148 Niagara. [April, 
the gorge above the whirlpool was pre-glacial, that the post- 
glacial river would have followed exactly the same line 
when it was bounded only by the superficial deposits that 
marked the older features of the country. I found that, 
above the whirlpool, the post-glacial river had run in 
different channels, having, apparently, often changed its 
course in the superficial deposits. Thus Lyell has described 
one of these deserted channels that ran from the muddy 
-river to the whirlpool.* Another, I noticed, ran down from 
behind the town of Niagara-falls. In ,some places, the 
terraces and ridges that bounded the old river come down 
to, and are cut off by, the present gorge; at other places 
they retire back for at least Ioo yards from it. They prove 
that, before the present river was confined in its rocky 
gorge, it often changed its channel, as rivers do now that 
run through superficial deposits over a nearly level plain. 
On the Canadian side, a little above the whirlpool, two of 
these terraces come down to the gorge, and are cut off by it. 
Their direction is shown by dotted lines in the sketch plan 
of the river gorges at the whirlpool (fig. 3, p. 147), and the 
following figure is a section through them at the line c D, in 
plan. 
Fig. 4. _E 
D 
oO 
G 2 PoC °F. 
Lm So OF Sa ae 
GEV > LILLE: LL 
CES yyy 
YI. 
Ky WVCCTTTTTTTZ@#|_ HD 
a 
Section through the line c D in Plan, Fig. 3, showing two terraces excavated in till and a river 
ridge capping the lower one. c, till with angular blocks; D, till without stones; E, rounded 
boulders of northern origin; G, river ridge. 
There are here shown two river terraces, of which the 
highest and oldest has been formed by the washing off by 
the river of the clay without boulders (pb), from that with 
boulder (c), leaving a level terrace, excepting where it is 
capped by the river ridge (G). The river at the whirlpool 
has cut back into the old gorge, clearing out the entrance 
to it and cutting off this terrace, but on the other side of the 
old gorge it re-appears and continues on, parallel to the 
course of the present river, and without any reference to 
* Travels in North America, vol. i., p. 42. 
