary. — The work of the ice sheet in Central Ontario seems to 

 have been that of smoothing off pinnacles, small spurs, and other out- 

 lying features of the limestone areas. Only the larger of these topo- 

 graphic forms were able to resist the ice, and these, more or less 



