194 Chemistry. [Lecture 30. 



The asbestos, or amianthus, is a fossil agree- 

 ing with talc, in having a regular structure, in 

 being flexible, but differing in being composed 

 of fibres instead of plates. When long exposed 

 to air, it dissolves into a sort of stony matter, 

 which has some degree of toughness, but the 

 fibres of which cannot be unravelled. Cloth and 

 paper have been made of this substance, which 

 resist the fire. 



Steatites, a kind of magnesian earth, is an in- 

 gredient in porcelain, the art of making which 

 was long confined to China ; but of late all the 

 necessary discoveries have been made in Europe. 

 A Jesuit missionary first sent an account of the 

 manufacture to France, and specimens of the 

 two ingredients, viz. kaolin (a white clayey earth), 

 and a stone called petuntze. Reaumur examined 

 them, and gives the following account : One of 

 the substances is not fusible, the other is by a 

 strong heat. He supposed that by union they 

 underwent an approach towards fusion ; this gives 

 the semi-transparency to china. Meeting with no 

 substances of equal purity with these, he made 

 experiments on common glass and talc, by which 

 he produced a substance white like porcelain, and 

 which resisted heat and cold. 



The qualities by which the best china is di- 

 stinguished from the worst are, that it has a 

 beautiful semi-transparency, and upon breaking 

 shows a sort of vitrification, yet withstands vio- 

 lent heat, &c. ; whereas the false china melts in 



