( 3'8 ) 



*vohen left to cool in the matrafs^ after haV" 

 ing been eight hours expofed to the fre — 

 No reafon to believe that the bubbles ijoere 

 an effect either of the atmofpheric air in- 

 cluded in the int erf ices of the glafs^ or of 

 any permanent gas — ConjeEliire that thefe 

 bubbles proceeded from the gaffication of 

 the glafs itfelf occafioned by the vehemence 

 cf the heat — Proof of this conjecture in the 

 piiref glafs of Lipari — 'The breaking of 

 the matrafs in the frongcf heat occafioned 

 by this gaff cation- — Caife "why the glafs 

 rendered gafeous does not pafs into the 

 pneumatic apparatus — Breaking of a third 

 matrafs by the violent gaffcatioji of aii 

 enamel of Ifchia — Ena?nel of Procida dur- 

 ing the gaff cation fiblimcd^ and adhered 

 to the fides of the matrafs in the form of a 

 thin crtfly and ena7nel points — Confrination 

 cf this in another matrafs^ ^f^'S ^^^ fame 

 enamel — Evident fgns of this fublimation 

 in the fufon of fome volcanic fubfances 

 placed in the furnace in covered crucibles 

 — Reafn why this fublimation does not 

 appear in every experiment — Black faBi- 



tious- 



