MODE IV. FELSITE. 



167' 



The kliagstein porphyry of Werner, which he 

 also absurdly calls porphyry slate, is a schistose 

 felsite, with crystals .of felspar; as it happens in 

 many substances that an earthy and compact base 

 is spotted with crystals of the same substance, the 

 forms of some of the molecules having disposed 

 them to crystallise, while the others became sedi- 

 mental. The klingstein porphyry is generally black 

 or grey, but sometimes of a green, yellow, or 

 brown tinge, like the klingstein, which seems to 

 admit most of the colours of felsite ; but is of a 

 schistose texture, and contains little cavities, often 

 lined with quartz crystals, much resembling lava 

 with a basis of felsite. 



As the French seem first to have observed this 

 rock, it may be called patrinite, in honour of Pa- 

 trin, an eminent French Geologist and Volcanist. 

 It sometimes contains zeolite, calcareous spar, and 

 crystals of siderite. Mr. Jameson has observed 

 that it is sometimes vesicular*, or full of little 

 cavities, " but not so much so as basalt." Part 

 of his description of patrinite may be transcribed. 

 " 2. It occurs sometimes in tables and columns ; 

 also in veins that traverse sand-stone and green- 

 stone, as in the island of Arran. 



" 3. It resists the action of the weather very 



Patrinite. 



Jameson's 

 description. 



* This epithet seems only applied to basalt, wacken, klingstein, 

 ava, pumice. 



