228 POTTERY. 



Method of obtaiiiing pure Coppe?\ 



Let the copper of commerce be dissolved in mu- 

 riatic acid, and precipitate it by a polished plate of 

 iron ; the precipitate is pure copper. 



Of making Brass, and other Alloys of Copper. 



Brass is made by fusing together lapis calami- 

 naris (which is an ore of zinc) and copper. 



Tombac is formed by melting together twelve 

 parts of copper with three of zinc. 



Gun 7netal consists of nine parts of copper and 

 one of tin. 



Bell metal is copper alloyed with one sixth of tin. 

 A smaller proportion of tin is used in making 

 church bells than clock bells, and a little zinc is 

 added for the bells of repeating-watches, and other 

 small bells. 



Cock metal is made with copper alloyed with zinc 

 and lead. 



The gold coins of this country are composed of 

 eleven parts of gold and one of copper. 



Standard silver contains fifteen parts of silver 

 and one of copper. 



POTTERY. 



Pottery, or the art of making vessels of baked 

 earth, is of the remotest antiquity. The ancient 

 Greeks and Etruscans particularly excelled in it. 

 Porcelain, the most perfect of species of pottery, 

 has been made in China from time immemorial. 



Alumine and silex are the two substances of which 

 every kind of earthen-ware is made. Clay alone 

 shrinks and cracks j the flint gives it solidity and 

 strength. 



