116 Hair 3 Remarks on Niagara Falls 



surface rock to some extent, before the period of that form- 

 ation. 



I will now proceed to consider, first the objections to the 

 theory that this ravine was produced by the combined action 

 of the stream and the waves of the sea ; and next the argu- 

 ments in favor of the hypothesis that the river has excavated 

 its own channel, or by far the greater portion of it. 



Examples are not unfrequent where the closing up of an 

 outlet by drift, has caused the excavation of a new channel 

 through solid rock. Perhaps the best illustration of this fact 

 occurs in the passage of the Genesee river from the upper to 

 the lower valley, from Portage to Mount Morris. The river, 

 flowing from the south as far as Portage, is suddenly turned 

 around to the opposite direction, and then again turns to the 

 north, cutting its channel for about two miles through solid 

 rock, in some parts to the depth of three hundred and fifty 

 feet. At the end of this chasm it emerges into a more an- 

 cient valley, and at a point which would communicate with 

 the river at Portage, before its deflection, by less than half the 

 distance which it has required in its present course to reach 

 this place. Now had this short space been occupied by a 

 bluff of rock, we should easily have found an explanation of 

 the reasons why the river did not pursue a direct course. But 

 what are the facts ? This shorter space, intervening between 

 the two portions of the channel, is occupied by a deep deposit 

 of drift, rising higher than the surface of the rocks where the 

 river has found its channel. In the process of examination 

 and excavation for the Genesee valley canal it has been found 

 that this drift is of great depth, extending even below the 

 level of the present bed of the river. The question presents 

 itself, why did not the stream remove the gravel and sand, 

 and make itself a channel in the shortest direction, instead of 

 going twice as far through rocky strata ? Or if we advance 

 the argument that this channel was excavated in part by the 

 aid of the sea, why did not this undermining agency affect 

 this deposit of sand and gravel ? The truth is incontroverti- 

 ble that many streams have excavated their channels to great 

 depths in rocky strata, long after the ocean left the surface. 



