2 POPULAR SCIENCE MONTHLY. 



itself, without flowing through any caflon whatever, and then 

 glance at the gorge of Niagara River, seven miles long, of which 

 Ka fragment can be seen in a picture (Fig. 4), the striking dif- 

 ference awakens inquiry. The cause does not lie in either the 

 magnitude of the streams or in the character of the rocks; it is a 

 question of the difference of the age, for Niagara Falls once cas- 

 caded from the edge of the mountain wall (Fig. 16) directly into 

 the expanded waters of the Ontario basin just as the Montmor- 

 ency stream is pouring into the St. Lawrence River to-day. 



Early Estimates op the Age op Niagara Falls. All at- 

 tempts at reducing geological time to solar years meet with great 

 difficulties, yet Niagara Falls have been used as a chronometer as 



Fig. 1. Facsimile of a View of Niagara Falls by Father Hennepin. 



frequently as any other natural phenomenon, and indeed Niagara 

 is perhaps the best measurer that we have. Even at an early date, 

 when the antiquity of the earth was not a popular doctrine, An- 

 drew Ellicott (in 1790) divided the length of the gorge by the sup- 

 posed rate of recession of the falls, and assigned fifty-five thou- 

 sand years as the age of the cataract. Forty years later Bake- 

 well reduced the time to twelve thousand years, and a few years 

 afterward Ly ell's estimate of thirty- six thousand years became 

 popular and remained so until about fifteen years ago. This 

 method of dividing the length of the chasm by the rate of reces- 

 sion was correct as far as it went, but even the rate was not then 

 known. 



Method of Computing the Age of the Falls. Many years 



