IRON. 243 



metal becomes stiffer as it loses carbon, and is then 

 hammered and rolled into bars. 



601. IRON WIRE. The bar. or wrought 



Mention an 



important iron thus produced, is highly malleable and 



wrought iL. ductile > aild ma 7 be rolled into she ets, or 

 How i$ iron drawn into the finest wire. Wire is made 



wire made ? 



by drawing a wrought iron bar, by ma- 

 chinery, through a hole of less than its own diameter, 

 and repeating the process until the required degree of 

 fineness is attained. Wrought iron loses its tenacity, 

 and becomes granular and brittle, like cast iron, by long 

 jarring. This effect sometimes occurs in the wheels 

 and axles of railway carriages, and is the occasion of 

 serious accidents. 



602. WELDING. Wrought iron becomes 



How is 



wrought iron soft at a certain heat, without melting. 

 This property, which adds greatly to its 

 usefulness, belongs to no other metal excepting plati- 

 num. In the soft state, two pieces may be united by 

 hammering. This process is called welding. The 

 surfaces to be welded are sprinkled with borax, to pro- 

 tect them from the air, which would form a crust of 

 oxide of iron, and prevent a perfect contact. Its fur- 

 ther action is explained in the chapter on Salts. Beside 

 borax, other materials having a similar effect are fre- 

 quently employed. 



How is steel 603. STEEL. Steel may be made from 

 made ? cast i ron by burning out half its carbon. 



Or it may be made from wrought iron, by return- 

 ing half of the carbon which was removed in its 

 preparation. The latter is the process generally pur- 



