Adams— Contribution to our knowledge of the Laurentian. 59 
The areas occupied by the Grenville Series although of very 
considerable extent, being known to aggregate many thousand 
square miles, are probably small as compared with those under- 
lain by the Fundamental Gneiss. The relative distribution of 
the two series has not been ascertained except in a general way 
in the more easily accessible parts of the great Archean pro- 
taxis. The Grenville Series is known to occupy a large part 
of its southern margin between the city of Quebec and the 
Georgian Bay, while the discovery of crystalline limestone in 
the gneiss elsewhere at widely separated points, as for instance 
on the Hamilton river in Labrador, in the southern part of 
Baffin Land, on the Melville Peninsula and at the head of 
Chesterfield Inlet, makes it probable that other considerable 
areas will with the progress of geological exploration be found 
in the far north. Overthe greater part of the protaxis, how- 
ever, the more monotonous development of the Fundamental 
Gneiss seems to prevail. 
In the present paper it is desired to present in a very con- 
densed form the chief results, more especially those bearing on 
the question of the origin of the series, of a somewhat extended 
study of the stratigraphical relations and petrography of a 
typical area of the Grenville Series containing subordinate 
masses of the Fundamental Gneiss and a number of anorthosite 
intrusions, which area lies immediately to the east of that 
examined by Logan and Ells and is continuous with it. The 
work was carried out for the Geological Survey of Canada and 
a detailed report on the area will appear shortly in the publica- 
tions of the Survey. I am indebted to Dr. Geo. M. Dawson, 
the Director of the Survey, for permission to reproduce the 
accompanying photograph. (Plate II.) 
Stratigraphy.—The area in question is represented in the 
accompanying map (Plate I). Its general geographical position 
is indicated by the River St. Lawrence with the city of Montreal 
at the southeast corner. Lying at the edge of the Archean pro- 
taxis, the northwest portion of the map is occupied exclusively 
by the erystalline rocks in question, whose eroded surface is to 
the southeast covered up by the flat-lying Cambrian (Potsdam) 
sandstone. The area underlain by the crystalline rocks is 3,500 
square miles, of which about 1,000 square miles is anorthosite, 
of which there is one large development known as the Morin 
anorthosite and ten smaller masses. This Morin anorthosite 
area is rudely circular in form, but sends off a large arm to the 
southeast which passes under the Potsdam sandstone. It 
encloses detached masses of the gneiss often of considerable 
extent. There are also two intrusions of acid rocks, one of 
syenite in the southwest covering an area of thirty-six square 
miles and a much larger one of granite in the northeast, a por- 
