( H ) 



While employed ia the examination of 

 thefe ftones, I refolved to compare tliem 

 with the Veruvian garnets j tor, in myexcur- 

 fion to that volcano, I had colledled feveral 

 different fpecies of them on Monte Somma, 

 which is the ancient Vefuvius. I made le- 

 veral experiments on four of thefe, of which 

 the following is the refult. 



The firft fpecies is found in a lava with a 

 horn-flone bafe, of a yellowifh grey colour, 

 an unequal furface, and of a confiftence 

 little different from earthy, from the great 

 alteration it has undergone ; not, as far as 

 appears, from fulphureous exhalations, but 

 from the acftion of the atmofphere. The 

 garnets it contains have likewife fuffered 

 injury, having loft a part of their native 

 luftre, and being eafily broken or crumbled 

 to pieces from the multitude of minute fif- 

 fures and cracks in them. They, however, 

 retain fomewhat of the vitreous chara<51:er. 

 Their colour is between a vvhite and a grey. 

 At firft view their figi-ire appears peife^lly 

 globular ; but on extrading them from the 

 lloncj their matrix, (which may eafily be 



done,) 



