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glafs in the furnaces of Pavia requires a 

 longer time to fufe it than common white 

 glafs, and that in its actual fufion it is little 

 or not at all inflated. The fadt, however, 

 is, that after remaining the ufual eight hours 

 in the furnace, the matrafs having been 

 broken, the ebulUtion and exaltation ap- 

 peared to have been fuch, that the glafs had 

 rifeJi to the middle of the neck ; though 

 when the heat had ceafed it had funk to 

 the bottom of the belly. This was evident 

 from a fhining thin vitreous coating, occu- 

 pying the whole interior furface of the 

 matrafs, beginning from the level furface of 

 the glafs lying at the bottom, and proceed- 

 ing to the middle of the neck, where there 

 remained a lump of glafs that entirely clofed 

 the aperture. 



The appearances which took place in this 

 faditious glafs, both in the matrafs and the 

 glafs-furnace, may be underftood and fatif- 

 fadlorily explained by the theory of the ga- 

 fitication of the fubftances hitherto treated 

 pf. The heat of the furnace was fufiicient 



tQ 



4 



