( 33^ ) 



cofity of the matter at the time it feparated 

 and formed this bubble. 



"Where the glafs was not full of bubbles 

 to the naked eye, it was fufficiently folid 

 and hard to give fparks with fteel ; I fay, 

 to the naked eye, becaufe, with the lens, 

 the folid parts likewiie were feen to be full 

 of innumerable extremely minute bubbles. 



When we compare the fufion obtained 

 in this matrafs with that obferved in open 

 crucibles, in a glafs furnace, when the fame 

 fpotted glafs is the fubjed:, we find the fame 



refults. " 



We will now proceed to treat on the 

 origin and caufe of thefe bubbles, Vv'hich, 

 in fad, is the principal objed of our prefent 

 enquiry. It feems undeniable that thefe 

 mud have been produced by an elaftic 

 fluid, which penetrated the glafs when in a 

 fl:ate of fufion, and compelled it to dilate 

 in that manner. This fuppofition I have 

 always made in the courfe of this work, 



when 



