NIAGARA AS A TIMEPIECE. 



15 



or more, and reduce the descent 

 of the river by eighty feet or 

 more. 



Episodes of the Niagara 

 River and their Duration.— 

 At first the river flowed without 

 falls, as shown by the old banks 

 and terraces, for a period esti- 

 mated at a thousand years. 

 Then the waters of the lower 

 lake began to subside, where- 

 upon the Niagara Falls had 

 their birth. The new cataract 

 slowly grew in height, although 

 characterized by temporary 

 pauses, until the river cascaded 

 two hundred feet from the table- 

 land into the edge of the gulf 

 or lake which occupied the On- 

 tario basin, as shown in Fig. 16. 



The volume of the water of 

 Lake Erie is about one fourth 

 that of all the upper lakes, and 

 only this proportion of the dis- 

 charge of the modern Niagara 

 River formed the abrading agent 

 of the falls at that early date. 

 This general condition lasted 

 for seventeen thousand two hun- 

 dred years.* After this episode, 

 the descent of the river was in- 

 creased to four hundred and 

 twenty feet, and the lake receded 

 twelve miles from the foot of 

 the mountain, and then there 

 was a series of three cascades, 

 the lower always gaining upon 

 the upper on account of the soft- 

 er rocks. Yet the increased 

 amount of work to be done, even 

 though easier than the recession 



* For the methods of computation of the 

 duration of the episodes of Niagara Falls see 

 Duration of Niagara Falls and the History of 

 the Great Lakes, pp. 1-126, 1895. Also see Duration 

 of Science, December, 1894, pp. 455-472 — both works 



W &:,S-S 



of Niagara Falls, American Journal 

 being by the writer. 



