DOMAIN X. TRANSIL1ENT. 



presents in its base a superabundance of what he 

 calls schorl ; that is, the hornblende of the Ger- 

 mans, or siderite of the present work. In some 

 porphyries, called by the Roman artists Ubria- 

 gones, the felspar appears, as it were, melted 

 into the base, so as only to present spots of a 

 different tint. It is now well known that the 

 base of the porphyries is a trap, or basaltin ; and 

 Dolomieu has the merit of having perhaps first 

 observed that it could not be a jasper, as it is 

 easily fusible by the blow-pipe: but many of 

 his observations will, in the present advanced 

 state of the science, be pronounced to be in- 

 accurate. 



Granite and granitic porphyry, from Mount 

 Sinai. 



The same, from the Alps. 



The same, from the Grampian mountains, iiii 

 Scotland. 



In general the Scotish granites are very irre- 

 gular ; and, in small fragments, often appear as 

 granitels, consisting chiefly of felspar with little 

 seams or particles of mica, while the quartz is 

 often rare and distant. 



