128 



The Falls of Niagara^ 



cess, being constantly in operation, the Falls have, crab-like, 

 travelled to their present situation. 



A cursory glance at what is now taking place at the Falls, 

 leaves not a doubt that the great cause of the comparatively 

 quick retrograde movement of the Falls is, the loose and soft 

 material on which the limestone rock rests, and the destruc- 

 tive action of the water upon it. The water, also, penetrating 

 the crevices between the strata of solid limestone, detaches 

 them from each other, and disposes them to fall. At present, 

 the limestone rock projects considerably over the shale at the 

 Falls, and it is this projection which makes it practicable to 

 pass between the water and the rock, nearly half way under 

 the Horse-shoe Fall. 



A few months before I was at Niagara, a very extensive 

 portion of rock, as before mentioned, fell down at the Horse- 



