IRON-MAKING.

I.—HISTORY.

- It is probable that iron was first accidentally obtained during the operation of carbonizing wood. If the surface of the country where this process was performed abounded in ores of iron, fragments might casually find admission to the fire, and, sinking through the ignited charcoal, become partially reduced. An analogous case is presented to us in the roasting of ironstone as now practised; some peculiar species of which, associated with a large quantity of bituminous matter, have, under favourable circumstances, produced, during that process, plates of imperfectly malleable iron.

Once discovered, whether by accident or otherwise, it is scarcely conceivable, that a metal possessed of so many valuable and obvious properties, would be long suffered to remain an unique specimen. The benefit likely to accrue, by being able to procure it at will, would lead at once to numerous experiments, probably at first attended with little success. The simple, turf-covered fire of charcoal, in which the discovery was made, being found inadequate to the regular attainment of the desired end, would give place to the rude structure of stone, and this, subject to various and gradual improvements during a long period of years, would at length be superseded by the powerful blast-furnace such as we find it at the present day.

To trace the causes and principles of these improvements, the manner in which they modified the original process, and to shew their influence on the extent and progress of the iron trade from its commencement, cannot be uninteresting. The first smelting-furnace peculiar to the manufacture, was undoubtedly the air-bloomery, a low conical structure, with small openings at the bottom for the admission of air, and a larger orifice at top, for carrying off the gaseous products of combustion. In order to produce iron, the interior was filled with alternate strata of charcoal and ore; fire was applied at the lowest part, and the heat was regulated by the narrowing or enlarging of the small apertures. Such a structure it probably was that the Romans made use of to smelt the ores of this island; scoria, the refuse of ancient bloomeries, occurs in various localities, in some cases more particularly identified with that people, by the coincident remains of altars inscribed to the god who presided ovdr iron. Park represents the rude furnace just described as employed by the Africans; indeed, with some slight modifications, it is still retained even in Spain, and along the coasts of the Mediterranean, where rich specular ores are worked.

At what time the simple air-bloomery ceased to be the iron-making furnace of this country, it is impossible to say, the event being so remote. It is certain, however, that the next era which marked the progress of the manufacture was occasioned by the introduction of bellows, a very obvious substitute for the natural current of air hitherto employed. This instrument, which had probably arrived at some degree of perfection before its application to the new purpose, presented at once considerable advantages. It obviated the necessity of an elevated site for the bloomery, and it put the blast more immediately under the dominion of the smelter, which before had been irregular or intermittent during the progress of the same process, and at all times more or less dependent on the weather. By the application of bellows, some slight alterations in the furnace were rendered necessary. The new construction was built of stone, capable of enduring a high temperature, about two feet in height, and from one and a half to two feet square within. Besides the orifice or chimney at top, there were two openings, one large in front, for drawing out the metal, the other of smaller dimensions behind, for the insertion of the bellows pipe. Such was the blast-bloomery.

Let us now contrast the operation, with its products in each case, as performed in the two furnaces which have been described, and which differ apparently so little. In the air-bloomery, the principle of reduction consisted in the deoxidation of a very rich ore, which, broken into moderately-sized pieces, was subjected to a long-continued cementation. The ore was, of course, never brought into a fluid state, although the fragments became soft, and tended to coalesce. A small quantity of the associated earthy matter was separated in the furnace. Accordingly, when taken out, the iron was imperfectly malleable, being mixed, to a greater or less extent, with scoria and unreduced oxide. This put at once under the hammer of the smith, was fashioned into a rude bloom, and, with other hammerings, the greater portion of extraneous ingredients was removed. In the blast-bloomery, on the other hand, although the furnace was probably charged in the same manner, and although the fire was still urged by common air, yet, on account of the greater strength and regularity of blast, and consequently greater heat produced, the result was very different. The ore, after being deoxygenated, imbibed a portion of carbon, and sunk in a fluid state to the bottom of the furnace. Thus the resulting metal was not, as with the air-bloomery, malleable; it was rather a species of steel, utterly useless to. the workmen of these days, unless we imagine that a sort of refining process had been invented. Here, then, it seems necessary to infer, that the fluid metal was covered afresh with charcoal, the slag or vitrid matter having been previously run off; and that the nozzle of the bellows -pipe being inclined, a continued stream of air was made to play upon the surface. In this manner the carbon was burned out, the metal worked thick and tough, and fresh surfaces being continually exposed, became eventually capable of extension under the hammer.

To form an accurate idea of what the iron trade must have been during the period that the blast-bloomery was the exclusive instrument of manufacture, is not permitted to us, by the existence of any authentic document. Some conjecture, however, favourable to the opinion of its extreme insignificance, may be advanced, when we call to recollection the diminutive size of the furnace, the small quantity of iron extracted from the ore (about one-half of what it contained), and the inconsiderable extent to which, at so early a stage of society, the division of labour had been carried. This, however, was a state of things which every day improved. To the progress of internal communication, then in its infancy, the appreciation and pursuit of new sources of wealth, the establishment of manufactures, and to various other causes, as continually favouring the rapid consumption of iron, are to be attributed those improvements in the bloomery, which finally led to the construction of the blast-furnace, with all the innovations on old-established practice, which its gradual introduction as naturally produced.

It is reasonable to suppose, that an increasing demand led the iron-smelter to speculate on the facilities which would be given to his trade, by enlarging the capacity of the bloomery. This, however, he probably did not foresee; namely, that every such enlargement, by prolonging the descent of the ore through the furnace, exposed it to a lengthened contact with the charcoal, and consequently to a proportionally great absorption of carbon, and that thus eventually the [7:12:429] different varieties of cast-iron, a compound till then perhaps unknown, would be produced.

From the time that cast-iron became the product of the smelting-furnace may be dated the refining of iron, considered as a separate operation, and requiring as such a separate furnace and machinery. Enlargements in the blast-bloomery, unaccompanied by any alteration in form, could not be so made beyond a certain limit. After the furnace had reached a certain height, the column of materials in the interior would be found to weigh so heavily downwards, as to repress the ascent, and render soft the quantity of blast, which had been sufficient to penetrate a column of three or four feet in the old bloomery. It was then that a suspending agent was first thought of, and those internal buttresses were introduced, which either then or subsequently received the name of boshes. These, by creating immediately above the tuyeres a lateral suspension of the materials, relieved the pressure on the central parts of the furnace, and allowed the blast to ascend with comparative freedom. Whilst the good quality of the iron and the regularity of the process were thus insured, increase in quantity was the result of improvements in the blowing apparatus, which, hitherto worked solely by animal power, was now made to depend on the greater efficiency afforded by the employment of water. With these modifications, the furnace, as regards construction, was essentially the same as that at present used, though not so large; indeed, until the introduction of coke at a much later period, the blast-furnace seldom exceeded fifteen feet in height, by six at the widest diameter. During the long period that the air and blast-bloomeries had been the only iron-making furnaces, large accumulations of scoria, containing from 30 to 40 per cent, of iron, had formed. The more perfect operation of the blast-furnace allowed these to be re-smelted with great advantage; a new species of property was thus created; extensive proprietorships of Danish and Roman cinders were formed; large deposits of scoria, which for ages had lain concealed beneath forests of decayed oak, were dug up; and in Dean Forest, it is computed that twenty furnaces, for a period of upwards of three hundred years, were supplied chiefly with the bloomery cinders, as a substitute for iron-ore.

At what period the complete transformation of the blast-bloomery into the blast-furnace was effected, it is impossible to say. It was probably during the early part of the sixteenth century, as we find that in the seventeenth the art of casting in metal had arrived at a great degree of perfection; and in the reign of Elizabeth there was a considerable export trade of cast-iron ordnance to the Continent.

In the forest of Dean are the remains of two blast-furnaces, which formerly belonged to the kings of England. But since the commencement of the struggle between Charles the First and his Parliament, these furnaces have not been in blast. Calculating from the quantity of scoria accumulated in the neighbourhood, and which appears to have lain undisturbed for the last two centuries, Mr Mushett^[1. See Philosophical Magazine for 1822. ] has attempted to deduce the period of their erection, which he conceives to have been about the year 1550, in the time of Edward the Sixth.

In reverting to the different facts which have been stated, there is one thing which immediately suggests itself to the imagination, namely, the influence which the gradual adoption of improvements must have exerted in changing the site and locality of the manufacture. The air-bloomery, as has been before noticed, was almost invariably placed on elevated ground. At the introduction of bellows, the furnace became, to a certain extent, independent of the causes which till then líad determined its site, and was removed to a lower level, more convenient, as being in the immediate neighbourhood of the ironstone, or of the hamlet where the workmen resided. Finally, the necessity of a more perfect blast than could be obtained by mere animal power, again changed the seat of manufacture, which now sought the deeper valleys, where the drainage of the surrounding country realized a powerful fall of water. In all that has hitherto been said, wood charcoal has been understood as supplying the requisite material for every operation. But the wants of a constantly increasing population, not less than the great consumption of the iron-furnaces themselves, at length gave a check to the manufacture, by depriving it of its vital support, the essential supply of fuel. In many counties, wood had been destroyed to such an extent, that the cutting down of timber for the use of the ironworks was prohibited by special enactments. The forests of Sus sex alone appear to have been exempted from this general decree of conservation.

A languishing period of manufacture accompanied the falling off in the supply of charcoal, the number of furnaces decreasing three-fourths; so that, in 1740, the amount of iron produced, which but a short time before is said to have been 180,000 tons a year, was only 17,350 tons. The counties which produced the iron, with the number of furnaces to each, were as follow:

Furnaces. Tons.

Brecon, . 2 600

Glamorgan, . . . 2 . . . 400

Carmarthen, . . . 1 . . . 100

Cheshire, 3 . 1,700

Denbigh, 2 ... 550

Gloucester, . . . 6 . . .2,850

Hereford, 3 ... 1,350

Hampshire, . . . 1 ... 200

Kent, . . . 4 ... 400

Mollmouth, . . . 2 ... 900

Nottingham, . . . 1 ... 200

Salop, . . . . 6 ... 2,000

Stafford, . . . 2 ... 1,000

Worcester, . . . 2 ... 700

Sussex, . . .10 . . . 1,400

Warwick, . . . 2 ... 700

York, . . . . 6 ... 1,400

Derby, ... 4 800

59 17,350

Tons. Cwt. Qr.

Annual average quantity for each furnace, 294 1 1

Weckly do. do. 5 13 0

James the First granted patents to ironmasters in different parts of the kingdom for using pit-coal in the manufacture of iron; many obstacles, however, arose in the way of this improvement. The denser substance and incombustibility of coke, and the less active affinity of its carbon as compared with charcoal, for iron and oxygen, required not only a more copious and powerful injection of air, but also that the iron-making materials should remain a longer time together in the interior of the furnace than had hitherto been necessary. An ignorance of the causes of failure herein implied, operated long and seriously; but all difficulties were at length surmounted by enlarging the height of the blast-furnace, so as to prolong the descent and contact of the ore and coke, and more especially by the eventual application of the steam-engine, which rendered the working of the blowing machinery at once regular and powerful.
[7:12:430]

It was now that furnaces arose, having a capacity of three, four, five, or six thousand cubic feet; whilst of late years, furnaces of ten or twelve thousand cubic feet have been erected, without the maximum effect being decidedly obtained. By the collation of the following table with that which was given as representing the state of the manufacture in 174Ö, it will be seen that, in 1788, although the absolute quantity of charcoal pig-iron produced was less by 4250 tons, that considerable improvements in the process must have been made, as indicated by the great increase in the amount of produce to each individual furnace.

Counties. Furnaces. Tons each. Total.

Gloucester, . . 4 . 650 . 2,600

Monmouth, . . 3 . 700 . 2,100

Glamorgan, . . 3 600 . 1,800

Carmarthen, . . 1 . 400 . 400

Merioneth, . . 1 . 400 . 400

Shropshire, . . 3 . 600 . 1,800

Derby, . . . 1 . 300 . 300

York, . . . 1 . 600 . 600

Westmoreland, . 1 . 400 . 400

Cumberland, . . 1 . 300 . 300

Lancashire, . . 3 . 700 . 2,100

Sussex, . . . 2 . 150 . 300

24 Making, 13,100

Tons. Cwt. Qrs.

Annual average produce from each furnace, 545 16 2

Do. of the former period (1740), 294 1 1

Annual increased produce in favour of the improved period, . . 251 15 1

Average weekly quantity produced in 1788, 10 9 3

Ditto . . . 1740, 5 3 0

Weckly increase in favour of the improved period, . . . . 4 16 3

At the same period the number of coke blast-furnaces, with the quantity of iron produced in each county, were as below:

Furnaces. Tons each. Total. Shropshire, . . 21 . 1,100 . 23,100

Stafford, . . 6 750 . 4,500

Cheshire, . . 1 600 . 600

Derby, ... 7 600 . 4,200

York, . . . 6 750 . 4,500

Cumberland, . . 1 . 700 . 700

Glamorgan, . . 6 ∙ 1,100 . 6,600

Stafford (about to blow), 3 . 800 . 2,400

Brecon, ... 2 800 . 1,600

53 48,200

Tons. Cwt.

Annual average produce, . 907 0

Weckly do. do. . 17 9

Annual manufacture at same period of charcoal iron, 13,100 In the same year there were erected and blowing in

Scotland the following furnaces: Furnaces. Tons. Total.

Goatfield, . . 1 . 700

Bunawe, . . 1 . 700 . 1,400

Coke furnaces.

Carron, 4 1,000 . 4,000

Wilsontown, . 2 . 800 . 1,600

In Britain, total quantity in 1788, . 68,300

Ditto in 1740, . 17,350

Annual increase of pig-iron, 50,950

About the year 1796 it was contemplated by Mr Pitt, to add to the revenue by a tax upon coal. This, of course, led to a powerful, opposition on the part of the manufacturing consumers, particularly in the iron trade. A committee was appointed, witnesses were examined, and the measure was abandoned as unwise and impracticable. The following table exhibits an abstract of the facts collected, and shews the rapid progress of the iron trade in the course of the eight preceding years:
[table]

The return from Scotland exhibited a list of seventeen furnaces, and an exact return of pig-iron manu-Tons, factured, ..... 16,086

Making a whole annual quantity of . 124,879

Annual average produce from each furnace, in cluding the charcoal furnaces, . . 1,032

Annual average of 1788, including the charcoal furnaces, ..... 800

Increase in tons, 232

As a proof of the rapid strides and progress which the trade was now making, it may be added, that, in the six following years, there were building in England and Wales, forty additional furnaces, and in Scotland seven; the collective manufacture of which was computed at upwards of 170,000 tons annually.

From the preceding statements, some interesting information may be elicited with regard to the extent of the manufacture of iron, at different periods, in various parts of the kingdom, where it is either still successfully prosecuted, or become altogether extinct as a branch of trade.

In the year 1740, the date of the earliest document in our possession with regard to the distribution of blast-furnaces, we find that Gloucester produced a much greater quantity of iron than any other county in Britain. There the manufacture was well understood; indeed, it had been carried on in the forest of Dean from the earliest period. The furnaces were large, as compared with those of other districts; and, in consequence, the amount of iron to each furnace exceeded the general average.

At the period to which we refer, Sussex contained the greatest number of furnaces. With a few in Kent, the residue required to make up the annual complement of iron, at that time about 17,000 tons, were scattered sparingly throughout the midland counties, and along the Welsh borders. Eight-and-forty years afterwards, a little subsequent to the introduction of coke in smelting, the coal counties began to assume that rank in connection with iron, which for ages had been more particularly accorded to the woodland districts; and we find Shropshire making rapid strides towards that importance as an iron-making county, which, in conjunction with Staffordshire, it has ever since maintained. In Shrop [7:12:431]shire, there was then made a proportion of charcoal iron little ' less than the produce in that article of Gloucester, Monmouth, or Lancashire, whilst the quantity of coke pig-iron which it turned out, amounted to the enormous sum (comparatively speaking) of 23,100 tons; thus equalling the collective manufacture of all the other coke pig-iron districts in Britain. In the year 1796, the iron manufacture had become well-nigh extinct in Sussex, and altogether so in Kent. On the other hand, South Wales had made great progress towards pre-eminence, though still exceeded by the Shropshire and Staffordshire iron-works. These latter counties, indeed, containing within themselves the seats of the most extensive manufactories of small iron articles, have always required, for their own supply and consumption, an incredible quantity of that material. For a long time, also, the Staffordshire iron-masters enjoyed almost exclusively the advantages conferred by the rolling-mill in the production of various descriptions of iron, such as nail-rods, boilerplates, hoop and sheet-iron, wire, &c. These advantages they still enjoy to a certain extent, and, in consequence, maintain a greater price for their iron than the Welsh iron-masters. It is in Staffordshire and Shropshire that the manufacture of iron is seen in its greatest perfection. The beauty and finish of their small rolling machinery, which is run at an immense speed, enabling them to secure almost the whole of the very small and extra sizes of iron, which they throw off at little more cost than the Welsh manufacturers do their common bars. It is in South Wales that the furnaces and manufactories produce the greatest quantity; in Shropshire and Staffordshire that the highest excellence in rolling has been attained.

In 1806, a bill was brought into parliament by Lord Henry Petty, having for its object a tax of L. 2 per ton on all pig-iron made. This measure, which exhibited throughout a remarkable ignorance of the nature and minutiae of the iron trade, excited at once a determined opposition, and was at length abandoned. Had it been carried into effect, the price of all kinds of ironmongery would have risen to an enormous extent; as will be obvious, from the following statement in reference to common nails. At that period, ten tons of pig-iron were required to make five tons of nails; shewing, in the various processes of puddling, rolling, slitting, forging, &c. a loss of precisely one-half the material. Thus, with intermediate expenses, the proposed tax of L. 2 would have advanced nail-rods at least per ton L. 4, 10s. Six tons of nail-rods would therefore have cost the nailironmonger more than he was then paying, about L.27, which, divided upon five tons of nails, is L. 5, 8s. per ton; and this laid out by the retail dealer, would have caused an additional charge of, let us say, 12s, making in all, on nails, L.6. per ton.

This statement, which is made from one drawn up at the time, is of course not altogether applicable in the present improved state of the iron manufacture. It affords, however, a very correct exposition of what the general consequences would have been, had the tax been imposed. During the time that the project was in agitation, a great many important facts were elicited; amongst others, the annual amount of pig-iron made in the country was shewn to be at least 250,000 tons.

Since then, the manufacture has gone on increasing, although subject to great depression in 1816. For a considerable time previous to the general peace which ensued in that year, the British and mercantile navies had been continually requiring immense quantities of manufactured goods, and the sudden cessation of large orders and contracts, of course, threw a damp over the iron trade.

In 1820, it was computed that the annual manufacture of pig-iron was,

In Wales, .... 150,000

Shropshire and Staffordshire, . 180,000

Yorkshire and Derbyshire, . . 50,000

Scotland and other places, . . 20,000

Total, 400,000

In 1827, the make had increased by 290,500 tons, as shewn below:

Furnaces. Produce in Tons.

South Wales, . . . 90 272,000

Staffordshire, . . . 95 216,000

Shropshire, . . . 31 78,000

Yorkshire, . . . 24 43,000

Scotland, . . . 18 36,000

North Wales, . . . 12 24,000

Derbyshire, . . . 14 20,500

Total, 690,500

of which three-tenths are supposed to have been foundry-iron. From this statement, it appears that the Welsh works are considerably more productive than those of any other district; a fact to be in part attributed to their comparatively great size.

Within these last few years, the produce of iron in Wales has greatly increased. The quantity sent down the Glamorganshire canal to Cardiff for exportation, chiefly manufactured in the immediate neighbourhood of Merthyr Tydvil in 1828, was 85,714 tons. At the same time, the shipments from the town of Newport amounted to 108,000 tons. In 1830. the iron exported was less from both places by 2000 tons; indeed the collective manufacture of this year was not more than in 1827, three years before. In 1833, the quantity exported from Cardiff was 112,315 tons, exceeding the exportation of 1828 by upwards of 26,000 tons; whilst, at the same time, the customhouse books at Newport exhibited a corresponding increase. In the year 1834, Cardiff exported 110,797 tons; of this quantity 68,420 tons were the manufacture of two works alone.

In glancing at the different iron and coalfields of Britain, it is matter of astonishment that Northumberland and Durham, possessing within themselves all the requisites for the iron manufacture, should yet be so far behind, compared with other much less favoured districts. The only way of accounting for this apparent apathy to extensive mineral treasure, is the fact, that the attention of capitalists in that part of the country has hitherto been exclusively devoted to the working and exportation of the coal alone.

Of late years, Scotland has made considerable progress in the iron manufacture. The opening out of the numerous railways through the immense coalfield in the neighbourhood of Glasgow, has brought to light strata of the richest ironstone, with coal of the most suitable quality for the manufacture of iron. A stimulus has consequently been given to the trade, which, with the general adoption of the hot-air process, promises to raise Glasgow into importance as an iron district. No town, in fact, possesses greater facilities for the sale of its produce, commanding, as it does, the east coast, London, and Liverpool markets, at two-thirds the cost of freight from either Wales or Staffordshire, and also a ready outlet to the Atlantic.

In 1835, a return was made to an order of the House of Commons, moved for by Mr Guest, containing an account of the quantities of iron imported into, and exported from, the United Kingdom in the years 1833 and 1834; also an account of the quantity of British iron, including unwrought steel, exported in the same years. From this document it would appear, that in 1833 there were 17,913 tons of bar-iron imported into this country from Russia, Sweden, and other places. In the year 1834, the quantity [7:12:432]imported was 16,215 tons, shewing a decrease in the importation of the preceding year, to the amount of 1698 tons; the exportation of this description of iron in 1833 being 2024 tons, and that of 1834 being 2885 tons. The account shews an increase of exportation in 1834, as compared with the previous year, of 861 tons. By the second account it appears, that the quantity of British iron, of all descriptions, exported in the year 1833, was 160,226 tons (exclusive of 1587 tons of unwrought steeD, and the quantity exported in the year 1834, being 156,456 tons (exclusive of 1709 tons of un wrought steeD, there is a decrease in the quantity of British iron exported in 1834, as compared with the preceding year, to the amount of 3770 tons. This falling off in thequantity of iron exported, is to be attributed, in great part, to the difference which took place in the United States with the President and the Bank, in consequence of which, large orders for iron sent here were withdrawn. The demand for that country is now larger than ever, and continues to increase, in addition to which, the numerous railways in progress in this and other countries, have given such an impulse to the trade, that in October 1835, No. 2. iron at Cardiff was quoted at L. 7 per ton. As in some measure connected with the subject under consideration, it may be added, that in 1833, 16,497 tons of hardwares and cutlery, of the declared value of L. 1,466,361, were exported from the United Kingdom; and that in 1834, 16,275 tons of the same of the declared value of L.1,485,233 were exported, shewing a decrease in the exportation of the year 1834, as compared with 1833, of 222 tons, whilst, at the same time, there is an increase on the value to the amount of L. 18,972.

Since the introduction of the blast furnace in its present form, many improvements have been made in the various processes of the manufacture, but none of such importance as the rolling-mill and puddling-furnace, these enabling the manufacturer to increase his quantity of finished iron at will, always having a stock of pigs on hand to meet the demand of the market. Previously to the introduction of puddling and rolling (by Mr Cort in 1785), so inadequate was this country to the supply of its own demands, that it imported from Russia and Sweden, the enormous quantity of 70,000 tons of bar-iron annually, being upwards of 40,000 tons more than the importation of 1834. For several years past, numerous patents have been taken out in connexion with iron-making, bearing upon various parts of the manufacture; for instance, the application of the spare-heat from the furnaces to the roasting of ore; the use of carburetted hydrogen in smelting; the introduction of forge and refinery cinder in the blast and puddling furnaces; the use of salts of soda and potash, to shorten the process in the latter, and bring the iron, as the workmen term it, “sooner to nature.” But none of the improvements here aimed at, are likely to be attended with any thing like the advantages which arise to the country from the application of heated air in smelting. This invaluable process, the invention of Mr Neilson of Glasgows will be described in an after part of this article. It has already been adopted with immense advantage in Scotland, France, Russia, and in several of the English and Welsh iron-making counties.

The following list of prices of bar-iron, shews the fluctuations in value undergone by that article during the last twelve years:

List of Prices.

1824, . . L.9 0 0 to L. 10 0 0

1825, . . 10 0 0 ... 14 0 0

1826, . . 8 10 0 ... 9 0 0

1827, . . 8 0 0 ... 9 0 0

1828, ∙ . 7 10 0 ... 8 0 0

1829, . . 5 10 0 t . 7 0 0

1830, . . L.5 5 0 to L.6 0 0

1831, . . 5 5 0 ... 5 10 0

1832, . . 5 0 0 ... 5 10 0

1833, . . 5 10 0 ... 6 0 0

1834, . .; 6 0 0 ... 6 10 0

1835, . . 5 10 0 ... 7 0 0

The superiority of bar-iron, manufactured solely from mine, without admixture of cinder, is so well established, that an extra charge is usually made for it of from 10s. to 15s. per ton at the work. The workmen are generally paid a fixed price per ton on all iron made, a ton weighing 20 cwt. of 120 lb. each. The manufacturer sells it out per ton of 20 cwt. of 112 lb. each, making an allowance to the buyer of 8 lb. per ton, which is denominated drafts. This allowance is now done away with, agreeably to the 4th and 5th of William III. cap. 49; a ton of iron is therefore now only 20 cwt. of 112 lb. to each.

II.—THE MANUFACTURE.

The manufacture of iron may be considered under two divisions; the one comprising all those particulars which relate to the production of crude or pig-iron in the blast-furnace; the other, a detail of the operations at the forge and rolling-mill, whereby the pig-iron is rendered malleable, and brought into a state fit for the manufacturing consumer.

The blast-furnace as generally used throughout this country, is a large mass of masonry, most frequently square, though sometimes round at the base, from which the walls are carried up slightly inclined to the vertical, thus forming externally a truncated pyramid or cone. At each side is a large arched opening, so placed for the more convenient insertion of blast-pipes, and for running out the melted metal. At the top is the tunnel-head, a cylindrical erection of brick-work, having one or more doors, through which the furnace is charged with the materials to be smelted. In front of the furnace a roof projects from the wall, beneath which is a bridge or cast-house, where the metal, being run into moulds of sand, forms pigs.

Plate CCCIX. fig. 1. is a section of a blast-furnace, in which the space marked A represents the hearth; CB the boshes, which in principle have been already explained; D the body of the furnace; E the tunnel-head with charging doors of iron; F FF the blast-pipes, entering just beneath the boshes, through small spaces in the brickwork, called tuyeres. Fig. 2. is a ground-plan corresponding with the above section. The greater part of the interior of the furnace is lined with fire-brick, between which and the masonry, a thin stratum or packing of sand is laid. In Wales the materials employed in the construction of the hearth and boshes, is a very infusible plumpudding-stone or quartz conglomerate, large detached blocks of which occur on the mountains, and are familiarly known amongst the workmen by the name of Noah stones. A species of coarse sandstone, belonging to the coal formation, and exceedingly refractory in the fire, is also advantageously used. Slight variations from the form of furnace here given, are of course to be met with; a point of much importance is the proper inclination of the boshes, so that the materials whilst smelting, may neither press too heavily downwards, nor yet be so much retarded, as to adhere in a half-liquid state to the brickwork, and cool there; thus forming what are known by the name of scaffolds, the removal of which is a source of great inconve-nience. No general standard for the size of blast-furnaces can be given, as they vary in this respect in almost every iron-making district of Britain. The largest furnaces are those of Wales and Monmouthshire, some of which are upwards of sixty feet in height. In Staffordshire and Scotland, they are generally much less, and from thirty to forty [7:12:433]feet in height, by about twelve or fourteen at the boshes, or widest interior diameter, may be stated as a very fair average size. Before leaving this part of the subject, it must be premised that of late years, the cupola-furnace has come extensively into use. Its characteristic feature is general slightness of structure, as compared with the more massive blast-furnace. The walls are circular, built of firebricks, and, excepting about twelve or fourteen feet of masonry at the bottom, in no part more than a single course in thickness; the whole, however, are strongly bound together at the joints with wrought-iron hoops, whilst pillars of cast-iron, bolted at each end to embedded rings of the same metal, rise through the foundation to the summit of the tuyere arches, giving considerable firmness and solidity to the structure. Objections have been made to the thin sides of the cupola, as permitting a great loss of heat; these, however, do not seem to have prevented its very general adoption. Cheapness and facility of construction are much in its favour, and a furnace of this kind, when blown with hot air, may certainly be used with great advantage. A cupola twenty feet high, six feet at tĥe boshes, and three feet at top, requiring a blowing-engine of five or six horsepower, can be run up in a week, and may have iron manufactured in it the next. Plate CCCXVII. contains a section and ground-plan of a cupola furnace lately erected at an iron-work in Glamorganshire.

The communication between the ground and the tunnel head is effected in various ways. The Welsh furnaces are invariably placed on the slope of a steep declivity, which affords ready means of access. Where this convenience does not present itself, a small self-acting incline is substituted, or an apparatus is affixed to the engine by which the workmen and smelting materials are carried up and down as may be required. Attached to every iron-work is a steam-engine (or water-wheeD, whose sole office is to throw a continued current of air into the furnaces. This is in most cases accomplished simply by attaching to the unoccupied extremity of the beam a piston, which is made to work in a cylinder of large diameter. At every stroke the air, entering this cylinder through proper valves in the covers, is forced into pipes inserted at top and bottom, which convey it to a large spherical vessel, built of boiler plate, whence its own elasticity causes it to flow in an equable and unintermitting stream into the furnace. Plate CCCX. shews the plan, elevation, and section of a blast-engine erected at the Wylam Ironworks, Northumberland, by the Messrs Hawthorn of Newcastle. This machine differs in many respects from the common construction, for a figure of which, in connexion with the blast furnace, see Plate CCCX. AA represent the pillar on which the engine is fixed, BB the blast-cylinder, cc the wind-boxes, in which are fixed the discharging valves, dd the blastpipe leading to the furnaces, EE the steam-cylinder, ff the force-pumps, g g the hand or working-gear, hk the cross-heads, i i i i the slides for guiding the piston-rods, k k the banging-boxes.

The pressure at which the blast enters the tuyeres is from 2∣ to 3ļ lb. on the square inch of course depending on the area of the blowing cylinder, and the pressure at which the engine is working.

At the Dowlais Ironworks, South Wales, is a blowing-cylinder 12 feet in diameter, with 9 feet stroke, and worked by engines of 260 horse power. By this machine ten or twelve furnaces can be blown.

The diameter of the blast-pipes at the tuyeres is regulated by their number. Where three tuyeres are used, and the pressure is about three pounds, the diameter should not exceed 3į or 3į inches. In practice, it is necessary to be very particular with regard to this point, the well-working of a furnace depending much on the attention which is given to the blast. The best quality of cast-iron is produced by a comparatively moderate quantity of air. On the contrary, a strong and powerful blast tends to the production of a large quantity of metal, inferior in every respect, and unfit for the purposes of the foundry.

Behind the furnace, and, if possible, on a level with the tunnel-head, are placed a number of small kilns or ovens for roasting the ore. The ironstone used in the blast-furnaces of this country is a carbonate of protoxide, or more simply a carbonate of iron, in conjunction with different earths, such as alumina, silica, lime, &c. The object in roasting is to drive off the carbonic acid, water, and sulphur. The stone loses in the operation from thirty-five to forty per cent., at the same time becoming partially peroxidized. To produce iron from an ore like this, it is requisite not only that a deoxidating agent should be used, but also that there should be some other substance, such as limestone, to act as a flux, and disengage the earthy from the metalliferous particles, leaving the latter free to the carbonizing influence of the coke. The materials, then, mine or ironstone, coke, and limestone; broken into small pieces, and weighed out in the proportions which have been determined by experience to be the right ones, are introduced into the furnace by the filler, who stands at the tunnel-head, and whose duty it is to see that these proportions be observed, and that the mine and coke are properly burned. He also takes account of the number of charges required to keep the furnace full during the time of his management (twelve hours to the day); and according to this the furnace is said to drive fast or slow. The charge, or quantity introduced into the furnace at once, is a barrowful of coke, containing about twenty cubic feet, with the requisite proportions of mine and flux. These of course differ slightly at different works, according to the quality of the ore and limestone; but it is the general practice to mix rich and poor ironstones together, and thus to bring the latter material as near as possible to some approved standard, containing, say from thirty-five to forty per cent, of iron.

The general action that takes place in the blast-furnace is this: The contents being raised to an intense heat by the combustion of the coke, are brought into a softened state; the limestone parts with its carbonic acid, and, combining with the earthy ingredients of the ironstone, forms with them a liquid slag or scoria; whilst the separated metallic particles, descending slowly through the furnace, imbibe in their passage a large quantity of carbon, pass the blast without oxidation, and, in virtue of superior gravity, settle in the hearth or lowest part of the furnace, from whence, at stated intervals, the fusion is removed in the state of liquid cast-iron. The slag which floats upon the surface of the metal, whilst accumulating in the furnace, is kept constantly running off by an aperture level with the top of the hearth; and it affords well-known indications, by its degree of heat, fluidity, and colour, of the manner in which the materials in the interior are performing the parts assigned them in the operation. Thus, if the cinder has a light greyish colour, or is nearly transparent, and flows freely from the furnace, unsullied by any of the various tints of blue, yellow, and green, afforded by oxide of iron in combination with different proportions of earthy matter, a favourable state of the furnace is indicated. If, from the charge affording such results, a portion of coke be abstracted, or if to it, which is the same thing, a portion of mine be added, the cinder immediately assumes a deep brown or black colour, and flows in a broad, hot, and rugged stream, shewing that the quantity of coke is insufficient to deoxidate the whole of the iron, and that a portion of it, consequently, to the great detriment of the furnace yield, is combining in its state of oxide with the slag, to which it communicates so deep a hue.

With regard to the constitution of blast-furnace scoriae, [7:12:434]they are in general compounds of earths and earthy salts, where silica acts the part of an acid, and lime, alumina, magnesia, oxide of iron, &c. are bases. Minerals are thus formed artificially, presenting the most perfect crystalline arrangement, and similar in every respect to some native silicates. Indeed, without mentioning the graphyte or kish which scales from the surface of newly-cast foundry pigs, the splendent copper-coloured cubes of metallic titanium so abundant in breaking up old furnace-hearths, or the dark blue crystallized metallic-looking compound of sand and oxide of iron, the slag from the bar-iron heating furnace, the rejected products of the iron manufacture present perhaps more features of interest to the mineralogist than the residua of any other chemical operation.

During the process of smelting, the interior of the furnace requires to be very carefully watched. The stream of cold air that is constantly rushing through the tuyeres exerts a chilling agency on the melted matter, directly opposed to it, at its entrance. The consequence of this is, the formation of rude perforated cones of indurated scoria, stretching from either side horizontally into the furnace, each one having its base directly over the embouchure of a blastpipe.

When these project only to a certain extent, they are favourable to the working of the furnace, as the blast is thrown right into the centre, and prevented from flowing up the sides and burning the brick-work.

Sometimes, however, when the furnace is driving cold and slow, these conduits of slag become so strong, and jut out so far as to meet at length in the middle, and thus cause a great obstruction to the entrance and ascension of the blast. When this happens, there is no remedy but to increase the burden, that is, to add more than the usual proportion of mine to the charge; this causes an intense heat, the furnace is said to work hot, and the tuyeres of slag drop clean off from the sides. But this is followed by bad as well as by good consequences; the brick-work is frequently melted, and for a time the iron produced is small in quantity, and of the worst quality.

To bring the furnace again into its proper state, it is now necessary to reduce the burden; the sides, in consequence, become gradually cool, new tuyeres are formed, and the iron produced is good.

At the end of every twelve hours, more or less, the furnace is tapped, that is to say, the aperture in the damstone, which, at the commencement, had been stopped up with a mixture of loam and sand, is re-opened, and the metal, the contents of the hearth, allowed to flow out into moulds made in the sand, of which the cast-house floor consists, thus forming a cast or sow of pigs. When this operation ceases, the damstone is again secured, and the work proceeds as before. In this manner a furnace is kept continually going, night and day, and never ceases to work until repairs are necessary. Incessant action has even been thought essential to the successful carrying on of an ironwork; but the example of perhaps the largest iron-master in South Wales has shewn, contrary to general practice in that district, that smelting may be discontinued for at least one day in the week without any very serious derangement of operations.

At Merthyr, in Glamorganshire, the yield, or quantity of materials required to make a ton of pig-iron, is as follows: 55 cwt. of roasted mine, 25 cwt. of limestone, and 2 J tons of coal. The charge, or quantity of materials introduced into the furnace at once, is 7 cwt. 2 qrs. of roasted mine, one barrow of coke containing about twenty cubic feet, with 3 cwt. 1 qr. 15 lb. of limestone. In all cases, the regular rule is to fill in the coke first, then the flux, and lastly the mine or ironstone. In the Glasgow district, the charge is 4ļ cwt. of coke, 3 cwt. of ironstone, 1 cwt. 7 lb. of limestone; total, 8 cwt. 2 qrs. 7 lb. In a furnace twelve feet at the boshes, fifty of these charges, in twelve hours, produce 4∣ tons of iron; the same proportions have been known to produce as much as 5∣ tons, and as little as 3£. Again, the iron is not always of the same quality; thus exemplifying different states of the furnace, blast, management, &c. In three successive casts of a furnace, in which the amount of charges was, in each case, coke, 11 tons 5 cwt.; ironstone, 7 tons 10 cwt.; limestone, 2 tons 13 cwt.:

The first cast produced 4 tons 10 cwt. of No. 1. iron,

, second do. 4 .., 12 ... No. 2. do.

third do. 3 ... 16 ... No. 3. do.

Two different qualities of cast-iron are frequently the product of the same cast. The best kind runs first from the hearth; and the pigs are distinguished from each other by the striae or furrows formed on their surfaces in cooling, No. 1. preserving a smoother surface than No. 2. or No. 3. P ’ g s ∙

The following are comparative estimates of the cost of making pig-iron in the neighbourhood of Merthyr, South Wales, and in the neighbourhood of Glasgow:

At Merthyr.

3 tons 7 cwt. 0 qrs. of Mine (raw), at 10s. L.l 13 6 2 ... 16 ... 0 ... Coal, at 6s. . . 0 16 6

1 ... 5 ... 2 ... Limestone, . . 0 14

All other charges, . 0 9 1

L.3 0 5

Glasgow District.

3 tons 10 cwt. Mine (raw), at 4s. 6d. . . L.0 16 3

5 ... 15 ... Splint-coal, at 2s. 5d. ,. . 0 14 0

0 ... 14 ... Limestone, at 3d. . . 0 3 6

1 ... 10 ... Coals for the engine, . . 0 3 0

All other charges, . . 110

L.2 17 9

Both of these estimates presume the iron to be made with cold air, coke, and the mine roasted in the usual way.

The process of smelting iron, even on the large scale of manufacture, where tons of the raw material are subjected to an intense heat in the blast furnace, is an operation affected in the result by more delicate circumstances than is generally supposed. The proportions of the materials must, as we have seen, be in every case most accurately determined; and even then, with his furnace in good order, the tuyeres of the right length, and the blast steady and regular, is it difficult for the founder to predicate the quality of the resulting iron. With the same charge, the same blast, the same furnace, and the same management, the pigs may be of the very best quality, or of the very worst.

There are other questions to be taken into consideration, as, for instance, What is the season of the year, the direction of the wind, the hygrometric state of the atmosphere ŕ For it is a fact well warranted by experience, that all these, circumstances affect the working of a furnace.

A furnace will produce, on an average, more and better iron in winter than in summer; the atmosphere being of a higher temperature in the latter season, and consequently capable of holding a greater quantity of moisture in solution. To this greater or less degree of humidity in the air supplying the blast-cylinder, is to be attributed the difference of product so generally observed at different periods of the year. There are many facts confirmatory of this. Thus, to regulate the influx of blast to the furnace, a machine called a water-regulator was formerly much employed, and, indeed, is not yet entirely done away with. The principle of this apparatus, as in the common gasometer, is by the pressure of a column of water, to produce an unintermitting stream of air from a large vessel into which it is forced by the blast-engine. The water-regulator has fallen [7:12:435] into disuse, chiefly for this reason, that the air, in passing through it, imbibes a large quantity of moisture, which, being carried into the furnace, deteriorates the iron. Again, when the hot blast was first brought into action, the water tuyeres (see Plate CCCXVII. fig. 4.), which the intensity of the heat rendered necessary, frequently burst, and the water was of course thrown into the furnace. Whenever this happened, the very worst kind of iron was produced.

Cast-iron, as it comes from the furnace hearth, is by no means a pure carburet of iron. The nature of the process is such as to render it liable to an intermixture of various extraneous ingredients. Thus, in newly cast pigs, fragments of charcoal, undecomposed ore, and earthy matter, can in general be detected by the eye alone; whilst analysis as generally makes known the presence, in greater or less proportion, of manganese, sulphur, or phosphorus. Three principal varieties of cast-iron exist, distinguished from each other in various particulars of colour, strength, and general capability of adaptation to the purposes of art. Grey, or No. 1. pig-iron, is comparatively dark coloured, and when broken, exhibits a large open grain. It is easily rendered fluid, runs freely and with such facility into moulds, that it is the sole material of all the smaller and more delicate sorts of foundry goods, which, when composed of No. 1. metal alone, are distinguished by great smoothness on the surface. It is tough, slightly capable of extension, and so soft as to admit of filing, chipping, turning, &c.; hence it is of extensive application in the formation of machinery, particularly such parts as are small, and require much fitting up. White, or No. 3. pig-iron, is in every respect precisely the reverse of what has just been stated concerning No. 1. It is characterized by its white silvery-like lustre, more crystalline structure, and by a brittleness so excessive, that it cracks like glass on any violent blow, or sudden alternation of temperature. The file glances from its hard and flinty surface without making any impression; and its fluidity, when melted, is of so viscid and imperfect a kind, that it runs with comparative difficulty into moulds. No. 2. or mottled cast-iron, is a variety seemingly intermediate between Nos. 1. and 3. Its colour, as the name imports, is not equable, but blends in unison two distinct shades of grey, which, individually, are those of Nos. 1. and 3. The degree of hardness is greater than in No. 1, though less than in white pig-iron. In this metal we find united, to a certain extent, the qualities of hardness and toughness. When mixed largely with No. 1. iron, a proper material is furnished for artillery, steam-engine cylinders, &c. In fact, by melting the different varieties of cast-iron together in various proportions, the founder is always able to procure a material suited to his purpose, whatever be the property required. This is also in some measure accomplished by the diversity of character belonging to iron from different districts. Thus the Staffordshire metal is generally remarkably fluid, and makes excellent small castings. The Welsh pig-iron is strong, and produces bar-iron of a very tough and good quality; whilst the Derbyshire, the Shropshire, the Scotch, and other irons, all differ in like manner, each being distinguished for the possession of some property not common to the rest.

From what has been said, it will be seen that grey and white cast-iron are more especially distinguished from each other. The different aspects which they assume in every particular, such as colour, strength, and fusibility, was long accounted for by supposing the grey metal to be more highly carbonized than the white. From experiments, however, of good authority, it would appear that, so far from this being the case, there is actually, in many instances, an appreciably greater quantity of carbon in the white than in the grey. Respecting the wide diversity in external appearance and physical properties which the metals exhibit, chemists are disposed to attribute it to the mode of combination of the constituent elements, rather than to any absolute difference in amount of carbon; and they say that there is no essential difference in this respect, for these reasons, that the white variety may be changed into the grey, by exposure to a strong heat, and cooling slowly; whilst the grey may be changed into the white, by being heated and rapidly cooled.

The latter circumstance, indeed, is no matter of speculation, being frequently taken advantage of in the arts, as presenting a convenient method of case-hardening wheels, rolls, plating anvils, &c., to effect which, it is simply sufficient to run the metal into a thick cast-iron mould, instead of one of loam or sand. This process is called chilling. As a mould, malleable iron, when the required shape can be given to it with facility, is preferable, because, being a better conductor of heat, it chills the metal in contact with it more rapidly, and is less liable to crack from the sudden change of temperature. That there is a difference in the mode of combination of the constituents in grey and white cast-iron, amply sufficient to account for the diversity in mechanical properties which they present, experiment testifies, “According to Karsten, the carbon of the latter is combined with the whole mass of iron, and amounts, as a maximum, to 5.25 per cent.; but in some specimens, its proportion is considerably less. The former, on the contrary, contains from 3.15 to 4.65 per cent, of carbon, of Which about three-fourths are in the state of graphite, and are left as such after the iron is dissolved by acids; whilst the remaining fourth is in combination with the whole mass of metal, constituting a carburet, which is very similar to steel. Grey cast-iron may hence be regarded as a kind of steel, in which graphite is mechanically mixed.”^[2. See Turner’s Chemistry, 5th edition. ]

The first operation which cast-iron undergoes in rendering it malleable, is that performed in the refinery, the object of which is to drive off a portion of the carbon.

The refinery is a small, low furnace, with a hearth of firebrick, about three feet square. There are two sides of cast-iron, opposite to each other, and made hollow, so as to allow the passage of a constant stream of water through them. This is necessary, in consequence of the intense heat to which they are subjected, and which, were there no such protection, would speedily burn them through. Each side is furnished with three water tuyeres, in which as many blast-pipes of an inch in diameter are inserted. The front of the furnace is left open, but at the back are iron doors, through which the hearth is charged with the necessary complement of pigs and coke. A low, hanging chimney surmounts the hearth. The description given is that of the double refinery; in the single refinery, the· blast enters only at one side.

The pigs to be refined being placed with the necessary proportion of coke on the hearth, are brought into a state of fusion, and the blast, which enters here at the same pressure as with the smelting furnace, is kept in action, until a considerable quantity of carbon has been burned out. The metal is then run from the hearth into a shallow oblong mould of cast-iron, about eight feet by two feet, which is kept cool by water running underneath. During the continuance of the operation, a lambent blue flame plays on the surface of the fused metal, indicating the combustion of carbonic oxide; and when the metal is run out into the mould, a quantity of scoria, or oxide of iron, collects at the top and floats there, a necessary consequence of the unequal rate of contraction in the two substances.

In the refinery, then, there are two effects produced. Carbon in moderate quantity is separated from the general mass of the iron, whilst, at the same time, a portion more [7:12:436]exposed than the rest becomes decarbonized to such an extent as to be free for combination with the oxygen of the atmosphere; and hence the production of cinder, which, it must be remembered, is also partly owing to impurities existing originally in the pigs. The metal which works with the least trouble, and to the greatest yield in the refinery, is No. 1, or grey pig; next to it stands No. 2, or mottled. As for white cast-iron, they are obliged to mix it largely with pig of a superior quality; when alone, it becomes thick, and does not flow readily from the hearth. The time from the commencement of the operation to the “running-out,” varies a little with the kind of metal and strength of blast employed; it may be said to average about two hours. The yield of coke and metal also varies in the same manner, and much depends on the attention of the refiner. Taking the best grey pig, the average yield to the ton of refined metal may be stated at 22 cwt.; the quantity of coke consumed will be from 9 to 10 cwt.; the charge or quantity of metal worked off at once is 25 cwt. Below are actual practical statements of the refinery yields at one of the largest works in Merthyr.
[table]

And the yield continues much the same to the present day, the chief saving being made in the puddling-furnace; a portion of which is, however, again lost in the mill-furnace.

Refiner’s metal is totally unlike the pig from which it was produced; it is as white as or whiter than No. 3. cast-iron, and so brittle as to be broken in pieces by a single stroke of a hammer. It is in fact, in every external particular, so similar to white or No. 3. metal, that, for some inferior kinds of iron, the refining process is altogether omitted, the metal as it comes from the blast-furnace being merely run into moulds of cast-iron, which, as before explained, chills, and renders it hard, brittle, and white. A considerable proportion of forge-pigs, as they are called, undergo no other refining process than this, if that can be called refining, which probably merely alters the arrangement of the elementary molecules, without removing a particle of carbon. The plate of refined metal is always more or less honeycombed and cellular on the surface. When this fretted and unsound texture extends to any great depth, the plate does not puddle well; it is pointed out as too much blown to be good.

The cinder or scoria produced during the refining of iron, formerly accounted of little or no value, is now made to reproduce great part of its iron in the blast-furnace. For this purpose, however, it is necessary to mix it very largely with earthy matter or common mine; because, when smelted alone, it is found, as seems also to be the case with the pure native oxides, to burn the furnace, and to produce the most ineffective result, both with regard to quantity and quality of yield. Made use of even in sparing proportions, the metal produced is rarely No. 1, or foundry-iron. The quantity of cinder generally used in the Welsh furnaces, is from 5 to 6 cwt. to the ton of good calcined mine; and, of course, the proportion of limestone to the charge need not be so much as usual. As the refiner finishes his plates of metal, they are weighed, and, if there be no stock on hand, carried directly to the puddling-furnace, where they lose carbon to a still further extent. Refined metal is said, like steel, to improve in quality by exposure to the atmosphere, and to be better fitted thereby for the next operation which it undergoes. Accordingly plates of metal which have been on hand for any length of time are preferred by the puddler; They work more easily, and produce a better quality of bar-iron, than if puddled directly from the refinery.

Puddling is performed in a common reverberatory-furnace, of which Plate CCCIX^figs. 3, 4, 5, are a section and elevation. In fig. 3, a is the grate, supplied with fuel by an aperture, also marked a in fig. 4, called the stoke-hole; and l> is the body of the furnace, where the gradual narrowing of height, by means of the arched ceiling, causes the flame in every part to beat on the hearth, or material placed there to be heated. C C, figs. 3 and 4, is a door of iron, through which the puddler charges his hearth, and performs other manipulations incidental to his process. It is opened and shut by raising or depressing the lever, to which the chain d is attached. The sides of the furnace are large plates of cast-iron, lined with firebrick; the plates E are protected from the heat, by having their lower sides immersed to a certain depth in a metal groove or socket, around which water is kept flowing. The hearth is of cast-iron, covered with a glaze or coating of finery cinder, to protect it from fusion. After the puddler has brought his furnace to the necessary temperature, he introduces his charge of metal broken into [7:12:437] small fragments, at the same time regulating the influx of air through the grate and stoke-hole, by means of the damper in the chimney, so as to produce a most intense heat. In about twenty minutes, the charge begins to shew signs of melting; and the whole being brought into a state of fusion, the puddler, with a long iron hoe-shaped instrument, keeps stirring up the imperfectly liquid mass, and incessantly presenting fresh surfaces to the action of the fire. Whilst he thus operates with the metal, it heaves and swells, and emits flashes of blue flame, shewing, as in the refinery, the formation and combustion of carbonic oxide. The stirring being still vigorously kept up, all appearances of an elastic fluid at length cease, the metal becomes curdy and clotted, and so totally deprived of cohesion, as to crumble away beneath the instrument of the puddler like dry earth.

The damper, which had been nearly shut, is now raised, fresh fuel is put on the fire, and an intense heat begins again to be excited. At this stage the puddler occasionally throws a little water on the charge, which now, in a fine granular state, is said to be coming round to nature, and as the temperature rises, every exposed point of surface assumes the vivid whiteness of welding iron. Presently the separated particles begin to coalesce, and to form into small masses, which work more and more heavy, until the whole are at length fashioned by the puddler into rude balls or blooms, which are carried at once to the shingling forge and rollers, there to be beaten and drawn into bars. The charge introduced into the puddling-furnace is 4 cwt., either wholly of refined metal, or mixed with a portion of No. 3, or forge-pig. The best kind of iron is produced without any the least particle of cinder or oxide being used; but the temptation to make profit is so irresistible, that the ironmaster allows his puddlers to introduce a large portion of cinder from the forge and rollers, to improve the yield. The consequence is, that the quality of the iron is deteriorated, whilst the puddler frequently brings as much or more iron out of the furnace than his charge of metal amounted to.

White cast-iron also, and forge-pig, when used in large quantity, tend to the production of a weak and inferior kind of iron; nor is this the only disadvantage attending their employment, the waste which they are subject to being very great. A considerable degree of certainty is given to the puddling furnace results by the previous operation of the refinery, because there the different qualities of cast-iron, blended in proper proportions, are reduced to one common standard, comparatively uniform in texture, and always presenting to the puddler a sameness of constitution in the material which he employs. Using cast-iron indifferently as it came from the blast furnace, was the great defect of puddling when first introduced; nothing connected with the operation could be reckoned on with safety; the waste was great, the quality of puddled iron irregular, and the duration of the process tedious. Notwithstanding this, however, it has of late been attempted to run the iron directly from the smelting into the puddling furnace, omitting the refinery altogether. Furnaces constructed with this view, have been erected in Staffordshire.

The toil and labour of puddling is excessive, and the men require to be frequently relieved; four sets or shifts of men, each set being six hours in and eighteen out, will run twenty heats, or from 80 to 85 cwt. in the course of the day. To effect this, .the furnace ought to be double, or so contrived that, whilst one charge is puddling, a fresh one is heating and preparing for the same operation.

Three qualities of British bar iron are recognised in commerce, No. 1, or puddled iron; No. 2, and No. 3. A tough and fibrous quality called cable iron, is also made. The manufacture of these will now be shortly described.

The rough balls of iron, just as they are formed in the puddling furnace, are carried directly to the shingling forge, where they are knobbled into oblong blooms, and from thence, without reheating, passed successively through the puddling rolls; first through a set of gradually decreasing elliptical holes, which rough them down, then through flat openings or groves, (see Plate CCCXI.fig. 3.) by which they are formed into long flat bars, 3, 4, or 5 inches in breadth, and from one-half to three-fourths of an inch in thickness. These bars are, of course, very ragged and unequal in texture, and still retain incorporated with them a considerable quantity of cinder, acquired in the puddling furnace, although much has been forcibly squeezed out by compression between the rollers. They are called No. 1, or puddled, or mill-bars, and though exported to some extent as a cheap article, are looked upon as requiring at least another process before they can be called finished iron. For this purpose they are carried to a large pair of shears (see Plate CCCXII. fig3.) where, being cut into lengths proportional to that of the intended bars, they are piled up with reference to the required thickness, and introduced into the mill-heating furnace (see Plate CCCXIL), where they are subject to a further loss of cinder or oxide, which, combined with sand, runs from die furnace in a fluid state. A period of from fifteen to twenty minutes is sufficient to bring the piles to a welding heat; they are then carried to another set of rollers, similar to those first described, and from thence to the finishing rollers, where they receive the most perfect form and accurate dimensions. These constitute No. 2. bars; when cut up, piled, reheated, and again passed through the rollers, No. 3. bars are formed, and the iron may then be said to have arrived at the maximum of strength and value possible to be given to it in the actual processes of manufacture; that is, supposing it to have been made from pure mine alone, without any admixture of cinder, either in the smelting or puddling furnaces. It must indeed be kept in mind that the best iron is invariably that which has been produced from the purest materials. If the ironstone or coke is bad, if they contain sulphur, phosphorus, arsenic, or any other equally deleterious ingredient, it may safely be pronounced that the pig-iron will be bad, that the refined metal will be bad, and that the bar-iron, no matter how many times it may have been hammered, rolled, heated, piled, and rerolled, will still be accompanied by the refractory ingredient which existed in the raw material.

There is undoubtedly a practical limit to the good effect produced in iron by beating and drawing out. All that rolling does, is merely to squeeze out the cinder and impure matter, blended with the rough bar, and thus to force the fibres into a more perfect state of juxtaposition. The strength which such a process imparts, is thus due entirely to a mechanical cause, and iron which has undergone the operation may be indeed very tough and flexible at a certain temperature; but cool it below, or elevate it above this, and you bring it within the sphere of a new and hitherto quiescent power; the deleterious substances, originally in the ore, come into play, you find that the iron is either cold-short or hot-short, and in fact that the whole of its good qualities are gone. In contradistinction to this, an iron that has been smelted from the most suitable and purest materials, and has gone through the usually prescribed course of manufacture, will be not only mechanically but chemically good. Its malleability will not be limited to one range of temperature, and its strength and toughness will be owing not more to the agency of rolling, than to the absence of all substances, by which such qualities could possibly be impaired.

In the contracts of the Admiralty for chain cables for the British navy, it is stipulated as an express condition, that the iron shall have been manufactured in the best manner from pig-iron, smelted from ironstone only, and selected of the best quality for the purpose, and shall not have received in any process whatever subsequent to the [7:12:438]smelting, the admixture of either the cinder or oxides, produced in the manufacture of iron; and shall also have been puddled in the best manner upon iron bottoms, and at least three times sufficiently drawn out at three distinct welding heats, and at least twice properly fagotted.”

The following is a table of the breaking proof of chain cables, and of the iron for the purpose of making them; also of the proofs required by his Majesty’s navy for chains.

Size of Bolt. Proof of Bolt. Proof of Chain.

or enain.

Inches. Tons. Cwt. Tons. Cwt. Tons.

⅛ 5 7 8 11 4į f 8 7 13 4 5⅛

I 12 1 19 5 10f ļ 16 4 26 5 13f

1 21 8 34 5 18

1⅜ 27 2 48 15 22f lį 33 10 53 11 28⅛

If 40 10 65 0 34

ìį 48 4 77 0 40⅛

If 56 11 90 10 47⅜

If 65 12 105 0 55⅜

Ilf 75 6 120 10 63⅜

2 85 14 137 0 72

2⅜ 96 15 155 0 81į

Besides the three varieties of bar-iron which have been noticed, several works, chiefly in Wales and Gloucestershire, make a very tough and strong quality called charcoal-iron, chiefly used for the manufacture of tinned plates, and of horse-shoe nail-roads. Charcoal-iron is made from the best pigs, and refined in the usual way; but, as a substitute for puddling, it undergoes a second refining process, in which charcoal, not coke, is used; the resulting bloom is taken to the forge hammer, drawn out into a slab, and is then ready for the manufacture of this plate.

The great defect of bar-iron, as before hinted at, is the limitation of malleability to one temperature. Cold-short is the term applied to iron which is brittle when cold, though malleable at a red heat. The defect is generally owing to the presence of phosphorus, but may be occasioned by remaining too long in the furnace.

Silica also renders iron cold-short. Thus, in producing a welding temperature, it is common to throw a little sand on the parts most exposed to the heat. A slag is thus formed on the surface which protects iron from wasting; on this account, however, that part of a bar where a weld has taken place, will always be found to be more brittle than any other. Red-short iron is malleable enough at common temperatures, but liable to crack and fly, when punched or beaten at a red heat. This quality is at once detected in giving to a bar any particular form. Thus, in turning links (which is done by machinery), numbers are frequently to be rejected on account of cracks at the outside of the bend.

The waste in the balling or heating furnace is much the same, whether Nos. 1 or 2 bars be taken; but the production of cinder ought seemingly to be greatest in the case of No. 1, as being a much more impure material, and such probably would be the case, had not puddled bars a comparatively loose and open texture, in consequence of which they are sooner heated, and remain a shorter time in the furnace. Sixteen tons, 7 cwt. 3 qr. 7 lb. of No. 2 iron were cut down, piled, heated, and roljed into bars; the produce weighed 15 tons 7 cwt. 3 qr. 7 lb., and consequently the yield to the ton was 21 cwt. 1 qr. 12 lb. Speaking generally, bar-iron may be said to work to a waste of from 1 to If cwts., allowing for differences in the purity and heating power of the coal, sizes of piles, &c.; for, when the pile or billet is very small, there will be a greater waste proportionally to the comparatively greater surface exposed in the furnace; and this, with increased trouble and loss of time in rolling, enhances very much the price of the smaller descriptions of iron.

From what has been said of the various deteriorating circumstances which are incidental to the manufacture, it will readily be conceived that bar-iron is by no means regular in quality. The following trials of round-iron, performed in the years 1832, 1833, and 1834, present some curious results, and certain cases particularly would seem to indicate that the having gone through an additional process of rolling, is not always a guarantee of superiority. The iron was all of Welsh manufacture, though from different companies, and the experiments were made in a testing machine on the lever principle.

Result of Experiments on the strength of Iron, intended for Chain Cable.

December 10. 1832.

lį in bolt, in the state of No. 3, cable (mine) iron, broke with 30∣ tons.

If in bolt, the same material, but put through another process, 311 tons.

lį in bolt, in the state of No. 3, cable (mine) iron, broke with 32∣ tons.

lį in bolt, another trial, 31 į tons.

January 5. 1833.

l į in bolt, in the state of No. 2 (mine) iron, broke with 34^ tons. .

lį in bolt, in the state of No. 2 (mine) iron, broke with 31 tons.

January 11.

lį in bolt, in the state of No. 2 (mine) iron, broke at 34į tons.

lį in bolt, in the state of No. 3 (mine) iron, broke at 31 tons.

Two trials of these with similar results.

January 11. 1833. Continued Experiments.

If in bolt, in the state of No. 3 (mine) iron, broke with 32; tons.

1 į in bolt, same material as the last, but put through another process, broke at 32∣ tons.

If in bolt, in the state of No. 2 (mine) iron, broke with 23f tons.

If in bolt, in the state of No. 2 (mine) iron, broke with 32į tons. The latter bolt had been previously, when in the state of No. 1 iron, rolled-down much smaller, and was consequently more worked in the roll.

January 14. 1833.

No. 1. If in bolt, in the state of No. 2 (mine) iron, broke with 32į tons.

No. 2. lį in bolt, in the state of No. 2 (mine) iron, broke with 30∣ tons.

These bolts, No. 1 and No. 2, were the produce of one pile, laid up above the ordinary size. After the pile was heated carefully, and roughed down to three inches diameter, it was taken to the shears and divided into two pieces. The No. 1 piece was instantly, and at the same heat, rolled off; the other half was rolled into a flat bar at the same heat. It was then cut down, piled, and rolled into a bolt, and on subjecting both pieces to the testing machine, it appeared to support a less strain than the No. 1 bolt.

One of the great advantages of the present system of manufacture, as compared with that of some fifty or more years ago, is the facility and cheapness of rolling-At [7:12:439]every great ironwork it has become necessary to have not only rolls for the manufacture of bar, bolt, and square iron, but also for numerous other articles, such as railway bars, boiler plates, sheet-iron, hoop-iron, &c. Slit nailroads are made with great dispatch, a number being cut at once from a thin bar of iron, which is passed hot between revolving cutters (see Plate CCCXIV. figs. 1 and 2). Boiler-plate rolling is most laborious work. The plate is rolled from a slab prepared previously under the forge hammer, and weighs generally from 1 to 4 cwt. Instances have been known of the slab weighing so much as 11 cwt.; the passage of so large a mass of matter between the rolls causes an enormous strain, and unless the mill pinions be of the strongest metal, there is great risk of their breaking. The various shapes and forms of rolled and hammered iron, turned out by an ironwork in active operation, are numerous beyond description. Any peculiarity of form suggested by the engineer, if the inducement be strong enough, is sure to be accomplished in some one of the many ironworks in the kingdom, and that with a dispatch and cheapness of execution which it would once have been thought impossible to attain. Shafts and beams, weighing from 3 to 4 tons, are now manufactured under the forge-hammer in from three to four days, that thirty years ago would have employed from fourteen to sixteen men for as many weeks. An establishment capable of throwing off weekly 200 tons of finished bars, bolts, boiler, plates, sheet-iron, nailrods, cooper’s hoops, &c. will require five blast furnaces; this is, supposing nearly 1∣ ton of pig-iron to produce a ton of bar-iron, and that a thousand tons per year are consumed as castings at the work. The necessary machinery for the manufacture of these goods are shewn in the plates annexed to this article.

Plate CCCXI. fig. 1, elevation of a puddling forge; A the forge-hammer; B the anvil-block; C the anvil; D the hammer helve; E the key or slot for securing the helve to F the camring ; G the spring-block for giving effect to the blow of the hammer; H tappet ; II cast-iron bedplate ; K cast-iron framing supporting the camring-harnmer, &c.; L framing to which the whole is secured; M carriage and axle connecting the forge and puddling-rolls. Fig. 3, elevation of puddling-rolls; AA pinions for connecting the forge and rolls; BB the rolls; DD standards; CC small pinions connecting the upper and lower rolls. Fig. 2, plan of the whole. Fig. 4, wood-frame or anvil-block on which the forge-anvil is supported, this is sunk into the foundation. .-.¾r r

Plate CCCXIV. fig 1 . -1, elevation of bar-iron mill; A A pinions connecting the upper and lower reducing -rolls F F; B clutch for throw ing the rolls in and out of gear; C driving-shaft; D pinion-standard; EE coupling-boxes; G G bar-iron rolls; HH coupling-boxes connecting the bar-iron and reducing-rolls; HI roll-standards; K pinion-standard; LL pinions; MINI coupling-boxes connecting the slitting machinery 00; NN standards, or frame for the cutters; PP bed-plate. Fig. 2, plan of bar-iron mill and slitting machinery. Fig. 3, elevation of pinion-standard. Fig. 4, elevation of roll-standard. Fig. 6, elevation of standard for the slitting machinery.

Plate CCCXV. fig. 1, elevation of boiler-plate and sheet-iron rolls, shews different diameters of the same, according to the work required to be done. Fig. 2, plan of the same.

Plate CCCXVI. fig. 1, elevation of small bolt and rod-mill; A driving-shaft; B clutch; C coupling-box; DDD rolls for reducing the billet; EEE coupling-boxes; FFF pinions; HH coupling-boxes; G G finishing rolls. Fig. 2, plan of the same. Fig. 3, elevation of hoop-mill; AA pinions; DD rolls; C driving-shaft. Fig. 4, plan of the same. Fig. 5, end view of standard for bolt and rod-mill. I⅛∙ 6, end view of standard for hoop-mill.

Plate CCCXII. fig. 1, elevation of wheels for bar-iron mill. Fig. 2, plan. Fig. 3, elevation of shears. Fig. 4, plan.

Plate CCCXIII. fig. 1, elevation of wheel for small bolt and hoop-mill; ABCD the several parts of the large spur-wheel; EFG pinions for connecting the rolls. Fig 2, is a plan of the same.

Figs. 3,4,5,6, Back and front elevations, and plan of heating-furnace, and section of stalk for the same; A stoke-hole; B charging-door; C bridge; D stalk; E ash-pit; FF furnace bars; G hole for running out the cinder or scoria.

Having thus considered the manufacture of pig and bar iron, some details are requisite in connexion with the improved method of smelting by heated air.

The origin of the invention, with the circumstances which led to the discovery that hot air does not, as once generally supposed, deteriorate iron in a liquid state, have already been dwelt on in a preceding article (see Glasgow). Nothing remains, therefore, but to mention some of the results which have been arrived at, and to detftil the present mode of applying the discovery, which is alike applicable to smelting, refining, and to the working of bar-iron,

Plate CCCXVII. fig. 1, shews the plan of a cuþola furnace in connexion with the hot-air apparatus, as at present in operation in several works in Glamorganshire; and a, a, a, &c. the metal pipe in which the air is heated as it passes from the blast cylinder to the cupola. At intervals along the range are placed the heating furnaces, b, b, b, &c., the flame and smoke from which are carried along a brick conduit or flue to the chimney, in the direction shewn by the arrows. The furnace has three working tuyeres. Near the entrance of two of these, the main pipes are laid down in a short double row, in each case, connected together by four smaller pipes, directly opposite to which are placed two of the heating furnaces.

Thus the air, on arriving here, already at a high temperature, is divided amongst several small tubes, exposing a much greater surface to the action of the fire than could conveniently be done in one single pipe.

Hence it becomes still more intensely heated, and the interval being so short, has no time to cool before entering the furnace.

With this apparatus water tuyeres are necessary, the air being heated to upwards of 612° Fahrenheit. Fig. 4. is a section of the water tuyere, shewn also in the other figures. It is merely a short duplex pipe of cast-iron, placed at the entrance to the furnace, and having a stream of water continually flowing through the interval formed by the two surfaces.

When the heating apparatus was first employed, the contraction and expansion to which the pipes were liable, from fluctuations of temperature, was so great, as very materially to derange the joints, which were then common flanches, bolted together in the usual way. Each length of pipe is now made with a small bead and dovetail groove at the extremity; and as the laying down proceeds, the joints are firmly secured by having a solid ring or fillet of metal cast on (see fig. 3).

Thus the whole range is as a single pipe, and the expansion is only felt at one extremity, where it is provided for by a stuffing-box, or enlargement of the engine blast-pipe, into which the heated air-pipe is inserted with the necessary play.

The advantage of heating the air for smelting arises chiefly from the great economy of materials produced.

. This has been invariably the case wherever the improved process has been adopted, the economy becoming more apparent, proportionably with the elevation of temperature given to the air. In the first place, the consumption of coal and limestone, especially of the former, is considerably lessened. In the neighbourhood of Glasgow, the aggregate [7:12:440]of materials required to make a ton of pig-iron is now little more than one-half of what was necessary when cold air was used. Much the same is the result of using the hot-blast in Derbyshire and Staffordshire. The following is an estimate of the quantity of materials required in the year 1829, to make a ton of pig-iron, with coke and cold air; and, in 1834, with crude coal, and the air heated to 612°. This statement refers only to the Glasgow district.
[table]

It appears from the above statement, that the expense of fuel for the blowing engine and heating apparatus, added together, does not amount to so much as did the coals for the blowing engine alone, before the heating apparatus was used, the quantity of cold air required to blow a furnace being much more than when raised to an elevated temperature, on account of the increase of volume attendant on the latter condition. To such an extent, indeed, is this the case, that blowing machines, which were only capable of working three furnaces, when cold air was used, blow with ease four furnaces, when the blast is heated to 612°.

The decrease in the requisite quantity of iron-making materials is accompanied by an increase of one-fourth in the quantity of iron produced in a given time; a furnace that with cold air made sixty tons of metal per week, now making as much as eighty tons during the same period. Whether the metal produced by the hot-blast be equal to that made in the usual way, admits of some doubt. The general opinion seems to be, that the iron is weaker, both in the pig and in the wrought bar.

There appears to be no possible reason why this should be the case, provided that coke only be employed in the blast-furnace. If the coal be used in a raw state, as it most commonly is, when the furnace is blown by hot air, then there certainly is room for suspicion that deleterious substances may come in contact with the iron, which, had the coal been coked, would, during that operation, have been in great part, if not wholly removed.

III.—ORES OF IRON, COAL, &c.

Although it is not intended in this part of the work to enter into a minute mineralogical examination of the various ores of iron; yet it seems necessary to a right comprehension of many facts and processes connected with the manufacture of that metal, that we should be acquainted to a certain extent with the chemical and physical characters of its most useful ores, and also of the fluxes and other adjuncts employed in their reduction. Notwithstanding the numerous forms in which iron occurs mineralized, and extending as it does in one or other of these, throughout the whole suite of rock formations, yet there are many circumstances which limit the sources of its supply within narrower bounds than would otherwise have existed, had there been no such difficulties to contend with. Sometimes the minuteness of the quantity, disseminated through a rock or stratum, is such as to preclude every idea of its being made profitable to the miner; whilst at other times the substances composing the ore, and existing in contact or combination with its metallic ingredient, are of a nature calculated to impart deleterious qualities to the iron with which they are associated.

Conceding, then, to these and other similar circumstances, their due weight, it arises that all the ores actually made available to the production of iron, may be essentially comprehended under two great divisions; the one including those which, .like the magnetic and specular, consist simply of iron in direct union with a greater or less definite proportion of oxygen; the other, those which, like the ironstones of secondary formations, consist of oxide of iron in union with carbonic acid, and in contact or mixture with numerous earths, &c. hereafter to be enumerated. The kind of ironstone existing in any district may in general be inferred from the geological character of the country. Thus the primary countries of Sweden and Scandinavia furnish us with the purest of all the iron-ores. In the transition districts of Lancashire and Cumberland we meet with a mineral, less, though scarcely less pure; and in the coalfields of Europe, America, and New Holland, with the most impure, yet certainly most valuable source of iron. The iron-ore occurring in Cumberland and Lancashire is the red glance, or haematite. In composition it is nearly a pure peroxide, affording a small per-centage of silica, water, and, according to Chevalier, a little ammonia. It possesses in general a high lustre, assumes the reniform and botryoidal shapes, and frequently contains crystals of quartz. Its situation in Cumberland and Lancashire, at a distance from coal, precludes it from being smelted in these districts to any great amount. Hence it is shipped, in the former county, at Whitehaven, and at Diverstone, in Lancashire, for different parts of the kingdom, where it is generally mixed with ironstone‘of a more meagre quality. Much ore from Workington in Lancashire is smelted in South Wales. The same material from the same neighbourhood is to be met with in Worcester, Shropshire, Staffordshire, Northumberland, Scotland, &c. The argillaceous ironstone is, with the exception of coal, the most important mineral product of our island. It is the source whence all the great iron districts of this country, Staffordshire, Wales, Shropshire, Derbyshire, Scotland, &c. derive their almost inexhaustible supplies. Occurring chiefly in the coal measures, it exists to a greater or less extent throughout the whole of the carboniferous group, forming in the different members of that series beds and layers of lenticular nodules, conformably with the other strata, which consist of argillaceous and bituminous shales, micaceous sandstones, and different varieties oev' 1 tye λ and coal. Every coal-field has thus the materials 1 , ∙ m the iron manufacture within its own geological limits, an abundance of metalliferous ore, coal to roast, reduce, and carbonise it, sandstone for building, refractory fireclays for the furnaces, and mountain limestone for fluxing the ore, generally at no great distance.

The ironstones of coal districts have been divided into classes, according as the different earths preponderate in their composition.

1 st , Argillaceous Ironstone, having fine clay as its chief component earth, lime in the next proportion, and nearly destitute of silica, when properly torrefied, exhibits fibres on its internal surface, of a brown, dark brown, or claret colour, running either in streaks, or radiated and adhering tenaciously to the tongue, will afford, with a moderate proportion of lime and coke, iron of the first quality, possessing strength conjoined with an intimate degree of fusibility·

2 nd , Calcareous Ironstone, that which contains lime as its principal earthy mixture, and holds clay in the next proportion, but is comparatively unalloyed with sand; when regularly torrefied, it assumes a variety of shades, generally lighter in colour than the former class, sometimes presenting internal fibres, and adheres less tenaciously to the tongue. Its vein can always be reduced and carbonised [7:12:441]with a comparatively small quantity of limestone and coke. Under this class are found those which produce iron of a fusible nature, seldom connected with strength, but valuable for fine castings, which require ornament more than durability.

3d, Those ironstones, the component parts of which are nearly an equalized mixture of clay, lime, and sand, which torrefy with a slight degree of adhesiveness to the tongue, assuming a darkened ore-brownish colour, void of every internal fibre, always afford an iron of an intermediate quality for fusibility and softness, but possessing strength in an eminent degree, and excellently adapted for artillery and the larger parts of machinery.

Ath, Ironstones which unite a large proportion of sand with sparing proportions of clay and lime, and which, upon being exposed slightly to heat, exhibit masses of semi-vitrification, neither obedient to the magnet, nor adhesive to the tongue, having a refractory disposition, and possessing a dark blue or blue colour, always afford, with the usual proportion of fuel, iron of the worst quality either as to strength or fusibility. Such metal is commonly brittle, and affords malleable iron of the cold short quality.

It is a matter of fact that phosphorus sometimes exists in iron to so great an extent, as very materially to injure its malleability at low temperature, rendering it, according to technical language, cold-short. That phosphorus is actually the agent productive of this effect, was ascertained by the experiments of Bergmann and Meyer, who w ere invariably enabled to detect a phosphurct in iron possessing the above-named quality. Tĥe existence of phosphorus in iron is a sufficient evidence of its presence in the ores of that metal, and would lead us to infer that there was a gradual deposition of animal matter during the formation of the ironstone beds. In this inference we are amply supported by observation; for traces of animal matter have been found very extensively in ferruginous beds and nodules, traces more particularly of membranous shells, and of the scales and bones of fish.

In the Mid-Lothian coal-field, ironstone nodules are described as occurring in great number, and, when broken open, exhibiting a very curious appearance. The mass of the stone is of a dark brown colour, compact and solid; in the centre, generally occupying about an inch, is an oblong body, the structure of which is disposed in laminae, or concentric layers. The round body, the appearance of a neck and head, the four projecting substances corresponding to legs, and the circular rings on the part corresponding to the abdomen, all evidently corroborate the supposition that the centre substance is an animal in a petrified state, or some organic substance which has served as the nucleus of the stone.

In the Annales des Mines for 1825, Μ. Berthier gives an account of his discovery of phosphate of lime, in association with the argillaceous ironstones of the coal formation at Riant in France. The specimen he examined had absolutely the same appearance as the argillaceous ore of iron with which it was found; and he adds that the fact, interesting as it may appear in a geological point of view, deserves also the notice of metallurgists, and should induce them to institute a strict examination of the ores with which the coal formation furnishes them.

The specimen of phosphate of lime, on being analyzed, gave the following result:

Lime, . . . 0.363 ì Phosph, lime(Apatite), 0.670

Phosph, acid, . 0.310; Carb, of Iron, . 0.157

Protox. iron, . 0.096

Alumina, . . 0.090 Alumina, . . 0.190

Water, bitumen,and ì n 1 on xκτ .,,.. n nm carbonic acid, ,J^θ∙ 12 θ Water and bitumen, 0.06Q

0.979 0.979

The mineral is found in nodules of a globular form, sometimes flattened, and always of rather small size; and these nodules occur in great quantity in the black argillaceous schists which separate the second bed of coal from the sandstones that support it. They are not homogeneous; their crust is almost entirely composed of carbonate of iron. Sometimes they contain a great quantity of transparent laminar carbonate of lime, which divides the mass into small prisms; sometimes it is a coally matter, and at other times they are enveloped in a crust of compact sulphuret of iron. In the centre there is a nucleus of a pale yellow or grey colour; compact, fine granular, and traversed by impressions of gramineae. It is this nucleus which contains the phosphate of lime. The crust of a nodule, assayed in a covered crucible without addition, gave 0.20 of hard cast-iron, equivalent to 0.43 of carbonate of iron; and a slag, weighing 0.56, which was opaque, of an apple-green colour, and entirely similar to melted phosphate of lime. The ore of iron called Bog Iron Ore, which is daily forming by deposition from pools, the waters of which have previously percolated through ferruginous strata, very frequently contains a large proportion of combined phosphoric acid. The iron macle from this ore is cold-short, but is excellent for producing distinct and well defined castings, as it swells in cooling. The greater part of the Berlin ornaments are made from bog-ore.

In enumerating the more general ingredients of ironstones, perhaps titanium should be noticed; which, since its first detection as a new substance at Merthyr Tydvil, where it had been supposed to be a species of pyrites, has been found in the slags of nearly every furnace in the kingdom, as well as in Germany and France, a pretty evident proof of its wide dissemination in connexion with minerals affording iron.

Whether titanium ever combines with the iron during the process of reduction, and is thereby productive of a good or bad effect, we do not feel competent to assert. It seems not improbable, that its presence in small quantities may tend to improve the quality of the iron, with which it is alloyed, in the same way that certain other hard and refractory metals, as rhodium, &c. are productive of an admirable effect in common steel. Indeed, the supposed case is not without analogy, as in reference to manganese, to the presence of which Berzelius attributes in a great measure the superiority of the Swedish over the British iron.

When magnesia exists to any great extent in an iron-ore, the infusibility of the combined mine and flux are greatly increased. Presenting itself under so deleterious an aspect, this earth is unfortunately of common occurrence both in ironstones, cokes, and limestones. On this account all the members of the magnesian limestone deposits are to be most carefully avoided.

In concluding these remarks upon ironstones, it may not be unimportant to add a few observations on coal, a mineral of so much importance in connexion with iron-making, when practised in thinly wooded countries. Of the different species of coal enumerated by mineralogists, the common varieties of the black or bituminous class appear to have been most extensively employed in smelting operations, a fact resulting not only from their more universal distribution, but also'from certain peculiarities in their organization, as contrasted with those coals which approximate in character to the anthracites. Nor does this preference appear to have been conceded wholly without trial. Thus, in South Wales, the extensive development of stone-coal seams, in connexion with rich deposits of ironstone, have led to frequent attempts at using this coal in the raw state as a substitute for coke. These attempts have hitherto proved unsuccessful, a result the more unexpected, considering that the coal is a dense and nearly pure mineral [7:12:442]carbon; and that the close-grained and more ponderous cokes have generally been regarded as best adapted for iron-smelting. It has been suggested that the imperfect conducting power of this mineral for heat, arising probably from the compactness of its texture and its want of bitumen, presents the obstacle, which has hitherto prevented its application with any success to processes conducted in the blast furnace. This imperfect transmitting power is so great, that the application of the blast to a furnace, in which the stone coal is placed as fuel, instead of producing ignition throughout the mass, actually extinguishes the fire.^[3. Foster, Trans. Nat. Hist. Soc. Newcastle. ]

In a patent taken out some years ago, it was proposed to smelt iron with stone coal, introducing at the same time a stream of carburetted hydrogen.

The following are analyses of several varieties of coal:

Carbon. Volatile matter. Ash.

No. 1, . . 89.00 . 8.00 . 3.00

No. 2, . . 82.00 . 14.50 . 3.50

No. 3, . . 69.00 . 28.00 . 3.00

No. 4, . . 85.60 . 13.40 . 1.00

No. 5, . . 52.45 . 45.50 . 2.04

No. 6, . . 52.88 . 42.83 . 4.28

No. 1. is an analysis of the Welsh stone coal.

No. 2. is an analysis of the furnace or iron-making coal of Wales. A most important and peculiar property resident in this coal is the proneness to ramification or swelling exhibited by it during combustion, which frequently gives the coke an arborescent appearance, and renders it in some varieties as light and porous as wood charcoal; whilst in others, as, for instance, the great seam at Merthyr, the coke is much harder, more ponderous, and admirably adapted for iron-smelting.

No. 3. is an analysis of the bituminous or binding coal of South Wales, many seams of which possess the important property of being free from sulphur. The coke of this coal, when it can be procured, is mixed with that of the branching coal in smelting.

No. 4. is an analysis of the great seam at Merthyr, the coal from which a great portion of the coke for the blast-furnaces is procured. It is coked in heaps in the open air, and produces a close-grained coke of a silvery lustre, and very free from sulphur.

No. 5. is an analysis of the Alfreton furnace-coal, and No. 6. is an analysis of the Butterly furnace-coal.

Besides the ingredients indicated by the analyses here given, as constituting coal, a great number of extraneous substances are commonly blended and associated with that mineral, such as sulphuret of iron, carbonate of lime, magnesia; and these of course exercise a detrimental influence when the coke is brought to play its part in the blast-furnace.

The object in coking is to obtain the carbon of the coal • in as insulated and independent a form as possible, by driving off the moisture, sulphur, and gaseous constituents. The earthy ingredients not being volatilisable, of course remain, and even the sulphur is never wholly driven off. The relative amount of these substances, as indicated in some degree by the quantity, weight, and colour of the ash, when a certain portion of coke is burnt, should in every case be ascertained before a coal is appropriated to smelting operations.

The method of coking varies in different places. In some iron districts the process is performed in small ovens, the access of air being prevented as much as possible. In South Wales, on the contrary, long heaps of coal are ignited in the open air, and allowed to burn from one end to the other beneath a slight covering of turf or ashes. After the cokes have done smoking, the cokers frequently stir the heaps, in order, as they say, to allow the escape of sublimed sulphur; and, after the ignition has continued a sufficient length of time, the burning cokes are extinguished with water, which is also said to favour the escape of sulphur; perhaps in this way. A portion of the water being decomposed by contact with the cokes at so elevated a temperature, the sulphur of the coke probably attaches itself to one of the liberated gases, and makes its escape in the form of sulphurous acid gas, or sulphuretted hydrogen. It cannot fail of being perceived, that the process here described must be of a very uneconomical nature; and, indeed, if the weather happen to be very windy, no exertions can at times prevent the loss of many tons of coal in a single night.

Coke is of various degrees of weight and quality, corresponding in great measure with the properties of the coal from which it is derived. Sometimes it has a dull grey fibrous fracture, very similar in appearance to charcoal of wood. More generally the fracture is porous, with a bright vitreous, nay almost metallic lustre. The quantity of coke that can be procured from a given quantity of coal, of course differs considerably; so much, indeed, in different seams and in different districts, as to render it difficult to give any numerical standard on the subject.

In the Glasgow Coal-field,

1 J tons of best splint coal produce 1 ton of coke.

2 tons of inferior do. do.

2į tons of the main do do.

3 tons of Pietshaw do do.

And it is generally observed, amongst the manufacturers of that district, that one ton of the best Scotch coals is only equal to three quarters of a ton of the best Newcastle.

The Welsh coals, as will be seen from the comparative analyses before given, contain a much less quantity of volatile matter than either the English or Scotch; and hence their great superiority as an iron-making coal.

IV —ROLLERS, FORGE, &c.

In the preceding pages we have given a description of the manufacture of iron, up to the time of producing finished bars in the rolling-mill; but as yet, nothing further has been said of the machinery employed, than the explanation of processes under consideration, rendered absolutely necessary. Supposing the manufactory in an active state of working, to turn out 200 tons of finished iron per week, it may be well to enter into some details connected with the making and fitting up of the rollers, describing at the same time that part of the establishment exclusively appropriated to this purpose. After the manufactory is furnished with the machinery in daily use, such as rollers, couplingboxes, pinions, spindles, hammers, anvils, the parts of the different furnaces, &c., it is usual to provide duplicates of all these.

The rougher pieces of apparatus, such as hammers, anvils, the several parts of the heating furnaces, plates for the floors, &c. are run at once from the blast-furnace. On the other hand, the finish, and accuracy of size and shape, which bars, bolts, and in fact, all other descriptions of rolled iron are required to have, demand that the greatest care and attention be paid to the getting up of the rollers. They should be made in the best possible manner, and of the [7:12:443]strongest metal, a proper melting furnace being provided, and kept entirely for the purpose. The best coals are indispensably necessary, otherwise the work will be deteriorated by the impurities which it cannot fail to take up when in a highly heated or liquid state. The material ought to consist wholly of No. 1. pigs. A mixture of Staffordshire, Shropshire, and Welsh metal is most suitable.

The best grained rollers for boiler-plates are cast in loam or sand. The mould, which is sunk perpendicularly in the cast-house floor, is capable of containing in an upper part, at least one-third more metal than is necessary to form the roller. The object of this is, to give weight and pressure to the fluid material below, and thereby insure a perfect casting. Without this precaution, the rollers generally turn out honeycombed and unsound. It is also necessary during the running of the metal into the mould, to keep it alive, by constantly stirring it with a stick, the extra metal or head at the same time making up for any deficiencies caused by shrinking or evolution of gas in the interior of the casting. The roller, for whatever purpose it might have been intended, used generally to be cast as a plain cylindrical mass, the grooves being afterwards all cut out by the slow and tedious process of turning. It is now moulded as near as possible to the form which it ought to have when finished, allowing only as much superfluous metal as will admit of its being cleaned up, and brought to a true centre in the lathe. Rollers for boiler-plates and sheet-iron, from the great strain to which they are occasionally subjected, should have the bearing part or neck turned in the shape represented at AA. The barrel or cylinder should also be slightly concave, because when the slab is first passed through the rollers, it comes in contact only with a small portion of the revolving surfaces. The central parts of the roller thus become highly heated, whilst the extremities are comparatively cool; the consequence is, that the expansion is greatest at the middle, so that, unless this be provided for by concavity in the barrel, the plates become buckled; that is, both warped and uneven in thickness, and consequently unfit for the purposes of the boiler builder. Bar and bolt-rolls are generally slightly case-hardened, this is effected by chilling in a mould or cast-iron case fit for the purpose. That the chilling may not exceed what is necessary, the roller, when cast, is turned out of the case red-hot. This prevents its hardening too much, and allows the turner to finish it with less injury to his turning tools.

We will now enter into a few particulars respecting the sizes of the different kinds of rollers, and the speed at which they are run. Rollers for roughing down are from 4 to 5 feet long, by 18 inches in diameter. The rollers for merchant bars and bolts are generally about 2 feet 6 inches long, 13 inches in diameter, and make about 70 revolutions per minute. With regard to boiler plate and black sheet iron rollers, much depends on the size of the work which they are to perform. They vary in size, from 2 feet 6 inches in length, by 13 inches in diameter, to 5 feet 6 inches in length, by 18 inches in diameter, the speed at which they are run varying from 35 to 40 revolutions per minute. For roughing down small iron, it is usual to run three rollers backwards and forwards; that is, the rollers run in opposite directions. These, and also the finishing rollers for the same descriptions of iron, are generally 10 inches in diameter, and make about 120 revolutions per minute. Guide rollers for small rounds and squares are 8 inches in diameter, and make about 200 revolutions per minute. In all the large works, the rollers vary as to size and also velocity; but the proportions we have here given are those in most general use. Of course, if the rollers are increased or decreased in diameter, the speed must be regulated accordingly. In some of the Staffordshire mills, guide rollers are run so small as 4 inches in diameter, with a speed equal to 400 revolutions per minute. All, except the roughing and boiler-plate rollers, are usually case-hardened. The small rollers, in particular, are fitted up with the greatest accuracy, and carefully chilled. Whilst the speed of rolling thus varies with the size and description of the roller, there is one condition which should be invariable: It is this, that the process ought always to proceed at a certain temperature, so that the particles of the iron may be compressed to the greatest possible degree, and the bar be turned out, with a clean and well-polished skin. For the general purposes of the rolling mill, the engine should be of eighty horse power. In rolling boiler plates, however, where, as was before mentioned, the slab sometimes weighs as much as 10 cwt., a hundred horse power will not be too much. The fly-wheel and shaft, to overcome the great resistance, ought to weigh from 25 to 30 tons. The whole of the boiler plate machinery should be proportionally strong, and detached from the other parts of the mill, so that, when necessary, the whole available power of the engine may be concentrated on the working of these rollers alone. The pinions, if not made of the strongest metal, are liable to almost constant breakage. The connecting spindles ought, if possible, to be made of wrought iron. At some manufactories, the coupling boxes are also made of wrought iron. The shaft of the spur-wheel, and indeed all the other shafts, should be of the same material, the bearings carefully turned, and well case-hardened. Associated with the rolling-mill should be a large and strong lathe of the most improved form and construction, with self-acting slide rests. When the mill is in an active state, this will be almost constantly employed in turning rollers, which, for railway bars and the like, require to be of an endless variety of forms and sizes.

So far the Forge has been considered merely as an auxiliary to the rolling mill, being employed to shingle the puddler’s blooms preparatory to their passing through the rollers, and being formed into mill-bars. Something further than this seems requisite, in order to a right appreciation of this most valuable piece of machinery in the manufacture of various large and heavy articles required by the engineer. Few of the larger works interest themselves in the manufacture of iron, after it leaves the rolling-mill. This, therefore, forms a separate branch, and is carried on to a great extent in Newcastle-upon-Tyne, Birmingham, Bristol, and several other large towns in the kingdom. It is at establishments in these towns and their neighbourhoods that shafts, cranks, crossheads, and other parts of the steam-engine are forged, and that large chains and mooring anchors are manufactured, not only for the British, but also for the Dutch, Swedish, French, Turkish, Egyptian, and American navies. So low, indeed, is the price at which British iron can be produced, and to so great a degree of perfection has the manufacture of anchors and chains been carried, that these powers pay little more for the latter articles than the cost of Russian or Swedish iron in their own country.

Until forty years ago, it was not attempted to make any work under the forge-hammer exceeding one cwt. We are now indebted to the forge for the manufacture of anchorshanks, weighing singly from 30 to 45 cwt.; arms for the same, of 18 cwt.; palms, 3 to 4 feet wide, and from 8 to 12 cwt.; steam-engine shafts, 25 feet long, and weighing from 5 to 6 tons.

To shew the improvements which have been made in the manufacturing of machinery since 1792, we subjoin a statement of the manual labour attending the making of an anchor for the British Navy at that time and now. In the year 1792, it required 16 men, each working 27 days, to forge and finish an anchor for a first-rate ship in the navy; the anchor when finished weighing 8960 lb.; total number of days, 27 × 16 = 432 days. In the year 1835, [7:12:444]with the assistance of the forge, the same quantity of work can now be finished in 173 days, making a saving of manual labour by the use of the forge of 259 days.

This statement, along with others which could be given, fully bears out the assertion, that in no part of the manufacture has so much progress been made as in the getting up of anchors and chains. In the year 1808, the sum paid for workmanship on one ton of chains amounted to L. 18; at present chain-cables can be bought for the same sum, including both iron and workmanship.

The “Sovereign of the Seas," built in 1637, carried eleven anchors, one of which weighed 4400 lb., or 39 cwt.; but the largest anchor now made for the navy weighs five tons. Fifty years ago, it was not thought possible to roll bolts and bars; at that time all the boltstaves requiredfor shipping were rounded under the smith’s hammer, from Russian and Swedish iron. In the same manner, so little were the uses of the forge understood, that it is only within these very few years that the great and increasing demand for large wrought-iron machinery for steam-boat and railway engines, has led the iron-manufacturer to attempt what had previously been thought impossible.

The forging of large machinery, which is carried on to a great extent at Bedlington, near Morpeth, is sufficiently interesting to claim a particular account in these pages. There the writér of this had the opportunity of seeing the manufacture of a large shaft for the rope-rollers of the Stanhope and Tyne Railway incline engine. It was laid up in a faggot from large flat bars, as shewn in the figure adjoining; a long bar of iron, called a “Porter,” being welded into the interior of the mass at one end, for the convenience of moving it about under the hammer. The weight of the iron, previous to being heated, was 7 tons 6 cwt. 1 qr. 26 lb., and the weight of the shaft, when finished at the forge, 5 tons 8 cwt. 2 qrs. 6 lb., shewing a waste in the process of manufacture of 1 ton 17 cwt. 3 qrs. 20lb., or about one-fourth of the whole. This shaft, which was 25 feet in length, with a cross sectional area of 13 square inches, was probably the largest single piece of iron ever manufactured under a forge hammer. It was finished in eight days. Had it been made under the small hammers, according to the method of working forty years ago, it would have required as many weeks.

Messrs Maudsley and Co. of London have occasionally had shafts forged at these works near five tons in weight; the same manufactory is not less celebrated on another account, namely, as having produced the first rolled malleable iron railway bars. After the shaft has been laid up in the manner described, it is carefully heated in an air furnace, constructed for the purpose, drawn out when ready, as quick as possible, swung upon the anvil, and worked under a very heavy hammer. The better to effect this, it is slung in a cradle working on a screw, which is suspended to a collar, playing over the jib of a strong and powerful crane, capable of sustaining at least twenty tons. This apparatus suffices for the purpose of enabling the forgeman and his assistants with strong iron levers or caul-hooks, to move about and turn round their work as the operation may demand. Sometimes it is urged forwards, at others, by the combined exertions of the workmen, turned over on the anvil, each side in succession being presented to the stroke of the hammer. In this manner it is astonishing to see with what ease and facility the massive shaft is handled during the progress of the heat, which generally lasts about half an hour. At its conclusion the shaft is returned into the furnace, raised afresh to the welding temperature, another heat is taken, and so on until it is finished. It is of the greatest importance that the work be accomplished in so complete a manner, under the forge hammer, that nothing further shall be required of the smith, as the shaft in the process of forging, has acquired a stiffness, which it is desirable that it should retain. After-heating weakens it much, loosening the fibres of the iron, and destroying its elasticity. Notwithstanding all the care of the workman, and repeated heavy hammerings, few shafts are solid to the centre; indeed, it is doubtful if it be possible by any means to obtain a perfectly homogeneous mass where the magnitude is so great.

Large masses of forged and hammered iron almost invariably exhibit a hollowness at or near the central axis. It is difficult to say exactly how this arises, as a curious and important fact, however, it deserves attention. Some time ago it was customary to lay up work of the kind we have been describing with feathered or wedge-shaped bars, as in the attached figure. During the French war, most of the large anchors for the British navy were manufactured in this manner; but many of the shanks of these anchors breaking, it was discovered that only a crust or exterior rim of the shank, exceeding little more than two inches in thickness, was perfectly welded, whilst the bars in the centre, although undergoing the same degree of heat and hammering, were quite loose, and might have been taken out unaltered, at least as to shape.

All the larger pieces of wrought-iron machinery ought to be made under a heavy hammer, capable of being felt to the very centre of the pile of bars, when in a welding state, finished there as far as possible, and then passed into the lathe, planing-machine, or drill, there to be further fashioned to the required shape. If the shaft or other piece of machinery be returned to the fire for a dressing up, it becomes brittle and considerably weakened, the fibre of the iron is destroyed, and the shaft rendered less susceptible of resistance to torsion or twists, that it may be subjected to, in any particular situation; as, for instance, in a steam-boat engine during a heavy sea and hard gale.

It is to be regretted that the iron manufacturer should ever be obliged, as he frequently is, to deteriorate from the quality of a well-forged piece of machinery, for the sake of accomplishing what, with a little more expense, could be as well or better done in the lathe, at the same time without the slightest risk of injury to the iron. When a shaft, which has been fabricated under circumstances of this kind, gives way or breaks, the cause of failure is seldom traced to the right source. The manufacturer is blamed for using a bad quality of iron; the engineer, in nine cases out of ten, little thinking that to his own misplaced economy, or ignorance of the properties and manufacture of iron, is to be attributed, in great part, the misfortune.

Shafts and large machinery are best made from scrap-iron, collected in the dockyards, shops of the large engineers, coach manufactories, and other places where refuse iron accumulates. The scraps, being of various sizes and descriptions, are cut into very small pieces, called nut-iron, blended together, carefully piled upon a flat freestone plate, or, if not convenient, a fire-clay tile, and put in this manner into the balling furnace. The piles heated at once amount from 6 to 8 cwt. After remaining in the furnace about twenty minutes, they are successively taken out with a pair of tongs, thrown under the forge-hammer, and speedily shingled into slabs or blooms. These are again heated in another furnace, and rolled into bars of the shape and size required.

Scrap-iron is the most suitable material for all kinds of [7:12:445]engine-work. It also makes the best boiler-plates, railbars, &c. Not being so fibrous as the best British iron, it is less liable to split or crack, bears the heat in a large body better, and makes sounder work. Some of the large ironmasters make a description of iron which they denominate scrap-iron. This is manufactured from the crop-ends of the bars, and other refuse collected in the work. It consists, consequently, of all the varieties of quality found in Nos. 1, 2, and 3 iron, the whole being blended together. The result of such a mixture is, the greatest irregularity in quality and texture. The No. 1. or puddled iron in the composition not having undergone the same working as the No. 3, does not unite or coalesce with it; the several parts of the bar have the appearance of being imperfectly welded, and exhibit splits and cracks on the edges.

On the contrary, good scrap-bars, of the description before mentioned, being made from old, and consequently well-worked iron, assume a sound and strong body; and the pieces also of which the bloom is fashioned being small, thrown together indiscriminately, and not piled regularly as the iron from crop-ends, meet together at various angles to each other; the fibres are thereby crossed, and the bar is rendered less subject to that longitudinal lamination so seriously felt in rail-bars, tyres for locomotive-engine wheels, and other similar work.

It is not by any means to be imagined that the advantages of the forge are confined to the putting together of such large masses of iron as have hitherto only been described. In fact, all kinds of edge-tools, agricultural and plantation hoes, sugar-cane bills, axes, adzes, spades, shovels, and the like, are now. made with an immense saving of manual labour by the forge; the machinery for this purpose being, of course, lighter in proportion, and the hammer made to work with a greater speed. Nor are the uses of the forge in the manufacture of large articles much more striking than the performances of the rolling-mill in the same department. We have seen large plates, containing as much as thirty-eight square feet of area, engine-beams weighing 11⅜ cwt. when finished, and 13 cwt. in the slab, respectively formed in the rollers, from a single piece of iron previously prepared beneath the forge-hammer. (c. c. c. c.)