228 N. L. BOW EN 



rugged, many of the important elevations of the Laurentian 

 Mountains of that region lying within the boundaries of the anortho- 

 site mass. As with the Adirondack Mountains, the Laurentian 

 Mountains have suffered glaciation and lakes abound, with the 

 result that even in the matter of popularity as a summer resort the 

 two regions are alike, the Laurentian region drawing a plentiful 

 supply of tourists on account of its proximity to the Canadian 

 metropolis. Coming to the more fundamental matters of geologic 

 structure and petrography we find again a remarkable degree of 

 similarity to which attention is directed in the sequel. 



An area of more than 3,000 square miles comprising the Morin 

 anorthosite was mapped nearly thirty years ago by F. D. Adams, 

 and a map published on a scale of four miles to one inch. 1 The map 

 is therefore not as detailed and does not form as useful a guide for 

 one who would see a great deal in limited time as do the quadrangle 

 maps of the New York State Museum, which are the result of the 

 labors of a number of workers. On the other hand, the text of the 

 report is full of minute descriptions of localities, and a brief visit 

 was paid to some of these in order to become familiar with them at 

 first hand. 



Relation of anorthosite to the surrounding rocks. — The Morin 

 anorthosite occurs, as does that in the Adirondacks, principally as 

 a single, great intrusive mass. There is, however, a greater number 

 of small outlying masses that give the area a somewhat greater 

 interest with reference to the problem of the origin of anorthosite. 

 The associated rocks are practically identical with those in the 

 Adirondacks, consisting of igneous gneisses largely of salic compo- 

 sition and of sediments of the Grenville series. Of all these Adams 

 concluded that the anorthosite was the youngest, a relation which 

 he appears to have considered a general one for the Canadian 

 anorthosites including the great Saguenay mass. Recent study of 

 the Saguenay area has shown, however, that there are associated 

 with the anorthosite certain more salic types, possibly consanguine- 

 ous with it, but of somewhat later age, 2 the whole being appar- 



1 "Geology of a Portion of the Laurentian Area North of the Island of Montreal," 

 Geol. Surv. Can. Ann. Rept., Vol. VII, Part J, 1896. 



2 Personal communication from Mr. Dresser. 



