174 T. S. Hunt on Lithology. 
ArT. XV.—Contributions to Lithology; by T. StzerRy Hunt, 
M.A., F.R.S.; of the Geol. Survey of Canada. 
(Concluded from p, 104.) 
Doterires. 
The anorthosites, which yet remain to be described, may be 
divided into two groups, those composed of anorthic feldspars 
with augite, constituting the dolerites, and those in which sim- 
ilar feldspars are associated with hornblende. The general geog- 
nostical relations of these two groups of rocks in the districts 
under discussion have already been indicated. 
Grenville.—It has already been stated on page 93, that the 
oldest known intrusive rocks which traverse the Laurentian 
syenite and granite in various parts of the Laurentian region, 
seems, like the hypersthenite and other anorthosites of the Lab- 
genous 
the plane of the dike. They are fine grained, dark greenish- 
gray in color, and weather grayish-white. Under a lens, the 
mica, and grains of pyrites. It contains no carbonates. Two 
analyses of portions of the dolerite, from dikes differing a little 
in texture, gave as follows under xv and XVI: 
‘ xv. xvi. xvit, 
oe i SBS 50-25 52-20 
IN 8 a On ee ra BERS 82-10 18-50 t 
Peroxydofiron, - - - 12650 } 130-00 
ee ee ey ae rc SO 9°63 7°34 
‘Magnesia, ee as 4:93 5°04 4:17 
ee Potash, oe a ee ge 58 2°14 
- Ci Oe 2-28 212 2°41 
i Webi 4 el ee 1-00 250 
ee: 99-04 100-72 99°26 
