NIAGARA FALLS AND VICINITY 43 



Tiver which followed the present course of the Grand river, 

 above Cayuga, past Seneca and Ancaster into the western end 

 of the Ontario valley. It is extremely doubtful that such a 

 -stream ever existed, certainly it is highly improbable that the 

 Dundas valley owes its existence to any stream which flowed 

 eastward or toward the old-land, for it is altogether too broad, 

 and continues too uniformly to permit its being regarded as the val- 

 ley of an obsequent stream. Moreover, its peculiar position at the 

 elbow of the escarpment is most suggestive of a consequent origin, 

 for we would expect the face of the cuesta to make a reentrant where 

 the master stream gathers its converging tributaries and flows out 

 through a great breach in the cuesta. 



The Dundas valley is 5 miles wide at Hamilton but rapidly de- 

 creases in width to 2 or 2\ miles at the top, where the limestone 

 forms decidedly sharp summit angles (Spencer). Its northern wall 

 has been traced westward for 6 miles to Copetown, and its southern 

 for 3^ miles to Ancaster. Beyond these points the valley is filled 

 with drift which has been much dissected by modern streams. The 

 axis of the gorge is about n 70 e, and the glacial scratches observed 

 on the rock surfaces at its summit, with few exceptions, make angles 

 of 30° or more with it (Spencer). 



At Hamilton the bedrock was found to be absent to a depth of 

 227 feet below the surface of Lake Ontario. The well from which 

 this record was obtained is about 1 mile distant from the southern 

 side of the Dundas valley, which is here 5 miles wide. The total 

 known depth of the canyon is, according to Spencer, 743 feet, but 

 he calculates that it reaches 1000 feet near the center. 1 Along the 

 northern shore of Lake Erie well records have shown the absence 

 of drift to a considerable depth. Thus, according to Spencer, at 

 Vienna, 100 miles due west of Buffalo, the drift is absent to a depth 

 of 200 feet below the surface of Lake Erie, while at Port Stanley, 

 20 miles farther west, it is absent to a depth of 150 feet below the 

 lake. At Detroit the drift is 130 feet deep. At St Marys on the 

 northwest and Tilsonburg on the southeast of a line connecting 



^Spencer. Pa. geol. sur. Q 4. p. 384-85. 



