OF THF 



X 



SITY 1 



UNIVERSITY 



i ir 



ON BIOLOGY. 39 



from one to three feet per annum. The process of reces- 

 sion has been carefully observed, and the reason why it 

 maintains its perpendicularity is very clear. The sur- 

 face rock of Erie plateau is a firm limestone. Beneath 

 this is a softer shale. This softer rock is rapidly eroded 

 by the force of the falling water, and leaves the harder 

 limestone, projecting as tablerocks. From time to time 

 these projecting tables are loosened and fall into the 

 chasm below." Taking into consideration the configura- 

 tion of the country; the nature of the strata and their 

 contents of the walls of the gorge; the carefully observed 

 progress of erosion, which has been noted for many 

 years by competent persons; it soon becomes evident to 

 any intelligent observer that, in the first place, the falls 

 of Niagara were originally situated at Queenstown, and 

 that during the present geologic epoch they have cut 

 their way back seven miles to their present position, and 

 that this erosion is advancing at a rate of about one foot 

 per annum. 



With the length and height of the gorge, and with the 

 rate of the recession of the falls each year, by the sim- 

 plest arithmetic we can easily get at the result we have 

 already mentioned. In the history of the formation of 

 the world, however, 36,000 years is an exceedingly small 

 matter, really but a moment as compared with a cen- 

 tury when we consider it in connection with the ab- 

 solutely inconceivable lapses of time recorded 

 in the older geologic eras. How insignificant, for 

 instance, as compared with those typical and vast 

 erosions as seen in the Grand Canon of 

 the Colorado and other canons of the same 

 enormous system. The plateau in which' that great 

 erosion occurs is elevated some seven or eight thousand 

 feet above the sea; and, in case of the Grand Canon of the 

 Colorado, the eroding stream it contains has cut its way 

 down through the earth for a distance of from three to 

 nearly seven thousand feet in some places. It has a 

 length of 300 miles. Its lateral walls clearly exhibit 

 nearly the entire geological series from the tertiary age 

 downward, and it shows the strata of the eroded plateau 

 to be very nearly horizontally deposed. There is not a 

 shadow of a doubt as to how that great abyss was sculpt, 

 for the same agencies are still in operation at the present 

 moment and the enormous eroding power can be seen as 

 the work goes on. If the comparatively short and shal- 

 low gorge of the Niagara River took 36,000 years to be 

 carved back to its present site, I beg to leave it to your 



