DOMAIN II. SILICEOUS. 



transparent opal, from Upper Hungary. Born 

 i. 213, 



The same, of a clear blue, from Telkobanya in 

 Upper Hungary. 



Green, from Meissen in Saxony. 



Green pitch-stone, with adherent sand-stone, 

 from Arran. 



The stalactitic kinds, and the petrified wood 

 from Hungary, cannot be said to constitute rocks. 



STRUCTURE II. LAMINAR. 



Laminar pitch-stone, in thin horizontal layers, 

 alternately white and violet, from Telkobanya. 



A laminar kind was also discovered by Mr. 

 Jameson in the island of Arran. 



MODE XIII. SILICEOUS INTRITE. 



These rocks present crystals of felspar, some- 

 times quartz, or calcareous spar, in a siliceous 

 ground or base. The most remarkable kinds 

 are those called keralite or hornstein porphyry, 

 and pitch-stone porphyry. They are vaguely 

 classed under the general name porphyry by 

 German the German theorists, while the crystals are so 



porphyries. 



unimportant, that in geology they should be 



