420 THE CANADIAN NATURALIST. [DeC. 



well as the small island immediately beneath, — upon which 

 island it has been proposed to erect a monument to the Prince 

 of Wales. 



The range of hills seen running along the north shore of the St. 

 Lawrence from its mouth to Quebec, and onward in a westerly 

 direction, along the north side of the Ottawa River, is looked upon 

 as being at one time the shore of an ancient ocean. A view from 

 the summit of one of these hills in a direction south, exhibits a 

 great tract of level country, low lying, and considered as the wide, 

 flat valley of an ancient ocean, whose waters, long since removed, 

 have left behind, in remembrance of their existence, the great beds of 

 Silurian rocks, abounding: in fossilized remains of the various 

 organisms which flourished during that interesting epoch. Of the 

 strata entering into the formations of this section, the lowest rock 

 is the Potsdam Sandstone, excepting the Metamorphic Kocks, 

 which, although stratified, may be distinguished by a more or less 

 granitic, and crystalline aspect, and are of older date. The greater 

 number of the boulders scattered so profusely over the entire face 

 of the country, are gneiss in one of two forms, — as either the mi- 

 caceous or ordinary gneiss, or hornblendic gneiss. The former 

 consists of quartz, feldspar, and mica ; the latter, of quartz, feld- 

 spar, and hornblende. Gneiss is generally known from granite 

 by its striped or banded character. 



Potsdam Sandstone is a term given by the New York geolo- 

 gists to a formation which is well developed at Potsdam, in northern 

 New York, and is there considered as forming the base of the 

 palseozoic series of rocks. Sir William Logan considers this forma- 

 tion as a member of the Potsdam Group. It crosses from St. 

 Lawrence County, New York, into Canada; the greatest develop- 

 ment on this side being at the County of Beauharnois. It is said 

 to fill up the inequalities of the underlying Laurentian series. 

 This formation is met with to the eastward, between Lake Chau- 

 diere and a spur of Laurentian rocks, from three to five miles 

 removed from the right bank of the Lac des Chats, to Nepean, a 

 distance of fully thirty miles. In Nepean the rock dips north- 

 ward, and thus sinks beneath the calciferous formation. By means 

 of a dislocation, the south side of the band, after leaving the gneiss, 

 is brought against the Chazy and Trenton formations. The con- 

 tinuation of the dislocation on the south side of the Laurentian 

 spur, accounts for the absence of Potsdam sandstone in that par- 

 ticular position. In the " Geology of Canada " it is here stated as 



