( n6 ) 



felves to the eye, which at firil: view may 

 excite a doubt to what kind of ft nes they 

 appertain ; but, when exatiiined atteniively 

 and under dilTerent refledions of the light, 

 we are convinced that they are t:ue fclt- 

 fpars, but in part calcined. Thefe feltfpars 

 are accompanied with the ufual hexagonal 

 micas, and fome fhoerlaceous points. 



This granite, liquefied by the volcanic 

 £re, reminds me of tlie great a(ftivity re- 

 quifite in our common fires, for the fulion 

 of granites that are not volcanic, and even 

 of thofe which are ; as I have ihown in 

 Chap. XII. I have fmce thougl t that pof- 

 fibly fo great a degree of beat was not ne- 

 ccflary in the prefent inftance, from this 

 granitous lava being deprived of quartz, 

 one of the elements of the granites on 

 which i made my experiment?,. and which 

 certainly is that among them m; ft relrado- 

 rj to fuhon. I have found, in fait, that 

 this iava, when continued a long time in 

 the furnace, affords a vitreous produd of a 

 black colour, and nearly homogeneous, 



fome 



