THE UlSTORY OF THE NIAGARA RIVER. 233 



geologic structure of the i)lateau. They are constituted of bedded 

 rocks — limestone, shale, and sandstone — lying nearly horizontal, and 

 a little examination shows that the same strata occur in the same order 

 on both sides. So evenly are they matched, and so uniform is the 

 general width of the gorge, that one might suspect, after a hasty exam- 

 ination, the two sides had been cleft asunder by some Plutonic agency. 

 But those who have made a study of the subject have reached a dif- 

 ferent and better conclusion — the conclusion that the trench was exca- 

 vated by running water, so that the strata of the two sides are alike 

 because they are parts of continucms sheets, from each of which a 

 narrow strip has here been cut. 



The contour of the cataract is subject to change. Fropi time to 

 time blocks of rock break away, falling into the pool below, and new 

 shapes are then given to the brink over which the water leai)s Many 

 such falls of rock have taken i^lace since the white man occufned the 

 banks of the river, and the breaking away of a very large section is 

 still a recent event, liy such observation we are assured that the 

 extent of the gorge is increasing at its end, that it is growing longer, 

 and that the cataract is the cause of its extension. 



This determination is the first element in the history of the river. 

 A change is in progress before our eyes. The river's histoiy, like 

 human history, is being enacted, and from that which occurs we can 

 draw inferences concerning what has occurred, and what will occur. 

 We can look forward to the time when the gorge now traversing the 

 fourt-h part of the width of the plateau will completely divide it, so 

 that the Niagara will drain Lake Erie to the bottom. We can look 

 back to the time when there was no gorge, but when the water tlowed 

 on the top of the plain to its edge, and the Falls of Niagara were at 

 Lewiston. 



We may think of the river as laboring at a task — the task of sawing 

 in two the })lateau. The task is i)artly accomplished. When it is done 

 the river will assume some other task. Before it was begun what did 

 the river do? 



How can we answer this question ? The surplus water discharge 

 from Lake Erie can not have tlowed by this course to Lake Ontario 

 without sawing at tlie plateau. Before it began the cutting of the 

 gorge it did not flow along this line. It may have flowed somewhere 

 else, but if so it did not constitute the Niagara River. The commence- 

 ment of the cutting of the Niagara gorge is the beginning of the his- 

 tory of the Niagara River. We have accom})lished somewhat of our 

 purpose if we have discovered that our river had a beginning. 



We are so accustomed to think of streams, and especially large 

 streams, as permanent, as flowing on forever, that the discovery of a 

 definite beginning to the life of a great river like the Niagara is im- 

 portant and impressive. But that discovery does not stand alone. 

 Indeed, it is but one of a large class of similar facts familiar to students 



