252 FRAGMENTS OF SCIENCE. 



sides as it passes them. 1 Hence the remarkable dis- 

 crepancy between the widths of the Niagara above and 

 below the Horseshoe. All along its course, from Lewis- 

 ton 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. 2 The river 

 bends ; the Horseshoe immediately accommodates it- 

 self to the bending, and will follow implicitly the direc- 

 tion of the deepest water in the upper stream. The 



1 In the discourse the excavation of the centre and drainage of 

 the sides action was illustrated by a model devised by my assistant, 

 Mr. John Cottrell. 



2 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. 



