No. 5.] SPENCER — SURFACE GEOLOGY. 207 



Ontario to the junction of the Ottawa river, though the lowest 

 portion of the river is conspicuously of ancient date, wMth pot- 

 holes indicating a depth of nearly 1200 feet. Without a con- 

 siderable change of level, such as either that which would be 

 produced by a local subsidence of north-eastern Ontario and the 

 upper St. Lawrence, or a very great northern subsidence during 

 a period of southern elevation, any possibilities of the preglacial 

 outlet of Ontario basin by the St. Lawrence seems impossible. 

 However, the oscillation hypothesis seems to be more and more 

 supported by observation. 



Possibilities of an outlet at the south-eastern end of the lake. 

 Between the eastern shores of Lake Ontario and the foot of the 

 Adirondacks, the broad plane appears to mark the former lake 

 bottom before the lake contracted to within the present limits. 



This remark holds good for the " Great J^evel '" between the 

 southern margin of the lake and the escarpment to the south, 

 although 150 feet above it. The level country south-east of the 

 lake is underlaid by almost horizontal Palaeozoic rocks, which 

 are exposed along many of the streams, and are covered generally 

 with no great thickness of drift. These rock exposures occur as 

 far south as a short distance north of Oneida lake. They are 

 also seen along the Oswego river, and the lower portion of the 

 Seneca. However, there is a deeply buried basin in the region 

 of Onondaga lake. Oneida lake is only 60 feet deep, and 12T 

 feet above lake Ontario, and is situated in a basin of drift. 



Onondaga lake is 119 feet above Lake Ontario, and is about 

 65 feet in the deepest sounding. It is a modern lake situated in 

 a great drift-jBlled basin. The shallower portion of this basin is 

 toward the northern end of the lake, it increases in depth on 

 approaching Syracuse, but again becomes somewhat shallower on 

 passing southward of this city. The drift-filled basin reaches to 

 a depth of about 290 feet below the surface of Lake Ontario. 

 Southward of Syracuse the country rises to the escarpment form- 

 ing the southern boundary of the Ontario valley. 



For many years, suggestions have been made that the Pre- 

 glacial outlet of Lake Ontario was by the buried basin just de- 

 .scribed, emptying its waters by the Mohawk and Hudson rivers 

 into the Atlantic. However, this suggested outlet is not pos- 

 sible, without considerrble local change of elevation, as shown 

 by Mr. Carll, for the Mohawk river passes over metamorphic 

 rocks at Little Falls, Herkimer County, at an elevation above 



