Glacial Phenomena of Canada. 341 



of Laurentine gneiss, and of Niagara limestones and other Silurian 

 rocks. The top of the upper escarpment of drift forms the h'ghest 

 part of the whole plateau. Being 135 feet above the edjje of the 

 fall, its top is 60 feet above Lake Erie, which is onlv 70 feet ibove 

 that edge. The edge of the great escarpment above Lewiston is 

 said by Mr. Hall to be 70 feet above the top of the fall ■ and 

 therefore the escarpment No. 1 of the accompanying diagram 

 (fig. 5) is also 65 feet, and No. 2, 50 feet higher than the 

 top of the escarpment above Lewiston, and 45 feet above Lake 

 Erie. If this drift once extended across the space now occupied 

 by the oorge, as shown by the dotted lines, Lake Erie may origi- 

 nally have extended thus fir, and after a time the river gradually 

 cut out a channel in the drift and formed both terrace^- or else 

 an original terraced channel existed, formed during the emergence 

 of the country, the terraces being formed by marine denudation.* 

 The lower terrace has, in part at least, been excavated by the 

 river, which, before the formation of the gorge, here spread into a 

 broad reach, like that above the Falls. It is on a continuation of 

 this platform, about a quarter of a mile below Clifton Hou^e, be- 

 tween the drift-terrace and the edge of the gorge, that the strata 

 containing existing river-shells occur (fig. 6). 



Fig. 6. — Section showing the position of the Freshwater beds above 



the Gorge of the Niagara. 



er J?!?) *• Freshwater beds. 



— .—-#£'•■'(. 2. Drift, with boulders. 



jy^^G', i J 3. Niagara Limestone. 



vfS^-f-* & ' 4. Niagara Shale. 



5. Talsus. 



This drift-terrace Sir Charles Lyell has shown to be as old as 

 the Mastodon-period. The freshwater beds lie in a shallow hollow 

 on the limestone. They consist of remodelled drift, and some of 



* It deserves to be stated, that half-way up the cutting, on the surface, 

 I found a Cyclas ; and another was found by SirWm. Logan, with whom 

 I measured the section, on the same terrace, behind Clifton House. Some 

 bits of plate of the " willow-pattern," however, lay near my shell ; and 

 that found by Sir Wm. Logan was on ground that had been stirred with 

 the spade ; and we came to the conclusion that the evidence they afford- 

 ed was of very doubtful value. 



