392 APPLIED SCIENCE 



cast iron. Moreover, cast iron is not malleable or ductile like 

 wrought iron. Neither cast nor wrought iron can be hard- 

 ened and tempered. 



439. Malleable Cast Iron. Ordinary white cast iron can 

 be rendered sufficiently malleable to admit of changes if 

 heated with iron oxide. By this means the carbon in the cast 

 iron is slowly oxidized by the oxygen in the surrounding 

 oxide. The iron should be as free as possible from phos- 

 phorus and should contain some manganese. This process 

 produces a layer of pure iron possessing the property of 

 wrought iron. Malleable iron is practically wrought iron 

 which can be hammered into any desired shape when cold, 

 but which is very brittle when hot. Cast iron can be made 

 harder by a chilling process. 



440. Blacksmithing. Blacksmi thing is a distinct me- 

 chanical trade, and consists of working and shaping iron 

 and steel for ornamental, structural, and general repair work. 

 One branch of the trade is devoted to horseshoeing. The 

 equipment of the blacksmith consists of a forge, an anvil, and 

 the necessary tools. 



The forge is generally a structure of iron, although it may 

 be built of brick or stone, upon which a smith's fire is built. 

 In the bottom of the hearth, upon which the coal is placed, is an 

 opening known as the tuyere through which a forced draught 

 is applied by bellows. The mouth of the tuyere is generally 

 covered with a perforated sheet which allows the air to pass 

 through freely, but prevents cinders or any other foreign 

 matter from dropping into the blast pipe. A hood, the pur- 

 pose of which is to catch and conduct the smoke to the chim- 

 ney, covers the forge. This hood is constructed of sheet 



