NIAGARA AS A TIMEPIECE. 17 



Niagara Falls narrowly escaped Extinction. — Fifteen 

 hundred years ago the terrestrial movements raised the Johnson 

 barrier to the Erie basin so high that the waters of that lake 

 reached not merely the level of Lake Michigan, but the point of 

 turning all the water of the ujjper lakes into the Mississippi drain- 

 age by way of Chicago. But the falls were then cutting through 

 the ridge, and when this was accomplished, before the change of 

 drainage was completed, the surface of Lake Erie was suddenly 

 lowered by many feet, and thus the falls were re-established for 

 some time longer. 



Death of the Falls. — Slowly, year by year, one sees the cata- 

 ract wearing back and suggesting the time when the river will be 

 turned into a series of rapids ; but another silent cause is at work, 

 and one not easily seen — namely, the effects of the changing of 

 level of the earth's crust. From the computations already referred 

 to it was found that for the first twenty- four thousand years of 

 the life of the river only the Erie waters flowed by way of the 

 Niagara River, and for only eight thousand years have all the 

 waters of the upper lakes been feeding the falls. If the terres- 

 trial movements continue as at present, and there appears no 

 reason to doubt it, for the continent was formerly vastly higher 

 than now, then in about five thousand years the rim of the Erie 

 basin promises to be raised so high that all the waters of the 

 upper lakes will flow out by way of the Chicago Canal. Thus the 

 duration of Niagara Falls will have continued about thirty-seven 

 thousand years. But the lakes will endure beyond the calcula- 

 tions of the boldest horologist. 



Relation of the Falls to the Ice Age. — In telling of the 

 times of the great mutations in the physical history of the lake 

 region, the story of Niagara Falls seems completed, but as a time- 

 piece they are much more important in being used as a stepping 

 stone back to the great period of frost which separated the former 

 order of the continent from the modern. Having ascertained the 

 approximate amount of the rising of the land recorded in the de- 

 serted beaches, before and since the birth of Niagara Falls, and 

 the rate of the rising of the land, and applying it to the movement 

 recorded in the abandoned shores, it is concluded that the epoch 

 when the lake region formed great expansions of more or less 

 open water commenced fifty or sixty thousand years since. Going 

 so far back in time, other conditions may have obtained to vary 

 the rate, but these have been allowed for as far as possible. 



Beyond the lake epoch the vicissitudes between the periods 

 of great regional submergence and the earlier high continental 

 elevation of the ice age proper are apparent, but the events 

 are certainly unexplained, for what was done by glacial action 

 and what by waves has not been determined. Niagara Falls 



VOL. XLIX. 2 



