DOMAIN II. SILICEOUS. 



peds, vary as to size ; there are some which are 

 an inch long, by six lines broad. They are of 

 a dull white, slightly translucent, little brilliant, 

 of the kind I have called dry ; under the blow- 

 pipe they yield a transparent glass, but with 

 bubbles, from which may be formed globules of 

 0,81, and consequently fusible at the 70th de- 

 gree of Wedgewood. Upon the rod of sapparc 

 the bubbles dissipate, and there remains a trans- 

 parent milky glass, which sinks without pene- 

 trating or dissolving. These crystals of felspar 

 appear here and there greenish and dull, on 

 account of a slight coat of earthy steatite which 

 covers them. 



<f The quartz, which forms a little less than 

 the fourth of the mass, As of a grey approaching 

 to violet colour; its fracture is uneven, brilliant 

 in some places, not scaly, but here and there 

 rather conchoidal, a little flat. Its fusibility is 

 nearly the same as that of the quartz of the gra- 

 nites of 198?. 



" The hornblende, which forms in the mass 

 too small a portion to be estimated, is of a black 

 approaching to green ; it shows some tendency 

 to the laminar and brilliant form ; but it is more 

 often merely glimmering, and almost earthy; 

 fusible into a brilliant black glass, but porous in 

 its interior ; and which on the rod of sappare 



