DOMAIN II. SILICEOUS. 



the siderite into iron, without changing denomi- 

 nations. Crystals of schorl, or garnets, not to 

 mention the precious stones, may also appear in 

 genuine granite; but the real and severe deno- 

 mination can in no case be further extended. 

 When there are only two essential substances, 

 with a granitic appearance, as particularly 

 Granitei. quartz and felspar, the term granitel must be 

 admitted, with Saussure, Kirwan, and other ce- 

 lebrated geologists; though in Italy granitello 

 is used by artisans for a complete granite, com- 

 posed of very small grains, here called granitin; 

 as basaltin is a fine basalt, and porphyrin^ a fine 

 porphyry. 



These observations become the more neces- 

 sary, as no substance has engaged more attention 

 in systems of geology, and no two authors seem 

 hitherto to be agreed in precise and formal 

 definitions of granitic substances : and in all 

 sciences it is well known that no question can 

 be settled, or even accurately discussed, without 

 the most precise definitions. Thus in the ques- 

 tion concerning the entrance of granitic veins 

 into primitive schisti, some deny that the granite 

 in these veins is of the same mixture with the 

 mass; and it certainly would considerably in- 

 fluence the discussion, if the mass be a complete 

 granite, and the veins only granitel. Nor in 



