S84 Mr Rogers on the Falls of' Niagara, 



Falls, to the whole breadth of the Brliish Fall, or only to that 

 portion of the latter which adjoins Table Rock ? To estimate it 

 where the loss of matter is greatest, in the hollow of the Great 

 Horse Shoe, can be done only by means of accurate triangulation, 

 which has not yet been attempted.* To apply the above rate 

 of recession, emanating to four feet per annum, to both Falls, 

 and to Goat Island likewise, as Mr Fairholme does, is, I con- 

 ceive, an extension of the same error. He imagined that the 

 whole irregular line across both Falls and Goat Island recedes 

 at this rate, though it is manifest that the American Fall is no 

 part of the receding cataract. It enters the gorge, laterally, 

 having been left by the other Fall at least a quarter of a mile in 

 the rear. The true width of the valley at the Falls is therefore 

 no greater than its average width below, as neither the Araeri- 

 eau cataract nor Goat Island contribute to its breadth. In re- 

 ply to Mr Fairholme's argument, I would remark, that although, 

 in his appendix, he has, on no better information, forsaken the 

 leading feature of his theory, the hypothesis that the ground 

 from the Falls to Queenstown is a regularly descending plane, 

 by which the section of the trough below the Falls would be- 

 come a triangle, he is still far from giving the ravine its proper 

 profile. The true form of the valley is this. From the Falls 

 to the abrupt slope at Queenstown, the land gently declines ; 

 but the bed of the river seems to decline equally, falling, in its 

 course of seven miles, 104 feet, and making the perpendicular 

 banks maintain, throughout their whole length, an average ele- 

 vation of 200 feet. 



If Mr Fairholme will reconstruct the section in the appendix 

 to his article, taking care to make it a faithful profile of the sur- 

 face from the Falls down to Queenstown, giving it the propor- 

 tions of the base of seven miles to a height of about 300 feet, 



• I obser^'e that Mr Conybeare entertains the same doubts of the above 

 rate of movement of the whole Falls. In the Philosophical Magazine for 

 1831, new series, vol. ix. p. 267, he says, " I must confess my doubts whether 

 the Falls actually do recede, as far as their general line is concerned, at the 

 rate of fifty yards in forty years. I suspect that some partial degradation of 

 the strata has here been mistaken for the general retrogradation." He farther 

 states as his opinion, that Goat Island has occupied, from the period of the 

 earliest account, exactly the same relative position with regard to the Falls 

 that it holds at the present moment. 



