180 THE CANADIAN NATURALIST. [June, 



with pyroxene, some mica, and a little magnetite. Its analysis 

 afforded silica 49.35, alumina 18.92, protoxyd of iron 4.51, lime 

 18v36, magnesia 6.3(5, loss (alkalies?) 2.50 ; = 100.00. 



In some portions of the dolerite of Mont.irville, the feldspar is 

 more abundant, and ;ippears in slender crystals with augite, and with 

 a smaller proportion of olivine than the last. A specimen of this 

 Variety, being crushed and washed, gave 3*9 percent, of magnetite, 

 and 10.0 percent of a mixture of ilmenite with o ivine. Theleldspir 

 was obtained nearly pure, in yellowish vitreous grains, having a 

 specific gravity of 2.73—2.74, and nearly the composition of 

 labradorite. The results of its analysis are seen under xviii. 



xvni. XIX. 



Silica 53.10 58.60 



Alumina 26 80 24.40 



Peroxyd of iron = 1.35 4.60 



Lime 11.48 8.62 



Magnesia .72 .86 



Potash .71 undet. 



Soda 4.24 " 



Volatile 60 .80 



99.00 



The dolerite of Montarville is traversed by veins belonging to 

 several different periods. In one instance, the black and highly 

 augitic mass is cut by a dyke of a fine-grained greyish-white dole- 

 rite. This is intersected by a dyke of a fine-grained greenish rock, 

 which, in its turn, is cut off by another small dyke which is grayish- 

 white lik-! the first. 



RoUGEMONT. — The rocks of Rougeraont offer a general resem- 

 blance to those of Montarville. Some portions are a coarse-grained 

 dolerite, in which augite greatly predominates, with grains of 

 feldspar, and a little disseminated carbonate of lime In some 

 parts, the augite crystals are an inch or more in diameter, with 

 brilliant cleavages ; and grains of pyrites are abundant, with cal- 

 oite in the interstices. This rock resembles the highly augitic 

 dolerite of Montarville. OUvine is very abundant in two varieties 

 of dolerite from Rougemont. One of these has a grayish white 

 finely granular feldspathic base, in which are disseminated black 

 augite and amber-colored olivine, the latter sometimes in distinct 

 crystals. The proportions of these elements sometimes vary in the 

 same specimen ^ the feldspar forming more than half the mass in 



