332 dii the Falls of Niagara. 



Niagara Itself, to perceive that all tliese interesting scenes are sur- 

 rounded by the evidences of extensive denudation. 



The numerous beautiful cascades which distinguish the first-named 

 scene, descend over a series of steps occupying a trough somewhat 

 similar to the one below Niagara, but much deeper and shorter. — 

 The total descent here is 300 feet, and the length of the ravine about 

 half a mile instead of seven. There is a striking analogy between 

 the structure of these falls upon the west Canada Creek, and that of 

 those upcn the Geness, e river, and there is this resemblance between 

 them both and those of Niagara, that they all consist of perfectly 

 horizontal strata. The Portage falls of the Genessee resemble the 

 falls of Niagara moreover in the great length of the ravine, that of 

 the Genessee being several miles long, and having also a depth in 

 many places of four or five hundred feet. 



Mr. Fairholme seems to consider our numerous falls and rapids as 

 the result of what he states to be a characteristic feature of this con- 

 tinent, the arrangement of the surface in several vast secondary 

 planes, principally composed as he conceives, of calcareous rocks in 

 horizontal stratification. This is a misapprehension, for it is well 

 known to all who have examined the physical features of the United 

 States that in the c reater number of our streams, particularly those 

 entering the Atlantic, the rapids are created by the passage of the 

 waters through mountain barriers and in nearly all cases over rocks 

 highly inclined. This is so, where the Potomac finds a pass through 

 the blue ridge, where the Delaware traverses the same mountain 

 in Pennsylvania, to form the lovely scenery of the water-gap, and 

 indeed in twenty other cases which might be cited. An arrange- 

 ment of our plains in successive plateaus is by no means frequent, 

 and neither Trenton falls nor those of the Genessee have resulted 

 from^any such structure of the surface. 



Mr. Fairholme has the following passage, " If this point be ad- 

 mitted, (the recession of the falls,) it is equally obvious that a con- 

 tinuation of the action must occasion a continuance of the effect and 

 that a time must consequently arrive, when the whole barrier between 

 the lakes must be intersected. This period is of course very re- 

 mote ; but is not the less certain and unavoidable, if the causes now 

 in force continue to exist. The consequences will be most extensive 

 and disastrous, more so indeed than any natural event vdthin the 

 range of history. The whole of the upper lakes of North America 

 which more resemble seas than inland collections of fresh water, will 



