94 MAN AND THE GLACIAL PERIOD. 



In the central part of New York the remarkable se- 

 ries of " Finger Lakes," tributary to Lake Ontario and 

 emptying into it through the Oswego and Genesee Rivers, 

 all have a glacial origin. Probably, however, they are not 

 due in any great degree to glacial erosion, but they seem 

 to occupy north- and-south valleys which had been largely 

 formed by streams running towards the St. Lawrence 

 when there was, by some means (probably through the 

 Mohawk River), a much deeper outlet than now exists, 

 but which has been filled up and obliterated by glacial 

 debris. The ice-movement naturally centred itself more 

 or less in these north-and-south valleys, and hence some- 

 what enlarged them, but probably did not deepen them. 

 The ice, however, did prevent them from becoming filled 

 with sediment, and on its final retreat gave place to 

 water. 



Between these lakes and Lake Ontario, also, and ex- 

 tending east and west nearly all the way from Syracuse to 

 Rochester, there is a remarkable series of hills, from one 

 hundred to two or three hundred feet in height, composed 

 of glacial debris. But while the range extends east and 

 west, the axis of the individual hills lies nearly north and 

 south. These are probably remnants of a morainic ac- 

 cumulation which were made during a pause in the first 

 advance of the ice, and were finally sculptured into their 

 present shape by the onward movement of the ice. These 

 are really " drumlins," similar to those already described 

 in northeastern Massachusetts and southeastern New 

 Hampshire. In the valley of central New York these 

 have determined the lines of drainage of the " Finger 

 Lakes," and formed dams across the natural outlets of 

 nearly all of them. 



North of the State of New York the innumerable 

 lakes in Canada are all of glacial origin, being mostly due 

 to depressions of the nature of kettle-holes, or to the dam- 

 ming up of old outlets by glacial deposits. A pretty well- 



