32 THE CANADIAN NATURALIST. [March 



rock composed almost entirely of a triclinic feldspar, whose 

 composition is generally near that of labradorite, but varies in 

 different examples from that of andesiue to near that of anorthite. 

 To these rocks I provisionally applied the name of anorthosites, 

 the pure feldspathic type being regarded as normal anorthosite ; 

 associated with which, however, were to be found hypersthenic 

 and pyroxenic varieties. Red garnet, epidote, a black mica, and 

 more rarely dichroite and quartz, are all occasionally found spar- 

 ingly disseminated in these anorthosites of New York and Canada, 

 which cannot be distinguished from those first observed by Mac- 

 Culloch in the Isle of Skye, as I have convinced myself by an 

 examination of the specimens there collected by him, and now 

 preserved in the collections of the G-eological Society of London. 

 Titaniferous iron ore (menaccanite) also occurs in grains and 

 masses frequently in these rocks, both in Skye and in North 

 America, where it sometimes forms beds or masses of considerable 

 size. Details as to the chemical and mineralogical characters of 

 these rocks, will be found in the L. E. & D. Philos. Magazine for 

 May, 1855, and in the Geology of Canada, 1863, pages 588-590. 

 The subsequent investigations of Sir William Logan have 

 shown that these anorthosites in Canada belong to a great series 

 of stratified crystalline rocks, which by the Geological Survey of 

 Canada have been designated the Labrador or Upper Laurentiaa 

 series, and which repose unconformably upon the older or true 

 Lauren tian oueiss and limestones. The area of the Labrador 

 formation most examined lies in the counties of Argenteuil and 

 Terrebonne, to the north and northwest of Montreal, and has a 

 breadth of more than forty miles. It is, however, met with on 

 the north-east shore of Lake Huron, according to Dr. Bigsby,* 

 and at several points below Quebec, notably in the parish of 

 Chateau-Richer, at Bay St. Paul and around Lake St. John on 

 the Saguenay, where it occupies a large area. Proceeding north- 

 eastward along the left bank of the St. Lawrence, Mr. Richardson 

 has lately observed it at the mouth of Pentecost River, about 160 

 miles below the entrance of the Saguenay, and I have found it 

 forming the shore of the Bay of Seven Islands, forty miles farther 

 down. This area is probably connected with the wide extent of 

 this rock observed by Prof Hind on the River Moisie. In all of 

 these regions it appears to be surrounded and limited by the 



* Geology of Canada, 1863, page 480. 



