ROCK RUINS. 81 
of the river. Professor Jules Marcou, who visited Niagara in 
1848-49 and 1850, remarked not only the changes which 
occurred in the Table Rock,* part of which fell in 1850, 
but observed also the increasing angularity of the curve at 
the centre of the horse-shoe, and the gradual deepening of 
the water. It seems certain that either the size of the river 
has greatly decreased since Father Hennepin’s visit, or else 
this part of the horse-shoe fall is much deeper and the 
sides shallower than formerly. In 1850, according to Pro- 
fessor Marcou, the curve was passably regular; in 1863, it 
was very much deeper, and notched near the centre. He 
also noticed that a large block, some six or seven feet in 
diameter, which had stood near the Terrapin Tower, had 
been engulfed, and together with it a long line of boulders 
figured by Professor Hall in his map of 1842. In 1852, por- 
tions of the cliff at this point fell, making a sensible differ- 
ence in its outline, and probably caused the disappearance 
of the boulders. 
The manner in which the tables of rock are undermined 
is as well known as the recession of the cataract itself. 
Every visitor is informed that the water, dashing against 
the lower layer of soft shale (7), cuts out cavernous hollows 
like the “Cave of the Winds,” and presently the projecting 
tables of limestone above (8), becoming too weak to support 
themselves, and the great weight of the river, are precipi- 
tated in immense masses to the bottom. 
These huge fragments, with every point and fractured 
edge rounded and smoothed by the ceaseless bombardment 
of the water, lie in huge piles under the American fall. 
There is no continuous flow, but a succession of blows, and 
one standing near them, feeling this distinct pulsation, as 
wave after wave rushes over the precipice and descends with 
a deafening roar upon the polished surfaces, no longer won- 
ders that the rocks are worn slippery, but rather that they 
*This is a tabular extension of the upper limestone on the Canadian side close to 
tho cataract. It once extended out some distance, and was probably te bos mennant 
Lid fall G 


+ 

