i 
do not constitute more than five per cent of the rock— 
the remaining 95 per cent being plagioclase which varies 
in composition from andesite to anorthite. The other 
constituents are almost invariably augite, hypersthene 
and ilmenite. These minerals become relatively more 
abundant in certain schlieren, while in most of the intru- 
sions places can be found where the ilmenite is segregated 
into large masses, some of which have been worked as ores 
of iron. 
THE MORIN ANORTHOSITE. 
EXTENT AND RELATION TO THE SURROUNDING GNEISS. 
The Morin anorthosite area is situated on the margin 
of the Laurentian protaxis 30 miles (48 kilometres) north 
of Montreal. It is a nearly circular mass from the south- 
eastern side of which, however, there is a wide apophysis 
extending in a southerly direction. The mass is about 
37 miles (59-5 km.) in diameter and has a total area of 
990 square miles (2,475 square kilometres). It cuts 
through the gneiss and associated rocks of the Laurentian 
system by which it is surrounded on all sides, except at 
the southern extremity of the arm-like apophysis above 
mentioned, where it is overlain and covered by the much 
more recent Palzozoic strata of the St. Lawrence valley 
which here are of Potsdam and Calciferous age. 
The country underlain by this anorthosite, leaving 
out of consideration the arm-like extension above mentioned, 
is very hilly, but the hills seldom rise to such height as 
to be properly designated as mountains, and, while often 
rugged and precipitous, still preserve the smooth flowing 
contours seen everywhere in the Laurentian in this part 
of Canada. Between the hills are valleys or plains, 
generally of no great size, occupied by drift. These valleys, 
as well as the hill sides, are year by year being cleared of 
their forest growth and converted into farms that support 
a hardy population. 
Scattered through these valleys are a great number of 
lakes, some of considerable size, in which North river and 
other streams take their rise, eventually finding their way 
into the Ottawa or St. Lawrence rivers. 
The highest hills in the area are those about Duck 
lake in the township of Cartier, and those in the district 
