PROCEEDINGS OF THE CANADIAN INSTITUTE. iQl 



Niagara as a Timepiece. By Dr. J. W. Spencer. 



(Read January 22, iSgS.) 



Although probably a thousand papers have been written upon Niagara, com- 

 mencing with the discoveries of La Salle and Hennepin, it is still less than twenty 

 years since the physical history of the river began to be understood. La Salle and 

 Hennepin visited Niagara, accompanied by an Indian chief; in 1678. Although they 

 were the first white men who saw Niagara, its existence was made known by Indians 

 to Jacques Cartier when he visited Montreal in 1535. Hennepin's rough sketch of 

 Niagara appears to have been the only one made for a long time. The oldest 

 drawing approaching accuracy, known to the writer, was one made by Lieut. Pierie 

 in 1768. 



In spite of the prejudices then existing against the anticiuity of the earth, Andrew 

 Ellicott, the surveyor and engineer, more than a hundred years ago, recognized 

 that the gorge had been excavated by the river, and concluded that its age was about 

 55,000 years. Subsequent estimates were made, but that of Sir Charles Lyell became 

 the most popular. Upon his conjecture that the Falls receded a foot a year, he 

 estimated their age at about 35,000 years. Prof. James Hall made the first instru- 

 mental survey of the cataract in 1842, from which comparisons of the amount of 

 recession can now be made. In 1890 the fourth survey was made, and the mean 

 annual recession was found to be about four feet. This factor would reduce the 

 age of the Falls to between 9,000 and 10,000 years, had it been a case of simple, 

 uninterrupted recession. But as the volume of water and the descent of the river 

 have varied so as to increase the time required, the estimate made by Lyell was 

 nearer the true one. Subsequent to the classic writings of Lyell and Hall, of more 

 than fifty years ago, one of the first papers which reopened the study of the physics 

 of the river was written by the writer, in 1881, showing that the Erie basin was not 

 drained by the Niagara river in pre-glacial times. This was confirmed by Dr. 

 Julius Pohlmaes, who, two years later, discovered certain fragments of ancient 

 streams, the valleys of which were taken possession of by the modern Niagara. 

 Again, Prof. G. K. Gilbert found, in 1886, that the river had a greater descent at 

 one time than now; but the earlier, long-continued and inferior height of the Falls 

 was first pointed out by the writer. Upon the backing of the water after the maxi- 

 mum descent of the river, the surface of Lake Ontario rose above the present level, 

 so as to again considerably reduce the height of the Falls. This second reduction 

 of their height is, perhaps, the last discovery in the physics of the river, and has 

 hitherto not been announced. 



Perhaps the most important change discovered in the physics of the river was 

 (in 1887-1888) that the three upper lakes— Huron, Michigan, and Superior— did not 

 drain into Lake Erie until recently, but emptied, through Georgian Bay, towards 

 the north-east. Thus for a long period Niagara river drained only the waters of the 

 Erie basin. These discoveries show that the determination of the mean rate of 

 recession of the modern Falls had to be greatly qualified in order to arrive at an 

 approximate determination of the age of the cataract; but the difficulty remained 

 of ascertaining the amount of work done during the dififerent episodes. However, 

 at Foster's Flats the bed of the old river and fragments of lateral terraces were 

 found in 1893. From these and other features the key to the situation was partly 

 obtained. Some of these results have since been confirmed by the estimate of the 

 depths in the dififerent basins of the modern channel made by Prof. Gilbert. 



