In the preceding chapter I have endeavoured to establish the conditions, under which are found in Ireland two elements, essential above all others to the prosecution of manufacturing industry, fuel and power, and to analyse the relation, which the cost of motive power in mechanical operations, bears to the other circumstances. There remain for examination, however, other subjects of not inferior interest or importance, and of these one will specially require a detailed notice, as it affects the industrial arts almost in an equal degree as the cost of fuel. I shall, therefore, endeavour to represent in the following notice, the circumstances under which this country exists with regard to the supply and manufacture of iron. This metal is, indeed, indispensable to an advanced condition of the arts. If we employ fuel to give motion to our machinery, we as inevitably
p.111employ iron in the construction of the machine. Its various properties adapt it to our uses in an unparalleled degree: as we require massive strength or delicacy of form, whether we wish our material to be rigid or highly elastic, hard or soft, iron is that which satisfies our wants; fusible in one condition, infusible, but highly plastic in another, it is capable of being moulded, welded, turned, ground, and polished; whilst by the wise economy of nature, fortunately for man, being found in every country, and available at a small expense, its supply is practically unlimited. Its use has hence become at once the cause and measure of material progress. A nation without iron cannot emerge from the condition of semi-barbarism. Its chiefs may be magnificent in gold and jewels; its warriors may be armed with shields and swords of bronze, on which the labour of long practised workmen may bestow a finish, admirable even at the present day; but the rarity and cost, as well of material as of artificer, deprives the general population of all power to render those precious metals available to their domestic comfort. It is only where iron is obtainable; where, cheap and abundant, it places within the reach of all, the means of constructing the various tools and instruments by which the arts and agriculture are so materially advanced, that civilization can become firmly grounded amongst a people. If we consider how each succeeding step in industry places the elements of material domestic comfort more cheaply in the power of a people; that by this greater cheapness and facility of procuring the means of animal existence, there is afforded time for mental cultivation, and growing out of that, by proper discipline, a sounder morality, a love of peace and justice, we may well recognize in coal and iron, agents of civilization and of intellectual happiness to man, of whose powers, astounding as they appear, we trace but the infant energiesof whose final results we can no more apply a measure, than could the savage, who, sensible of the value of the tool, barters his golden ornaments for a knife, estimate the industrial and educational movements of the present age.
The variety of properties which fits iron so wonderfully for its uses in the arts, is the foundation also of a variety in its
p.112money value, which I shall here notice, as it will be found to affect, in a very material degree, the circumstances of this country as to its manufacture. In fact, so cheaply is the metal itself obtained, that its subsequent adaptation to different uses, demands a degree of mechanical skill and labour which overshadows totally the cost of the iron employed; and hence, in the following table, selected from results given by Babbage and Friedenberg, the increase of value is for the most part made up of the cost of labour bestowed upon the article in the various processes it passes through.
The quantity of cast iron worth £1 sterling becomes worth the following sums, when converted into
|Larger ornamental work||£ 45|
|Buckles, Berlin work||£ 660|
|Neck chains||£ 1386|
|Shirt buttons||£ 5896|
|Horse shoes, worth||£2 10s.|
|Knives (table)||£ 36 0|
|Needles||£ 71 0|
|Penknife blades||£ 657 0|
|Polished buttons and buckles||£ 897 0|
|Balance springs of watches||£ 50,000 0|
Some centuries ago Ireland presented a picture of manufacturing industry, such as we would now find, perhaps, in the interior of Russia, or the mountainous districts of northern Spain, but which the progress of the arts has banished from Britain and from central Europe. Covered with forests, and possessing iron ore, as we shall hereafter show, of the highest purity in great abundance, Ireland was sprinkled over with small iron works, in which the wood charcoal was employed, and thus iron manufactured of excellent quality; in fact, such as we now import from Sweden and Russia for all the finer purposes of cutlery and mechanism. Such kinds of iron furnaces may be considered as now belonging but to the history of art;
p.113yet in an historical point of view it is not uninteresting to extract some particulars of this industry amongst ourselves, from the remarkable work on the natural history of Ireland, written by Dr. Boate two centuries ago.
Of the iron mines there are three sorts in Ireland, for in some places the oar of the iron is drawn out of moores and bogs, in others it is hewen out of rocks, and in others it is digged out of mountains: of which three sorts the first is called bog-mine, the other rock-mine, and the third with several names, white-mine, pin-mine, and shel-mine.
The first sort, as we have said, and as the name itself doth shew, is found in low and boggie places, out of the which it is raised with very little charge, as lying not deep at all, commonly on the superficies of the earth, and about a foot in thickness. This oar is very rich of metal, and that very good and tough, nevertheless in the melting it must be mingled with some of the mine or oar of some of the other sorts: for else it is too harsh, and keeping the furnace too hot, it melteth too suddenly, and stoppeth the mouth of the furnace, or, to use the workmen's own expression, choaketh the furnace.
The second sort, that which is taken out of rocks, being a hard and meer stony substance, of a dark and rustie colour, doth not lye scattered in several places, but is a piece of the very rock, of the which it is hewen: which rock being covered over with earth, is within equally every where of the same substance; so as the whole rock, and every parcel thereof, is oar of iron. This mine, as well as the former, is raised with little trouble, for the iron-rock, being full of joints, is with pick-axes easily divided and broken into pieces of what bigness one will: which by reason of the same joints, whereof they are full every where, may easily be broke into other lesser pieces; as that is necessary, before they be put into the furnace.
Of this kind hitherto there hath but two mines been discovered in Ireland, the one in Munster, near the town of Tallow, by the Earl of Cork's iron works; the other in Leinster, in King's County, in a place called Desart land, belonging to one Serjeant-Major Piggot, which rock is of so great a compass, that before this rebellion it furnished divers great iron
p.114works, and could have furnished many more, without any notable diminution; seeing the deepest pits that have been yet made in it, were not above two yards deep. The land, under which this rock lieth, is very good and fruitful, as much as any other land thereabouts, the mold being generally two feet and two a half, and in many places three feet deep.
The third sort of iron-mine is digg'd out of the mountains in several parts of the kingdom; in Ulster, in the county of Fermanagh, upon Lough Earn, in the county of Cavan, in a place called Doubally, in a dry mountain; and in the county of nether-Tyrone, by the side of the rivulet Lishan, not far from Lough Neagh; at the foot of the mountains Slew-galen, mentioned by us upon another occasion, in the beginning of this chapter; in Leinster; in King's-county, hard by Mountmellick; and in Queen's-county, two miles from Montrath; in Connaught; in Tomound, or the county of Clare, six miles from Limerick; in the county of Roscommon, by the side of Lough Allen; and in the county of Leitrim, on the east side of the said lough, where the mountains are so full of this metal, that thereof it hath got in Irish the name of Slew Neren, that is, mountains of iron: aud in the province of Munster also in sundry places.
This sort is of a whitish or grey colour, like that of ashes; and one needs not take much pains for to find it out, for the mountains which do contain it within themselves, do commonly shew it of their own accord, so as one may see the veins thereof at the very outside in the side of the mountains, being not very broad, but of great length, and commonly divers in one place, five or six ridges the one above the other, with ridges of earth between them.
These veins or ridges are vulgarly called pins, from whence the mine hath the name of pin-mine; being also called white-mine, because of its whitish colour; and shell-mine, for the following reason; for this stuff or oar being neither loose or soft as earth or clay, neither firm and hard as stone, is of a middle substance between both, somewhat like unto slate, composed of shells or scales, the which do lye one upon another, and may be separated and taken asunder very easily, without
p.115any great force or trouble. This stuff is digged out of the ground in lumps of the bigness of a man's head, bigger or less, according as the vein affordeth opportunity. Within every one of these lumps, when the mine is very rich and of the best sort (for all the oar of this kind is not of equal goodness, some yielding more and better iron than other), lieth a small kernel, which hath the name of hony-comb given to it, because it is full of little holes, in the same manner as that substance whereof it borroweth its appellation.
The iron coming of this oar is not brittle, as that of the rock-mine, but tough, and in many places as good as any Spanish iron.
It would be difficult at the present day, independent of chemical analysis, to furnish a better description than that given two centuries ago by Boate, as just quoted, of the bog iron, which is found in patches in almost every part of this island, and of the ironstone, of which the very rich quality of Lough Allen, and that of the Leinster district, was even then recognized. I shall return in a few minutes to the question of their composition, but before leaving Dr. Boate I shall extract his account of the financial condition of the iron trade in Ireland, as it will show the difference between the cost of manufacture then, and in the present day.
To speak somewhat more particularly both of the charges and profits of these iron-works, we shall instance the matter in one of the works of the said Sir Charles Coot, namely that which he had in the lordship of Mountrath, in Queen's-county. At that work the tun (that is twenty hundred weight) of rock-mine at the furnace head came in all to stand in five shillings and six pence sterling, and the tun of white-mine, which he had brought him from a place two miles further off, in seven shillings. These two were mixed in that proportion, that to one part of rock-mine were taken two parts of white-mine: for if more of the rock-mine had been taken, the iron would not have been so good, and too brittle; and being thus mixed, they yielded one-third part of iron: that is to say, of two tuns of white mine, and one of rock-mine, being mingled and melted together, they had one tun of good iron, such as is called merchant's
p.116iron, being not of the first, but second melting, and hammered out into bars, and consequently fit for all kinds of use.
This iron he sent down the river Oure (by others called the Nure) to Rosse and Waterford, in that kind of Irish boats which are called cots in that country, being made of one piece of timber: which kind of ill favoured boats (mentioned also by us above) are very common throughout all Ireland, both for to pass rivers in, and to carry goods from one place to another; and not only upon shallow waters, such as the aforenamed river is, in the greatest part of its course, but even upon the great rivers and loughs.
At Waterford the iron was put aboard of ships going for London, where it was sold for sixteen, otherwhiles for seventeen pounds sterling, and sometimes for seventeen and a half; whereas it did not stand Sir Charles Coot in more than betwixt ten and eleven pounds sterling, all charges reckoned, as well of digging, melting, fining, as of carrying, boat-hire and freight, even the custom also comprehended in it.
In most of the other places did a tun of the iron-mine or oar come to stand in five, five and a half, and six shillings sterling at the furnace head; and it was an ordinary thing, as well where they used white-mine, as where they mixed rock-mine with it, to have a tun of good iron out of three tuns of oar: in some places, where the mine was richer, they would have a tun of iron out of only two tuns and a half of oar. Nevertheless few of them gained more or as much as Sir Charles Coot, because they had not the same conveniency of transportation: and he himself did not gain so much by his iron works in Connaught, as by that near Mountrath, although the mines there afforded a richer oar, and that the tun thereof did cost him but three shillings at the furnace, because that Lough Allen, whereunto the same mines and works are contiguous, gave him the opportunity of carrying the oar by water from the mine unto the work, and that in boats of forty tuns.
The Earl of Cork whose iron works being seated in Munster, afforded unto him very good opportunity of sending his iron out of the land by shipping, did in this particular surpass all others, so as he hath gained great treasures thereby: and
p.117knowing persons, who have had a particular insight into his affairs, do assure me, that he hath profited above one hundred thousand pounds clear gain by his said iron works.
We thus see that two hundred years ago iron was an article of export from Ireland to London.
In fact, as well in Ireland as in England, where, at the same time, the same processes of manufacture were followed, the vast quantity of wood consumed, to make charcoal for the iron works, gradually stripped the country of its forests, and with the supply of fuel, of course the working of iron was abandoned. Similar causes are at the present moment in operation on the Continent of Europe, and limit the economic manufacture of iron by means of wood, to those countries in which a thinly scattered population admits of large tracts being occupied in growing timber. The wonderfully fortunate destiny of England, however, intervened at that very time, when her iron trade was in process of rapid annihilation. The energy and genius of one man, to whose name the deserved honour has never yet been paid by England, rescued her from becoming a mere dependant for iron on the north of Europe, and by inventing the process of reducing iron by means of coke, made the first step in the path of technical discovery which rendered that country the industrial sovereign of the world. It would not be difficult to show, that had not Dudley substituted coke for charcoal in smelting iron, the conditions of industry which gave field for Watt and Arkwright, could scarcely have existed. In Ireland there was no man like Dudley. The iron manufacture in England assumed a new and enlarged existence. The iron manufacture of Ireland rapidly declined, and finally, a century ago, in Kerry, the last charcoal furnace was extinguished, when they had burned out the last remaining wood.
It is necessary now to examine, with all the aid which modern science, and the experience of other countries, may afford us, how the materials necessary for the manufacture of iron are circumstanced with us.
The ores of iron that are actually employed as sources of the metal are of three kinds, the anhydrous peroxide, or specular iron; the hydrous peroxide, including hematite and bog ore;
p.118and the carbonate of iron, to which the clay-ironstone of the coal formations belongs.
Of the first kind of ore, there is but one locality in which it has hitherto become of industrial importance, the island of Elba, which has been celebrated from the earliest ages for the goodness of its iron and steel, obtained by the working of this ore. It is the richest ore of iron that is known, containing 70 per cent. of metal; but as it cannot be smelted on the spot, it has been rendered unimportant by the superior economy of working inferior ores in more suitable localities, and the celebrity of Elba as a source of iron is now but a fact in history. To us this ore is not without interest nevertheless. It has been found, and in some quantity, in the south of Ireland. I possess excellent specimens from the Cosheen mine at Skibbereen, and from the Glandore mines in Carberry. It is there associated with ores of copper and of manganese, which being of far greater value, the iron ore is not looked after: but it might be of considerable use to mix with the poorer ores of other districts, should circumstances ever justify the practical development of iron working in Ireland.
The second kind of ore is of more practical importance, being probably the most extensively diffused of all the compounds of iron. It presents itself under a great variety of forms, according to the rocks with which it is associated, and the circumstances under which it has had its origin, and hence furnishes to the mineralogist a number of species, the detailed description of which I need not enter upon. When quite pure this ore is a hydrate of the peroxide of iron, in which the oxide contains twice as much oxygen as the water, having the formula, 2 Fe2O3 + 3 HO, and containing:
|Iron||60 0 per cent.|
|Oxygen||25.6 per cent.|
Various forms of it support the majority of the iron furnaces of France and Germany. In England it is not employed, except to bring up, by its richness of produce, the poorer ores of the coal districts, to the standard at which their working becomes
p.119most easy. The forms of it require notice as to their composition and distribution in Ireland. These are the brown nodular hematite, and the ochrey or bog iron ore. In the pure state it is but rarely found, and is then associated with the specular iron, and with other ores in the rocks of the older formations. It is hence not smelted by itself.
The brown iron ore is found in abundance associated with the beds of coal and fire-clay, and the ordinary ironstone in the coal district of Tyrone. I have examined specimens of it, not picked, but taken at random from heaps of it thrown out of the pits, and which may, therefore, represent its usual quality. It is the variety termed popularly eagle-stone, and forms globular masses of a deep brown colour, which are generally hollow, and contain a kernel of a lighter colour than the exterior, with which, however, it agrees in constitution. The specimens I analysed yielded:
|Peroxide of iron||80.79 per cent.|
|Water||11.97 per cent.|
|Oxide of manganese||1.16|
This ore should hence have given by appropriate treatment 57 of iron per cent., or from 35 cwt. of ore a ton of iron.
Of the similar ores actually employed upon the Continent, there are scarcely any actually richer than this. The following numbers show the composition of the richest French and German1 ores.
|Peroxide of iron||82.8||79.6||78.5||77.5|
|Oxide of Manganese||3.6||3.5||1.9||2.7|
|Lime and Magnesia||0.7||1.0||9.6||1.7|
Although we do not know exactly the causes which led to the formation of these concretionary masses of hydrated oxide of iron, it is quite certain that these causes are now in operation, and that the production of considerable quantities of this material is actually going on. We find in almost every deep morass, beds of it, sometimes a foot thick. It is hence called bog iron ore. This ore supported the majority of the small iron furnaces formerly scattered over the surface of this country. It appears as a brownish clay, which dries to a mass, sometimes dense and hard, at others friable, and becomes much darker in colour when it dries. Its origin appears to be connected with the former existence of tribes of minute animals, of which the fossilized remains may be detected in it by the microscope. This also explains a fact in its composition which seriously affects the quality of the iron obtained from it, the presence of phosphoric acid, and there occurs also black oxide of manganese, sometimes in such quantity that it might as well be called an ore of manganese as of iron.
The bog iron ore of Ireland has not yet been analysed, but I annex the composition of three foreign specimens, in order that the nature of this mineral may be shewn.
|Peroxide of iron||62.92||23.24||56.45|
|Oxide of Manganese||4.18||20.40||2.60|
These bog iron ores are smelted with the greatest ease. They are at once very fusible and easily reduced. They produce a metal which runs very thin and congeals slowly, so that it is proper for the manufacture of cast iron articles which do
p.121not require much strength. As all the phosphorus of the ore passes into the metal, this is sometimes very fragile. The Berlin ornaments, which as specimens of casting, and as objects of art, excite so much admiration, are made of iron smelted from the bog iron ore of the vast morasses of the west of Prussia: analyses of two of these ores are amongst those just now given. I have not been able to ascertain the extent to which this ore of iron may now exist within our bogs; nor do I consider it a question of much importance, as it will be hereafter seen, that ores of much richer character, and yielding a purer metal, are so abundant, as to render the bog iron ore merely an object of curiosity to us.
The substitution by Dudley of coal coke for charcoal in the manufacture of iron, created a revolution, not only in the kind of fuel, but in the kind of ore employed, and indeed in the localities where the manufacture could advantageously be carried on. Before that time, the minerals employed were the various kinds of hematites, more or less pure, such as we have in Tyrone, and the bog iron ores; but it was found, that in almost every coal district there occurs an ore of iron, quite different from those, and which is now known as clay-iron stone. The richness of this ore varies very much, but being found in immediate proximity to the fuel, and still more the coal beds presenting various other mineral materials of use in the manufacture, it was found more advantageous to smelt it than to bring either richer ores from a distance to the fuel, or the fuel any distance to the richer ores, and hence the iron manufacture was located, and has since remained, in the coal districts of Great Britain, which the superior economy of its processes and of its materials will probably maintain as its head quarters for numerous ages to come.
In fact, the manufacture of iron requires a variety of materials, which it would be very expensive to bring together, did their sources lie at considerable distances, and hence the cost of the metal produced should be considerably higher, and thereby its extent of use and of manufacture limited in proportion. But by an organization of nature, of which it is impossible to exaggerate the wisdom and the importance to mankind, the coal measures rest upon, and contain beds of hard and
p.122infusible sandstone, of which the most refractory portions of the furnaces may be built. The coal rests usually on clay, of which the best fire-bricks may be formed; dispersed in layers through the slate which covers the coal, is found in abundance the iron ore, whilst the limestone necessary as a flux, lies on the edges of the coal basin where the underlying calcareous strata come to the surface.
Now this combination of sandstone for hearths, clay for crucibles and for bricks, lime for flux, ore and coal for smelting, is not restricted to any one coal district. The same is found in England and Wales, the same in Scotland, and in fact, were any one of those materials absent or difficult to be procured, the economic manufacture of the metal would be impossible.
A knowledge of these circumstances is necessary, that we may compare the means which we possess in Ireland for making iron, with those of other countries. That there is ore is certain, that there is fuel is certain, but if the ore, the fuel, the clay, and all the other conditions do not conspire, the economic manufacture becomes impossible, and an attempt would only ruin those who unadvisedly engaged upon it.
The clay ironstone which has thus become almost the exclusive source of iron to Great Britain, occurs in great abundance in this country, in the coal districts of Leinster and of Connaught; it is not of the same quality or appearance in both, and as the difference is not without importance in its application, it will be necessary to notice each in turn.
It will hence be easily understood, how, in order to trace the localities of the clay ironstone, it is necessary to revert to the description of the coal formations given in a former chapter, and indeed to complete their history by an account of the ores of iron which they contain. I shall, however, only enter into detail with regard to two of those districts, those of Connaught and of Leinster, as the other coal districts do not appear to me to present any features sufficiently promising in relation to iron to render them important.
In the Leinster district a succession of beds of slate, sandstone, and clay, are associated with the coal, according to an
p.123order which has been very perfectly illustrated by the reports of Mr. Griffith, already noticed. The clay ironstone occurs abundantly in nodules disseminated through the layers of slate, from which they separate spontaneously by weathering, or are easily detached. The total thickness of this slate is estimated at 239 feet, distributed in eight beds. Its characters are represented by those given in the following words of Mr. Griffith's description of the second bed from below. Its thickness was thirty feet.
Spheroidal slate clay, containing balls of clay ironstone frequently one foot in thickness. By spheroidal slate-clay is meant a species of hard slate, which on being exposed to the atmosphere, divides into large flattened spheroids; on being struck the outer coat comes off, and leaves a smaller spheroid, which being again struck, a second concentric coat is separated, and so on until the nucleus is met with, which sometimes is composed of hard claystone, and sometimes of clay ironstone. The ironstone contained in this bed is very rich, and in many places remains of ancient excavations are still visible where this bed has been wrought in search of ironstone, and indeed some of the iron furnaces may yet be seen.
All the other beds assimilate to this in character. The quantity of ironstone present is of course in proportion to that of the rock in which it is disseminated; its quantity may be inferred from the results of borings given by Mr. Griffith. Thus in a deep bore-hole at Massford, down to the four foot coal, where the total depth was sixty-eight yards, the layers of pure ironstone amounted to thirty-eight inches, and the strata were found to be constituted of
Sinking to rock, . . . 8 yards.
Sandstone, . . . 31 yards.
Slate-clay, . . . 25 yards.
Ironstone, . . . 1 yard 2 inches.
Coal and kelve . . . 3 yards.
In a boring at Moneen Roe, near Massford, which extended to
p.124eighty-four yards, six feet nine inches of pure ironstone were found. The strata consisting of
It is necessary to describe more specially the properties and composition of this ironstone. Specimens presented to me by Mr. Wandesford, from his collieries at Castlecomer, gave the following results:
The colour is dark gray when fresh, but becoming rust coloured by long exposure to the air. The specific gravity is about 3.250. When ignited it loses 29 per cent. of its weight, and the residue is strongly attracted by the magnet. Two different specimens analysed, gave the following results:
|No. 1||No. 2|
|Protoxide of iron||51.08||48.03|
Of these ores No. 1 contains 39.7 per cent. of iron, and No. 2 37.6. As they were not selected for analysis on account of any apparent superiority to other specimens, they may probably represent the ordinary run of the ironstone of the Leinster district.
The supply of the iron ore in this district is not limited to the clay slate lying deep among the coal strata. The other sources of it are thus described by Mr. Tighe in his Survey of the county of Kilkenny: We have already seen that the slate covering the collieries contains nodules of iron ore, and this
p.125ore is very heavy and rich, but some of the best iron mines lie open to the surface, and form the upper strata of entire hills. Hills of this kind run in a north-east direction from Lady Ormond's demesne towards the colliery. On the lands of Aghamucky is a hollow road cut to a great depth through a rich mine of iron, from this place the ore was formerly carried to be smelted at Mountrath, in the Queen's County, as long as the timber lasted in that neighbourhood. The richness of these ores may be inferred from the account of Boate, that when the ore was good, two and a half tons of it gave a ton of iron, but in common, one ton for three was expected.
The abundance of ironstone found in the Connaught coal district gave origin to several works for the reduction of the metal at that early period, when the extensive woods supplied charcoal for the furnaces; and almost without intermission, since the invention of the method of smelting by means of coal and coke, attempts have been made at various times, and by different individuals, to carry on iron works in that locality. These attempts have hitherto failed, owing to circumstances, of which most were of a nature purely personal, and cannot be noticed here. Other sources of failure were connected with the conditions of the manufacture and of the locality itself, and it will be in another place important to trace and illustrate those, in order that we may judge whether the difficulties, before which so many have sunk, are in themselves really insurmountable.
It is necessary first to describe the composition and distribution of the ore.
On the eastern shore of Lough Allen rises the Iron Mountain (Slieve Neeran), a hill of considerable elevation. It consists of alternate beds of sandstone and slate-clay resting upon the basis of the upper limestone. The great bed of slate-clay varies from 300 to 500 feet in thickness; others are of different but lesser magnitude. In this clay the nodules of ironstone are disseminated in abundance; and the rains, washing away the softened and decomposing clay, the balls of ore are carried down to the shore of the lake, whence, and from the beds of the rivulets, they are collected by the peasantry and brought
p.126to the works for use. At the base of this mountain, on the eastern side of the outlet of the lake, lies Drumshambo, where this ore was formerly smelted. I shall hence designate this ore from the eastern side of the basin as Drumshambo ore. In purity it is somewhat superior to that which is found on the western side.
The southern and western division of this coal field is popularly known from the River Arigna, which is its northern boundary, and whose name became notorious by the iron works established on its banks, the history of which has so fatally influenced industrial enterprize in Ireland. The stratification of the mountain is similar to that of the opposite side; resting on the limestone of the surrounding country, occurs the great bed of slate-clay, 600 feet in thickness, and containing numerous beds of ironstone, from half an inch to two feet in thickness. Their number is, as Mr. Griffith mentions, almost incredible, but the most important occur from 200 to 300 feet above the limestone. The same eminent geologist describes the thin beds as being in most cases the best, but that of Altagowlan, which is a foot thick, was amongst the richest ironstone Mr. Griffith ever saw. The usual form is that of nodules, in size from an egg to that of a bull's head; but it forms also strata, or sheets of considerable extent. In many places the bed of the River Arigna in its whole breadth is formed of a flag of ironstone, which is often many perches in length. On this side of the lake also, owing to the weathering of the slate-clay, the nodules of ironstone are deposited in vast quantities in the beds of the mountain streams. Were this ore employed this source would soon become exhausted, and of course the beds of ironstone should then be worked in situ, as they are elsewhere.
Mr. Twigg, whose observations on the Arigna district are the most recent, thus speaks, in his report made to the Directors of the Arigna Company in 1830: The ironstone mines have been examined, and the result found extremely favourable. A greater variety of ironstones I never met with, from which, by a proper admixture and proper management, I have no hesitation in saying, that pig-iron of best marks, and fit for
p.127foundry work of every kind, may be obtained. The iron mines begin in Rover, aud continue for two miles and a half. I measured several of the beds to more than two feet thick, in some places laid bare in the ravines, and in the bed of the Arigna river we can get any quantity at the shortest notice. There is enough to last two furnaces for 250 years.
In quantity there is no doubt but that the ironstone of this district is practically inexhaustible. In order to ascertain its quality, I have effected accurate analyses of numerous specimens of it, obtained from different portions of the district.
Their detailed characters and composition follow:
Clay Ironstone Nodules from Arigna
|No. 1||No. 2||No. 3|
|Protoxide of iron||53.65||54.42||51.52|
Of these ores, No. 1 lost 31.5 per cent. in roasting, and contained 41.7 per cent. of iron; No. 2 lost 30.9 per cent. by roasting, and contained 42.3 per cent. of iron; No 3 lost 30.7 per cent. by roasting, and contained 40 per cent. of iron.
Of the veins of ironstone, two specimens were analysed taken in situ. They gave:
|No. 4||No. 5|
|Protoxide of iron||47.28||49.94|
No. 4 lost by roasting 32.14 per cent. of its weight, and contains
p.12837.7 of metallic iron. No. 5 loses 29.80 per cent. of its weight, and contained 38.8 per cent. of iron.
As none of these were picked specimens, the average of all of them may be fairly calculated as the material available on the large scale at Lough Allen, and the mean of the above five analyses gives:
|Protoxide of iron||51.36|
And this contains 40 per cent. of metallic iron.
The loss by calcining the iron remaining as protoxide, should be in average 31.33 per cent., and the calcined ore should consist in 100 parts of
|Lime and Magnesia||5.1|
It is not enough thus to have determined the composition of the ironstones of the Leinster and Connaught coal fields, but in order to ascertain how far they may become of use, we must compare them with the ores employed in the principal seats of the iron trade in the sister kingdom.
MM. Dufresnoy and Berthier have analysed the ores of iron worked in Staffordshire and in South Wales. Their results are briefly the following. In Staffordshire the thick, rounded nodules, having a blackish grey fracture, are called gubbins; these are rare. The usual ore is in thin flattened veins, bluish grey in colour, and is called blue-flat. These consist, in 100 parts, of
|Protoxide of iron||36.25|
|Protoxide of iron||52.50|
|Carbonic acid, &c.||32.18|
Every thing which gives more than 20 per cent. of iron is reckoned as ore, but the price depends on the quality. Thus the gubbins are worth more than twice as much as the blue-flats.
The following analyses give in a similar manner the composition of the rich and usual kinds of the Welsh ore:
|Usual Ore||Rich Ore|
|Protoxide of iron||41.4||54.1|
|Yield of iron||31.4||42.1|
The ironstone of the coal field of Lanarkshire is well known for its richness, and has been, indeed, the foundation stone of the commercial prosperity of Glasgow. A series of accurate analyses of those ores has been made by Dr. Colquhoun, of which the most important are subjoined.
Cross Basket Ironstone.
|Protoxide of iron||42.15|
Mushet's black band.
|Protoxide of iron||53.03|
|Peroxide of iron||0.23|
|Moisture and loss||1.41|
The latter ore, the richest known, except some Welsh specimens, yields 41 of metallic iron per cent. The Cross Basket ore, which may be taken as the usual run of the ores of the Clyde district, yields 31.6 per cent. of iron.
I shall now compare more directly the contents in metallic iron of the native ores, and of the English, Scotch, and Welsh. 100 parts of ore give of metal:
|Richest Arigna ore||42.3||61.4|
|Poorest Arigna ore||37.7||53.2|
|Average Arigna ore||40.0||58.2|
|Common Staffordshire ore||28.0||40.4|
|Richest Staffordshire ore||40.5||60.0|
|Ordinary Welsh ore||31.4||44.7|
|Richest Welsh ore||42.1||60.0|
|Ordinary Glasgow ore||31.6||45.8|
|Mushet's black band||41.0||63.1|
|Average Kilkenny ore||38.7||55.3|
There is hence no doubt but that the ores of the Leinster and Connaught coal fields are equal, and even in average superior, to those generally employed in Great Britain. The ironstone of Kilkenny is but little inferior to that of Arigna, whilst the ores of Lough Allen attain a richness in iron, only equalled by the black band ironstone of Glasgow.
It is necessary, however, to trace further the conditions of the iron manufacture in these districts, for, as has been already mentioned, such is the economy required in this department of industry, that unless there be upon the spot all the materials to be used, the cost of obtaining them would be too high. Now in order to smelt and work iron, there are required building materials for the furnaces, which must be formed of infusible sandstone and of the most refractory bricks, for which fire-clay is necessary. These substances are found abundantly interstratified with the slate-clay and coal; their detailed description will be given elsewhere, but their properties are such, as may be now assumed to present no obstacle to the manufacture. To flux the earthy material of the ore, lime must be added. This is in all cases accessible, as the whole coal field rests on limestone, which presents itself on every side within short distances. Finally, the coal necessary for the smelting of the ore is derivable from the same formation; but as our coal beds are thin and limited in size, and hence more difficult to work than the larger beds of the British coal fields, it becomes a question whether the greater price of the coals in Ireland is not prohibitory to the manufacture. In order to appreciate how far this acts, it is necessary to trace somewhat in detail the conditions of the smelting process, and the proportions of the materials used.
The smelting of iron from the ore is accomplished in furnaces of great size, generally termed high furnaces. Their dimensions vary; the height is usually from forty to fifty feet; the external form is that of a massive tower, the interior is divided
p.132into four portions of different forms, and acting differently in the smelting process. The lowest is the hearth or crucible, formed of the most refractory sandstone of the coal field, built as a rectangular prism, and widening at top into the second portion, which is built also of sandstone. From this the dimensions of the cavity rapidly expand, forming the lower body, or boshes; this part of the furnace is conical, with its base upwards, on which the body of the furnace rises, constituting about two-thirds of the entire height, and extending to the top, where it supports a chimney of about ten feet high.
Near the bottom of the furnace are formed apertures, by which the pipes from the blowing machines are introduced, to force air into the furnace. These apertures are termed tuyeres. On one side of the hearth is the arrangement for opening, so that the melted metal may be run out as soon as a suitable quantity has collected, and also that the slags formed in the process may be discharged as they come down.
Such being the structure of the furnace, the process followed is easily understood. The ore contains oxide of iron; the fuel contains carbon; when these are heated together the oxygen unites with the carbon, and the iron is set free. The iron itself combines also with some carbon, so that it assumes the state of metal or cast iron, in which, being fusible, it melts, runs down to the bottom, and accumulating in the crucible, is run off at certain intervals into moulds prepared on the floor of the apartment in sand, where solidifying, it forms the masses commercially termed pigs. It may have been remarked, however, that the ore contains from 10 to 20 per cent. of foreign materials, such as silica, alumina, magnesia, and that the fuel employed contains ashes from 5 to 15 per cent. of the same materials. These, at a high temperature, would react on the oxide of iron, and interfere with its reduction; and also forming difficultly fusible clinkers would impede the descent of the fuel and ore, and disturb the progress of the operation. All this evil is avoided by the use of a certain quantity of lime. This, uniting with the silica and alumina, forms an easily fusible slag, a kind of glass, which runs down into the crucible, where it floats upon the liquid iron, and as it accumulates, is run off. through an aperture temporarily opened for the purpose.
Before placing these materials in the high furnace, there are two preliminary operations performed. First, the calcining of the ore, and second, the cokeing of the coal. For these processes, as they involve the expulsion of a large body of volatile matter at a low heat, would, if carried on in the high furnace, produce such a cooling effect as might retard, if not stop, the work entirely. The mineral is broken into small pieces, and being mixed with some coal, this is set on fire and allowed to burn slowly. About 30 per cent. of the weight of the ore is thus driven off, consisting of carbonic acid, and of any water that it contained.
The loss which the Irish ores suffered by calcination has been described already. It may be mentioned, however, that when the roasting takes place in the air, the iron is partially converted into peroxide, whilst, when it has been effected in close vessels, the residue contains the iron as black magnetic oxide, and carbonic oxide is evolved.
The cokeing of the coal for the purposes of the iron furnaces is accomplished by a partial combustion in great heaps, by means of such a limited supply of air, that little but the volatile portions of the coal is driven off. The quantity of coke produced varies, according to the quality of the coal and the care with which the process is conducted, being from 50 to 65 per cent. of the weight of the coal. The quantity and quality of the coke obtained from the different varieties of Irish fuel have been given already.
Such being the general conditions of the process of smelting iron from the ore, it now remains to trace the elements of its money cost, and to apply the experience and results of other districts to the circumstances which prevail in Ireland. I shall, therefore, first briefly describe the estimates of cost of fabricating pig-iron in Staffordshire and Wales. The facts and numbers I shall give are derived from the Voyage Metallurgiqune en Angleterre, published in 1837, by a commission of the most eminent French engineers. The market price of iron has changed very much since that period, but the cost of production has altered but very little: certainly not in any degree to affect the conclusions we may draw.
From an examination of the work of six high furnaces in the
p.134vicinity of Dudley in Staffordshire, it results that the average materials necessary to produce a ton of good pig-iron are:
The coal for roasting the ore, as well as that for making coke, is included; but it is necessary to add the small coal used in the engine to drive the blowing machine. This may be taken at ten cwt. Now the prices of these materials are,
Small coal, from 2s. to 3s. per ton. Coal for coke, from 6s. to 7s. per ton. It may be taken at 6s.
The ores vary from 4s. to 10s. per ton, seldom falling below 7s., which may be taken as the average.
Finally, it has been found, from an experience of several years, that the sundry expenses of labour, superintendence, interest, &c, incurred in producing a ton of pig-iron, are from 22s. to 23s. The cost of production is, therefore, as follows:
Coal for roasting and cokeing at 6s. . . . £1 3 0
Ore for roasting and cokeing at 7s. . . . £1 0 8
Limestone for flux, at 6s. . . . £0 3 11
Small coal for engine, at 3s. . . . £0 1 6
Labour and general expenses . . . £1 2 6
£3 11 7
Mr. Aikin has given an account in the Technical Repository of the proportions used in Shropshire, which are, in order to form a ton of iron.
2 tons, 16 cwt. of ironstone;
Or, 2 tons of roasted ore.
12 cwt. of coal for the roasting.
4 tons, 10 cwt. of coal for the furnace;
Or, 2 tons, 4½ cwt., coke.
10½ limestone for flux.
There is here much more coal used than in Staffordshire, where it is dearer. Mr. Aikin does not give the pecuniary estimate of the process.
In Wales the iron works are on a much larger scale than in
p.135Staffordshire, and most of the iron is made for refining into bars. These circumstances affect very materially the proportions of the materials, and the cost of production of the metal. At the great ironworks of Cy-fartha, near Merthyr, belonging to Mr. Crayshaw, the proportions and cost of the materials, and other expenses for producing a ton of iron, were, when the French Engineers wrote, as follows:
At Mr. Hunt's of Pontypool, for the ton of metal the material required and the cost were:
6 tons of coal, at 4s. . . . £1 4 0
14 cwt. of small coal for roasting and engine, at 1s. 6d. . . . £0 1 1
3 tons 3 cwt. of ore, at 7s. . . . £1 2 1
15 cwt. limestone, at 2s. 6d. . . . £0 1 10
General expenses and interest . . . £1 1 0
£3 10 0
The coal used in these works is of bad quality, and hence the large quantity consumed.
Finally, the following estimate shows the cost of production of iron at Abersichan, where, however, it must be remarked, the cost of materials is but the mere cost of raising the ore and coal from the pit, as the mines are on the works themselves.
Labour . . . £0 7 5½
Carriage of materials . . . £0 1 7½
Coal, 3 tons 2 cwt., at 2s. 5d. . . . £0 7 6
£0 16 7
p.136Brought forward, £0 16 7
The Commissioners could not obtain so accurate estimates of the cost of production of iron in the Glasgow district, as those given above; but the general calculation was, that including engine and roasting, there was used in making a ton of iron eight tons of coal. The Scotch coal is very bituminous and loses greatly in cokeing, which is one cause of the large quantity used; but another is found in its cheapness. The coal was found to cost 4s. 6d. per ton, and the mineral the same. I shall have occasion immediately to notice how fully this estimate for Glasgow has been verified by more recent inquiries.
We thus see that the quantity of materials used in making a ton of pig-iron varies within very wide limits; and of course affects the cost of production in a very considerable degree. Some of this certainly depends on the quality of the ore and fuel; some also on the peculiar quality of metal which it is necessary to produce; but much also results from the sources of loss and imperfection in the working, which are better known and guarded against in some places than in others.
In order that we may trace the probable cost of producing iron in Ireland by the analogy of those estimates, it is necessary to consider for the present only the Connaught coal field, as the Kilkenny coal, being anthracite, requires quite separate consideration. I shall first quote the estimates made by various persons of the cost of smelting iron at Arigna, and then see what alterations they may now require.
In 1800 Mr. John Grieve made a report on the performance and capabilities of the Arigna iron works, and gave the following estimate of the cost of production of a ton of pig-iron.
p.1375½ tons of raw coals, at 4s. 11d. . . . £1 7 0
At the time of Mr. Grieve's report the coals cost on the furnace bank, 8s. 4d. per ton, but he pointed out simple means by which the cost of raising could be reduced, so as to deliver the coals for 4s. 11d., and on this value his estimate is founded. The other values are those actually paid, and the proportions are those on which the manufacture was carried on.
In 1804, Mr. Guest of the Dowlais's iron works in Wales, reported on the state of the Arigna works, and estimated the cost of production as follows. He considered that the coal of the Aughabehy and Rover collieries may be delivered at 6s. 4d., per ton, and that the ironstone, of which the greater part must be raised on the east side of the lake, will ultimately cost 6s. per ton, and the limestone 4s. Therefore:
5 tons raw coal, at 6s. 4d. . . . £1 11 8
4 tons ironstone, at 6s. . . . £1 4 0
1 ton limestone . . . £0 4 0
Labour . . . £0 10 0
Rent, wear and tear, and other incidental
expenses . . . £1 5 4
£4 15 0
Finally, in 1818, Mr. Griffith, in his valuable Report on the Connaught Coal District, estimated as follows the cost of production. He had shewn very fully that the coal could be
p.138raised at 4s. per ton, and assuming that the ironstone should be worked from the beds he calculated the cost at 5s. per ton. As he was not himself conversant with the proportions of the process, he assumed as correct the proportions given by Mr. Guest, which had been used at the works. There were, therefore:
From Mr. Grieve's and Mr. Griffith's estimate it hence appears, that the cost of making iron at Arigna is not greater than in the most favoured localities of England. Mr. Guest's estimate makes it much higher, but it is easy to show that his statement is too high. First it is not easy to see how the charge of £1 5s. for contingencies could be incurred. Neither Mr. Griffith nor Mr. Grieve admits such an expenditure, nor in any of the estimates of the English and Welsh processes given by Dufresnoy, does so large a sum occur; and yet those latter are not speculative, being all returns of the actual working of large establishments for many months. Hence, I think it must be considered seriously overcharged. As to the price of the coal, also, it is important to recollect, that the sum he charges is the maximum. The price of the Aughabehy coal is now 6s. 4d. per ton. It is a most excellent coal, and yields two-thirds of its weight of good coke. The Rover coal, however, of which the accurate analysis (as also of the Aughabehy) is given page 21, is sold at present at 4s. 9d. per ton, and it is excellent for preparing iron, as its composition indicates, and as is also shewn by the testimony of Mr. Guest, who in his Report says: I have seen some of the Rover coal coked and used in the cupola; it melted the iron very quick and well, which I consider is a symptom of its good quality, and, from what I could judge, have little reason to doubt its answering the purpose of making iron. He might have no doubt about it; analysis
p.139shews that it is constituted as the best Welsh coal, and gives 82.3 per cent. of coke.
In 1827, the review of the circumstances of these works, made by Mr. Twigg, at the request of the Arigna Company, which has been already fully quoted with regard to the conditions of the collieries, lead to an estimate of the cost of manufacture of the iron, which I now subjoin:
5½ tons of best raw coal, at 7s. 10d. per
ton, the supposed average price of 25
years . . . £2 3 1
3 tons 4 cwt. of ironstone, at 4s. 10d. . . . £0 15 5
1 ton of limestone, at 3s. . . . £3 0 0
Workmen's wages for making No. 1 pig-iron,
as now paid to English workmen . . . £0 13 3
Cost of engine sleek, agency, and all incidentals
of furnaces, &c. . . . £0 1 1
£4 5 9
If limestone be supplied by a railway, deduct
1s. 11d. per ton . . . £ 0 1 11
Final cost of a ton of No. 1 pig . . . £4 3 10
There are two cardinal errors in this estimate of Mr. Twigg's. First, that the price of the coal is overcharged. The best Aughabehy coal is now sold for 6s. 4d. per ton. The Rover coal is sold for 4s. 9d.; and how can arise an average cost of 7s. 10d.? The second is that the richness of the ironstone is much undervalued. He takes the ore at 30 per cent. of metal, whereas it contains in average fully 40 per cent.; therefore, the quantity of ore should be two tons and a half, and it costs, at 4s. 10d., only 12s. 1d. In fact, all these estimates by English writers are in that respect faulty, that they do not take into account at all, differences in the composition, either of the ore or fuel, but reckon down all in the same proportion as they have been habituated to in the routine of their own immediate locality, beyond which their knowledge, in very few cases indeed, is found to extend.
Since the periods of those Arigna estimates, the quantity of
p.140materials necessary to produce a ton of iron has been diminished by improvements in the modes of treatment, and if we consider that the Irish ore is far superior to the average Welsh, the coal not inferior, and that for the blowing machine, &c, there is water power in abundance, the cost of production, and the quantity of materials required, may, as I consider, be fairly estimated as follows:
The last item is taken the same as at Dudley, where it is given by Dufresnoy as higher than elsewhere in England and Wales. Labour is not likely to be dearer at Arigna, and although we will require to distinguish carefully hereafter between nominal and real dearness of labour, for illustrating which, indeed, this very subject will supply examples, we may, by adding 5s., certainly cover all contingencies, and leave the estimated cost of pig-iron at Arigna at £3 3s. sterling per ton.
These estimates are founded on the mode of preparing iron, until lately universal, in which the furnaces were blown with air at ordinary temperatures. A vast revolution has, however, been produced in this manufacture by the plan invented by Mr. Neilson of Glasgow, of blowing the furnaces with hot air; working, as it is termed, with the hot blast. It is necessary to describe the changes this method has made in the English and Scotch iron manufacture, in order that its influence upon our own industry may be estimated.
In 1829 it occurred to Mr. Neilson, Manager of the Gas Works in Glasgow, that there would be an advantage gained in previously heating the air with which the blast furnaces of the iron works are supplied, and having carried on some experiments in conjunction with Mr. Mackintosh and Mr. Wilson, at the Clyde Iron Works, they became satisfied of the accuracy of the idea, and took out a patent for the process. The
p.141mode of heating the air now generally in use, consists in passing it through a contorted iron tube around which the flame of a small furnace plays. The tube having numerous turns, a great surface is exposed to the action of the heat, so that the air attains a temperature, such as the worker wishes it to possess. The effect of the introduction of this process has been, 1st, very materially to diminish the quantity of coal employed; 2nd, to enable raw coal to be used in place of its being previously coked; 3rd, to increase the work of the furnace; and 4th, to enable a smaller quantity of flux to suffice. These consequences are shewn by the following numbers, published by Dr. Clark, deduced from the working of three furnaces at the Clyde Iron Works.
In 1829 with cold air, the three furnaces gave per week 111 tons of iron with 403 tons of coke from 888 tons of coal.
In 1830, with air at 300[deg ] Fah., they gave 162 tons of iron with 376 of coke from 836 of coal.
In 1833, four furnaces gave 245 tons of iron with 554 tons of coal.
Throughout, the power of the blast was the same. The yield of iron was doubled from the same furnace. It was trebled from the same fuel.
In 1829, 1 ton of iron required 8 tons, 1 cwt., 1 qr. coal.
In 1830, 1 ton of iron required 5 tons, 3 cwt., 1 qr. coal.
In 1833, 1 ton of iron required 2 tons, 5 cwt., 1 qr. coal.
The charge for the furnace was in
|Coke||5 cwt||Coal, 5 cwt|
|Roasted ironstone||3 cwt. 1 qr. 14 lb||Coal, 5 cwt|
|Limestone||3 qrs. 16lb||Coal, 5 cwt|
The effect of this enormous alteration may easily be imagined. The iron trade of Scotland received an impulse of the most healthful and permanent kind, and the use of the hot blast has since been extending into all the other iron districts; subject however to some conditions which must be noticed.
The great economy of fuel which arose in Scotland was, in part, derivable from two sources independent of the hot blast.
p.142First, that the iron manufacture had previously been badly managed there, and a great deal of fuel wasted; and second, that the coal employed being highly bituminous, it lost, when employed as coke, more than half its weight. Thus, the coal of the Clyde works gives but 45 per cent. of coke.
Now in Staffordshire the coal gives 65 per cent. of coke. Consequently, the 8 tons, 1 cwt. of Scotch coal represent but 72 cwt. coke, whilst the 3 tons, 16 cwt., 60lb, of Staffordshire coal used to make a ton of iron, represent 50 cwt. coke. The excess in Scotland was, therefore, in reality but 50 per cent. of available fuel in place of 110 per cent. as it might at first appear. Accordingly, the saving effected by the hot blast has been found to vary in different localities, according as the manufacture had been previously in a more or less perfect state, and as the coals used lost more or less by cokeing. Mr. Mushet, than whom there is no higher authority, states the savings to be per ton of iron:
On Scotch coals from . . . 3½ to 4 tons.
In Yorkshire, . . . 2½ to 3 tons.
Staffordshire, . . . 2 to 2½ tons.
Gloucestershire, . . . 1 to 1½ tons.
South Wales, . . . 3/4 to 1½ tons
Two tons of Merthyr-Tydvil coal give as much coke as three tons of Scotch coal, which may be considered 67 per cent.
The coal of Plymouth Works gave 83 per cent. of coke, and at Dowlais's 66 per cent.
It has been shewn that the coals of Arigna all belong to the moderately bituminous family. The percentage of coke being:
Aughabehy coal . . . 76.9
Santnavena coal . . . 80.9
Meeneshama coal . . . 81.1
Rover coal . . . 82.3
Hence no such difference could arise as to the consumption of coal at Arigna from the use of hot blast, as was found to occur in Scotland. It is more likely that the saving of fuel would not exceed what has been found to occur in South Wales,
p.143which may be averaged at a ton of coal per ton of iron. This would, of course, be a saving of 4s. 9d., and also a saving of time and labour in the previous cokeing.
It may, therefore, be concluded, that the difference between hot and cold blast in the iron district of Lough Allen, cannot be of such importance as to affect the other conditions of its success or failure; and finally, that from the various estimates drawn up by those who have inspected the locality, as well as from the analysis of the cost of production of iron in Scotland, England, and Wales, there remains little doubt, but that cast iron of the best quality can be obtained at Arigna, at an expense of production, probably falling sensibly under, but certainly not exceeding, £3 sterling per ton.
We shall now pass to the examination of the conditions of the manufacture of iron in the coal districts of Leinster.
Until very lately, the smelting of iron by means of anthracite was looked upon as impracticable, although from the vast deposits of that kind of coal in many countries, experiments had frequently been made upon it. These experiments were all failures as to the use of the anthracite alone. The condition of the process will be shewn well, by the following extract from the Report of M. Perdonnet on the manufacture of iron in France. He says:
I will now speak of some experiments made with a curious combustible substance, called anthracite,a kind of pure carbon, without any mixture of bitumen, compact, igniting with great difficulty, and giving out such a heat, when once in a state of combustion, that it is very difficult to procure materials for the construction of the blast furnaces which will not melt. It has been ascertained that cast-iron cannot be made with anthracite, except by excessive care, and that the furnace will not work regular unless three parts of coke be mixed with seven of the anthracite; and indeed, by reason of its burning so slowly, it has been found more advantageous to use them in equal quantities.
The cast-iron obtained with these different proportions of anthracite has always been of excellent quality. This may cause surprise, as the combustible used without preparation as
p.144it comes from the mine always contains a large quantity of sulphur.
The trials in England took place in Brecknockshire, and are described by Mr. Scrivenor as follows:
Nearly twenty years back a patent was taken out, and a furnace erected on the borders of Brecknockshire, for the smelting of iron with stone coal (anthracite); many experiments were made with different proportions of the stone coal and bituminous coal used together. The iron produced was of good quality, but the object being to use the anthracite in its raw state, which could not then be effected, the furnace, after a few months' trial, was blown out.
Such having been the results in England and in France, it is interesting to do justice to a fellow-countryman, who appears, from Mr. Tighe's Survey of Kilkenny, to have succeeded in the attempt long before. Mr. Tighe's statement is:
It has been said that this coal will not answer for smelting iron, but Finlan did actually smelt the iron ore of Castlecomer with it, in a small furnace before mentioned, and said that the quality of the iron was good. If the coal always answers to Mr. Kirwan's analysis, the iron could not be injured by it, except where it contained any martial pyrites, which should be carefully separated. But it is objected to this coal, that igniting slowly, and consuming without flame, it does not bear the operation of a blast furnace, nor can its heat be rapidly increased; and to remove this difficulty Finlan suggested the expedient of mixing it with charred or dried turf, or any other fuel that would open and separate its parts. For the purposes of cementing steel, it seems peculiarly calculated, as it does also for potteries, and almost every other manufacturing purpose; and that it should not be applied to these purposes at Castlecomer, where materials for earthen ware are to be found, and where iron mines of the best quality lie, as it were, above ground, seems a national loss.
Very recently attempts have been again made, and with more success, so that at present there are at work in South Wales, works in which anthracite is used with the air blast at ordinary temperature; but the final and perfect solution of the problem
p.145of smelting iron by anthracite, has received its solution from Mr. Crane of the Yniscedwin Iron Works, by whom the process has been patented. The improvement which he has made consists simply in the application of the hot blast to the anthracite coal, and the result shall be briefly stated in his words, extracted from the account read by him to the British Association at Liverpool, and the facts contained in which have been fully verified by continued working since.
When he used bituminous coal the ton of iron had required in his furnaces the coke produced from a quantity of coal, varying from four to five tons. The average consumption of anthracite has been found to be, per ton of iron, twenty-seven cwt.
The work of the furnace with coke from bituminous coal had been from twenty-two to twenty-four tons of iron. On using the anthracite this was raised so as to vary from thirty to thirty-six tons, and once to thirty-nine tons. With respect to quality, Mr. Crane considers, that the iron made with the anthracite is superior to any he ever made before, and his works have always ranked high for the quality of iron they produced.
Referring to the analyses of the ironstone of the Leinster district, it will be found to contain in average 38.7 per cent. of iron. It is, therefore, much superior to the average ore worked in Wales, and the cost of the fuel per ton of iron, assuming that the consumption should be thirty cwt. per ton of iron produced, should not exceed, at the pit mouth, where of course, if any where, iron works should be established, 13s. 6d. If we consider all other expenses to be the same as they are estimated to be in Wales, by Dufresnoy, and as we have taken them at Arigna, the ton of cast iron manufactured with anthracite, in the Leinster or Tipperary coal fields, should not exceed £2 10s., and should certainly fall below £2 15s. Further, should the development of this branch of industry, leading to an increased demand for coals, be the means of introducing better systems of working the collieries, so that the cost of raising the coals may be materially diminished, there may result a diminution of the cost of fuel, though with an increased
p.146profit to the coal owners, by which again the manufacture of the iron should be rendered still more economical.
Such, as far as I am able to represent them, are the circumstances under which this important branch of industry may be placed in Ireland. But I am far from believing that it would be prudent in any person now to enter upon this branch of manufacture. We are not yet ready for it, nor is the time fitting. The iron trade of England and Scotland is in a ruinously depressed state. The prices of pig-iron are from £2 5s. for Clyde iron, to £3 5s. for No. 1 Welsh iron, on which it may be at once calculated, from the estimates already given, there can be absolutely no profit. Now this is not the sort of trade in which it would be proper to disturb our fortunate neighbours. If the iron trade revives; if other circumstances, stimulating our industrial energies, and increasing our domestic wants, determine an increased demand for iron in Ireland, where all charges, risks, and trouble of freight and transport, should tell against the imported metal, it will be important for our capitalists to recollect, that the ironstone of Arigna is equal to the celebrated black band of Glasgow, and that, taking all circumstances into account, iron can be made as cheaply and as good in Ireland as in any other portion of the empire.
The iron produced by the operations which alone have hitherto been noticed, is in the form of metal, which, from its fusibility, adapts itself to so great a variety of purposes; but the preparation of malleable iron from the pig metal requires additional processes, and the subject would remain imperfect were not the circumstances of those further branches of the manufacture of iron noticed.
The change of pig-iron into bar requires three operations, viz., refining, puddling, and balling. This last is not universally practised; but it is best to consider it here as being employed. The refining is conducted in a small blast furnace, with a shallow rectangular crucible. The crucible is filled with coke, the pigs of metal are laid on it and covered up with coke, and the fire being lighted, and the air let on, the metal fuses, runs down into the crucible, and much of its carbon is disengaged as carbonic oxide gas. Some slags from other operations
p.147are added to save the crucible from being cut up, and often scoriae of iron from the forges, or haematite, or oxide of manganese is added, which favour the elimination of the carbon from the metal, and diminish the loss which occurs. When the treatment of the metal has been completed, the fine metal is run out on a level surface of sand, so that it forms a thin plate, which is cooled rapidly by throwing water on it, and it is then broken and transferred to the puddling furnace.
As an example of the proportions of expense of this process, the following abstract of the work at Verteg in South Wales may be taken; it does not differ materially from Staffordshire. To produce a ton of fine metal it took
1 ton, 2 cwt., 1 qr. of pig, at £3 6s. . . . £3 13 5
14 cwt. of coal, at 4s. per ton . . . £0 2 10
Cost of cokeing the coal . . . £0 0 4
Cost of labour, made up of
Weighing, 0s. 3d., Refining, 1s. 7d., Carriage, 0s. 6 1/4 . . . £0 2 4½
Blast and management . . . £0 0 9
Cost of 1 ton of fine metal, . . . £ 3 19 8 1/4
The fine metal is transferred to the floor of reverberatory furnaces, where it is fused, and whilst liquid carefully agitated. It appears to burn, the carbon which gave it its fusibility is gradually worked out, and it becomes less liquid, and finally breaks into granules like sand. On increasing the heat, these agglutinate, and the workman, kneading them together with suitable tools, gradually works the entire up into a mass, which taken from the furnace is already plastic and malleable. It is rolled into bars by being placed between grooved cylinders, made to revolve by a powerful engine, and these bars, if the iron be wanted of superior quality, are balled, by being heated in a reverberatory furnace still more intensely than in puddling, and many bars being welded together, and drawn out again by the roller, the highest degree of purity and homogeneity is given to the material.
The total cost of these processes, as carried on in Staffordshire, was found the French Commission of Inquiry to be in the period from 1828 to 1837:
To produce a ton of fine metal:
22 1/4 cwt. of pig. at £3 12s. . . . £4 0 1
3 packs of coke . . . £0 4 1
Workmen . . . £0 1 4
Blast and management . . . £0 1 1
Repairs and sundries . . . £0 0 11
Cost of a ton of fine metal . . . £4 7 6
To covert this fine metal into mill bar iron by puddling and rolling, there is for a ton of product:
22 cwt. of fine metal as above . . . £4 16 3
30 cwt. of coal . . . £0 5 6
10 cwt. of slack for engine . . . £0 1 4
Labour: Puddling, 7s. 8d., Rolling 2s. 1d., Weighing 7d. . . . £0 10 4
Repairs of furnaces and machinery . . . £0 3 0
Management . . . £0 1 10
Cost of a ton of mill bar . . . £5 18 3
To form from this the common merchantable bar iron, there
22½ cwt. of mill bar as above . . . £6 14 1
12 cwt. of coal . . . £0 3 6
10 cwt. of slack . . . £0 1 6
Cost of rolling . . . £0 5 0
General expenses . . . £0 5 6
Total cost of a ton of iron bars . . . £7 9 7
It is now interesting to add all these various processes together, and see how this final cost of the ton of bar iron is distributed throughout the entire manufacture. On doing so in suitable proportions it is found that there is paid for
p.1494 tons 9 cwt. of ore at 7s. . . . £1 11 3
The total quantity of fuel consumed is therefore just ten times the weight of the bar iron produced, and makes 40 per cent. of the entire cost. It is hence easily intelligible how the iron manufacture naturally limits itself to the coal districts.
It must be recollected that the above estimates are derived from Staffordshire, where the cost of making iron is high, and were taken some years ago, when the cost of labour and materials was much greater than at present. Thus the merchant bar iron would now be sold for about £6 per ton. And if we take a final estimate at the prices for which it has been already shewn that pig iron can be made at Arigna, considering labour and superintendence to be the same as in Staffordshire:
4 tons of ore at 5s. . . . £1 0 0
10 tons of coal at 4s. 9d. . . . £2 7 6
1 ton of limestone . . . £2 7 6
Labour and general expenses . . . £2 17 6
£6 7 6
Thus merchant bar iron can be made at Arigna at the same price as it is now made in Staffordshire, and indeed cheaper, as the quantity of ore is calculated from the average of Staffordshire, of 30 per cent., whilst Arigna ore yields 40 per cent. of iron. Hence 5s. might have been taken from the above estimate of cost.
It is now necessary to pass to a branch of this subject which is of considerable importance to Ireland. The refining of iron by means of turf or turf charcoal. A few words will briefly point out its bearings. The iron which is smelted by means of pit coal always preserves a degree of impurity of constitution which reduces its strength and deteriorates its structure, so that for the finer purposes of machinery and of cutlery England
p.150is indebted for much iron to Russia and Sweden, as in these countries, the smelting and refining being carried on by means of wood, the metal is obtained in absolute purity. Hence the great difference of price between the British and foreign iron. Common English bar being sold at £6 per ton; whilst Swedish and Russian iron bars will cost £15, £25, or even £35 per ton, according to their quality. Now we possess in Ireland the means of preparing those irons of superior quality and of replacing, if not the finest, at least the ordinary sorts of Baltic iron. The elements necessary to produce such metal, are ores of great purity and a vegetable fuel of proper kind. The ores we have already seen to be abundant. The vegetable fuel is found abundantly in our turf.
In England it can be easily understood that the manufacture of iron by turf is not thought worthy of notice. On the Continent, however, where the promotion of native industry is an object of primary importance, and where the limited development of the coal districts obliges them to economize every source of fuel, it has been not merely tried, but is extensively carried on at present in France, in Prussia, and in Bavaria. These countries resemble our's in their relations to fuel, and it is by observation of what they do, that we may learn how to economize our own resources. I shall accordingly proceed to describe how turf is applied in the manufacture of iron abroad, and then endeavour to apply their results to the peculiar circumstances of Ireland.
At Ransko in Bohemia, there is an extensive iron work consisting of high furnaces for the smelting of pig-iron from the ores; of cupolas for the remelting of pig and making castings, and the reverberatory furnaces and machinery for the manufacture of bar and plate. The ore that is employed is the clay ironstone, and is of very moderate quality. For fuel, is used a mixture of turf and charcoal. The turf is light, it is dried in the air, but not in any way prepared or pressed. The cubic metre of it weighs 225 kilos, and costs 1.34 franc. This is at the rate of 5s. per ton. The furnaces are blown with hot air at the temperature of 280[deg ] Fah. The proportions of materials and products that are given from an average of long
p.151experience, is, that to make a ton of iron, there is consumed 34 cwt. 3 qrs. of turf, which costs 8s. 9d., and 30 cwt. of charcoal costing 24s. 7d. The fuel for the smelting costs, therefore, 33s. 4d., and the other expenses bring the total cost of the pig iron to £3 15s. per ton. The fuel used in the cupolas and furnaces is the same, and the quality of iron is of the very highest character.
At Königsbrunn in Bavaria, are iron works peculiarly worthy of attention, as from the report of the French engineers sent to examine them, it appears, that they execute with turf alone the puddling and second fusion, reheating and rolling, finally, all the operations which are effected with coal in the English furnaces.
The turf employed is prepared with unusual care, as, owing to the excessively high price of fuel, every economy is important. It is not pressed, but is dried perfectly in stores of various kinds, of which two deserve especial notice. The first kind of store is heated by a fire-place belonging to itself. The other mode of drying the turf consists in an arrangement by which the waste heat, of the various puddling and reheating furnaces is economized.
The turf, as finally delivered at the furnaces, is charged at the rate of 13s. per ton. It is of an average quality. Berthier found it to consist of
The furnaces employed in these works all require peculiarities of construction, arising from the bulk of the fuel being so much greater in proportion to its weight than when wood or coal is used. These peculiarities it would, however, be tedious to describe here. They can be found on reference to the original memoirs and drawings; it is only the results that are of importance to the immediate object of this work.
It is found that in order to deliver a ton of puddled iron, there are required twenty-two and a half cwt. of pig, and there are consumed thirty and a quarter cwt. of turf, for which the densest is always selected. Of this puddled iron twenty-four and a half cwt. are reheated and rolled, with the consumption of thirty cwt. of dense turf, and the produce is a ton of small bars of iron of fine quality.
The cost of manufacturing the fine bar iron by this turf is therefore, per ton:
27½ cwt. of pig-iron, which is charged at £6 13s. per ton, that being the selling price, . . . £9 14
Turf, at 14s. per ton:
37 cwt. for puddling and
30 cwt. for reheating . . . £2 7 6
Labour and general expenses . . . £0 10 10
Cost of fine bars per ton . . . £11 19 8
Such are the financial circumstances of the manufacture of iron in a country, where there is really a scarcity of fuel, and where the introduction of English iron is practically prohibited.
I may add, that the consumption of turf has been found to be
For running a ton of iron in eastings, twenty-one and a half cwt. of pig, and twenty-two cwt. of turf.
For heating and rolling a ton of sheet iron, twenty-one cwt. of flat iron and thirty cwt. of turf.
In the iron works of Ichoux, department of the Landes in France, no fuel is used in puddling but turf. The turf of moderate quality costs at the rate of 8s. per ton. The ton of puddled iron is given by twenty-two cwt, of pig, and forty-five cwt. of turf. M. Alex of Lauchhammer has substituted turf for coal in his puddling furnaces. It requires two and a half times as much turf as coal: the usual work being, that twenty-five cwt. of pig, worked up with twenty-six cubic feet of turf gives twenty cwt. of iron rolled into bars.
The perfect similarity of the charcoal of dense turf, and especially
p.153of compressed turf, to that of wood, has been mentioned in a former place. It has been tried as a substitute for wood charcoal in iron works, and with perfect success. In the high furnaces of M. Müller at Wendenhammer, wood charcoal has been replaced by an equal volume of turf charcoal, and this method has been so beneficial, that the quantity of ore worked off was materially increased. In the high furnaces of Wachter at Neunhammer, when half of the charcoal of wood was replaced by turf coke, the charge of ore was raised from 386 lb to 464 lb. The quality of iron produced was excellent. Finally, MM. Moser and Wagner, who have examined minutely into the various conditions of this branch of industry, conclude, that both for smelting and refining iron, the coke of turf is as good and useful as an equal weight of wood charcoal.
It is unnecessary to multiply quotations of evidence of this kind. The great fact which is to be recollected is, that turf and turf coke answer perfectly for making and refining iron, and from the quantities of materials and products, which the experience of the French and German workers has found to answer, and the cost of those materials, as we know they can be had with us, we may proceed to calculate what are the financial conditions of the subject.
To produce a ton of pig-iron at Ransko, there are required thirty-five cwt. of turf and thirty cwt. of wood charcoal. Now for the latter may be substituted the turf coke, provided it be compressed; and as the turf may be taken at 4s. per ton, and the coke at 20s., taking the ore and labour to be the same as in our final estimate regarding the manufacture at Lough Allen, with coal, it becomes:
2½ tons of ore, at 5s. . . . £0 12 6
15 cwt. of limestone, at 2s. 6d. . . . £0 1 9
35 cwt. of turf, at 4s. . . . £0 7 0
30 cwt. of turf coke, at 20s. . . . £1 10 0
Labour and general expenses . . . £1 2 6
Total cost of a ton of pig . . . £3 13 9
Such iron should, however, not be sold as mere pig or used in castings. Its fine quality would peculiarly fit it for being
p.154made into bars; now the Königsbrunn results enable us to see what those bars would cost in Ireland. The calculation is:
Hence the ton of charcoal iron in bars would be made for six guineas. Now the price of the foreign charcoal iron ranges from £15 to £35 per ton. It cannot be made in England, for the wood charcoal is £4 per ton in the Forest of Dean, where some little remnant of the manufacture lingers. They have no extensive peat deposits. If they boast of their greater extent of underground repositories of fuel, we may point to our's which lie upon the surface. We must learn, however, to employ them properly, and with economy, or else we would show ourselves utterly unworthy of the riches with which Providence has blessed our country.
The consumption of fuel at Ransko is greater than elsewhere with charcoal furnaces. Thus in Pennsylvania, a ton of metal is obtained from forty-one cwt. of ore, and between twenty-five and twenty-seven cwt. of wood charcoal. On the Continent, the ton of metal requires from thirty to thirty-four cwt. of charcoal. So that if turf coke alone can be substituted for the wood charcoal, the above estimate may have the cost of the turf removed, and the ton of pig iron should come to about £3 10s. The introduction of the hot blast into charcoal furnaces has been found attended with the remarkable saving of from one-fourth to one-third of the entire quantity of fuel. With turf charcoal a similar economy might possibly arise, but I shall retain as illustration the cost of production already calculated.
Although the iron is not prepared from the ore by means of
p.155charcoal in any part of England, yet iron bar is manufactured by a mixed process of refining with coke and charcoal, from which a product is obtained of such excellent quality as to sell for £14 per ton, and to replace for such purposes as chain cables, nail-rods, boiler plate, piston rods, &c, the iron of the north of Europe, which is now, indeed, employed only for conversion into steel for the purposes of cutlery. The quantity of charcoal used in processes of refining is about four cwt. and a half per ton of iron. In this method of working also the charcoal from turf may ultimately be utilized.
The consumption of fuel in these processes is so great, and its cost enters so largely into the expense of the manufacture, that it becomes important to fix attention upon every mode by which any economy may be effected. The attention of chemists and engineers has been especially directed to this point upon the Continent, and now also in England it is attracting the notice it deserves.
During the work of a high iron furnace, the air which is blown into the fire escapes from the top, changed essentially in composition. Its oxygen has, of course, gone to support the combustion of the furnace, but in place of the escape of useless products, as nitrogen and carbonic acid, there is generated a large quantity of combustible gas, which takes fire on escaping, and generates that pale cone of flame by which the high furnace is so well characterized. The gaseous material thus passing off was found, on analysis by Bunsen and Ebelmen, to consist of:
|Nitrogen||from 63.0||to 60.2|
|Carbonic oxide||from 30.7||to 19.7|
|Carbonic acid||from 5.9||to 12.8|
|Hydrogen||from 0.4||to 7.3|
Now as the quantity of air blown in may be calculated, the quantity of the combustible gases given off may be inferred, and the conclusion finally arrived at is, that in the high furnaces a quantity of fuel is carried off under the form of combustible gases, which amounts to from 55 to 65 per cent. of the
p.156total heating value of the fuel introduced into the furnace, and also as the gases pass off at an intense heat, they carry away thereby at least 10 per cent. of the heat produced by the combustion, so that the quantity of fuel that is really employed in producing the heat by which the iron is smelted, does not amount to more than from 25 to 35 per cent. of that which is actually consumed. This vast loss, of course, more than doubles the cost of fuel in the process, and the following means have been devised and successfully employed for utilizing it in other ways.
The upper portion of the high furnace, where the charge of ore and fuel does not be yet ignited, is lined with a cylinder of iron, sustained by stays some inches from the brick work. The great body of the gas rushes into this space, where it has not to act against the solid mass of smelting materials. Into this space horizontal flues open on each side, leading to a metal chamber, where they unite, and from which the gas is delivered by nozzles on the floor of the reverberatory furnaces, in which the puddling and reheating is carried on. The chimney of the puddling furnace gives draft sufficient to draw in all the gas.
The result practically found is, that the temperature produced by the combustion of the combustible gases of the high furnace is fully sufficient for the puddling and refining of the iron; and thus the fuel (coal, charcoal, or coke), with which the high furnace is charged, may be made to serve for the entire conversion of the ore into fine bar iron. Now if we consider that it is usually taken in average, that to produce a ton of bars requires ten ton of coals, of which four tons only are used in the high furnace, it is evident that the economy of heat, by the methods now described, may reduce the cost of the bar iron per ton by the price of six tons of coal, and of course the advantage will be proportionally greatest where fuel is dearest.
The proportion of hydrogen in the gas evolved, depends on the presence of watery vapour in the air blown into the furnace, and of course varies with it. On this principle is founded another method of economy. I have mentioned, when speaking of the modes of applying anthracite, that when the vapour of
p.157water is passed over it at a high temperature, a mixture of hydrogen and carbonic oxide gases are evolved, by means of which a flaming property is given to that coal: this is the basis of Kymer's and Leighton's patent. This process is employed on the Continent, in order to economize very inferior fuels, such as slaty coal or earthy turf. The plan was originally invented by Ebelmen, but it is now applied in many places. A small furnace is built like an iron furnace, which may be blown either with air or steam. The top may be closed, except at the times of introducing fuel. From near the top pass lateral flues, which conduct the gaseous products to a chamber, from whence they are led to the furnaces where they are to be burned. Such a furnace is termed a generator. If it be blown with air, the products are the same as the gases of the high iron furnace. If it be blown with steam, the products are similar to those given with steam and anthracite. The following analyses give the composition of the gases resulting from a generator with very bad coal:
|Blown w/ air||Blown w/ mixed air and steam|
In the same generator, a fire of turf blown with air in its usual condition, gave:
It is hence evident that even with the worst fuel, by proper arrangements, the purest fire, that of flame, can be obtained; and thus the local differences of quality of coal or turf almost obliterated by the application of suitable mechanical constructions, guided by a correct knowledge of chemical principles.
It remains to notice one further mode of economy of fuel that
p.158has been adopted with complete success, not merely on the Continent, but also in certain works in Staffordshire. It consists in conducting the flues from the puddling furnaces under and round the boilers of the steam engines, so that the water in these last may be boiled, and the steam power for rolling, &c, may be generated by the heat, which should otherwise pass up the chimney and be lost.
The results obtained at Abbainville may be taken as an example of the amount of the saving so effected. It is there found that each pound of coal burned in the puddling furnace, evaporates 3.7 pounds of water in the steam boilers. Hence, the economy is at least half of the practical value of the fuel. The steam engine is thirty horse power, and is in almost constant activity for driving the cutters, rollers, and punches.
The works contain two puddling furnaces. The produce was 1000 tons of bar iron from 487 of coal and 1137 of pig, and this proportion of fuel remained the same, whether the steam engine was driven by the waste heat, or by independent fires.
I have noticed these sources of economy, because they, and all similar ameliorations, are not merely important to be known in order that the cheapest means of manufacture may be adopted, but that they are peculiarly of vital interest to us, who labour, as compared with the sister kingdom, under a certain disadvantage in regard to fuel. Every thing which diminishes the quantity of fuel, diminishes the amount of this disadvantage, and hence removes the greatest difficulty felt in the financial success of industry in Ireland. Thus, if the English manufacturer have an advantage of 1s. per ton in the price of coals, and that there be ten tons of coal used to make a ton of iron bars, his advantage is 10s.; and that 10s. may enable him to send his iron to every part of Ireland, and to destroy our market. But if, by processes in which fuel is economized, the bars be made with five tons of coal, in place of ten, then his total advantage in fuel becomes but 5s., and this may not be, indeed would not be sufficient to enable him to keep possession of the Irish market. It is evident also, that if one party adopt methods of economy, and the other party do not, the scale is at once and decisively turned in favour of the party who avails himself most rapidly of all improvements.