304 MINETRALS AND GEOLOGY 



siliceous rock-mattev, and are rather ferruginous schists than work- 

 able ore. Many however are rich in metal, and are especially free 

 from titanium and phosphorus. Finally, it may be mentioned, the 

 granite masses which occur so abundantly within the district, yield 

 excellent building stone, and have been largely quarried near the 

 Lake of the Woods and at other spois for use in the construction of 

 the Canadian Pacific Railwav. 



THE EASTERN ARCHAEAN DISTRICT. 



This district is a south-eastern extension of the great archsean 

 district of the northern lakes, described above. It is separated only 

 conventionally from the latter, and chiefly for facility of description. 

 At the same time, it presents certain points of difference : more 

 especially in the absence of any clearly recognised Huronian strata, 

 and in the apparently total absence of the Animikie and Keweenian 

 Formations. Its bands of crystalline limestone differ also very 

 generally from those of the more northern and western region by 

 containing various crystalline silicates and other minerals : pyroxene, 

 zircon, garnets, brown tourmaline, phlogopite mica, apatite, and 

 graphite, being especially prevalent. 



Its north-western boundary is a conventional line running from 

 Lake Temiscamingue to a short distance beyond French River on the 

 north shore of Georgian Bay. Its northern and north-eastern 

 boundary is the river Ottawa to the vicinity of Arnprior ; and frcm 

 this point its eastern limit runs south by Pakenham, Carleton Place, 

 Perth, and Charleston Lake, to the St. Lawrence. The rocks of the 

 district form a narrow-belt along the St. Lawrence, roughly, between 

 Brockville and a few miles west of Gananoque. From the latter 

 point, its southern boundary passes through the back townships of 

 Frontenac, Addington, Hastings, Peterborough, and Simcoe, and 

 strikes Georgian Bay near the mouth of the Severn. The average 

 elevation is about 800 feet above the sea. Lake Nipissing lies at an 

 elevation of 640 feet, but the ground to the south and east of the 

 lake is considerably higher. Around Haliburton, for instance, the 

 elevation above the sea-level exceeds 1000 feet. Lake Nipissing is 

 its largest body of water. Numerous smaller lakes, as Lake Opiongo 



