20 Ancient Drainage of JVorth America, SfC. 



whole of the shale has been, appears not unreasonable, and may 

 account for the absence of a great portion of the fragments. 

 There is scarce a single circumstance connected with this ma- 

 jestic cataract, which does not assist in the explanation of its 

 retrocession. 



As to the period which has elapsed since the waters first be- 

 gan to open the gorge, it is difficult to open a plausible ground 

 upon which a reasonable calculation could be made ; but there 

 is one circumstance connected with them, which marks a differ- 

 ence of progress, at certain points of their retrocession. The 

 distance from Queenstown to the falls, is between six and seven 

 miles by the line of the gorge, the average breadth of which on 

 approaching the falls, is about 1200 feet. By a reference to the 

 plan,* it will appear, that up to the period when the waters which 

 fall on the American side, first divided Goat Island from the 

 main land, the whole force of the river Niagara, was exerted in 

 one volume, upon a surface of 1200 feet in extent, forming the 

 width of the gorge. Since that time the operative power of 

 the water, has spread itself over a greater surface ; for the stream 

 on the American side, is 1072 feet wide, and the curvature of 

 the great Horse Shoe fall 2376 feet wide, making a surface of 

 3448 feet long, being near three times the extent of the line it 

 previously exerted itself upon. 



This diminished exertion would necessarily be attended by a 

 retardation in the retrocession of the cataract. There is also 

 another circumstance which at present adds to this cause of re- 

 tardation. The Horse Shoe fall has reached a point, where the 

 limestone beds begin to thicken, and the foam of the rapids,+ 

 marks the presence of the terraces of cherty layers, which are 

 here found superincumbent, and giving additional strength and 

 durability to the limestone strata. I might offer as evidence of 

 the very prolonged projection of the waters at this point, the 

 deep basin in the bed of the river, immediately at the foot of 

 the falls, which does not occur in the narrower parts of the gorge, 

 and which has been hitherto unaccounted for. 



It has often been proposed to mark in some well regulated 

 manner, the future disintegration of the bed of this cataract, 



» Vide plate 2d. 



t On the Brititih side where the current is most rapid, tlic bed of the river is 

 1 3 feet lower than on the American side. 



