392 
GEOLOGY OF THE FOURTH DISTRICT. 
have the whole height divided into three falls, at some distance from each other. In conse¬ 
quence of the thinness of the upper limestone, that fall would recede faster than either of those 
below it; and the middle faster than the lower one. Even under these circumstances, the 
wearing action would go on much faster than at present. Finally, however, the recession 
would become less and less rapid, from the thickening of the limestone above ; and from this 
cause, the two lower falls having only the same resistance to overcome as at first, would 
gradually approach the upper, till the whole become one.* 
At the same time there are other circumstances to be taken into consideration, and among 
the most important of these are the dip of the strata and the ascent of the bed of the stream ; 
both together tending to bring the strata down to the level of the water as we progress 
southward. This fact has also an important bearing upon the rate of recession; for while 
a hard mass remains at a considerable height above water, with a soft one below, the exca¬ 
vation of the softer one and undermining of the upper hard one, tends to the recession 
much more rapidly than if the whole were of uniform character. Thus it must have been 
that the fall over the sandstone (No. 2), receded much more rapidly while there was a 
considerable thickness of shale below, than when it approached the level of the water. This 
would happen after the falls had retreated about three miles, or nearly to the whirlpool. At 
this point the recession would go on very slowly for a long period; for this hard mass, being 
at the level of the water, would effectually suspend the undermining process. Even at the 
present time this rock may be seen stretching into the river, from either side, beyond the 
others, and at the point where it crosses, producing a descent of eight or ten feet within a few 
rods. 
After this long and almost stationary period at the whirlpool, the recession would again go 
on more rajudly ; soft materials being presented at the river level to be excavated by the force 
of the falling water, which would thus undermine the harder mass above. 
When the cascade had receded to near its present position, another pause, similar to that at 
the whirlpool, would occur, from the approach of the higher layers of sandstone (No. 4), and 
the hard limestone (No. 6), to the surface of the water. There are various proofs of this 
halting, both in the form of the chasm below the present fall, and from the fact that the higher 
layers of sandstone still remain in place ; for it is seen that having passed a few feet beneath 
the water at the cascade, it supports the large fragments of the upper limestone which have 
fallen down. 
The conclusion then, seems inevitable, that the river has been the great agent in excavating 
its own channel, from near the escarpment between Lewiston and Queenston, to the present 
position of the cataract; that the recession has been aided by the character of the rocks, pre¬ 
senting alternate hard and soft strata; and that the descent was overcome, not by one per¬ 
pendicular fall, but by several. In support of this latter assertion, a single analogous case 
will furnish stronger evidence than a long argument. The course of the Oak-orchard creek, 
* See diagram on explanation of the falls of the Genesee, page 3S1. 
