200 FRAGMENTS OF SCIENCE. 



draining the sides as it passes them.* Hence the re- 

 markable discrepancy between the widths of the Niag- 

 ara above and below the Horseshoe. All along its 

 course, from Lewiston Heights to its present position, 

 the form of the fall was probably that of a horseshoe; 

 for this is merely the expression of the greater depth, 

 and consequently greater excavating power, of the 

 centre of the river. The gorge, moreover, varies in 

 width, as the depth of the centre of the ancient river 

 varied, being narrowest where that depth was greatest. 

 The vast comparative erosive energy of the Horse- 

 shoe Fall comes strikingly into view when it and the 

 American Fall are compared together. The American 

 branch of the river is cut at a right angle by the gorge 

 of the Niagara. Here the Horseshoe Fall was the real 

 excavator. It cut the rock, and formed the precipice, 

 over which the American Fall tumbles. But since its 

 formation, the erosive action of the American Fall has 

 been almost nil, while the Horseshoe has cut its way 

 for 500 yards across the end of Goat Island, and is now 

 doubling back to excavate its channel parallel to the 

 length of the island. This point, which impressed me 

 forcibly, has not, I have just learned, escaped the acute 

 observation of Professor Eamsay.f The river bends; 

 the Horseshoe immediately accommodates itself to the 

 bending, and will follow implicitly the direction of 

 the deepest water in the upper stream. The flexures 



* In the discourse the excavation of the centre and drainage 

 of the sides action was illustrated by a model devised by my as- 

 sistant, Mr. John Cottrell. 



f His words are : ' Where the body of water is small in the 

 American Fall, the edge has only receded a few yards (where 

 most eroded) during the time that the Canadian Fall has receded 

 from the north corner of Goat Island to the innermost curve of 

 the Horseshoe Fall.' Quarterly Journal of Geological Society, 

 May, 1859. 



