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When the matrafs had cooled, I broke it 

 lengthwife, and obferved the following ap- 

 pearances : The glafs when fufed had filled 

 two thirds and more of the body of the ma- 

 traf?, to which it was ftrongly attached, and 

 formed in the upper part a plain furfacc, 

 from which rofe a prodigious number of 

 fmall, vitreous, femitranfparent veficles or 

 bubbles, partly entire, and partly broken at 

 the top. 



On breaking the mafs of glafs I found it 

 entirely full of bubbles, of various fizes, 

 from thofe which were only a third or 

 quarter of a line in diameter, to thofe which 

 were half an inch. They all inclined, more 

 or lefs, to an orbicular form, and their in- 

 ternal furface w^as fmooth and fhining. But 

 on one fide of the glafs, which corre- 

 fponded to the place where the fire was 

 hotteft, there was a bubble nearly as large 

 as a hen's egg ; in which w-as obfervable a 

 thick vitreous thread, that crofled it with 

 the two ends adhering to its fides, and 

 \thich no doubt was produced by the vif- 



cofity 



