426 Canartvai Record of Science. 



constituents. According to Emmons, quartz is not found 

 in the rock itself, but occurs only in small infiltrated 

 veins and fissures. 



A hand-specimen of this anorthosite from the neigh- 

 bourhood of the Poke o' Moonshine Pass, in Essex County, 

 for which I am indebted to Professor G. H. Williams, did 

 not differ at all from the more highly granular varieties 

 of the Morin and Saguenay areas. It is rather coarse, 

 granular, grey in colour, and composed almost exclusively 

 of plagioclase. This mineral has a white or grey colour, 

 but a few dark blue fragments of larger grains indicate 

 that the rock has undergone a thorough granulation. We 

 find, furthermore, a little pyroxene, which is almost com- 

 pletely changed into zoisite, epidote and chlorite, and a 

 few small red, isotropic garnets, whose presence indicates 

 that the hand-specimens probably came from near the 

 limit of the area, and a few grains of rutile. A little 

 quartz is also present, the grains of which are at times 

 intermixed with the feldspar, producing a kind of grano- 

 phyric structure. It might be inferred from this that 

 the quartz is an original constituent, but this cannot be 

 definitely demonstrated. 



The relation existing between these rocks, and the cha- 

 racter of the iron ores which accompany them, which has 

 already been discussed above, is also discernible in this 

 area. Whenever iron ores are found in the anorthosite, 

 they without exception contain titanic acid, while the 

 large deposits in the Laurentian gneisses, in the neigh- 

 bourhood of Port Henry and elsewhere, consist of mag- 

 netite free from titanic acid. As far as can be ascertained 

 from existing descriptions, these New York anorthosites 

 resemble in all respects those found in the Canadian 

 Laurentian. 



