328 On the Falls of Niagara. 



I hold it to be impossible, with tbe means of measurement hereto- 

 fore employed, to ascertain with any approach to precision, the amount 

 of retrograde movement. Does the recession of forty or fifty yards 

 asserted by Mr. Forsyth, apply to both falls, to the whole breadth of 

 the British 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 ap- 

 ply the above rate of recession amounting to four feet per annum, 

 to both falls, and to Goat island likewise, as Mr. Fairholrae does, is, 

 I conceive, 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 re- 

 ceding 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 ave- 

 rage width below ; as neither the American cataract nor Goat island 

 contribute to its breadth. In reply to Mr. Fairholrae's argument, I 

 wouldremark, that although in his appendix, he has, on better informa- 

 tion, 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 become 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 ahrupt slope 

 at Queenstown the land gently declines, but the bed of the river 

 seems to decline equally, falling in its course of seven miles one 

 hundred and four feet, and making the perpendicular banks maintain 

 throughout their whole length an average elevation of two hundred 

 feet. 



If Mr. Fairholme will reconstruct the section in the appendix to 

 his article, taking care to make it a faithful profile of the surface from 

 the falls down to Queenstown, giving it the proportions of a base of 

 seven miles to a height of about three hundred feet he will at once 



* I observe that Mr. Conybeare entertains the same doubts of the above rate of 

 movement of the whole falls. In the Philosophical Magazine for 1831, new se- 

 ries, Vol. 9, page 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. 



