The Manufacture of Iron

8/14/2019 The Manufacture of Iron

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REESE LIBRARY1.1 K THKUNIVERSITY OF CALIFORNIA

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UNIVERSITYMANUFACTURE OF IRON.

AT a period when the iron trade hasarrived at an extent and importancehitherto unknown, some account of thevarious processes of the manufacture ofiron in the district of South Wales maynot, perhaps, be uninteresting.That district, from the establishmentof several new works in the course ofthe last five years, as well as the in-crease of many of those before existing,has had its relative importance mostmaterially increased, and is at presentproducing between two and -three hun-dred thousand tons of iron annually. Theiron-works of South Wales and Mon-mouthshire are comprised in a range ofcountry of about 25 miles from one ex-tremity to the other, stretching in thedirection of north-west and south-east.The works at Hirwain, in Brecknock-shire, and Aberdare, in Glamorganshire,form the extreme points to the west-ward. Then comes Merthyr Tidvil,with its thickly-peopled neighbourhoodand important works, the focus, as itwere, of the manufacture; and fromMerthyr there is a continued line offurnaces formed by the works at Dow-lais, Romney, Tredegar, Sir Howey,Beaufort, Nant y Glo, Blaenafon, theVarteg, Abersychan, and Ponty Pool,which finishes the mineral

rangein that

direction.It is not proposed to give any accounthere of the method of working the coaland iron-stone, as that forms a distinct

subject of itself. Suffice it to say that,from the nature of the country, thedraining of the underground workingsby steam-engines, as well as the sinkingof shafts or pits, is in a great measureavoided. The minerals are obtained byexcavating a tunnel, or driving a head-ing, as it is technically termed, into theside of a hill. This tunnel is availableas a road along which to bring out thecoal and iron-stone, and at the sametime as a drain for the whole of thework with which it communicates.

7The manufacture of iron may be di-vided into two great heads : first, the

production of pig-iron from the ore bysmelting ; and secondly, the conversionof pig-iron into a malleable state, andthe rolling it into bars.The first process, the production ofthe pig-iron, is effected by means ofblast furnaces. These differ materiallyin their form and structure. The leadingpeculiarity of those in Wales is, thatthey are much larger than those in useelsewhere, and produce, of course, amuch greater quantity of iron. Thegeneral external form of a Welsh fur-nace is a square mass of masonry, witha base of from 30 to 50 feet ; these di-mensions gradually diminishing to about25 feet at the .height of 45 feet from theground. A cylinder of brickwork isthen carried on to the height of 10 or 15feet more, making a total height of 55to 60 feet, somewhat resembling the ac-companying sketch. There is a large

Fig. 1.

roof extending trom one or more sidesof the furnace, to shelter the workmen,and keep the cast-house dry, which isnot exhibited in this figure, that theJ3


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OMANUFACTURE OF IRON.

shape of the furnace may be more dis-tinctly seen ; and there is also a coveredcommunication between the top of thesquare masonry and the high ground atthe back, for the purpose of supplyingthe materials, which is left out for thesame reason. The cylinder at the top,called the tunnel head, is furnishedwith from one to four doors or openings

generally two opposite each other,through which are introduced the mate-rials for the supply of the furnace : it ismade of fire-bricks, hooped togetherwith iron, and is about eight feet in dia-meter. The masonry of the whole fur-nace is also strongly bound togetherwith iron stays. There are arches inthe centres of the four sides, forming-recesses in the solid masonry. That infront is to enable the workmen to workthe furnace and run out the iron ; thoseat the sides are for the more convenientintroduction of the blast.

Fig. 2 is a ground-plan of a furnace,in which the square in the centre is thehearth for the reception of the meltediron as it is formed. The recesses arealso seen here, and the pipes for the in-

Fig. 2.

troduction of the blast. The hearth isa cube of about 3 feet each way.The section of a blast furnace is seenin Jig. 3, in which the broadest part ofthe interior (a) is called the boshes, andis from 14 to 17 feet in diameter. Abovethe boshes fire-bricks are used as aliningto the masonry, and the diameter is gra-dually decreased to 7, 8, or 9 feet at thetunnel head.The hearth and boshes are generallymade of large pieces of a coarse grit, orplum-pudding stone, carefully jointedwith fire-clay, so as to resist as much as

Fig. 3.

possible the action of the intense heat towhich they are to be subjected. Re-cently, however, some hearths havebeen constructed of fire-bricks, which isa great saving in expense ; and the planhas been found to answer in durabilitybetter than was expected.As a proof of the importance thatwas formerly attached to the quality ofthe hearth stones, or of the prejudiceand ,want of enterprise of our forefa-thers, there is a legend that, on theestablishment, many years ago, of awork in Monmouthshire, by a Stafford-shire person, it was thought necessaryto take the stones for the furnace hearthsfrom Staffordshire, and that a stone ofsome tons weight was actually removedto within a few miles of its destination,when it was discovered that the gritstones to be found in abundance on thespot would answer the purpose as well !Whether this tradition be true or not, itis a fact that a large stone is now to beseen on the London and Milford road,which is pointed out as the identical onealluded to in the above tale.Much has been said about the bestform and dimensions of the hearthmore, probably, than the question de-serves, as it is found that, in a very shorttime, the sides and bottom are so wornaway by the constant action of themelted iron, as to become of a sort ofrude hemispherical shape.The inclination of the sides of the in-


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MANUFACTURE OF IRON.terior of the furnace, from the boshes tothe hearth, is a matter of more import-ance. If they are too steep, the mate-rials press with too great a weight uponthe melted and melting mass ; if, on thecontrary, they are not steep enough, theaction of the furnace is injured and im-peded by the adhesion of the half- meltedmasses to the sides, sometimes leavinga hollow space underneath, and at otherssuddenly dropping down in large quan-tities. These lumps adhering to thesides are called scaffolds, and when afurnace is in this state, it is said to bescaffolding.There is another and more simpleform of constructing furnaces, whichhas been resorted to in Wales, andwhich is called a cupola. It is in theform of a large chimney (fig. 4), andfrom the boshes upwards is simply thelength of a single brick in thickness. Itis held together by an iron hoop at everyjoint. The bricks are laid in fire-clayinstead of mortar, and are from 15 to 17inches long at the boshes, and gra-

dually diminished upwards to the tunnelhead.The lower part of the furnace is ofmasonry, carefully and very stronglyconnected with cast iron rings and up"-rights. The hoops in the upper partare of wrought iron, about 3 inches wideby half an inch thick at the boshes, andproportionably smaller towards the top.This form of furnace is rather cheaperand more simple than the other ; but ithas been thought that the thinness ofthe sides occasions a greater escape ofheat, and thereby causes a greater con-sumption of fuel in proportion to the

weight of iron produced. If this shouldbe proved to be the case, it is certainlyno economy to make use of them, forthe saving in the first cost of a furnaceis a drop in the ocean, compared withthe amount of what may be lost or savedby even a very slight constant differencein its working. This will be seen by andby, when the amounts of the materialsconsumed will be stated.One very important particular of afurnace remains to be described. Thisis the application of the blast. The threerecesses, with the blast pipes, are seenin/-. 2. The holes through which theblast is admitted to the furnace are calledtwyeres (pronounced tweers). The ge-neral practice in Wales is to blow withthree twyeres, as seen skfig- 2, althoughvery frequently but two are used, andoccasionally only one. It is evident thatthe same quantity of air, or blast, maybe introduced into the furnace throughone twyere as through three by merelyincreasing the size of the pipe.The management of the twyeres re-quires very considerable practice andskill ; and the profitable working of afurnace depends very much upon theway in which this part of the business isconducted.

It has been stated that the twyere isthe orifice through which the blast isadmitted to the furnace ; this orifice,however, does not always assume thesame aspect; the constant rushing inof the stream of cold air chills the massof melting matter to which it is opposedon its entrance to the furnace, and pro-duces a sort of artificial pipe or channel,extending more or less into the interior.It is a rude perforated cone, adheringby its base to the side of the interior ofthe furnace, and stretching its apexhorizontally towards the centre. Thedifferent appearances which it exhibitsindicate the manner in which the fur-nace is working, and are the signals tothe workman who has the charge of it,(the keeper, as he is called,) to makethe necessary changes in the proportionsof the materials or the application ofthe blast. Sometimes the twyeres willbecome so strong, and project so far, asto meet together in the middle of thefurnace. When this is the case, theprogress of the blast is, of course, muchobstructed. At other times, the twyerewill drop off close to the side, which isas prejudicial as the opposite extreme.All these variations are met or preventedby the careful keeper, who will watchB 2


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MANUFACTURE OF IRON.every indication of change, and take hismeasures according to the emergency ofthe case. Sometimes he will stop onetwyere entirely, and provide for theadmission of the same blast to the fur-nace by increasing the size of the re-maining blast pipes ; at other times hewill increase or diminish the total quan-tity of blast, or he will alter the propor-tions of the materials at the tunnel head.With all these precautions, he is unablealways to keep the furnace in the mostadvantageous state of working, and,what is more extraordinary, he is unableto account for the changes that fre-quently occur.The iron trade can, perhaps, hardlybe said to be still in its infancy ; but wehave certainly much, very much, tolearn, before we can boast of anythinglike a complete knowledge of its differentprocesses. We observe many facts inthis, as well as in other branches of themanufactory, of which the most that wecan say is, that they are connected withor caused by certain other accompany-ing facts, though we are ignorant howthis connexion exists ; often, indeed, ourknowledge does not extend so far.We come now to the method of gene-rating the requisite blast, and the modeof equalizing and applying it. It is pro-duced by powerful steam-engines, withone or two exceptions, where a greatlocal facility of water power obviates thenecessity of steam. Water, however,can only be used where it can be de-pended upon in a constant and amplestream even through a dry summer, asit is of the first importance that the blastof a furnace should not be withheld evenfor a few hours. Instances have beenknown of the whole contents of a fur-nace becoming one solid mass fromhaving been cooled by the accidentalstoppage of the blast.The blast- engine is supplied with alarge cylinder at the opposite end of thebeam to the steam cylinder, and ofdouble its diameter ; i. e. four times itsarea. The blowing piston, therefore,will produce a volume of air at eachstroke of the engine equal to four timesthe contents of the steam cylinder, butat a pressure of only one-fourth of thaton the steam piston by the joint actionof the vacuum and the steam, frictiondeducted. Thus, suppose that an en-gine with a steam cylinder 54 inchesdiameter, and a pressure of 5 pounds perinch of steam, is supplied with a blow-ing cylinder of 108 inches diameter, it

will be capable of keeping up a blast ata pressure of 2^ pounds per square inch;for it is calculated that the pressure inthe steam cylinder of such an engine,deducting the friction, is about 1 poundsper square inch. This pressure may bereduced at pleasure, by working the en-gine more slowly, or with a lower pres-sure of steam in the boilers.

If the volume of air thus generatedwere to be passed immediately throughsmall pipes to the twyeres, it would pro-duce an intermitting, irregular blast,almost dying away at the end of everystroke of the engine, and exerting itsutmost force between the pauses. Thiswould be very injurious to the furnace,for which great regularity in the blast isa desideratum. To obviate this incon-venience, the air is passed from theengine into a large iron reservoir, calleda regulator, from its effect in equalizingthe current to the twyeres. The regu-lator is sometimes in the shape of asphere, entirely closed up, with the ex-ception of the passages for the ingressand egress of the air, and produces therequired effect simply by the elasticityof the large volume of condensed airwhich it contains : it is then called a dryregulator. Sometimes it is in the shapeof a cube or cylinder, open at the bottom,and fixed in a larger vessel or cistern ofwater. In this case it is called a waterregulator, and the column of water atthe sides keeps up the requisite pressurewithin ; but there is an inconvenienceattending this construction, that is likelygradually to bring it out of use. Theintroduction of moisture into a furnacewith the blast has a bad effect both onthe working of the furnace and the qua-lity of the iron produced ; and it isfound that the condensed air in the wa-ter regulator, exposed as it is to a largeand constantly agitated surface of water,has the property of taking up a veryconsiderable quantity of moisture in so-lution. This is particularly the case insummer, as the higher the temperatureof the air, the more moisture it is capableof dissolving. This circumstance ac-counts in part for the fact, that furnacesnever work so advantageously in sum-mer as in cool weather ; so sensitive arethey in this respect, that, after workingextremely well for some time with a drynorth or east wind, they will frequentlychange all at once when the wind veersto the west or south, with moisture orrain. It was long thought that the dis-advantage experienced in the summer


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MANUFACTURE OF IRON.months was to be attributed (by someunknown connexion) simply to the heatof the weather ; and it was, therefore,supposed that a cool blast was mostfavourable to the smelting of iron. Somistaken does this notion now appear,that a patent has been recently obtainedfor heating the blast artificially beforeit is passed to the furnace. Care is, ofcourse, taken that it has no opportunityof absorbing moisture with its increaseof temperature ; otherwise the effectwould be injurious, instead of advanta-geous. The invention has not yet beenbrought into general use, and thereforeno certain decision can be pronouncedas to its efficacy : there seems, however,to be a strong probability of its ultimategeneral adoption and success.

It is ascertained that air cannot sup-port combustion until heated to 1000degrees of Fahrenheit; and, therefore,until it acquires that temperature frombeing in contact with the heated medium,it must produce an inverse effect ; andthe nearer it can be brought to thatpoint before entering the furnace, thebetter. The natural effect to be anti-cipated from the change is economy ofmaterials from their more speedy andcomplete conversion under the action ofthe hot blast. The degree of heat pro-duced in the blast by the new system isfrom 300 to 320 degrees of Fahrenheit.The diameter of the blast pipes at thetwyeres is various, according to circum-

stances. With a strong pressure ofblast and three twyeres, a diameter of3 5 inches may be considered a maxi-mum. The greater the quantity of blastthat is introduced, the greater generallywill be the quantity of iron produced,though the quality will be deteriorated.Thus, if foundry or melting iron iswanted that is, the best quality tobe used for melting and running intoarticles of cast iron, the blast used isnot so great as when an inferior qualityis made, to be subsequently refined andmanufactured into bar iron. In thesecases, the quantity of the iron producedis generally increased in proportion asthe quality is deteriorated.But to proceed to the materials usedin the production of pig-ironto thefood required to satisfy the voraciousappetite of the furnace. The iron stone,or mine, as it is technically termed,stands foremost in importance. To thisis added a proper supply of coke to keepup the necessary combustion, and a por-tion of limestone to act as a flux, as

will be afterwards explained. The minein South Wales is the argillaceous orclay iron ore, occurring sometimes instrata, sometimes in detached lumps orballs. We cannot here enter into detailwith regard to the method of workingthe minerals, as that would be too greata departure from the immediate subjectbefore us. The mine contains differentproportions of iron in different parts ofthe South Wales district, and also indifferent strata at the same work. Whatis generally used may be stated to con-tain from 18 to 55 per cent, after havingremained some time in the air, and be-fore it has been calcined or roasted.From 30 to 35 per cent, may be consi-derednot a bad average of mine through-out a work.

Carbonic acid and clay enter largelyinto the composition of the ore ; andwater, sulphur, silex, and perhaps a littlearsenic, complete the list of ingredients.It is an important point to get rid of theimpurities as completely as possible be-fore the mine is used in the furnace,and for this purpose it is roasted orcalcined in kilns, which are kept sup-plied at the top, as the mine is with-drawn fit for use at the bottom. Caremust be taken in this process to givethe necessary degree of heat to the kiln,and no more. If there be too muchheat, the pieces of mine partially meltand adhere together ; if too little, theystill contain a portion of water or sul-phur, and are obliged to be thrown asideby the filler, or workman at the tunnelhead, as raw orgreen mine. In the ope-ration ofroasting there is a loss ofweightin the mine of from 20 to 30 per cent.The coke is also of great importancein the smelting ofiron. There is a greatdifference in the quality of the coal inthis district. At one extremity, wherethe works of the British Company, theVarteg and Blaenafon, are situated, thecoal is of a bituminous nature, swellingand caking together in the coking, andbinding like the Newcastle coal, but ina less degree, in common fires. AtMerthyr Tidvil, on the contrary, it doesnot possess these qualities. There, itis capable of being coked in a muchshorter time, nor does it bind togetherin the manner just described. In theformer case, the ton of coal will produceabout 13 cwt. of coke ; in the latter, theproportion of coke to coal is greater,though the coke produced will not go sofar in the manufacture of iron. .,The method of coking in Wales is not


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6 MANUFACTURE OF IRON.remarkable for that economy to whichit may and will probably be broughtwhen coal is of more value than it is atpresent. The general system is to placethe coal in long open heaps, containing30 or 40 tons, laying the pieces of coalas loose and open as possible, to allowof their swelling, and covering the wholewith smaller pieces so as to give the ex-ternal surface a tolerably level appear-ance. The heap is then set on fire indifferent places, and suffered to burntill the whole surface is completely ig-nited. When this is the case, the cokercovers it entirely over with the dust andashes of former fires, to exclude the airand prevent waste, and it is left to burnput, or rather to cool gradually, till it isin a proper state to be uncovered andcarried to the tunnel head of the fur-nace. The cooling is generally, how-ever, expedited by pouring water uponthe cokes before they are uncovered.This is sometimes done to a great ex-tent,and is found to improve the qualityof the coke, by making it harder, andexpelling more of the sulphur of the coalthan would be got rid of without theapplication of water.By the system of open fires much ofthe coal must be reduced to ashes be-fore the air is excluded. This is moreparticularly the case when the wind ishigh, as it not unfrequently is in thosemountainous and exposed situations.On a stormy night, the unremittingexertions of a double set of cokers areperhaps required on the coke hearth tokeep the fires tolerably covered ; and inan extensive work, probably sixty or ahundred tons of coal may be wasted inone night in spite of all their labour.The coke-hearth of an iron work infull operation presents a grand and im-posing spectacle

in a dark night. Thelong rows of flame produced by theburning of many hundred tons of coal,extended over a vast space of ground,and flickering in the wind, the black,grotesque figures of the cokers bran-dishing their long rakes, and partiallyvisible through the thick lurid smoke,with the roaring of the blast and thenoise of machinery, seem to realize thedescriptions

of the infernal regions byVirgil or Dante, rather than anythingfamiliar to our experience in this habit-able world.The bituminous coal of Monmouth-shire requires from five to nine days tobecome thoroughly coked, whilst thatabout Merthyr takes only about half,

or less than half of that time. The coalwhen coked, has parted with all itsmoisture, tar, and hydrogen gas, and agreat part of its sulphur ; and accordingto its properties, is either of a dull jetblack, with the appearance of charcoal,or exhibits a bright metallic or vitreouslustre, with a porous texture. The morecarbonaceous matter it contains, thebetter ; and those beds ofcoal are there-fore the most esteemed which present inthe fracture the dull, soft appearance ofcarbonized vegetable matter. Smallpieces of coke may be occasionally se-lected from such a quality that canhardly be discriminated from charcoal,having that fibrous texture and peculia-rity of lustre by which it is characterised.Coke, indeed, may be considered onlyas a substitute for charcoal in the smelt-ing of iron, and was formerly unknownas applicable to this purpose. Charcoalis at present in general use in Russiaand Sweden, and indeed is now used ata few works in this country. The ironproduced from it is particularly calcu-lated for conversion into steel ; but itshigh price and insufficient quantitywould totally preclude its general use,even were it a much greater desidera-tum than it is. The impurities of thecoke of South Wales, or, in other words,the ashes that are left after combus-tion, are a very important subject forthe investigation of the iron-master.They are of many different kinds, someof which are much more prejudicial tothe working of the furnace than others ;and the strata of coal in which theseprevail the most should therefore beavoided altogether, or used with caution,mixed with other qualities of coal. Ifthe coke, after combustion, leaves ared ash or residuum, sulphuret of ironis indicated, the sulphur

of which pro-duces a positively bad effect on the qua-lity of the iron smelted in the furnace.If the ashes are white, they probablycontain magnesia, silex, or alumine,either singly or combined. The twolatter of these earths are only detrimen-tal as so much extraneous matter; in-deed, they may each singly be of serviceas a flux, according to the nature of theiron-stone with which they come in con-tact ; but magnesia is injurious, as itproduces an opposite effect in renderingthe flux less fusible by combining withit. To understand the mode of workingthe Welsh furnaces, it should be stated,that they are invariably situated on some


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MANUFACTURE OF IRON.natural steep declivity, so that, by a littleartificial excavation, the ground is madelevel with the tunnel head at the backof the furnace, and with the bottom ofthe hearth in front. Thus a perpendi-cular cliff is formed of about forty feethigh immediately in the rear of the fur-nace, supported, if necessary, by a wallof masonry. The mine kilns are on theupper level, immediately behind the fur-nace ; and thus the calcined mine whendrawn from them is at hand ready forthe filler at the tunnel head. On thesame level, and as near the furnace aspossible, is the coke hearth, a largelevel space, capable of containing somehundreds or thousands of tons, accord-ing to the number of furnaces. Again,in front of the furnace, on the lowerlevel, is the cast-house, in which thepigs and castings are run from the fur-nace ; and also a proper space for theconvenience of weighing, stocking, orsending them off.The limestone, the remaining ingre-dient in the manufacture of iron, is ge-nerally procured at some distance, andbrought to the tunnel head, where it isbroken into small pieces, that it maymix more intimately in the furnace withthe mine and coke. It is used as aflux, combining with the clay of theore, and forming with it a fusible com-pound, which runs off below in a slagor cinder. Although limestone is theuniversal flux in South Wales, its usein other districts would not answer thispurpose. In South Wales, as has beenstated, the iron-stone is argillaceous,but in other places, in the forest ofDean, for instance, in Gloucestershire,it is found in combination with lime orcalcareous spar. Now as lime, silex,and alumine are not of themselves rea-dily fusible, they are combined in theblast furnace ; and in the selection of theflux, the object of the iron-master is toseparate the impurities from the iron inthe most complete manner possible. Itwould obviously be absurd to attemptto use limestone as a flux with the cal-careous iron-stone of the forest of Dean,as that would be only adding to whatexisted in excess before it would beworse than useless, as it would be fillingup the furnace with additional impuri-ties, without facilitating its working. Inthat district, therefore, clay is the fluxand lime the substance which it is toseparate from the iron-stone just thecontrary of what takes place in SouthWales. If these two kinds of ore (the

argillaceous and the calcareous) couldbe found so near to each other as to beused in the same furnace, no flux wouldbe necessary, as the extraneous matterof each, if used in the proper propor-tions, would combine together, melt,and detach themselves in the state ofcinder without any addition.In the selection of limestone, all thosebeds which contain magnesia should besedulously avoided. The necessity ofthis will be evident from what has beensaid above of the injury produced by themagnesia found in coke. The same in-jury, of course, would arise, in whateverway magnesia is introduced into the fur-nace. The magnesian limestones ofWales are generally of a coarser texturethan those that are aluminous or sili-ceous, and of a reddish colour; butpractice and analysis only will enablethe iron-master to determine the qualityof stone best calculated for his purpose.The materials are introduced into thefurnace at the tunnel head by the filler,whose business it is to see that thecoke is brought to him from the coke-hearth properly burned ; that the mineis sufficiently calcined and unmixedwith clay or rubbish; that the lime-stone is broken small enough ; thatthe proportion of each material, as di-rected by the keeper or manager, ismaintained ; and also to take an ac-count of the number of charges that heputs into the furnace during his ' turn'of twelve hours. A charge is one bar-row of coke, with its proportion of mineand limestone ; and the furnace is saidto drive fast or slow, according to thenumber of charges required to keep itfull during the twelve hours. The bar-row of coke contains about twenty cubicfeet, and weighs about six cwt. It is,therefore, the product of about nine cwt.of coal, according to the calculationstated above. The proportion of burntmine used to the charge varies consider-ably, according to the working of thefurnace, and the quality of the ironwanted to be produced. If foundryiron is wanted, the ' burden ' of mine tothe charge must not be so heavy aswhen forge pigs are to be made. Thegreater the quantity of mine used to thecharge, the warmer, and the more dis-posed to burn, as it is called, the furnacebecomes. If there be an excess of mine,a great additional heat is created, thetwyeres will perhaps come short off thesides of the furnace, and all the portionsadhering to its interior will melt away.


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MANUFACTURE OF IRON.Even parts of the brick work about thetwyeres will be injured by the intense-ness of the heat, requiring to be repairedfrom the outside. Under these circum-stances the iron will become thick in thehearth, the quality of it will be verybad, and the quantity small. To re-medy all these evils a portion of theburden must be immediately taken off;that is, a less weight of mine must beused to the charge. After a short time,the effect of this change begins to ma-nifest itself. New twyeres begin toform, and to run in towards the centre ;the sides of the furnace become cooler,and the quality of the iron improves.Sometimes, when a scaffold has formedon the side, occasioning that irregularityin the working of the furnace which hasbeen before described, it becomes neces-sary to scour the furnace out, as it iscalled; that is, to remedy one evil byanother to increase the burden, andproduce all this heat and burning, bywhich the offending mass is melted andgot rid of. The burden is then againreduced, and the furnace works regu-larly as before.Let us now inquire into the quantitiesof raw mine (iron stone), coal, and lime-stone required to make a ton of pig iron.The iron is run from the furnace everytwelve hours, and we will assume sixtons as the quantity produced in thattime, although perhaps five would benearer the mark as an average. Wewill assume also, that the furnace isdriving 50 charges a turn, with a bur-den of 6 cwt. of mine ; the quantity ofburnt mine, therefore, required to make6 tons of iron will be 50 times G cwt., or15 tons, equal to about 18 tons of rawmine. Thus, according to this calcula-tion, 3 tons of raw mine are used forthe production of one of pig iron. Thecoke for the turn, reckoning 9 cwt. ofcoal to the barrow (or 6 cwt. of coke),will, in the same way, amount to 50times 9, or 450 cwt. = 22^ tons, or 3 tons15 cwt. to the ton of iron. This is theactual consumption of coal for the sup-ply of the furnace : a further quantity isused at the mine-kilns and engine-fires,which should properly be included in theaccount, and which will amount to aboutanother ton, making a total of 4 tons15 cwt. of coal to the ton of iron. Theseare called the yields of coal and mine,or, more indefinitely, the furnace yields,and are the objects of great attentionwith the iron master.The facilities or local advantages of

an iron work depend very much uponthe capability of the materials to workto a good yield. The importance of thispoint must be obvious when it is recol-lected that, by the above calculation,the daily consumption of a single fur-nace amounts to 57 tons of coal and 36of mine.The limestone is a matter of less im-portance, being generally obtained at asmall expense, and used in smallerquantity, only about a ton being re-quired to the ton of iron.

It has been stated, that the iron iscast, or the furnace tapped, every twelvehours. This operation is managed bythe keeper at the bottom. He will occa-sionally be obliged to cast more fre-quently, as it is possible, from the hearthbeing partially choked up, or from thefurnace making an unusually largequantity of iron, that it will not hold allthat is produced in that time.The hole through which the iron islet out is, of course, on a level with thebottom of the hearth, and in front of thefurnace. It is stopped with a mixtureof sand and clay, to prevent the escapeof the iron between the times of casting.There is also an aperture level withthe top of the hearth, by which the liquidscoria or cinder is constantly runningoff, except immediately after casting.The iron, being much heavier than thecinder, sinks to the bottom of the hearthas it is melted ; whilst the cinder, form-ing much more rapidly, soon fills thehearth and escapes, not, however, ob-structing the constant passage of theiron, which falls through it to the bottom.The appearance of the cinder is con-stantly watched by the keeper, as anindication of the working of the furnace,and he can generally tell with tolerablecertainty the quality of the iron he isabout to cast, by this criterion alone.If it is of a whitish-grey colour, with afracture somewhat resembling limestoneand running freely from the furnace to aconsiderable distance, he augurs well ofthe furnace ; the materials are then doingtheir duty, combining properly with eachother, and leaving the whole of the ironin the hearth without loss ; the furnaceis making good iron and to a good yield.At other times the cinder will assumea glassy appearance, being very tena-cious and tough whilst hot, and runningdown sluggishly. The colour is, per-

haps, of a light blue, or dirty yellow, orsea-green. This shows the furnace to beworking cold, driving slow, and probably


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MANUFACTURE OF IRON.not producing iron to so good a yield asin the former case.But the most unfavourable aspect

observable in the cinder is a jet-blackcolour, both on the surface and in thefracture ; the surface being rough anduneven ; and the stream broad, hot, andshallow. These symptoms are alwaysaccompanied by an unfavourable yield,as a portion of the iron combines withthe clay and limestone in the furnace,and comes away in the state of a blackoxide with the cinder, causing its darkcolour. Theory would teach us that themost favourable aspect of the cinderwould be that ofa perfect glass, indica-ting neither the presence of iron by theblack colour, nor the excess of the fluxby the stony opaque appearance of thefracture. But in practice, this precisepoint is found so difficult of attainment,that the appearance of the cinder isalways considered the most favourablewhen it is " strong of the stone," as theworkmen say.The keeper has a personal interest inthe well working of his furnace, and, ifhe is a good and steady workman, willwatch all these points with constant

care. He is paid on the ton of ironproduced, and, indeed, the fillers, co-kers, limestone breakers, mine burners,and all others connected with the fur-nace, are generally paid in the same way;for if any one of these various operationsis neglected, the furnace is sure to suffer,and by uniting the men in one commoninterest, the best security is obtained forthe well regulation of the whole. Thewages of labour constitute so very greata proportion of the cost of iron, that itis a matter of first-rate importance toeconomise them as much as possible ;and it has been said, with too muchtruth, that the business of the iron mas-ter is a constant struggle with his work-men, the endeavour on his part being tokeep down or to reduce their wages ;and, on theirs, to get as much for theirlabour as possible.This contest, unpleasant as it maybe,is to a certain extent unavoidable andnatural, and neither masters nor menare to be blamed for making the bestbargain for themselves that they can.It may be said, that there is a naturaland imperious standard of wages in thestate of the trade, beyond the control ofthe master or the workman ; that, wheniron is low and the demand dull, it is asimpossible for the former to give highwages as it is for him to keep them

down in an opposite state of things.This is true ; but it is sometimes difficultto convince the workmen of its truth,when the consequence to him will be adiminution of his gains ; and, from thesame cause, the master will sometimesbe unwilling to acknowledge the neces-sity of an advance of wages so soon ashis men desire. His object should be toinduce, as much as possible, a mutualconfidence between his men and him-self; to anticipate their demand for anadvance, if he feels that, from the stateof the trade, it is unavoidable, and toact with decision and firmness when heis under the necessity of opposing theirwishes.But to return to the furnaces. It maybe supposed that the quantity of cinderproducedby a furnace is very great, whenit is recollected that the weight of the ma-terials put in is 36 tons in the twelvehours, whilst the iron produced in thesame time weighs only 6 tons. Theweight of the cinder will not, however,by any means balance the account, ithaving been found that there is a loss ofweight, in the process of smelting,greater in amount than the quantity ofcoke used; that is, from 36 tons ofmaterials put in at the tunnel head, thetotal process at the bottom in cinder,iron, and ashes, will not exceed 20 tons.The deficiency is occasioned in the pro-cess of combustion by the escape ofoxygen, carbon, &c., from the mine andlimestone, as well as from the coke.

Still the quantity of cinder continuallyaccumulating is so great, as sometimesto occasion considerable expense in itsdisposal. The situations in Wales aregenerally very favourable for this object,being upon elevated ground. The cin-ders being carried in the direction of thedeclivity, and formed into a horizontalterrace, soon acquire, from the natureof the ground, a very great thickness,the road remaining level. Large ridgesor hillocks of cinder are thus produced,called cinder tips; and often, from theirgreat extent and elevated position, forma remarkable, though dreary, feature inthe aspect of the country. "Where theworks are situated on a flat ground,without any great fall in the immediateneighbourhood, this facility in the re-moval of the cinders is not afforded, anda serious item of expense is consequentlyincurred. In one or two instances, theyare obliged to be taken about two milesfrom the furnaces before they can bedisposed of.


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10 MANUFACTURE OF IRON.The pig iron produced in the operationof smelting is of very various qualities,

according to the purpose for which it iswanted, and the circumstances underwhich it is manufactured. It may bedivided, first, into foundry iron and forgeiron ; the former being used in the stateof pigs, for casting ; the latter being onlyapplicable to the manufacture of bariron. The reason of this is, that, fromits nature, it is too thick, when melted,to adapt itself to the shape of the mould,and, when cold, is too weak and brittleto be serviceable as cast iron, even ifthe other objection did not exist.But the foundry iron comes first to bedescribed. There are three qualities ofit, first, second, and third.No. 1 foundry iron differs in its che-mical composition from the other sorts,by containing more carbon. It is, in-deed, combined with as much carbon asit is capable of holding ; and to effectthis combination in its full extent, thecoke containing the fibrous appearanceof charcoal, or the purest carbon, isselected. The tendency of this combi-nation is to render the iron soft, and tomake it very fluid when melted, so thatit will run into the finest and most deli-cate mouldings. It is used for smalland ornamental castings, and anythingthat requires a minute and perfectadaptation to the shape of the mould.It is distinguished in its appearance bygreat smoothness on the face or surfaceof the pig; and in the fracture it ex-hibits a large, dark, bright, open grain,intermixed with dead spots of a lightercolour and closer texture. When broken,the pig does not ring, but sounds ratherlike lead, falling dull and dead upon theblock over which it is broken. It is alsoso soft as to yield readily to the chisel.In running from the furnace, the sur-face of the melted metal is smooth anddull, breaking occasionally into streaksand cracks of a darker and brighter red.When it is highly carbonized, the pigsand the cinder are frequently coveredwith small bright black laminae of asubstance called kish. It is a pure car-buret of iron, or black lead, and evincesan excess of carbon in the pig.No. 2 foundry iron is less carbonizedthan No. 1 ; not so soft, closer grainedand more regular in the fracture, notso fluid when melted, nor so smooth onthe face of the pig ; it is, however, harderand stronger, and is preferred for all theless delicate parts of machinery, wherestrength and durability are required.

These two sorts are all that are re-cognized in some places as foundry iron.Their being combined with so lar^e adose of carbon and oxygen renders themunfit for remanufacture into bars ; butiron of the next quality, or No. 3, havingless foreign admixture in its composi-tion, is destined indifferently for theforge or the foundry. It is used exten-sively for castings where great strengthis required, or in situations where it isto be exposed to constant wear and tear,such as tram plates, heavy shafts, andwheels, cylinders for steam-engines andmany descriptions of heavy work. It isselected for these purposes from being stillharder than No. 2, and possessing sogreat a degree of toughness as well ashardness as to make very strong anddurable castings. In appearance itdiffers from No. 2, in the same way asthat does from No. 1, being closergrained and more regular, and darkerwhen broken. From its appearance, itis often called dark grey iron ; by whichterm it is, indeed, as well known as bythat of No. 3.The next quality, bright iron, is nevercalled foundry iron, although used ex-tensively for large castings. It possessesgreat strength and hardness, but notfluidity enough to adapt itself to intricateor minute mouldings. It derives itsname from its appearance, which is of alighter colour and brighter lustre thanthat which has hitherto been described.

Mottled iron is used exclusively forthe purposes of the forge, as it is toothick and brittle for the foundry. It issmooth in the fracture, hardly exhibitingany grain, and appears to be com-pounded of two qualities imperfectlycombined, being spotted or mottled withgrey and white.White iron is supposed to contain avery small portion of carbon less thanany other sort of pig iron. It is totallyunfit for casting, and is sometimes sothick as hardly to run into the pig moulds,although they are purposely made verylarge ; and so brittle, that the largestand most unwieldy pigs may be readilybroken by a blow with a sledge-hammer.It is too hard to yield in any degree tothe chisel. The colour of the fractureis a silvery white ; shining and smoothin its texture, with a foliated or crys-tallized structure.Thus we have six distinct gradationsof pig iron, produced under differentcircumstances in the blast furnace:No. 1 and No. 2 foundry, No. 3 foundry


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MANUFACTURE OF IRON. 11or dark grey ; bright, mottled, and white.The difference in the properties and ap-pearance of these sorts has been at-tempted to be described; but any de-scription must be imperfect, unlessillustrated by reference to specimens.Accuracy in determining the precisequality of any particular specimen isonly to be attained by experience ; forwhen one sort is approaching to thenext either below it or above it, theshades of difference are so minute as tomake it difficult to determine its properrank. For instance, we often hear ironspoken of as good bright or indifferentdark, or perhaps as second foundry, butso good that it may do as first. Expe-rience also is necessary as to the localdifferences in the appearance of the pig;for foundry iron, especially, is found tovary materially in appearance at differentworks, the quality being the same.All these six descriptions of pig ironcontain oxygen and carbon. The car-bon exists in the greatest proportion inthe No. 1 foundry iron ; and in the leastin the white iron last described ; its pro-portion being gradually diminished inthe intermediate stages. Its tendencyseems to be, to give a softness and tough-ness to the pig, so that, as far as carbonis concerned, the purer the iron is whenrun from the furnace, the less fit it is forfoundry purposes.In describing the management of afurnace, and the selection of the mate-rials, there has been no reference to adiscovery made some time ago, and re-cently brought into very general appli-cation. Messrs. Hill and Co., of thePlymouth works, near Merthyr, ob-tained a patent many years ago for theuse of forge and refinery cinder, as asubstitute for mine, in the furnace.These materials are the scoria or drossproduced in the different operations ofthe forge and the refinery hereafter tobe described. It is an oxide of iron,with but little foreign matter, and there-fore containing a great proportion ofiron, frequently 60 or 70 per cent. Ithad not been generally used before forany purpose ; for although it was knownto contain a large proportion of iron, allattempts to smelt it effectively and eco-nomically had failed. It was thoughtto be so prejudicial to the working of afurnace, and the quality of the iron pro-duced, as to render its extensive appli-cation impracticable. The effect it pro-duced was to make the furnace burn,although a light burden was used. The

twyeres could not be kept strong ; thecinder became black, and the iron of avery inferior quality, being entirely whiteand very thick in running out of thefurnace. Under all these discouragingcircumstances, it was thought that nosubstitution of forge or refinery cinderfor mine could be advantageously made,and the cinder was consequently laidaside as entirely worthless.The contrivance of Messrs. Hill andCo. consisted in mixing the cinder withargillaceous matter, so as to form a morecomplete imitation of the ore in its na-tural state. A portion of the shale orclunch adhering to the natural ore whenfirst raised, was to be put into the fur-nace with every charge of cinder. Thiscombination was to make the materialless rich, or leaner, as it is termed, andthereby to prevent the injurious effectbefore described of the burning of thefurnace. The experiment succeeded,and a patent was obtained, which pro-mised to be very lucrative. It was,however, soon invaded. An action wasbrought for the infringement of the pa-tent, which was successfully defended, aprior use of the system in question hav-ing been proved. Thus, then, every ironmaster had it in his power to avail him-self of his large stores of cinder, the ac-cumulation perhaps of many years, inany quantity or proportion that hemight find expedient. Many were theexperiments made, and numberless thetons of bad iron produced in consequence.It was thought that the substitution,even in small proportions, of a cheapfor an expensive material, must morethan counterbalance all the disadvan-tages that would arise in quality, &c. ;but time and experience sobered downthese anticipations, and counteractedthese erroneous impressions. The ge-neral opinion of the application of cinderin Wales now is, that it can be advan-tageously used only to a certain extent,and with great care. Indeed, it isthought to be very fair work if the con-stant production of the cinder at theforge and refineries can be used at thefurnaces as it is made, so that the largestores before collected may, still be inpart at least, preserved, to be madeavailable at some future time when themanufacture of iron has undergone fur-ther improvement.The use of cinder certainly deterioratesthe quality of the iron. It rarely pro-duces foundry iron, even when mixed insmall proportions with mine ; and when


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12 MANUFACTURE OF IRON.the proportion is increased, or whenit is used entirely by itself, the pig pro-duced is not of a clear bright white colour,or compact solid texture, but of a dirtydull colour, very rough and uneven onthe surface, and somewhat porous in itsinternal structure. In the subsequentprocesses of conversion into bar iron,there is a greater loss of weight in pigproduced from cinder than from mine,with also a certain deterioration of qua-lity in the finished bar. All these cir-cumstances show that the greatest caremust be taken to ensure the advantage-ous application of cinder. It should beremembered that these remarks are onlyapplicable to Wales ; the cinder in Staf-fordshire having been more extensivelyand profitably applied.There is little doubt that the time willcome when this material will be foundmuch more valuable than it can nowbe considered ; that when chemicalscience has made further advances, amore effectual method will be disco-vered of separating the metal, which isknown to exist in a very large propor-tion, and combined with so few impuri-ties. We must be content, however, toproceed gradually. When we look backto the process of manufacturing irontwenty years ago, we have every reasonto be satisfied with the progress whichhas been made in the knowledge andimprovement of the subject; and wemay confidently anticipate that the nexttwenty years may be equally marked byadvancement. It is true that manyschemes projected by scientific and ex-perienced men have failed ; that manyfavourite speculations, which have ap-peared most plausible in the closet orlaboratory, have been incapable of beingfollowed up in practice on a large scale.But this want of success should by nomeans dishearten us. The very failuresthemselves lead us on to more accurateknowledge and correct results, and thuspave the way, slowly it is true, butsurely also, to ultimate success and cer-tainty.Our present want of knowledge is re-markably displayed in the different ope-rations of converting pig iron into mal-leable, or wrought iron. Pig iron iscommonly supposed to be a combinationof the pure metal with carbon and oxy-gen ; bar iron is the same metal freedfrom these impurities. It is not ascer-tained in what proportions oxygen existsin the pig ; but we know that the carbonis more abundant in proportion as the iron

is soft and tough. Thus then we arestruck with this apparent contradiction,that the purer the iron is in the state ofpig, as far at least as carbon is con-cerned, and in that respect the more itresembles malleable iron in its chemicalproperties, the more removed it becomesfrom it in its appearance and mechanicalproperties ; the white iron of the furnacebeing, as we have seen, the hardestand most brittle that can be produced.It is, however, so difficult to follow upchemical analysis and obtain resultswith minute accuracy, in a process re-quiring intense heat, that hitherto thephenomena attendant upon the refiningof pig iron, and its conversion into bars,may be said rather to be guessed at thanperfectly explained.The operation of refining the pig ironis performed in small, low furnaces,called refineries. They are about threefeet square at the base in the inside.The bottom of the hearth is of fire brick,and the front, back, and sides, of castiron. The castings used for the sidesare made hollow, and so contrived as toallow the passage of a constant streamof water through them. This contriv-ance is necessary as a precaution againstthe intense heat of the fire, which wouldotherwise soon burn away, and destroythe sides of the refinery. Near the topof this square are three holes in the side,for the introduction of the blast pipes.Refineries are of two kinds, accordingas the blast is applied on both sides oronly on one. In the former case, theyare called double fires ; and in the latter,single. The double fire being largerthan the single, and having a more am-ple supply of blast, will make a muchgreater quantity of refined metal. Itwould have been therefore universallypreferred, if it had not been thought tocarry on the process of refining at agreater expense of iron and coke thanthe single fire ; that is, in .the technicallanguage of the trade, ' to work to aworse yield.' This may be the case un-der peculiar circumstances of materials ;but generally it will be found, that, allother things being equal,~ the greaterthe quantity produced in one fire, in-stead of distributing the production be-tween two, the greater will be the eco-nomy of fuel ; for a portion of heat willalways be lost at the surface and sidesof the fire ; and therefore the smallerthe fire, the greater will be the propor-tion of surface and consequent loss ofheat. _ But the yield of iron in the re-


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MANUFACTURE OF IRON. 13finery is of more consequence than theyield of coke, inasmuch as the formermaterial is much more costly than thelatter. If, therefore, the yield of iron isw.orse in the double fire than in thesingle one, Ihe latter ought to be pre-ferred, in spite of the greater loss ofcoke. This, however, is not generallythe case ; and the double refineries areconsequently the most commonly in use.They are furnished with three smalltwyeres on each side, the pipes beingabout an inch in diameter, and the pres-sure of the blast the same as for the fur-nace, viz. from 1 fib. to 2 ^Ibs. or even 3lbs.on the square inch. The twyeres are pro-tected by a conical case of wrought iron,projecting a little into the fire, and madehollow, or double, so as to allow of theconstant circulation of a stream of coldwater. These are called water twyeres,and are found necessary to keep thesides of the refinery cool, and the twyerepipes from being burned. Water twyeresare also occasionally used at the smeltingfurnace, when it is working hot andthere is a propensity to burn, and theyare then of much advantage in checkingthe heat of the furnace and preservingthe masonry of the sides.The refinery is furnished with irondoors at the back, but is open in front ;and when the doors behind are closed,it looks not unlike an old-fashionedkitchen fire-place, though by no meansso approachable, for the heat thrown outis too great for any one but the work-men who are accustomed to it, to comenear. The- whole is surmounted by alow, wide, square chimney of brick-work, the entire edifice not being morethan 18 to 20 feet high. In front, theworkman is protected from the weatherby a shed coming forward from the fire.There is a hole at the bottom of thehearth in front, for running out the me-tal, similar to that in the furnace. Itcommunicates by a short channel withan oblong flat mould of cast iron, about20 feet long by 2 broad. This is placedover a cistern ofwater, with the surfaceof which it is in contact, and is thuskept cool, and chills the metal as it runsinto it. It is necessary to cast themould very thick, to provide against thefrequent cracking to which it is liable,from the unequal contraction and ex-pansion of the iron.The process of refining consists inseparating a portion of the carbon fromthe pig, and thus reducing the iron to agreater degree of purity preparatory to

the subsequent operations which it hasto undergo. This is effected by keepingthe pigs in the state of fusion for sometime, exposed to a very great heat anda strong blast. How the change is pro-duced, what is the quantity of carbonseparated, and combined in what pro-portion with oxygen, are rather subjectsof speculation than demonstrated facts.It would appear that there is a certaincombination of carbon and oxygen inthe pig more favourable than any otherfor the process of refining, for dark greypigs will produce a much better qualityof refined metal than mottled or white,though it might be supposed, from thelatter being combined with less carbonthan the former, that they would t themore readily part with what they docontain. The white pig, in its chemicalproperties, as far as we know them, ap-proaches very nearly to the refined me-tal. In its appearance, also, and me-chanical properties it is very similar toit. The plate of metal run into the re-finery mould is very brittle, and easilybroken into convenient pieces for use atthe forge. In its fracture, it presentsthe same bright silvery whiteness thathas been described in the white pig.With all this apparent similarity, whiteiron is disliked by the refiner, as occa-sioning more trouble in working, andproducing refined metal of a worsequality than dark grey, bright, or mot-tled pigs ; and it will be seen afterwardsthat the white pig cannot be wholly sub-stituted for refined metal at the forge.There is then an essential difference inthe composition of the iron in these twostates, though what this difference ishas not hitherto been accurately ascer-tained.The refiner selects his materials ac-cording to the quality of the iron wanted.The best quality is made from the darkgrey pig, or No. 3, and the inferior sortsfrom bright, mottled, and white, in theirorder. The very worst white iron can-not be used by itself in the refinery,being too thick to be readily run out,and consequently clogging up and set-ting in the hearth. It is got rid of bybeing mixed with pigs of a better qua-lity, by which means little inconvenienceis occasioned to the refiner.From the time the pigs are put intothe refinery, it requires^about two hoursbefore they are in a proper state to runout. Thus, the refiner will run out hismould of metal six times in his turn oftwelve hours ; and as there is always a


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14 MANUFACTURE OF IRON.double set of men, to avoid the loss oftime and fuel consequent upon allowing1the fires to go out, the refineries willcontinue at this rate from the Mondaymorning to the Saturday night. Theweight of each plate of metal is about aton. The quantity then produced in adouble fire in the week will be fromsixty to seventy tons. Let us now seeat what expense of material it is pro-duced, or, in technical language, whatare the refinery yields.The yield of iron to the ton of refinedmetal, like every thing else in the trade,varies according to good or bad manage-ment, to the quality of the purs, and alsoto the quality of the coke. Dark greypigs, with well carbonized coke, willsometimes work to a yield of 2 cwt.,i.e. 22 cwt. of pigs will only be requiredto produce the ton of refined metal.More will be required with the inferiorqualities of pig ; and 23 cwt. will notprobably be too much to state as theaverage quantity of pig to the ton of re-fined metal in Wales. This deficiencyof weight is more than balanced by thequantity of cinder produced, showingthe combination of a portion of the ironwith oxygen and other impurities. Ateach running out of the refined metal,a quantity of the cinder comes with it,and being lighter than the metal, it floatson the top, and detaches itself as itcools. It is an oxide of iron, and, as hasbeen seen, is now duly appreciated as avaluable substitute for mine at the fur-naces. From an actual trial, carefullymade during one week at two refineries,the following results were obtained :

Tons. Cwt.Pigs used - - - - 151 7Refined metal produced 135Showing a loss of - 16 7

from which it appears that the yield was2 cwt. 1 qr. 22 Ibs., or that 1 ton 2 cwt.1 qr. 22 Ibs. of pig iron was used tomake the ton of metal. During theabove period, the refinery cinder pro-duced was 3 1 tons 4 cwt. which, it will beobserved, more than balances the wasteof the pig iron by 1 4 tons 17 cwt., show-ing a combination of iron with extra-neous matter to that extent. The cin-der, therefore, in this instance, wouldcontain rather more than 50 per cent,of iron.The quantity of coal used to the tonof metal is not great, ten or twelve cwt.being sufficient. It is used in the stateof coke at the refinery ; but the most

satisfactory way of stating the yield is togive it in the coal, as some qualities willproduce a greater quantity of coke thanothers. The running out a mould ofrefined iron, or metal as it is called forshortness, is a brilliant and beautifulspectacle. The impetuosity of the streamas it issues from the hearth when firstopened, the hissing of the liquid metal,the beautiful sparks of ignited iron fan-tastically dancing in all directions, andafterwards the sluggish progress of thecinder bubbling up, and frequently ris-ing into grotesque forms, cannot fail tobe striking and interesting to the ob-server, however unacquainted he maybe with the chemical and scientific solu-tion of the phenomena he is witnessing.The refiners, like the furnace men,are paid on the quantity of metal pro-duced. It requires considerable expe-rience and skill to be a good refiner.Their occupation also is one of greatexertion, and occasional exposure to anintense heat. Their business consistsin putting the charge of pigs on the fire,which they do by opening the iron doorsat the back ; in attending to the pro-gress of the melting, supplying the firewith coke from time to time, and fre-quently stirring it up to equalize theheat in all parts of the hearth ; in at-tending to the twyeres, and taking carethat the circulation of the water conti-nues uninterrupted ; in running out themetal when it is ready ; and finally, inraising the plate from the mould, whenit has a little cooled, by means of a lever,and wheeling it forwards beyond hisshed, removing the cinder, and prepar-ing the mould for the reception of thenext supply of metal. The metal isweighed by a person appointed for thepurpose, who keeps a separate accountof the work of each refiner, to be car-ried to his credit in the pay book.Having now got through the businessof the furnace and the refinery, the va-rious operations of the forge come nextunder our notice. The forge and millare perhaps the most interesting depart-ment of an iron work. In what hasbeen hitherto before us, there has beenno succession of active business broughtpalpably to the view of the spectator.It is true that things are constantlyprogressing, but the proceeds are onlyoccasionally brought to light. ' A sowof pigs ' is cast at the furnace everytwelve hours, and then all is compara-tively quiet again. A plate of metal isrun out at the refinery only at intervals.


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MANUFACTURE OF IRON.The continued action is carried on insecret as it were, out of our sight, andbeyond our observation. We see therough materials put into the furnace atthe tunnel head, and are told that suchand such combinations and results areto follow ; but, unfortunately, we can-not ourselves observe these operations,and we must therefore content ourselveswith a partial and imperfect contempla-tion of the progress of the manufactureso far.

In the forge and mill, on the contrary,all is bustle and activity ; nothing isleft to itself ; all is under the constantobservation of the workman ; and wecan watch the progress of convertingthe refined metal into bars, through allits different states and stages.Steam power here, as with the fur-naces, is in most general use; conve-nient situations affording an ample sup-ply of water being extremely rare. Butas* it is not so important to have an un-interrupted power for the forge as it isfor the furnace, water power might beapplicable to the former, though itwould be rejected for the latter purpose.Stoppage at the forge is not attendedwith the fatal consequences that wouldresult at the furnace. It is an incon-venience rather than a positive injury ;merely a loss of production, a hinderanceto the progress of the work.

Supposing then that steam power isthe primum mobile at the forge, andthat one engine is used, let us inquirewhat it has to do. The forge consists,we will say, of a hammer and two pairof rollers, (or rolls, as they are termed,the workman being called the roller,)with a pair or two of strong shears tocut the bars. We will not stop to de-scribe these now, as they will comeagain under our observation. We willassume also, that the mill contains twopair of rolls of fourteen inches diameter,for making large sizes of bolts and bars ;two pair of ten inches, as an interme-diate size ; and two or three pair onlyseven inches in diameter, for rolling thesmallest sizes of iron. The mill also,as well as the forge, should be providedwith strong shears, for cutting the bars.If nail rods are required to be made,there must be the proper machinery forthem also viz. a pair of rolls and apair of slitters, as they are called. Toconclude, a heavy and powerful latheis necessary, for the purpose of turningthe iron rolls. The engine then willbe required to put in motion nine pair

of rolls, the hammer, shears, and lathe.To effect these objects, an engine witha steam cylinder of forty-five inches willbe required. The work to be done bythis engine is of a peculiar kind ; thestrain, or the force and friction to beovercome, being at one time very great,and at another comparatively nothing.If it has only the machinery to keep inmotion, which is occasionally the caseduring short intervals, it has of courselittle resistance to overcome. If, onthe other hand, there is a bar passingthrough every pair of rolls at the sametime, the resistance becomes so great,that if it were continued instead of beingtemporary, the engine would be stag-gered and finally stopped. This greatvariation ought to be avoided as muchas possible by the workmen, who shouldso contrive as to keep the work of theengine tolerably regular, neither allow-ing the rolls to remain long idle, norsupplying them all with bars at thesame time and in quick succession.This equalization of power is also pro-vided for necessarily by other means.It is well known that all engines thatcommunicate power by means of acrank must be furnished with a flywheel, to carry the crank over thecentres. This they do by their momen-tum ; and if it were not for the fly wheel,the engine would be liable to stop at theend of every stroke ; that is, wheneverthe piston and the crank get to theirlowest point ofdepression or their highestpoint of elevation. At these points thepower of the engine is nothing, as it hasno leverage upon which to act in thecrank. At the intermediate parts ofthe ascending and descending strokethe power varies, being the greatest atthe half stroke, when the crank presentsthe longest lever to the connecting rod,and proportionably smaller as it ap-proaches the top or bottom.This irregularity of power is commonto all engines working with a crank,and they are all therefore provided witha fly wheel. But when, in addition tothis unavoidable variation in the actionof an engine, it has to perform work ofan intermitting kind to resist greatand sudden strains, that come at inter-vals, and last for only a short time, thefly wheel becomes eminently useful. Inengines of this description, therefore, itis made unusually large and heavy,weighing perhaps 8, 10 or 12 tons, andof the diameter of 16 feet, the weightbeing disposed as much at the circum-


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16 MANUFACTURE OF IRON.ference as is consistent with the strengthof the wheel. The speed at which it ispropelled is also very much greater thanin ordinary cases, being 70, 80, and even100 revolutions in the minute so fast,that the spokes or radii of the wheel aresometimes not discernible. The mo-mentum of such a mass of iron movingat so great a velocity, may readily beconceived to be tremendous, and to bea most effectual coadjutor to the enginein carrying it through sudden strains.Indeed, hardly any force that could beopposed to it would be sufficient to stopit all at once. So irresistible is itspower, that in case of any sudden impe-diment, too great for the machinery tosurmount, some part of it must giveway, and as these cases will sometimesoccur, it is contrived to make a subor-dinate part of the machinery weakerthan the rest, so that, by breaking, itsaves the more valuable parts from in-jury, and is itself easily replaced.As may be supposed, all the ma-chinery of a forge is obliged to be par-ticularly firm and strong. Very heavycast iron plates are imbedded in ma-sonry underground, to form a firmfoundation. These beds are furnishedwith grooves and other conveniences,by which the uprights or sides of therolls are immoveably secured. Thedifferent sets of rolls require to beturned at different speeds, and a num-ber of wheels and shafts are thereforenecessary, which are carried chiefly un-der ground for the greater accommoda-tion of the work. Thus there is almostas much weight of machinery underground as above ; and the spectator willat first be at a loss to trace the con-nexion from the engine to the more dis-tant parts of the machinery.The rolls are cast solid ; and to pro-vide for the great and constant wearthey have to sustain from the pressureof the bar, as it passes through them,they are made of bright iron, as beingthe hardest quality that is consistentwith a proper degree of strength. Nowit is found that in very heavy castingsthe body of the iron is not uniformlyfirm and solid throughout. The outsidemay not, and probably will not, betraythis defect, as it cools and hardens be-fore the rest ; but the shrinking of theiron within, as it cools, occasions smallholes and a partial honeycomb texture,which of course is prejudicial in all cases.It is particularly so in rolls, which havethe outside taken off in turning, and

which ought, when finished, to presentan uniformly smooth and firm surface.The founder, however, has a means ofobviating this unsoundness of texture.The mould of the roll is sunk in the casthouse in a perpendicular direction be-low the surface, and above it is a secondmould or head, as it is called, which,when that of the roll is filled, receivesan additional quantity of the meltedmetal. The founder introduces a barthrough this head into the body of theroll, with which he gently stirs the ironas long as it is sufficiently fluid to admitof his doing so. The deficiency occa-sioned by the shrinking of the iron inthe body of the roll is thus suppliedfrom above, and the whole casting issound and solid throughout.In turning so large a body, and onecomposed of so hard a material, a veryslow motion is necessary, otherwise thesteel tools would soon become so hot asto lose their edge. This is accordinglyprovided for by a succession of largeand small wheels, which reduce thespeed at the lathe to about a revolutionand a half in a minute.From what has been stated of thenumber of shafts and wheels in the ma-chinery of a forge and mill, each ofwhich must have its axles or bearings,it may be supposed that the friction tobe overcome is of itself enormous. Itis increased from the necessity of allthese axles and bearings being large andstrong ; and the only means there are ofkeeping it at all within bounds are there-fore anxiously resorted to. The first ofthese is to have all the machinery con-structed and put together with greataccuracy ; the wheels correctly centred,perfectly true, and in line with eachother ; the shafts carefully levelled, andin line also ; and the rolls exactly pa-rallel. The next is to have brass bear-ings for all the necks of the rolls, theaxles of the wheels, and the ends of theshafts, the friction occasioned by therubbing of two different metals beingwell known to be much less than thatof two pieces of the same metal. Thethird of these means is, to keep all thepoints of friction well oiled and perfectlycool. If the axle of a wheel or neckof a roll be suffered to become hot, thefriction is prodigiously increased atonce, and the parts in question beginrapidly to rub and wear against eachother ; thus producing a double evil,the immediate one of increasing thework of the engine, and the more re-


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MANUFACTURE OF IRON. 17mote, though not less important one, ofbringing the machinery out of line orlevel hy the unequal wearing of its parts.In describing the manufacture of bars,we shall have to encounter many tech-nical terms, all of which will be noticedand explained as they occur ; not that itis necessary to introduce them all forthe purposes of clear definition to thegeneral reader, but it is surely desirablethat those who interest themselves inany subject should be made acquaintedwith the terms in which they would hearthat subject explained by those imme-diately engaged in it.The first grand process at the forgeis the puddling, an operation by whichthe oxygen and carbon are still furtherand more completely separated from theiron than could be accomplished in therefinery. It is performed in a reverbe-ratory furnace, called a puddling fur-nace, of which a section is annexed, infig. 5, to give an idea of its structure.

Fig. 5.

a more intense heat than at others. Thedraft and heat of these furnaces are sogreat, that the flame is carried com-pletely through to the top of the stack,where it comes in contact with thedamper, which is frequently nearlyred hot. The bottom of the furnace (c)was formerly always composed of sand,and occasionally is so still ; but themost general plan is to construct it of athick cast iron plate, which is preservedfrom fusion by a coat of the oxide ofiron or cinder, which is formed in pud-dling. An artificial bottom is thuscreated, and found to answer better thanone constructed upon sand.

Fig, 6 is an outline of the exterior ofFig. 6.

In this figure, a is the grate, suppliedwith coal through an aperture in theside, called the stoke-hole, and furnishedwith bars at the bottom for the propersupply of air and escape of the ashes.b is the body of the furnace, where therefined metal is placed and exposed tothe heat of the flames, which are drawnfrom the fire by the current of air overthe little brick-work division between aand b, and are turned downwards againby the inclination of the roof, so as tocurl and play upon the surface of themelted iron at b ; they are then carriedthrough the narrow part, or neck of thefurnace, to the stack or chimney c. Thechimney is carried up to the height ofabout 30 feet, and bound together atdifferent points with iron, to keep itfirmly together. There is a damper atthe top of it, by which the puddler regu-lates the degree of draft (and conse-quently heat) to his furnace ; for, duringsome parts of his operations, he wants

a puddling furnace, in which the wholeside is of one or more plates of cast ironlined with brick, the two sides beingconnected by bars at the top, over thebrickwork of the roof, a is the stoke-hole, so contrived as to be stopped witha piece of coal, which is used to equalizethe heat, by preventing the ingress ofair to the furnace, except through thebars at the bottom, b is the door^, raisedwhen necessary by the lever and chain d.c is the stack, where a portion of thechain is shown by which the damper israised or lowered. The furnace, whenfirst lighted, requires three or four hoursbefore it is ready to be charged, or toreceive a heat of metal, as it is called ;that is, the proper quantity of refinediron.The first department at the forge isthe weighing out of these charges, anddelivering them at the puddling furnaces.The general weight of the charge isabout 3^ cwt., or from that to 4 cwt. ;it cannot be stated with precision, asthe practice varies at different works.Indeed, all the statements of quantity,and weight, and yield, that have hithertobeen made, as well as those which willC


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MANUFACTURE OF IRON. 19qui vive for all 'possible projects of re-trenchment and economy. Indeed, eco-nomy may be considered as the veryessence and soul of their manufacture.One change to which they have recentlyturned their attention more than for-merly, is the substitution of white pigiron for refined metal in the puddlingfurnace. As far as chemical analysisgoes, the quality of the one differs veryslightly, as we have seen, from that ofthe other. If, therefore, the white pigwere found to answer at the forge aswell as metal, the saving would be verygreat. In the first place, the 3 cwt. lossper ton in the refinery yield would besaved ; this, supposing pig iron to beworth 31., is of itself nine shillings. Tothis is to be added, the wages of therefiner, the cost of the coke, and thecharge for weighing and loading themetal; so that, altogether, we may putdown the refined metal at 31. 15s. perton, supposing the pig as above to be 31.The saving, therefore, being so great asfifteen shillings on the puddler's mate-rial, there is a great inducement for thesubstitution, provided it can be madewithout any correspondent disadvantage.This is the consideration ; and the diffi-culties and disadvantages are by nomeans trifling. To put a case in itsstrongest colours it is best to make it anextreme one. Let us suppose, then,that white pig iron is exclusively usedin the puddling furnace, without anyadmixture of refined metal. In the firstplace, the charge of pig works hot andfluid in the puddling furnace. It takes along time to ' come round to nature,' andis, therefore, more laborious for the pud-dler, who requires a higher price for hiswork per ton. It will admit of little orno cinder being used, as its own depositof cinder in the operation is great. By itsgreat heat and fluidity in working, itburns through the artificial coating ofcinder on the bottom of the furnace, andwears out the iron bottom very fast,occasioning much care and trouble tothe puddler. As it deposits a greaterquantity of cinder than metal does, it,of course, loses weight in proportion,and works to a bad yield. Probably, inthis way, there is nearly 1 cwt. differencebetween pig and metal in the yield. Allthese are drawbacks, though not verymaterial ones; but the chief disadvan-tage is the deterioration in the qualityof the bar iron produced in this way.This mode of manufacture has uniformlya tendency to impair its strength and

body. This is an argument which ad-mits of no reply. The very same cir-cumstances of flat demand and lowprices, that force the cheap manufactureof iron, require also that the greatestattention be paid to its quality. If awork acquires a reputation for quality,it will at least have a preference in themarket over others, if not an advantagein price ; and in times of extraordinarydepression, such as we have recentlywitnessed, it is essential to preserve thisadvantage, to maintain this preference ;otherwise very much more is lost by theiron master being obliged to accumulatea stock of iron, or to force it into themarket, than can be saved by the unduesubstitution of pig for metal. No doubta portion of it may be advantageouslyused for common iron, although it is farfrom being the important saving that itwould at first appear to be.When the puddler has completed allhis balls, his underhand proceeds todeliver them over to the shingler, or theroller ; for, in some works, the processof shingling is omitted, the puddled ballbeing rolled at once into the rough bar.The shingling consists in giving thepuddled balls a few blows with a veryheavy hammer, which makes them moresolid, and reduces them to an oblongshape, better calculated for going be-tween the rolls. It also squeezes outa portion of the liquid cinder or oxide,which is separated from the pure iron inthe puddling. The hammer, generallyweighing about four tons, is representedinfig. 7, in which it appears as at rest,

- Fig. 7.

being supported by the upright bar a.When this bar is removed, the six littleprojections or arms in the solid wheel braise the point of the hammer c, and letit fall again in the course of their revo-lution. From ten to twenty blows aregenerally sufficient to give the bloom itsdue form. Whilst under the action ofthe hammer, the sparks and pieces ofcinder fly with great force in all direc-tions, and the shingler or hammer-manis obliged to protect himself by verythick leather leggings and apron. TheC 2


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20 MANUFACTURE OF IRON.bloom itself hisses, and bubbles, andflames under the operation, showing thatthe escape of an elastic fluid is still go-ing on. If properly puddled, it is broughtto a firm and tolerably tenacious mass.Sometimes, when not well puddled, itdoes not adhere equally together, a por-tion appearing harder than the rest, andnot amalgamating well with it. It isthen turned back to the puddler, under

the quaint denomination of a shadrach.This term has, no doubt, a scripturalderivation ; the thing to which it is ap-plied having come out of the fiery fur-nace unchanged, or, at least, not suffi-ciently changed from its previous nature.For every shadrach the puddler has afine set down to him, which is deductedfrom his wages on the day of reckoning.The roller takes the bloom from the

Fig. 8.

shingler, and, whilst it is still hot, passesit through the puddle-rolls, which areshown in Jig. 8. It is first put throughthe largest hole in the rolls at a, andthen goes through the smaller ones insuccession. It is received by a boy onthe opposite side, called the catcher,and handed back by him, with a pair oftongs, over the rolls, to the roller, who,when he has reduced the size of the barin the first pair of rolls, passes it throughdifferent grooves of the second. Thereit is reduced to a more accurate form,and to the required width and thickness.The pressure of the rolls upon the baras it passes between them expels a fur-ther portion of cinder, some of whichflies violently off, but the greater partfalls into a hollow beneath the rolls,where it is afterwards gathered up andlaid aside.The iron is now in the state of a roughbar, having undergone a most signalchange. The metal that was put intothe puddling furnace was easily fusible,very hard, and very brittle ; it has nowbecome a long, slender bar of malleableiron, soft, tough, and hardly fusible ; andthis great change, it is supposed, iseffected merely by the separation of alittle oxygen and a minute portion ofcarbon from the pure iron. It mustnot, however, be supposed that the barin this state is finished, or fit for sale ;it is scaly and uneven on its surface,rough and imperfect on the edges, and

unsound in the body, and therefore notyet calculated for the smith's use. Ithas still to undergo a further purifica-tion at the mill, the operations at theforge being now concluded.At some works there is no forge-hammer, and the blooms are there com-pressed into an oblong form, or * nobbled,'by the puddlers with a heavy iron bar,before they are taken out of the fur-nace. But as they are in this way veryimperfectly formed, the first groove ofthe rolls is necessarily much larger thanwhere a hammer is used. The puddleris paid on the weight of rough bars pro-duced ; and the weight of each furnaceis, therefore, kept separate, an accountbeing taken of each man's performance.The yield of the puddling furnace de-pends very much on the quality of therefined metal used, and the degree oflicence that the workman has in the useof cinder. If he is allowed to use asmuch as he pleases, and is working upongood metal, the weight of the rough barswill sometimes be as great as that of themetal put into the furnace ; but this isnot to be desired, as it indicates an ex-cessive use of cinder, and what is gainedhere is lost afterwards in the mill, as therough bar is unsound, and contains stillso great a portion of cinder as to loseweight considerably when again heatedin the mill. 22 cwt. is about the usualquantity of metal required to make a tonof rough bars, supposing the puddler is


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MANUFACTURE OF IRON. 21allowed to use little or no cinder; andabout 17 cwt. of coal is consumed tothe ton of rough bars.There is a species of puddling furnace,of which no mention has hitherto beenmade, but which may with propriety benoticed before we quit this part of thesubject. In the process of puddling, asabove described, there is an obvious lossof time from the point when the metalis first put in, to that when it is suffi-ciently heated for the puddler to beginhis operations, a period of from twentyminutes to half an hour. Now the timerequired to complete the heat is underan hour and three-quarters, the puddlerusually finishing seven heats in his turn.The produce of these seven heats willbe about 25 cwt.; so that, reckoningeleven turns in the week, the make ofone furnace in a week is between thir-teen and fourteen tons. But if half anhour in each heat could be saved, andthe workman be kept regularly on with-out interruption, many more heats couldbe completed in the same time, andthere would be a considerable saving incoal.To this end there have been severalcontrivances for warming the freshcharge of metal whilst the precedingheat is in progress. One plan is, tomake the flue rather wider, so as toform a sort of recess for the receptionof the fresh

charge,which is

placedthere by the puddler' s underhand througha small door for the purpose, withoutany interruption to him, and, when hisheat is finished, is drawn forward, andis ready for him to go on with, withoutany delay. The simplest method, how-ever, yet used, is to make the body ofthe furnace longer than according to theold plan, and to have a second door,between that where the puddler worksand the stack. This affords sufficientconvenience and room for the succeed-ing charge of metal, which at the sametime is so near the workman that, whenhe has completed the heat and sent theballs to the shingler, it can be instantlydrawn to the scene of action, and, if putin at the right time, is just in the properstate. With these furnaces, nine heatscan readily be worked by one man intwelve hours ; and if, as is sometimesthe case, the furnace is provided withthree sets of men instead of two, (eachset working eight hours out of the twenty-four, instead of twelve,) ten or even twelveheats may be finished in the twelvehours. The additional number of turns

being, of course, attended with a propor-tionate increase in the weight of the pro-duce, it follows that there must be aconsiderable economy of coal; for thequantity used at the furnace is only thesame, or nearly the same, whether it beconstructed on the old or on the newsyslem.The rough bars, when they come fromthe puddle rolls, are cut into lengths bya strong pair of shears, worked from theengine. In some works, they are cuthot, immediately after being rolled, andweighed afterwards ; in others, they arelaid aside in the first instance to cool,the work of each puddler being keptseparate, and then weighed and shearedwhen cold. The first of these plans is,perhaps, rather more econoimcal inlabour, but the saving is not great ; theother method affords the greatest facilityof seeing and comparing the work ofeach puddler. The rough bars are ofsuch sizes and cut into such lengths asare best adapted to the size of the fi-nished bar wanted. They are generally2, 3, or 4 inches wide, by or J- of aninch thick. These, when cut into theproper lengths, according to the sizeswanted, are wheeled to the balling orheating furnaces, and delivered to thepilers.The construction and shape of theballing furnace is very similar to thepuddling furnace. It is a reverberatoryfurnace, heated by a coal fire at the end,the flame of which is drawn on by thecurrent of air, and turned downwards inits course to the flue by the inclinationof the interior of the roof. Instead,however, of its having the iron bottom,with the protecting coat of cinder, as inthe puddling furnace, it is of loose sand,renewed from time to time as it becomesuneven or wears away. The stack ofthe balling furnace is of the same heightand proportions as that of the puddlingfurnace, and, like it, is furnished with adamper at the top to regulate the heat.A similarly constructed door at the sidecompletes the resemblance.The term balling furnace is not, in thepresent day, by any means an applicableone, as its use is simply to give a weldingheat to an oblong pile of the rough bars,which are then to be reduced by the rollsto the shape of finished bars. The pro-cess is called indifferently ' balling ' and' heating,' the latter term correctly de-fining the operation ; but, in Wales, thefurnace is always designated as a ballingfurnace, and the workmen as bailers;


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22 MANUFACTURE OF IRON.and we must therefore adhere to the com-monly received nomenclature, howeverfalse may be the impression it conveys.The business of the pilers, generallyboys or women, is to pile up or placetogether the lengths of the rough bars,which are delivered to them from theshears. The pile generally consists offive or six of these pieces laid evenlyone upon another, all being of the samelength, so that one does not project

The Manufacture of Iron

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