The Industries of Scotland: Their Rise, Progress and Present Condition

by David Bremner, 1869

The Manufacture of Ironstone

The Origin and Progress of the Manufacture of Iron In Scotland - Statistics of the Trade - Effects of Over-speculation - Coatbridge and its Furnaces - Description of the Gartsherrie Ironworks - The Smelting Process - Invention of the Hot Blast and its Effect on the Trade

Though the existence of ironstone in the Scotch coal measures was known many years previously, no attempt was made to turn it to account until the year 1760, when the Carron Ironworks were established. Only one kind of ironstone was then used — namely, the argillaceous or "clayband;" for the more valuable carbonaceous or " blackband " was not discovered till the beginning of the present century. These two varieties are known as the coal measure ironstones, and are found in all the great coal fields of Britain except those of Northumberland, Durham, and Lancashire. Though there are nineteen kinds of iron ore known to the mineralogist, it has been calculated that nine-tenths of the iron produced is derived from the clayband and blackband ironstones, the relative value of which is thus stated in a paper read before the Scottish Society of Arts by Mr Ralph Moore, Government inspector of Mines : — "Clay ironstones contain from thirty to fifty per cent. of metallic iron. Before being melted, they are mixed with coal, and calcined in kilns or large heaps, to drive off the carbonic acid gas, sulphur, and other impurities. This description of ironstone is found in seams or bands, and in nodules, throughout the whole of the measures, but is most plentiful in the lower part of the section. Blackband ironstone is a carbonate of iron, laminated with coal, generally in sufficient quantity for calcination without further admixture of coal ; and leaves, when calcined, a metallic coke containing from fifty to seventy per cent. of metallic iron. This description of ironstone is found in seams or bands in well-defined positions in the measures, but these are neither persistent in position nor equable in quality. Sometimes the seam is wanting altogether, or so thin as to be unworkable ; at other times, the coaly element so predominates that its metallic value is of small amount, while not unfrequently it contains nothing but coal. A good black band ironstone contains from two to eight per cent. of coal. When it contains more than twenty per cent. of coal, it is of little value unless mixed with clayband, which uses up the excess of coal. It is more easily melted than clayband, and requires less coal ; and the weekly produce of a furnace from blackband is fifty per cent. greater than from clayband."

Deposits of hematite, or red iron ore, have been discovered recently in Haddingtonshire, Dumfriesshire, and Kirkcudbright, and operations for utilising the ore are in progress.

From the establishment of the Carron Ironworks in 1760 till 1788, the quantity of iron produced in Scotland did not exceed 1500 tons per annum ; but during the succeeding eight years a number of new furnaces were erected in the counties of Lanark, Fife, and Ayr. In 1706 the number of furnaces was seventeen, and the quantity of iron made in that year was 18,640 tons. Thirty-three years afterwards the prod action had reached 29,000 tons ; and from that figure the invention of the hot-blast process raised it to 75,000 tons in 1836. By that time the construction of railways had begun to open a new market for the iron-merchant ; and to supply the demand, many new ironstone pits were opened, and furnaces erected. In the ten years from 1835 to 1845, the production of iron increased about 700 per cent. — the quantity made in the latter year being 475,000 tons. Ten years later, 825,000 tons were made ; and another decade gave an addition of 339,000 — the quantity manufactured in 1865 being 1,164,000 tons. Over speculation, and the consequent financial crisis in 1866, operated most prejudicially on the iron trade, and the production for that year fell to 994,000 tons. Matters gave promise of taking a turn for the better in 1867 ; but the promise was realised only to a limited extent, the revelations made in connection with several of the principal railway companies, and other causes, having had an unfavourable effect on the trade. The total quantity made in 1867 was 1,031,000 tons — an increase of 37,000 as compared with the preceding year, but 133,000 tons short of the production of 1865. The quantity shipped in each of the past ten years has not varied much. In 1867 it was 593,277 tons, of which 338,364 tons were for foreign ports, and the remainder went coastwise. Of the quantity shipped to foreign ports, France took 60,500 tons ; Germany and Holland 99,600 tons; Belgium, Denmark, Sweden, and Norway, 20,100; Russia, 9600; Spain and Portugal, 5100; Italy, 14,200; United States, 117,300; British America, 43,000; East Indies, China, Australia, and South America, 14,000. The largest quantity ever consumed in Scotland in one year was 532,000 tons, in 1865. In 1867, the quantity taken was 420,262 tons. The make of malleable iron in 1867 was 142,800 tons, being a reduction of 11,400 tons as compared with 1866.

The rapid development of the iron trade has not been peculiar to Scotland. England, Wales, and a number of Continental countries have had a similar experience, arising from the same causes — namely, the formation of railways, the substitution of iron for wood in the construction of ships, and its increased application, in the form of machinery, to the industrial arts. The number of blast furnaces in Scotland is 164, of which 108 were in blast during 1867. Each furnace produced on the average about 9546 tons. One furnace gives employment, directly and indirectly, to fully two hundred men and boys, so that the number of persons engaged in the production of pig-iron during the year could not be less than 22,000, with wages ranging from 2s. to 6s. a-day. It will thus be seen that the "damping out," or stoppage of a furnace is a serious matter for the working population in the iron districts. Were the entire number of furnaces in blast, employment would be given to upwards of 33,000 men and boys, while the annual production would exceed 1,500,000 tons. The number of ironstone miners in Scotland is about 13,000, and the largest quantity of ore put out in a year was 2,500,000 tons in 1857.

The occupation of the ironstone miner differs little from that of the coal-miner, and the two occupy nearly the same position as regards wages, &c. The ironstone seams are generally only from six to eighteen inches in thickness, so that in taking out the ore a considerable quantity of rock has to be excavated. As the miner advances, he builds up behind him as much as possible of the stone and rubbish, and sends out the ironstone and surplus material in small waggons or " hutches."

The price of pig-iron has been subject to considerable fluctuations. In 1854, the mean average price of a ton of Scotch pig-iron was 79s. 7d. ; it was 54s. 4d. in 1858 ; and 49s. 3d. in 1861. In 1866 the market was much disturbed by the operations of certain bold speculators, who forced the top price up to 82s. 6d. — an increase of 21s. on the price at the close of the preceding year. Then came financial disasters ; and the brief space of four weeks witnessed a fall of 31s. 6d. a ton. After rising and falling several times subsequently, the price at the close of 1866 was 54s. 6d. In order to enable them to overcome the effects of the crisis brought about by the speculators alluded to, the ironmasters resolved to reduce the production, and forty furnaces were "blown out." Nearly eight thousand men and boys were thus thrown idle, while at the same time the wages of the men retained were considerably reduced. In the course of 1867 a number of the furnaces which had been stopped were set on, and about one-third of the men who had been thrown idle were restored to work. The average price of pig-iron during 1867 was 53s. 6d. per ton. The lowest figure reached in the course of the year was 51s. 3d., in the month of March, and the highest 55s. 6d., in October.

From the convenient situation and facilities for transport enjoyed by Scotch ironmasters, coupled with the cheapness of labour, it might be thought that no English or other producers of the metal could undersell them ; but it is, nevertheless, a fact that something like 70,000 tons of pig-iron were in 1867 imported into Scotland, from Middlesborough, in Yorkshire, where ironstone costs less than one-fourth of its value in Scotland. The iron is, however, of a much lower quality than the native Scotch, and is used for mixing with the latter for the production of certain kinds of material. A small quantity of fine pig-iron is brought from West Cumberland by some of the malleable iron makers, who use it to mix with and improve the quality of the native iron. It is expected that, when the Solway Junction Railway is opened, a large quantity of Cumberland iron ore will be brought into Scotland. In 1868 the price of malleable bars ranged from L.6, 15s. to L.7, 5s. a ton; plates, L.8, 10s. ; and rails, L.6 to L.7. Cast-iron pipes were quoted at from L.4, 15s. to L.6 per ton, and railway chairs at from L.3, 12s. 6d. to L.4.

The most valuable deposits of ironstone are in Lanarkshire and Ayrshire, and in the former county two-thirds of the pig-iron made in Scotland is produced. The blast furnaces are chiefly concentrated in the vicinity of Coatbridge, Airdrie, and Wishaw, all of which towns were rapidly raised to importance by the development of the mineral treasures which lay beneath and around them. Coatbridge stands within a crescent of blast furnaces, and in the town are a large number of rolling mills, forges, and tube works, the hundred chimneys of which form quite a forest of brickwork capped with fire.

Though Coatbridge is a most interesting seat of industry, it is anything but beautiful. Dense clouds of smoke roll over it incessantly, and impart to all the buildings a peculiarly dingy aspect. A coat of black dust overlies everything, and in a few hours the visitor finds his complexion considerably deteriorated by the flakes of soot which fill the air, and settle on his face. To appreciate Coatbridge, it must be visited at night, when it presents a most extraordinary and — when seen for the first time — startling spectacle. From the steeple of the parish church, which stands on a considerable eminence, the flames of no fewer than fifty blast furnaces may be seen. In the daytime these flames are pale and unimpressive ; but when night comes on, they appear to burn more fiercely, and gradually there is developed in the sky a lurid glow similar to that which hangs over a city when a great conflagration is in progress. For half-a-mile round each group of furnaces, the country is as well illumined as during full moon, and the good folks of Coatbridge have their streets lighted without tax or trouble. There is something grand in even a distant view of the furnaces ; but the effect is much enhanced when they are approached to within a hundred yards or so. The flames then have a positively fascinating effect. No production of the pyrotechnist can match their wild gyrations. Their form is ever changing, and the variety of their movements is endless. Now they shoot far upward, and breaking short off, expire among the smoke ; again spreading outward, they curl over the lips of the furnace, and dart through the doorways, as if determined to annihilate the bounds within which they are confined ; then they sink low into the crater, and come forth with renewed strength in the shape of great tongues of fire, which sway backward and forward, as if seeking with a fierce eagerness something to devour.

The most extensive ironmasters in Scotland are Messrs Baird and Co., who own forty-two blast furnaces, employ nine thousand men and boys, and produce about three hundred thousand tons of pig-iron per annum, or one-fourth of the entire quantity made north of the Tweed. Twenty-six of their furnaces are situated in various parts of Ayrshire, and the remaining sixteen are concentrated at Gartsherrie, in the neighbourhood of Coatbridge. Gartsherrie Ironworks are the largest in Scotland, and it is stated there is only one establishment in Britain which has a greater number of furnaces. The quantity of pig-iron made is one hundred thousand tons per annum, and the number of men and boys connected with the works is three thousand two hundred. More than a thousand tons of coal are consumed every twenty-four hours ; and, as showing how well chosen is the site of the works, it may be mentioned that nineteen-twentieths of the coal required is obtained within a distance of half-a-mile from the furnaces. One coal-pit is situated close to the furnaces, and has been in operation since the works were established, forty years ago.

The coal from this pit is conveyed to the furnaces by means of a self-acting incline. Most of the ironstone was at one time obtained from pits in the nighbourhood, but now it has to be brought from a distance of from two to twenty miles ; and a complete system of railways connects the pits with the works. The total length of the railways is about fifty miles, and the traffic is carried on by means of six locomotives and an immense number of trucks. The establishment is also connected with the great railway systems of the country, and possesses additional facilities for transport in a branch of the Monklands Canal, which has been carried through the centre of the works. For the canal traffic, there is a fleet of eighteen barges, of about sixty tons each ; and eight of these are screw steamers. A great proportion of the manufactured iron is sent out by the canal.

As the Gartsherrie Ironworks have a widespread reputation for producing iron of a superior quality, and are among the best organised manufactories in the country, a description of them may be interesting.

The furnaces, sixteen in number, stand in two rows, one on each side of the canal, and about forty yards distant from it. A constant supply of coal and ironstone can be reckoned upon, and therefore only a small stock is kept at the works. The mineral trains are worked with unfailing regularity, and their cargoes are deposited conveniently for immediate use. There is thus no superfluous shovelling about of the materials, nor is any expense incurred by piling them into heaps. The proportions of ironstone, coal, and limestone, laid down are exactly what are required in the process of smelting. Manual labour has, by a variety of ingenious appliances, been reduced to a minimum, and the amount of waste is infinitesimal. Everything is done according to a well-defined system, and nothing connected with the works is considered to be too insignificant to merit attention. No heaps of rubbish are allowed to accumulate, no scraps of iron or cinder lie about, and every nook and cranny about the vast place is as tidily kept as it can possibly be. The workmen are liberally treated, but they must do their work carefully and well. Negligence and irregularity are unfailingly punished, while merit is as certainly rewarded. All the men employed about the furnaces, even the firemen and engineers of the blast engines, are paid according to the quantity and quality of iron produced. This arrangement is found to work admirably, as each man knows that, by attending to his work, he is not only putting money into the pockets of his fellow-labourers, but also improving his own earnings.

Before the ironstone is ready for smelting it has to be calcined, which operation is performed at the pits. The object of calcining is to separate carbonic acid, water, sulphur, and other deleterious substances, which are volatile at a red heat ; and it is performed in this way : — A layer of rough coal is first laid down, and on that the ore, mixed with a certain quantity of small coal, is piled. The blackband ironstone, as it contains a large proportion of carbon, requires less coal to calcine it than the clayband. When the heap is completed, fire is applied to the windward side, and combustion goes on gradually until the desired effect is produced. When the ore cools, it is ready for the furnace ; but when the heat has been too intense, the ore is found to have run into large masses, the breaking up of which takes a considerable amount of labour.

Having been built at different periods, the Gartsherrie furnaces are of various patterns. The general shape is cylindrical, the diameter twenty-two feet, and the height sixty feet. The Nelson Monument, on Calton Hill, Edinburgh, would, were it less lofty, bear a close resemblance to one of the most recently erected furnaces. The furnace is fed from the top, and, in order to protect the "fillers," the mouth of it is surrounded by a light wall of brick, pierced with convenient openings. This brick wall is so much thinner than the main wall of the furnace on which it stands, that a gallery or footway several feet in width is left clear all round. Externally, there are four arched recesses in the base of the furnace, three of which are occupied by the "tuyeres," or pipes conveying the "blast;" while the fourth contains a doorway by which the "slag " is drawn off, and also the opening through which the molten iron is discharged. The interior of the furnace consists of a circular cavity, seven and a half feet in diameter at the lower part or hearth. At a height of five or six feet from the bottom of the hearth, the cavity begins to increase in diameter, until, at half the height of the furnace, it measures eighteen feet across. It is then gradually contracted, and at the top the diameter is eleven feet. The materials with which the furnace is fed are roasted ore, coal, and limestone. The proportions of these vary according to their quality. In some cases, a small quantity of red-iron ore or hematite is used along with the blackband ironstone, and then the proportions of what are called a "charge" are these : — Coal, about 10 cwt. ; roasted ore, 6 1/2 cwt.; red ore, 1/2 cwt. ; and lime, 2 5/8 cwt. About sixty "charges " are thrown into the furnace in the course of twelve hours, and at six o'clock in the morning and at six at night the furnace is " tapped" and the iron run off. The chemical changes undergone by the materials introduced into the furnace are thus described : — The iron ore consists of iron, oxygen, and sand, and the object of the iron smelter is to separate the two latter substances from the former. The coal introduced has two functions to fulfil — in part it is burned so as to raise the contents of the furnace to such a high temperature that they will be enabled to act on each other ; and, at the same time, it carries away the oxygen which was originally in combination with the iron in the roasted ore. The lime plays the part of a flux, and combines with the sandy matter to form a slag. During the whole operation, hot air is being constantly forced in at the lower part of the furnace, so as to aid in the necessary combustion. The roasted iron ore being thus deprived of its oxygen by the coal, and of its sand by the lime, allows the other constituent — the iron — to trickle down through the mass of red-hot cinders to the lower part or hearth of the furnace.

In front of each furnace is a level piece of ground covered with coarse sand, in which before the "tapping" takes place a number of small furrows are formed. These communicate with larger channels leading from the opening in the furnace ; and when the iron is let out, it runs along the main channels in a glowing, bubbling stream, and distributes itself into all the hollows. The large channels are called "sows," and the small ones "pigs;" hence the term "pig-iron." Two men are employed to feed each furnace. One fills half a charge of coal into a large iron barrow, and the other half a charge of the other materials into a second barrow. The men and the barrows reach the staging communicating with the mouth of the furnace by means of a hydraulic lift. The coal is thrown in first, and the other materials immediately afterwards. The occupation of the " fillers " appears to be a somewhat dangerous one, as the flames at times shoot out upon, and almost surround them. Two men are employed at the hearth scooping out the slag and cinders with a huge spoon suspended from a crane, and from time to time stirring up the contents of the furnace. This is very severe labour, and the faces of the men engaged in it have a half-roasted appearance. The slag is poured into iron trucks, and, when it consolidates, is wheeled away to be emptied on the waste heap — which, it may be mentioned, contains as much material as would build a copy of the Great Pyramid. The pig moulds are formed in the sand by boys, the operation being a very simple one.

Up till about forty years ago the air forced into blast-furnaces was cold, and the process of smelting was slow, and also costly, in consequence of the great quantity of coal that was required. In 1827, Mr J. B. Neilson, engineer of the Glasgow Gas-Works, conceived the idea of heating the air before injecting it into the furnace ; and two years afterwards a most successful trial was given to the invention at the Clyde Ironworks. With the cold blast coke had to he used, and 8 tons 1 1/4 cwt. of coal converted into coke was required to reduce one ton of iron. It was found that when heated air was employed the coal might be used raw, and that 2 tons 13 1/4cwt. was sufficient to smelt a ton of iron, including 8 cwt. required for heating the air. This discovery gave an extraordinary impetus to the iron trade, and the patentee and his partners are said to have realised L.300,000 by the invention. At Gartsherrie there are three immense engines for generating the blast — two for one range of furnaces, and one for the other. The engines are on the beam principle, and their united "duty" is equal to about 500 horse power. The steam cylinder of the largest is five and a-half feet in diameter, and ten feet deep, and the air cylinder is ten feet in diameter and depth. The air cylinders are simply gigantic pumps, which force the air into receivers, whence it flows at an equal pressure through the tubes of the heating oven, and into the furnace. By passing through the oven the temperature of the air is raised to 800°. It has been calculated that the quantity of air thrown into a blast-furnace in full work exceeds in weight all the solid material used in smelting.

In the vicinity of Gartsherrie there are about five hundred houses belonging to Messrs Baird & Co., and occupied by their workmen. Nearly all the houses have two apartments, and a few have a third room. A bit of garden ground is attached to each house, and all are supplied with water and gas at a cheap rate. The miners get as much coal as they require without payment — only they must dig it out for themselves ; and the other workmen are charged only 3s. 6d. for a cartload. Liberal provision is made for the education of the children of the workpeople. There are three schools in direct connection with the works, each being divided into separate apartments for infants, boys, and girls. The workmen seem to appreciate highly all that has been done for their welfare, and few of them leave the place. They own one of the most successful co-operative stores in the country. It is managed by a committee of the workmen, but its prosperity is in a great measure owing to the fostering care of the employers, who, however, have no interest in the concern beyond seeing that it is properly conducted. There are seven hundred members in the society, nearly all of whom are heads of families, and the business done amounts to about L.1200 a-month. In addition to general grocery goods, wines, spirits, butcher meat, and potatoes, are sold in the store.

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