( "I ) 



The third fpecles has for its bafe, fhoerl 

 in the mafs. It is black, without pores, ra- 

 ther heavy, and of a granular fradure. 



The heterogeneous floncs, which arc 

 mixed with the fubftance of this lava_ are of 

 three kinds : fmali irregular quartzofe par- 

 ticles, which, from their whitenefs, are mod 

 confpicuous ; a few minute feltfpars ; and 

 numerous rhomboidal fhoerls, of a dark 

 violet colour, and remarkable for their fize, 

 fome of them extending-to feven lines. 



The feltfpars and quartzofe grains are 

 refradory in the furnace; though their bafe 

 is eafily fufible, and produces a fhining, 

 opake, and porous enamel. 



The internal part of the ifland, as far, at 

 leaft, as appears from the furface, is com- 

 pofed of thefe three lavas and their varieties; 

 which lavas form currents, that, from their 

 great antiquity, do not exhibit thofe tu- 

 mours, wavings, and inequalities, which are 

 obfervable in recent lavas, or thofe of a mo- 

 derate 



