T. S. Hunt on Lithology. 97 
grains of black hornblende, about the size of grains of rice, were 
sparingly disseminated through the mass, together with very 
small portions of magnetite and yellowish sphene. Fragments 
of the rock had a density of 2°607-2°657. The feldspar was 
yellowish-white and sub-translucent, with a somewhat pearly 
lustre. By crushing and washing the mass, the grains of feld- 
Spar were separated from the heavier minerals, and found to 
have a specific gravity of 2561. The results of its analysis, 
which scarcely differs from that of Brome, is given under rv. 
’ II. In. Iv. 
Silica, - - . - - - 65°70 65°30 65°15 
Alumina, : - . - - 20°80 20°70 20°55 
Lime, - - - - . . 84 "84 “13 
Potash so ek Sy ae es peg See 6°39 
Mee ee ieee 6-67 
"Volatile, - = - - - - 50 seme 50 
99:99 
Yamaska mountain.—A bout twelve miles to the north of west 
from Shefford mountain rises the hill of intrusive rock known 
as Yamaska mountain, which has an area of about four square 
miles, and breaks through the strata of the Quebec group near 
the line of the great dislocation which brings these up against 
the limestones of the Trenton group. The southeastern part of 
this hill consists of a granitoid diorite hereafter to be noticed; 
but the greater portion of the mass may be described as a gran- 
Itoid trachyte, differing in aspect from that of Brome and Shef- 
rd, in being somewhat more micaceous and more fissile. e 
mica, which is dark brown, is in elongated flakes, and there is 
v. vi. 
Re se OP 58°60 
Alumina, a ee ee a oe SO 21-60 
ee ae a ee 
Magnesia, Se ee “19 eek) 
Potash, ee 3-08 
- - 5°93 551 
oi ei OO "80 
98-41 99°71 
» XXXVI, No. 112—Juxy, 1864, 
