482 Canadian Record of Science. 



so much decomposed that their true characters are not 

 determinable even in specimens obtained from a consider- 

 able distance beneath the surface of the ground, are to a 

 large extent grouped in such a way that a face of the 

 rock shows numerous dark patches, often two inches or 

 more in diameter. In some of the most acid of these 

 granites, there are basic segregations which consist of lime- 

 soda feldspar, together with small amounts of pyroxene. 

 The granite dyke rocks, in many cases, are very coarse- 

 grained, and consist of microcline and other alkali feldspars, 

 quartz, and a light-coloured mica which occurs in varying 

 amounts. 



Many of the schistose rocks of the district, with the 

 exception of the crystalline limestones, are in all proba- 

 bility of eruptive origin ; but very little work has so far 

 been done on them. 



The scapolite rocks are among the most interesting 

 representatives of the schistose group. While it is likely 

 that some of these have been produced by the alteration 

 of gabbros, there are others in which such evidence of 

 their origin has not been obtained. The writers have 

 examined specimens, taken in some cases from a consider- 

 able distance beneath the surface of the ground, which 

 consisted of the two essential minerals, scapolite and 

 pyroxene. Some grains of the latter constituent were 

 seen to be quite fresh, while others, especially in those 

 specimens from near the surface, were more or less changed 

 to hornblende. In the rock referred to, no plagioclase 

 was noticed. 



Another rock of a very striking character, when exam- 

 ined microscopically, consists of the minerals microperthite 

 and pyroxene, together with small amounts of orthoclase, 

 lime-soda feldspar, and a finely-striated plagioclase which 

 is probably anorthoclase. The microperthite is present 

 in much greater quantity than the other constituents. 

 The rock is undoubtedly of eruptive origin, and occurs in. 



