NIAGARA FALLS. 
385 
this part of the surface. The basin of Ontario, on the north of this terrace, has evidently been 
excavated from the sedimentary strata ; the limit of the force, and the extent of the lake basin, 
being the line of this escarpment. 
It is quite unnecessary, in the present instance, to controvert the opinion which has been 
advanced, of a dislocation of the strata, by which those forming the terrace have been elevated 
to their present position. They are continuously exposed both on the north and south of the 
escarpment, and it is very plain that no such change has taken place. The accompanying 
section, and also the section, Plate IV., illustrate the order of succession among the strata. 
Here, instead of any evidence of disturbance in the strata, we find the most unequivocal 
proofs of denuding action, which has entirely removed the materials once forming the continua¬ 
tion of these strata on the north. It will be seen that the strata, consisting of alternating hard 
and soft beds, offer great facilities for the operation of any excavating force. The action of 
water would thus undermine the harder beds, leaving them to fall by their own weight, while 
the softer materials were removed. The manner in which this denudation was effected, and 
the period of its occurrence, have already been noticed; and by the same means we are able 
to account for this and other extensive lines of escarpment, where the succession of strata 
presents a very different structure and ability to endure abrasion. In the same way we are to 
account for the broad valleys in other situations, and the numerous gorges in the edge of this 
escarpment. These are of little extent, scarcely reaching beyond a quarter of a mile, and 
usually less ; they present broad expanded openings on the north, and are very similar to the 
indentations upon lines of seacoast. 
[Geol. 4th Dist.J 
49 
