84 ROCK RUINS. 





























and Niagara, with perhaps a slight descent over the time 
stones (10) at the outlet of Lake Erie, will be uninterrupted 
in its course to Lake Ontario. 
According to the estimate of Sir Charles Lyell, shoal 
thirty-five thousand years ago the falls were at Lewiston. | 
Now they are seven miles away, and have yet two miles 
to traverse, each step harder and more difficult as the 
becomes thinner, before they reach the point (č), where, — 
should they preserve their present structure, they will no 
be over one hundred feet high. Following out Sir Charles | 
Lyell’s estimate, this would ako ten thousand years, even if 
the disappearance of the shale. Although these calculi | 
are based upon the observed rate of retrogression of the fi i 
they can only be very rough approximations, until sufficient | 
time has elapsed for other observations to be made and com- 
pared with the monuments erected by Professor Hall in 1842. 
They are, however, sufiiciently close and reliable to $ 
that Niagara was not carved out in a day, nor yet in a th 
sand years ; but that for tens of thousands of years the stea 
rush of the river has ground the rocks to powder, and swe 
away, piece by piece, the solid layers, until the gorge it 
cut is now seven miles long, from two to three hundred 
fifty feet deep, and eight to twenty-four hundred feet ¥ 
at the top. 
Of late, the public have been alarmed by the sta 
that about half a mile back of the horse-shoe, the motio g 
the stream indicate a breach in the upper limestone, % ; 
speculations are indulged in that through this hole a $ 
terranean stream is eating away the underlying shale 
great rapidity. The sagacious inhabitants, who have gI% 
birth to this story, predict the probable destruction of t i 
great cataract by the caving in of the tables of limestone 
with such rapidity that the whole will form only & 
It is difficult to understand, first, how such a breach ¢ 
have been made; second, how if made it could swa 
