May 15. 18So. 



SCIENCE. 



401 



taking that as the dividend, if we can deter- 

 mine the annual rate at which the falls recede, 

 and take that for the divisor, our quotient will 

 represent the time that has elapsed since the 

 glacial period. The accompanying map gives 

 a more definite idea of that divisor than we 

 have ever before had. The lower clotted line 

 represents the margin of the horse-shoe fall 

 as mapped by the New- York geological sur- 

 vey in 1841, under the direction of Professor 

 James Hall. The upper line is that made 

 in 1875 for the U.S. geodetic survey. By 

 comparing the two, a pretty correct calculation 

 may be made as to the amount of recession 

 of the horseshoe fall in the interval of thirty- 

 four 3'ears. This cannot vary much from a 

 hundred feet upon the whole line, being, as 

 the commissioners calculate, two hundred and 

 seventy feet at certain points. 



Until this last survey, the attempts to esti- 

 mate the time required for the cataract to 

 recede from Queenston to its present position 

 have been based upon very insufficient data. 

 Mr. Bakewell, an eminent English geologist, 

 gave personal attention to the problem as early 

 as 1830, and, from eveiy thing he could learn 

 at that time, estimated that the falls had re- 

 ceded about a hundred and twenty feet in 

 the fort}' years preceding. He recurred to the 

 problem again in 1846, 1851, 1856 {American 

 journal of science, January, 1857, pp. 87, 

 93), and was each time confirmed in the belief 

 that the apex of the horseshoe fall was reced- 

 ing, on an average, three feet a year. On the 

 other hand, Sir Charles Lyell, upon his first 

 visit, in 1841, 'conceived' (upon what basis 

 he does not tell us), that, at the utmost, the 

 rate could not be more than one foot a year, 

 which would give us thirty-five thousand years 

 as the minimum time. But, as it appears, 

 the result of the recent survey is to confirm 

 the estimate of Mr. Bakewell, thus bringing the 

 period down to about seven thousand 3'ears. 



Two elements of uncertainty, however, tend- 

 ing to lengthen the estimate, should be noticed. 

 In the first place, the recession may have been 

 somewhat slower while the hard stratum, No. 

 3, was exposed. In the second place, the de- 

 posits of gravel running southward from St. 

 David's, and corresponding to the lake-ridges, 

 indicate that subsequent to the glacial period 

 this whole region was slightl}' submerged be- 

 neath a shallow body of water ; in which case, 

 the recession of the gorge would have begun 

 only upon the emergence of the land. And 

 we have no means of telling how long an inter- 

 val may have elapsed between the withdrawal 

 of the ice and the withdrawal of the water. 



On the other hand, it is probable that the 

 channel of the preglacial stream extended 

 somewhat above the whirlpool, thus reducing 

 amount of work done since glacial time. 



The above estimates are confirmed, also, by 

 the small amount of change that has taken 

 place in the species of animals during that 

 period. The mollusks found in the river above 

 the falls at the present time, are identical species 

 with the shells found in the deserted river- 

 channel at the top of the escarpment opposite 

 the whirlpool, while nearer the falls the bones 

 of the mastodon have been found in the same 

 deposits ; all which corresponds with a vast 

 amount of other evidence, going to show that 

 the present species are, in the main, identical 

 with those existing at the close of the glacial 

 period. The theory of evolution is relieved 

 from a heavy burden by supposing a recent 

 date for the close of the glacial epoch ; for 

 the changes since that epoch have been so 

 slight, that the time allowed by the plrrsicists 

 is insufficient for the whole development of 

 organic forms, unless the rate of change is 

 more rapid than must be the case if the glacial 

 period is thrown very far back. 



G. Frederick Wright. 



NIAGARA FALLS CONSIDERED AS A 

 SOURCE OF ELECTRICAL ENERGY. 



The first suggestion of the possible employ- 

 ment of Niagara Falls as a source of electrical 

 energy, and the distribution of this energy in 

 the shape of light and power, is due to C. W. 

 Siemens. It was a large suggestion ; and it 

 took root speedily in what may be termed 

 ' cosmical minds.' The waj', however, to its 

 fulfilment, has not been made plain to business 

 enterprise. The most noteworthy remarks 

 upon the subject were made by Sir William 

 Thomson in 1881, at the York meeting of the 

 British association. His remarks and calcula- 

 tions were in substance as follows : With the 

 idea of bringing the energy of Niagara Falls. 

 to Montreal, Boston, New York, and Philadel- 

 phia, a total electromotive force produced by 

 the d} T namo-machines at the falls was taken at 

 80,000 volts. This was between a good earth 

 connection at the falls, and one end of a solid 

 copper wire of half an inch in diameter, and 

 three hundred statute miles in length. The 

 resistance of the circuit was so arranged that 

 there should be an electromotive force of 

 64,000 volts at the remote end. between the 

 wire and the earth connection. The calcula- 

 tions showed that a current of 240 webers 



