1002 IRON 



workman becomes more oppressive from the additional heat to which he is subjected 

 from the close proximity of the blast-furnace. Ironmasters are not agreed as to tho 

 respective merits of the 'boiling' and 'puddling' systems; some maintain that tlm 

 former is more economical than the latter, which involves ' refining; ' others think 

 that boiling iron has a tendency to communicate to it the ' red short' quality. Ac- 

 cording to the observations of Mr. Truran, in several works where both methods are 

 employed, the largest quantity of iron is first passed through the refinery. 



Mr. Hall, the inventor of the boiling system, in descanting on the merits of his pro- 

 cess, describes how, with the same pig, the iron may be made weak and cold short ; 

 or tough, ductile, and malleable. For the first proceed thus : Pass the pig through 

 the refinery, then puddle agreeably to the old plan on the sand bottom ; that is, melt 

 it as cold as possible ; drop the damper quite close before the iron is all melted, dry the 

 iron as expeditiously as may be, with a large quantity of water ; and, lastly, proceed 

 to ball in a proper number of ' young ' balls ; the result will be a very inferior quality 

 of manufactured iron. On the other hand, to produce a malleable iron of very superior 

 quality, first charge the furnace with good forge pig-iron, adding, if required, a 

 sufficiency of flux, increasing or diminishing the same in proportion to the quality 

 and nature of the pig-iron used. Secondly, molt the iron to a boiling consistency. 

 Thirdly, clear the iron thoroughly before dropping down the hamper. Fourthly, 

 keep a plentiful supply of fire upon the grate. Fifthly, regulate the draught of tho 

 furnace by the damper. Sixthly, work the iron into one mass, before it is divided 

 into balls ; when thus in balls, take the whole to the hammer as quickly as possible, 

 after which roll the same into bars. The bars being cut into lengths, and piled to 

 the desired weights are then heated in the mill furnace, welded and compressed by 

 passing through the rolls, and thus finished for the market. In this way, from the pig 

 to the finished mill bar, one entire process that of the refinery, is saved. Mr. Jlall 

 states that, by his process, he can obtain malleable iron of any character (premising 

 that the ores from which the pig is smelted are of good quality), from the softness of 

 lead to the hardness of steel, and further that he can exhibit different qualities in the 

 same bar, one end being crystalline, nearly as brittle as glass, the other end equal to 

 the best iron that can be produced for fibre and tenacity, while the middle exhibits a 

 character approximating to both ; and, as a further illustration of the excellence of 

 the iron that may be made by the ' pig-boiling ' process, he refers to a specimen in 

 the Geological Museum, Jermyn Street, London, labelled ' Specimen of two-and-a- 

 quarter inch round iron, tied cold, manufactured at the Bloomfield Ironworks, Tipton, 

 Staffordshire.' This specimen has been called a ' Staffordshire knot ' ; it was made 

 from a bar 2 inches in diameter, and nearly 7 inches in circumference : also to a 

 ' Punched Bar,' inch thick, made at one process for the smithy, commencing with 

 a -inch punch, and terminating with one 6, without exhibiting the slightest frac- 

 ture. 



Mr. Hall was led to the discovery of the 'boiling' principle, by noticing the 

 exceedingly high fusion which took place on subjecting puddling-furnace slag to a 

 high degree of heat, and the excellence of the bloom of iron produced by the 

 operation : it occurred to him, that if such good iron could be made from cinder 

 alone, a very superior product ought to be obtained from good pig-iron, with equally 

 good fluxes, and the result of experiments fully answered his expectation, though 

 for a long time he was unable to make his discovery practically useful, on account 

 of the difficulty of getting furnaces constructed capable of rendering the intenso 

 heat required and the corroding action of the fluxes. Puddling furnaces wen; then 

 made of brick and clay, with sand bottoms. He succeeded at last, by lining tho 

 interior of the furnace with iron, and protecting them with a coating of prepared 

 tap cinders. 



In America the 'puddling' and 'boiling' processes are both in use. Overman gives 

 preference to the latter as being the most profitable, but it can only bo employed to a 

 limited extent for lack of cinder ; in a rolling-mill forge, therefore, half the furnaces 

 are employed for boiling, and half for puddling, tin; latter supplying cinder for tin* 

 former. In the eastern States, where the fuel is anthracite, double puddling furnaces 

 are employed, and a blast is used, tho incombustibility of this variety of coal render- 

 ing it impossible to get the requisite heat merely by the draught of tho chimney. 

 Fig. 1262 represents an anthracite furnace bisected vertically through tho grate, 

 hearth, and chimney. It differs from tho ordinary puddling furnace chiefly in the 

 greater depth of the grate, which is made to contain from 20 to 24 inches of coal, and 

 in the lesser height of the chimney, which, as a I. last is cni].loyed, need only bo suffi- 

 ciently high to carry the hot gases out of tho furnace ; tho letters a, a, a, a, a, indicate 

 the position of the iron cross binders, which serve to bind together the cast-iron plates 

 of the enclosure, and to prevent the sinking of the roof from tho expansion and con- 

 traction of the brickwork. 



