( H ) 



thefe vefTels is a compofition of black flint, and a 

 ftrong clay, that bakes white. Their outfides 

 are glazed by throwing into the furnace, when 

 well heated, common or fea fait decrepitated ; 

 the fleam or acid of which, flying up among the 

 veflels, vitrifies the outfides of them, and gives 

 them the glazing. This flone ware does not ap- 

 pear to be injured or afFedled by any kind of falts, 

 either acid or alkaline, or any liquors, hot or 

 cold. They are therefore extremely proper for 

 til common ufes, but require a careful manage- 

 ment, as they are much apter to crack with any 

 fudden heat, than china. 



The Heflian ware, or the vefl^els made of the 

 fame fubftance with the Duke d'Alva's bottles, 

 commonly called grey-beards, feem Co be made of 

 ftrong pipe clay, mixed with fand, and glazed in 

 the baking, by the alkaline fait, which arifes from 

 the wood uied in baking them, wood having al- 

 ways the effefl, when the furnace is intenfe, to vi- 

 trify the outfide of all clays*. 



DilTsrt. by James Lind, M. D. 



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