294 Canadian Record of Science. 



in Laurentian rocks, and empties into the St. Lawrence 

 River about 120 miles below the city of Quebec. The 

 southern limit of the anorthosite in question is about 100 

 miles north of that city. It embraces an area of not less 

 than 5,800 square miles, and is almost completely covered 

 with forest, being one of the wildest districts of the 

 Dominian of Canada. The southern corner of the area is 

 level and inhabited. Here the rocks have there been 

 carefully investigated, whilst towards the north explora- 

 tions were made only on the three rivers Peribonka, 

 Little Peribonka, and Shipshaw, which run parallel to 

 the longitudinal direction of the area, one on each 

 side of it, and one through the centre. The rocks 

 have been traced along these rivers considerably more 

 than 100 miles north of the southern limits of the 

 area. The Peribonka was explored to its forks, while 

 the Shipshaw and Little Peribonka were followed up 

 through the rough mountainous country to their sources 

 without reaching the northern limit of the anorthosite 

 area. Mr. Low, however, found no more anorthosite on 

 his exploratory trip to Lake Mistassini, during which he 

 crossed 1 the head waters of the Peribonka and examined 

 the district directly to the north of the one investigated 

 by myself. But he did find some on the Betsiamites and 

 afterwards on Rat River, a tributary of the Mistassini. 

 We therefore know within narrow limits the course of 

 its northern boundary. The Shipshaw and the Little 

 Peribonka, which flow respectively on the east and west 

 side of the area, are several times crossed by the contact 

 of the anorthosite with the gneiss ; they consequently 

 mark the breadth of the former. We thus possess a good 

 general knowledge of the extension of the area. The only 

 previous geological examination of the district was that 

 made by Richardson, which was cursory and confined to 



1 "Low, on the Mistassini Expedition, Report of the Geological Survey of Canada, 

 1SS5, D. 



