288 GEOLOGY. 



er level, though, as they were formed earlier than the 

 terraces, they extend down under them, and are there- 

 fore, geologically speaking, lower. They often form a 

 sort of upper terrace in the series, making a fringe along 

 the sides of the hills that shut in a valley. Though ir- 

 regular in form, they have a certain general level, if ob- 

 servation be made of one for any considerable length 

 along the hills that it skirts. They consist mostly of 

 sand and gravel, all the stones in them being rounded, 

 thus showing the influence of long-continued water fric- 

 tion. It is supposed that they are beaches left by the re- 

 tiring sea, as the submergence of the Champlain period 

 passed away. 



399. Niagara River. Great changes occurred in this 

 river during the Post-tertiary period. Just previous to 

 the beginning of this epoch the river ran in entirely a 

 different bed from what it now runs in from the whirl- 

 pool on to its outlet in Lake Ontario. The evidence is 

 this: The west bank of the gorge at the whirlpool 

 shows the beginning of a deep ravine filled with drift in 

 the form of gravel and sand, and this ravine can be 

 traced on to Lake Ontario. The inference is clear, there- 

 fore, that the water ran through this passage of four 

 miles to the lake until it was filled up with drift in the 

 Glacial period ; and this bed being filled up, the water 

 sought, and, to a great extent at least, made for itself, 

 by its erosive power, another passage, the one in which 

 it now runs. But this is not all. The water has effect- 

 ed in this passage, as I have before stated in 183, the 

 removal of the falls from the neighborhood of Queens- 

 town back seven miles to their present position. The 

 process by which this has been done has been explained 

 in 183 ; but the story of the changes which have been 

 effected in the Niagara River is not all told yet. The 

 still waters of a lake once lay over all the neighborhood 

 where the falls now are, for there are lake deposits there, 

 as shown by the fossils which the strata contain. The 



