IRON 213 



the iron, hence the name reverberator y. The flame passes 

 onwards and finally escapes from a chimney. 



The walls of the compartment are lined with oxide of iron, 

 and the heat causes the oxygen of the oxide to be set free ; 

 some of it unites with the impurities of the iron and forms 

 other oxides. 



The purified iron is not melted, only made soft by the heat, 

 and while in this condition is worked or wrought by long 

 bars of iron put through a hole in the furnace door. It is 

 then taken out, and, while still soft, is hammered with great 

 steam hammers, and then rolled under steam rollers. Wrought 

 iron is not brittle, and at a red heat may be hammered into 

 any shape required, and two pieces may be welded together. 

 This latter quality is a very valuable one, and is possessed by 

 very few of the metals. 



STEEL is iron combined with a small quantity of carbon, 

 the proportion of carbon varying from i to 2j per cent. The 

 ancient iron makers had no means of regulating the amount 

 of carbon contained in their steel, and, in consequence, though 

 it was often of excellent quality, there was no fixed standard 

 by which it could be judged. Modern methods have overcome 

 this difficulty. 



There are various methods of producing steel, and we can 

 now obtain it from ores of various degrees of purity, though 

 the finest steel, called crucible steel, is made from the purest 

 ores and the purest carbon. This is the steel used in making 

 cutlery. 



In 1856 Sir Henry Bessemer invented his method of making 

 steel. The principle is first to get rid of all the carbon, and 

 some of the other impurities of pig-iron, and then to put back 

 carbon in the proportion required. 



Impure molten pig-iron is poured into a great pear-shaped 

 vessel, called a converter, at the bottom of which is a plug 

 riddled with holes. 



Through these a fierce blast of air is driven, the pressure 

 of which is so great that not only is the molten iron prevented 



