354* *^'' JOITAXITY or EARTHENWARt, 



really, with regard to the ware itfelf, only the inconvenience 

 of a dirty appearance, provided the bifcuit is always compa6i, 

 and well baked. But it is different in the common pottery iq 

 ■which the dropping, the fcaling, and the flaws produce more in-^ 

 jurious defeds. As the earth is more porous and left; baked in 

 thore,the liquids preferred in them enter into the pores where 

 they become altered and decompofed, and produce fulphur* 

 ated hydrogen, which injures -every thing kept in them. 

 Cavities or pits jj^^ ^^q^ noxious defeds in pottery are the cavities or 

 from bad firing. ... , , , • _,, . , rr in 



pits, and the underbaking. The pits are roughnelTes or hollow 



bubbles which are found on thofe pieces, whofe enamel being 

 injured by rubbing, or being too little aded on by the fire, 

 has not been fufed into a vitreous fubftance. In thefe the 

 metallic oxides are in a ftate capable of doing injury, being 

 Underbaking or ^'" ^o^uhle in fat or acid fubftances, 



impertcft t'ufion The underbaking occaiions one of the moft dangerous de- 

 o tie glaze. f^fts in potteryj the pieces thus aflfe6led have not had fuf- 

 ficient heat to caufe the enamel to do more than agglutinate 

 together, and in fome cafes it even ftill remains in powder, 

 It is therefore capable of being divided, and taken up by all 

 the liquids with which it may come in contad. 



It is eafy to fliew the danger to which the public muft be 

 expofed in buying thofe articles at a low price which are 

 called wafte or refufe and which ought to be carefully thrown 

 away. In vain may it be faid that they are ufed daily without 

 any immediate mifchief happening; from the injury being 

 more concealed, it is no lefs deftru6live. It is known that 

 lead and its oxides ad infenfibly on the organs of digefiion, 

 efpepially when taken in fmall quantities : They do not, how- 

 ever, lefs certainly caufe, at length, ern?ciation, cholics, 

 convulfions, fometimes of all parts of the body, with obftinate 

 diarrhoeas; and the wretched people who ufe fuch velfels 

 become the vidims of their own ignorance, and of thq im- 

 prudent avarice of the manufadurer. 



It would be to the honour of enlightened manufadurers^ 

 not tp offer to the public pieces which have imperfedions 

 beyond a certain degree, and to make thisfacrifice to the good 

 pf national commerce, efpecially as they can avoid the lofs by 

 a greater attention to their materials. 



XVIII. Extraa 



