390 Manufacture of Bar Iron in Southern India. 



and day, for several years together ; the metal being allow- 

 ed to flow out every twelve hours in quantities of about six 

 tons at a time. The material used in building the blast 

 furnace is principally fire brick, and a pair of furnaces cost 

 upwards of 1,800£. sterling. The proportion of coal used 

 in making a ton of cast iron, varies very much, from three 

 tons in Wales, to sometimes eight tons in Derbyshire ; but 

 the use of heated air in blowing the furnaces has very much 

 increased the quantity of the products of the blast furnace, 

 and has also diminished the expenditure of fuel, but the 

 quality of the cast iron is said to be deteriorated. The 

 estimated expense of making a ton of cast iron is about 

 SI. sterling. 



6. For converting cast iron into bar iron, the first process 

 generally employed in England is called " refining," and 

 consists in fusing about a ton of cast iron at once in flat 

 open furnaces about three feet square, where it is exposed 

 for two hours or more to the action of a strong blast, by 

 which it is supposed a portion of the carbon it contains is 

 burnt off. Much gas escapes from the surface of the metal 

 during the operation, and a large quantity of black bubbly 

 slag separates, after which the metal when run out and 

 allowed to cool, has a white silvery appearance, is full of 

 bubbles, is very brittle, and has acquired the property 

 of hardening by being suddenly cooled. In " refining," 

 about four or five hundred weight of coals is used to the 

 ton of cast iron, and the metal loses from twelve to 

 seventeen per cent of its weight. 



7. The " refined" cast iron, now termed l( fine metal," is 

 then exposed in a reverbatory furnace, called the " puddling 

 furnace", to the action of the flame of a large coal fire, by 

 which it is first partially melted, then falls into a coarse 

 powder; and on being stirred up and presented to the 

 flame, becomes at last adhesive and tenacious. It is then 

 formed into large balls, and after receiving a few blows from 



