MODE VI. GRANITIN. 201 



of the auger in the obelisk of Heliopolis ; and 

 affirms, that without this instrument characters 

 could not be cut in a granitic rock. But he seems 

 to discuss a subject which he had not studied ; for 

 there could be no use for the common auger, also 

 called a trepan, in this stone, which is harder than 

 iron. But the other auger, which is a brass tube 

 contrived to act on emery, though a convenient 

 instrument, is yet unnecessary, and is only used 

 by our artists in forming deep furrows."* 



MODE VI. GRANITIN. 



When granite is composed of extremely mi- Description, 

 nute particles, it is not easily distinguished from 

 basalt, or rather from basalton, the grunstein of 

 Werner. But where particles of siderite, oY 

 even of basalt, which is an earthy siderite, are 

 mingled with particles both of quartz and felspar, 

 the substance is a granitin. When siderite is 

 mixed with felspar alone, it is basalton, or the 

 green-stone of Werner; the real basalt, or iron- 

 stone of the ancients, seeming properly to admit 

 of no mixture, except spangles of siderite. 



Several ancient monuments, supposed to be 



* Zoega de Obeliscis, p. 1 89, seq. 



