542 



THE A M ERIC A N NA TURA LIST [Vol. XLI 



recediiiff upstn-ain, that the gorge below the falls is the result of this 

 recession, and that it would be possible, by sufficiently accurate obser- 

 vations, to determine the rate of recession. He then discusses the data 

 upon which computations of the rate of recession must be based, con- 

 sisting of surveys of the crest-line of the falls made in 1842, 1875, 1886, 

 1890, and in 1905; and camera-lucida sketches made in 1827. After 

 considering the relative accuracy of the different surveys and sketches, 

 and platting the results together, the author concludes that a gradual 

 recession of the Horseshoe Falls is demonstrated, while a much slower 

 rate of recession is indicated for the American Falls. These changes 

 are strikingly represented by contrasted photographs and sketches 

 made from the same view-point, but many years apart. 



Conc(;rning quantitative results of the study, the author points out 

 that the available data may be treated in a variety of ways, and made 

 to yield widely di wrgcM.t' nvsults. The lack of' harmony is dii<^ in 



must Ik- taken into account in estimatiiiir su. li time. A >l,(.rt iv,..>i( 

 by \\. Carvel Hall on the latest survey ,.f llic civ^f lin<- ..f (he li.lU 

 appended to the paper. 



A sprinkling of "reformed" (one i> templed to >ay deronned ") 

 spelling throughout the paper occ asiounlly distraets the reader's 

 attention from the matter itself to the maiuu-r in which it is i)re.setited. 



I). VV, JOIIN.SON. 



