2£^^ ON tChe improvement of pottert. 



Delft. Delft ware, which was a grand invention in its time, on 



account of the beauty of its coating, has likewise the defect 

 of being baked only so far as to vitrify the enamel, as a de- 

 gree of heat beyond tliis would spoil it. This renders it ne- 

 cessary, to employ a sufficient quantity of lime in it, to give 

 it a little consistency by a conamencement of fusion* 



Its defects. "^ Its coating, composed of glass of lead and silex, rendered 

 white and opake by oxide of tin, cannot support changes 

 from heat to cold, and its biscuit is liable to imbibe grease. 



Queen's ware. The white or pipe ware, after the English fashion, is 

 lighter; its biscuit has more solidity, being composed of 

 purer clay, and prepared flints ; and it is previously baked : 

 but the coating given it is much more fusible than that of 

 delft ; it is a glass, incapable of enduring an equal heat; is 

 subject to crack; is very easily scratched, when any oily 

 matter will penetrate the biscuit and leave spots ; and if the 

 glass of lead be in excess, which is unfortunately a too com- 

 mon case, oils and vegetable acids attack it, and render its 

 use dangerous. 



Its glaze defec- The memoir published by an able chemist, Mr. Proust, 



tive and dan- ^^ remove any apprehension of injury from its use, induced 

 Mr. Gay-Lussac and myself, to pay great attention to this 

 subject, at the time of the last exhibition of the products of 

 French Industry. We found very little, that was capable 

 of completely resisting the edge of a knife ; and after this 

 it could not stand the test even of boiling acetic acid, or the 

 yolk of egg boiled hard. We cannot therefore avoid adopt- 

 ing the opinion of Mr. Jousselin, that, whatever attempts 

 be made to improve this manufacture, it can never form 

 good pottery. 



Is stone-ware Hence then it may be admitted as a general principle, 



capable of be- ^^^^^ ^^^j ^.^^^^ kinds are admissible, stone-ware and porce- 



ing made a *^ . ., , 



substitute for lain. But is it possible, to answer every purpose of strength, 



every thing but gjggj^,^(,g^ wholesomeness, and economy, in a word, to ren- 

 der stone-ware capable of supplying the place of common 

 earthen-ware, or such as is required to stand the tire, of 

 delft, ixnd of pipe-ivare ? Mr. Jousselin affirms, that he is 



Tes. convinced it is by numerous experiments. As he is esta- 



blishing a manufactorj% it is natural for him to keep secret 



th(e 



