CHAMBERS'S INFORMATION FOR THE PEOPLE. 



of the Monkland Iron-works in Lanarkshire, to 

 try another and very ingenious method, which 

 an experience of more than two years has proved 

 to be singularly successful. It is shewn in figs. 

 3 and 4. The furnace requires to be about 80 feet 



Fig. 3. Feme's Patent Blast-furnace : 

 A, body of furnace ; B, vertical retorts or coking chambers ; C, 

 gas flues for beating retorts ; D, pipe for conveying waste gases 

 to boilers, &c. 



Fig. 4. Plan of Feme's Furnace on Line SS : 

 B, retorts ; C, gas flues. 



high, and the upper 30 feet of this height is divided 

 internally into four large vertical retorts, the walls 

 of which are supported on two narrow arched 

 rings, like flying buttresses, at right angles to 

 each other. Round this four-chambered portion 

 of the furnace, and through the cross divisional 

 walls separating the chambers or retorts, flues 

 travel in a kind of spiral direction. In these 

 flues the gas from the furnace is burned with a 

 proper supply of air, and keeps them at a bright 

 red-heat. The lower portion of the furnace is 

 constructed in the ordinary way. The object of 

 the arrangement is to convert the raw coal into 

 coke in the retorts before it descends into the lower 

 zones of the furnace, and so economise the heat 

 which in ordinary furnaces is spent in distilling the 

 volatile products from the coal. The reduction of 

 the iron is thus effected with much the same ease 

 as when coke is used to begin with, while the gases 

 generated by coking the coal in the upper or retort 

 portion of the furnace, are employed in heating 

 these retorts. In other words, the gaseous pro- 

 ducts from the fuel of an earlier, are used to distil 

 off these same products from the coal of a later, 

 charge. But the available gas is not nearly all 

 consumed in doing this ; a large quantity being 



408 



used in raising steam, heating the blast-pipes, and 

 for other purposes. By this self-coking furnace 

 of Mr Feme's, only 34 cwt. of coal are required 

 to produce a ton of pig-iron, while 53 cwt. are 

 necessary with open-topped furnaces. 



Cast-iron contains from 3 to 5 per cent, of 

 carbon ; steel contains a less quantity of this 

 element ; while malleable iron is practically free 

 of it. Carbon has an extraordinary influence in 

 changing or modifying the properties of iron ; so 

 much so, that any specimen of the metal con- 

 taining, say, 3 per cent, another containing I per 

 cent, and another containing no carbon, differ 

 as much from each other as three quite distinct 

 metals. Of the three principal varieties of iron, 

 cast-iron is the most brittle and the most fusible ; 

 but, unlike steel or wrought-iron, it can neither 

 be forged nor welded. It is used for all kinds of 

 iron castings, large quantities being consumed 

 for the heavier portions of machinery, for building 

 purposes in the form of pillars and beams, for 

 hollow ware, and for ornamental work. Much 

 of the cast-iron made is converted into malleable 

 iron and steel; but before taking up the manu- 

 facture of these, it is well to state that, in addition 

 to carbon, cast-iron nearly always contains from 

 I to 2 per cent of silicon, with smaller quantities 

 of phosphorus and sulphur. It is the getting 

 rid of these deleterious substances, and not the 

 removal of the carbon, which constitutes the great 

 practical difficulty in the making of the more 

 useful kinds of wrought-iron and steel. 



The ancient method of converting cast into 

 malleable iron by a charcoal finery or hearth, is 

 still practised in this and other countries ; but the 

 conversion is now much more largely accom- 

 plished by the process of puddling. 



When pig-iron is to be converted into malleable 

 iron by the puddling process, as a preliminary 

 step it is sometimes, but not always, refined. 

 That is, it is melted on a hearth called a refinery, 

 covered with coke, and exposed to a powerful 

 blast of cold air. The operation lasts about two 

 hours, during which time the iron loses a con- 

 siderable proportion of carbon, and is termed 

 ' refined iron ' or ' refined metal,' neither of which 

 is a very appropriate term for a half-finished 

 product. As a rule, only the best qualities of 

 iron now pass through the refining stage, but 

 sometimes there is a convenience in partially 

 charging the puddling furnace with ' refined iron ' 

 for the commoner kinds. Puddling was invented 

 by Henry Cort in 1784, and time has proved it 

 to be one of the greatest improvements ever intro- 

 duced into the manufacture of wrought-iron. The 

 ordinary puddling furnace is represented in fig. 5. 

 It is reverberatory, and has a hearth, B ; a fire, A; 

 a fire-bridge, D ; and a chimney at C. A charge 

 usually amounts to about 5 cwt. of which from 

 one-fifth to one-half is refined iron, and the rest 

 consists mainly of pig-iron with a variable pro- 

 portion of hammer- slag and iron scale. In about 

 half an hour, when the furnace is in working 

 order, the charge is melted, and is then stirred or 

 ' rabbled ' for a considerable time, when it begins 

 to 'boil' by the formation and escape of carbonic 

 oxide, which forms jets of blue flame all over the 

 surface. Gradually, as the carbon of the pig- 

 iron is more and more oxidised, pasty masses of 

 malleable iron separate, and these are removed 

 in balls commonly weighing about 80 Ibs. but 



