12 
boulder. In such cases, the bisilicate individuals are 
arranged with their larger axes in a direction rudely parallel 
to the band. 
But another structure is also presented by the anothro- 
sites. When any of the anorthosites in the area embraced 
by the present report are carefully examined, this streaked 
or irregularly banded structure is seen to be accompanied 
in most, if not in all cases, by a peculiar breaking or 
granulation of the constituent minerals of the rock. This 
is often beautifully displayed on the large weathered sur- 
faces. The rock presents a peculiar brecciated structure, 
fragments of plagioclase and of the other constituents of 
the rock being imbedded in a species of groundmass made 
up of smaller grains. As plagioclase in most cases pre- 
ponderates almost to the exclusion of the other constituents, 
the fragments are usually of this mineral, and, although 
occasionally showing an approximation to good crystalline 
form, they are almost invariably quire irregular or even 
tattered in outlines. The groundmass of smaller grains 
also consists of plagioclase. In some places these fragments 
constitute the greater part ot the rock; elsewhere they are 
present very sparingly and the groundmass preponderates. 
The larger individuals can, moreover, be frequently seen in 
the very act of breaking up, the several fragments having 
shifted their position but very slightly. 
When examined under the microscope in thin sections, 
hardly a specimen of any coarse-grained variety can be 
obtained from any part of the area which does not show at 
least traces of this clastic or granulated structure; and if 
a series of specimens be studied, every step can be traced in 
the passage from massive anorthosite, showing the merest 
traces of this structure through intermediate breccia-like 
stages, to anorthosite consisting entirely of broken grains, 
or with mere remnants of the original large individuals. 
The three accompanying micro-photographs illustrate 
successive stages in this granulation. They are taken from 
three thin sections of anorthosite from different parts of the 
Morin area, photographed in polarized light between 
crossed nicols and equally magnified, the enlargement in 
each case being 18 diameters. 
(a) This section, from the large exposures about five 
miles northwest of the village of Ste. Adéle, in the town- 
ship of Morin, represents the massive anorthosite. It 
shows only the merest traces of granulation on the left 
