( 397 ) 



I took 19 ounces, 2 drams, and 7 j grains 

 of black glafs of Llpari, broke it into fix 

 pieces, put them in diftiiled water, and left 

 them during forty hours in a fatid-bath, but 

 v/ithout boiling. I did the fame by a 

 quantity of the fpotted glafs, broken into kven 

 pieces, and weighing 20 oiuices, 2 drams, 

 and i^ grain. Having dried the two 

 glaiTes in the air and the fun, I found them 

 of the fame weight. Into thefe two waters, 

 diminifhed by evaporation, I poured the 

 nitrate of filver, which caufed a flight tur- 

 bidnefs, and a proportionate fediment. 



By all thefe fad:s I think it is inconteft- 

 ably proved that the muriatic acid, in thefe 

 two volcanic glaffes, is not combined with 

 them fo as to enter Into them as a conRitu- 

 ent principle ; but is only mechanically at- 

 tached to their parts. 



Befides thefe two glafTes, the black and 

 the fpotted of Lipari, I made experiments, 

 as I have mentioned in the preceding chap* 

 ter, on fix other volcanic piodu6ls. The 



gafeous 



