IRON. 107 



able, soft, and easily filed, and also capable of 

 being forged and welded. There are several va- 

 rieties of iron in this state, arising from the ores 

 from which they were procured, the process of 

 smelting, or the intermixture of foreign substances. 



One variety is called hot sJiort iron ; it is ex- 

 tremely ductile when cold, and on this account is 

 employed for making wire ; but when heated it is 

 extremely brittle : it is also fusible. Cold short 

 iron, on the contrary, is highly ductile when hot, but 

 brittle when cold. The causes of these qualities 

 are not precisely known, but it is said that the first 

 is iron combined with arsenic, and that the latter 

 contains phosphoric acid. 



Iron is capable of being reduced to a third state, 

 which is that of steel. It is converted into steel, 

 by exposing it to heat in contact with carbonaceous 

 substances, which unite themselves with it. Steel 

 is, therefore, iron united to carbon, and is made by 

 three processes. 



Natural steel is made by keeping cast iron in a 

 state of fusion in a furnace, its surface being all 

 the while covered deep with scoriee ; part of the 

 carbonic acid gas escapes, while another part com- 

 bines with the iron. This steel is inferior to the 

 other kinds. 



Steel of cementatmi is made by placing bars of 

 iron in charcoal powder, and exposing them to a 

 strong heat in a furnace for six or eight days. 

 The iron and the carbon thus combined constitute 

 what is here called blistered steel. When this is 

 rendered more malleable by the operation of the 

 hammer, it is called sheer steel. 



Cast steel is made by fusing bhstered steel with 

 pounded glass and charcoal powder, in a close cru- 

 cible. It is also made merely by fusing iron with 



