Invention of the Hot Blast

Many people will have seen the large memorial stone erected on Barstobrick Hill, near Ringford, and some will know that it was erected in memory of James Neilson of Queenshill, Ringford. Neilson’s story, however, is much less well known…. but this chapter, written by Samuel Smiles in 1863, recounts his career; and in particular his invention of the HOT BLAST furnace from which he made his fortune.


By Samuel Smiles




“Whilst the exploits of the conqueror and the intrigues of the demagogue are faithfully preserved through a succession of ages, the persevering and unobtrusive efforts of genius, developing the best blessings of the Deity to man, are often consigned to oblivion.”– David Mushet.

The extraordinary value of the Black Band ironstone was not at first duly recognised, perhaps not even by Mr. Mushet himself. For several years after its discovery by him, its use was confined to the Calder Iron Works, where it was employed in mixture with other ironstones of the argillaceous class. It was afterwards partially used at the Clyde Iron Works, but nowhere else, a strong feeling of prejudice being entertained against it on the part of the iron trade generally. It was not until the year 1825 that the Monkland Company used it alone, without any other mixture than the necessary quantity of limestone for a flux. “The success of this Company,” says Mr. Mushet, “soon gave rise to the Gartsherrie and Dundyvan furnaces, in the midst of which progress came the use of raw pit-coal and the Hot Blast–the latter one of the greatest discoveries in metallurgy of the present age, and, above every other process, admirably adapted for smelting the Blackband ironstone.” From the introduction of this process the extraordinary development of the iron-manufacture of Scotland may be said to date; and we accordingly propose to devote the present chapter to an account of its meritorious inventor.

James Beaumont Neilson was born at Shettleston, a roadside village about three miles eastward of Glasgow, on the 22nd of June, 1792. His parents belonged to the working class. His father’s earnings during many laborious years of his life did not exceed sixteen shillings a week. He had been bred to the trade of a mill-wright, and was for some time in the employment of Dr. Roebuck as an engine-wright at his colliery near Boroughstoness. He was next employed in a like capacity by Mr. Beaumont, the mineral-manager of the collieries of Mrs. Cunningham of Lainshaw, near Irvine in Ayrshire; after which he was appointed engine-wright at Ayr, and subsequently at the Govan Coal Works near Glasgow, where he remained until his death. It was while working at the Irvine Works that he first became acquainted with his future wife, Marion Smith, the daughter of a Renfrewshire bleacher, a woman remarkable through life for her clever, managing, and industrious habits. She had the charge of Mrs. Cunningham’s children for some time after the marriage of that lady to Mr. Beaumont, and it was in compliment to her former mistress and her husband that she named her youngest son James Beaumont after the latter.

The boy’s education was confined to the common elements of reading, writing, and arithmetic, which he partly acquired at the parish school of Strathbungo near Glasgow, and partly at the Chapel School, as it was called, in the Gorbals at Glasgow. He had finally left school before he was fourteen. Some time before he left, he had been partially set to work, and earned four shillings a week by employing a part of each day in driving a small condensing engine which his father had put up in a neighbouring quarry. After leaving school, he was employed for two years as a gig boy on one of the winding engines at the Govan colliery. His parents now considered him of fit age to be apprenticed to some special trade, and as Beaumont had much of his father’s tastes for mechanical pursuits, it was determined to put him apprentice to a working engineer. His elder brother John was then acting as engineman at Oakbank near Glasgow, and Beaumont was apprenticed under him to learn the trade. John was a person of a studious and serious turn of mind, and had been strongly attracted to follow the example of the brothers Haldane, who were then exciting great interest by their preaching throughout the North; but his father set his face against his son’s “preaching at the back o’ dikes,” as he called it; and so John quietly settled down to his work. The engine which the two brothers managed was a very small one, and the master and apprentice served for engineman and fireman. Here the youth worked for three years, employing his leisure hours in the evenings in remedying the defects of his early education, and endeavouring to acquire a knowledge of English grammar, drawing, and mathematics.

On the expiry of his apprenticeship, Beaumont continued for a time to work under his brother as journeyman at a guinea a week; after which, in 1814, he entered the employment of William Taylor, coal-master at Irvine, and he was appointed engine-wright of the colliery at a salary of from 70L. to 80L. a year. One of the improvements which he introduced in the working of the colliery, while he held that office, was the laying down of an edge railway of cast-iron, in lengths of three feet, from the pit to the harbour of Irvine, a distance of three miles. At the age of 23 he married his first wife, Barbara Montgomerie, an Irvine lass, with a “tocher” of 250L. This little provision was all the more serviceable to him, as his master, Taylor, becoming unfortunate in business, he was suddenly thrown out of employment, and the little fortune enabled the newly-married pair to hold their heads above water till better days came round. They took a humble tenement, consisting of a room and a kitchen, in the Cowcaddens, Glasgow, where their first child was born.

About this time a gas-work, the first in Glasgow, was projected, and the company having been formed, the directors advertised for a superintendent and foreman, to whom they offered a “liberal salary.” Though Beaumont had never seen gaslight before, except at the illumination of his father’s colliery office after the Peace of Amiens, which was accomplished in a very simple and original manner, without either condenser, purifier, or gas-holder, and though he knew nothing of the art of gas-making, he had the courage to apply for the situation. He was one of twenty candidates, and the fortunate one; and in August, 1817, we find him appointed foreman of the Glasgow Gasworks, for five years, at the salary of 90L. a year. Before the expiry of his term he was reappointed for six years more, at the advanced salary of 200L., with the status of manager and engineer of the works. His salary was gradually increased to 400L. a year, with a free dwelling-house, until 1847, when, after a faithful service of thirty years, during which he had largely extended the central works, and erected branch works in Tradeston and Partick, he finally resigned the management.

The situation of manager of the Glasgow Gas-works was in many respects well suited for the development of Mr. Neilson’s peculiar abilities. In the first place it afforded him facilities for obtaining theoretical as well as practical knowledge in Chemical Science, of which he was a diligent student at the Andersonian University, as well as of Natural Philosophy and Mathematics in their higher branches. In the next place it gave free scope for his ingenuity in introducing improvements in the manufacture of gas, then in its infancy. He was the first to employ clay retorts; and he introduced sulphate of iron as a self-acting purifier, passing the gas through beds of charcoal to remove its oily and tarry elements. The swallow-tail or union jet was also his invention, and it has since come into general use.

While managing the Gas-works, one of Mr.Neilson’s labours of love was the establishment and direction by him of a Workmen’s Institution for mutual improvement. Having been a workman himself, and experienced the disadvantages of an imperfect education in early life, as well as the benefits arising from improved culture in later years, he desired to impart some of these advantages to the workmen in his employment, who consisted chiefly of persons from remote parts of the Highlands or from Ireland. Most of them could not even read, and his principal difficulty consisted in persuading them that it was of any use to learn. For some time they resisted his persuasions to form a Workmen’s Institution, with a view to the establishment of a library, classes, and lectures, urging as a sufficient plea for not joining it, that they could not read, and that books would be of no use to them. At last Mr. Neilson succeeded, though with considerable difficulty, in inducing fourteen of the workmen to adopt his plan. Each member was to contribute a small sum monthly, to be laid out in books, the Gas Company providing the members with a comfortable room in which they might meet to read and converse in the evenings instead of going to the alehouse. The members were afterwards allowed to take the books home to read, and the room was used for the purpose of conversation on the subjects of the books read by them, and occasionally for lectures delivered by the members themselves on geography, arithmetic, chemistry, and mechanics. Their numbers increased so that the room in which they met became insufficient for their accommodation, when the Gas Company provided them with a new and larger place of meeting, together with a laboratory and workshop. In the former they studied practical chemistry, and in the latter they studied practical mechanics, making for themselves an air pump and an electrifying machine, as well as preparing the various models used in the course of the lectures. The effects on the workmen were eminently beneficial, and the institution came to be cited as among the most valuable of its kind in the kingdom.* [footnote… Article by Dugald Bannatyne in Glasgow Mechanic’s Magazine, No. 53, Dec. 1824. ]

Mr. Neilson throughout watched carefully over its working, and exerted himself in all ways to promote its usefulness, in which he had the zealous co-operation of the leading workmen themselves, and the gratitude of all. On the opening of the new and enlarged rooms in 1825, we find him delivering an admirable address, which was thought worthy of republication, together with the reply of George Sutherland, one of the workmen, in which Mr. Neilson’s exertions as its founder and chief supporter were gratefully and forcibly expressed.* [footnote… Glasgow Mechanic’s Magazine, vol. iii. p. 159.]

It was during the period of his connection with the Glasgow Gas-works that Mr. Neilson directed his attention to the smelting of iron. His views in regard to the subject were at first somewhat crude, as appears from a paper read by him before the Glasgow Philosophical Society early in 1825. It appears that in the course of the preceding year his attention had been called to the subject by an iron-maker, who asked him if he thought it possible to purify the air blown into the blast furnaces, in like manner as carburetted hydrogen gas was purified. The ironmaster supposed that it was the presence of sulphur in the air that caused blast-furnaces to work irregularly, and to make bad iron in the summer months. Mr. Neilson was of opinion that this was not the true cause, and he was rather disposed to think it attributable to the want of a due proportion of oxygen in summer, when the air was more rarefied, besides containing more aqueous vapour than in winter. He therefore thought the true remedy was in some way or other to throw in a greater proportion of oxygen; and he suggested that, in order to dry the air, it should be passed, on its way to the furnace, through two long tunnels containing calcined lime. But further inquiry served to correct his views, and eventually led him to the true theory of blasting.

Shortly after, his attention was directed by Mr. James Ewing to a defect in one of the Muirkirk blast-furnaces, situated about half a mile distant from the blowing-engine, which was found not to work so well as others which were situated close to it. The circumstances of the case led Mr. Neilson to form the opinion that, as air increases in volume according to temperature, if he were to heat it by passing it through a red-hot vessel, its volume would be increased, according to the well-known law, and the blast might thus be enabled to do more duty in the distant furnace. He proceeded to make a series of experiments at the Gas-works, trying the effect of heated air on the illuminating power of gas, by bringing up a stream of it in a tube so as to surround the gas-burner. He found that by this means the combustion of the gas was rendered more intense, and its illuminating power greatly increased. He proceeded to try a similar experiment on a common smith’s fire, by blowing the fire with heated air, and the effect was the same; the fire was much more brilliant, and accompanied by an unusually intense degree of heat.

Having obtained such marked results by these small experiments, it naturally occurred to him that a similar increase in intensity of combustion and temperature would attend the application of the process to the blast-furnace on a large scale; but being only a gas-maker, he had the greatest difficulty in persuading any ironmaster to permit him to make the necessary experiment’s with blast-furnaces actually at work. Besides, his theory was altogether at variance with the established practice, which was to supply air as cold as possible, the prevailing idea being that the coldness of the air in winter was the cause of the best iron being then produced. Acting on these views, the efforts of the ironmasters had always been directed to the cooling of the blast, and various expedients were devised for the purpose. Thus the regulator was painted white, as being the coolest colour; the air was passed over cold water, and in some cases the air pipes were even surrounded by ice, all with the object of keeping the blast cold. When, therefore, Mr. Neilson proposed entirely to reverse the process, and to employ hot instead of cold blast, the incredulity of the ironmasters may well be imagined. What! Neilson, a mere maker of gas, undertake to instruct practical men in the manufacture of iron! And to suppose that heated air can be used for the purpose! It was presumption in the extreme, or at best the mere visionary idea of a person altogether unacquainted with the subject!

At length, however, Mr. Neilson succeeded in inducing Mr. Charles Macintosh of Crossbasket, and Mr. Colin Dunlop of the Clyde Iron Works, to allow him to make a trial of the hot air process. In the first imperfect attempts the air was heated to little more than 80 degrees Fahrenheit, yet the results were satisfactory, and the scoriae from the furnace evidently contained less iron. He was therefore desirous of trying his plan upon a more extensive scale, with the object, if possible, of thoroughly establishing the soundness of his principle. In this he was a good deal hampered even by those ironmasters who were his friends, and had promised him the requisite opportunities for making a fair trial of the new process. They strongly objected to his making the necessary alterations in the furnaces, and he seemed to be as far from a satisfactory experiment as ever. In one instance, where he had so far succeeded as to be allowed to heat the blast-main, he asked permission to introduce deflecting plates in the main or to put a bend in the pipe, so as to bring the blast more closely against the heated sides of the pipe, and also increase the area of heating surface, in order to raise the temperature to a higher point; but this was refused, and it was said that if even a bend were put in the pipe the furnace would stop working. These prejudices proved a serious difficulty in the way of our inventor, and several more years passed before he was allowed to put a bend in the blast-main. After many years of perseverance, he was, however, at length enabled to work out his plan into a definite shape at the Clyde Iron Works, and its practical value was at once admitted. At the meeting of the Mechanical Engineers’ Society held in May, 1859, Mr. Neilson explained that his invention consisted solely in the principle of heating the blast between the engine and the furnace, and was not associated with any particular construction of the intermediate heating apparatus. This, he said, was the cause of its success; and in some respects it resembled the invention of his countryman, James Watt, who, in connection with the steam-engine, invented the plan of condensing the steam in a separate vessel, and was successful in maintaining his invention by not limiting it to any particular construction of the condenser. On the same occasion he took the opportunity of acknowledging the firmness with which the English ironmasters had stood by him when attempts were made to deprive him of the benefits of his invention; and to them he acknowledged he was mainly indebted for the successful issue of the severe contests he had to undergo. For there were, of course, certain of the ironmasters, both English and Scotch, supporters of the cause of free trade in others’ inventions, who sought to resist the patent, after it had come into general use, and had been recognised as one of the most valuable improvements of modem times.* [footnote… Mr. Mushet described it as “a wonderful discovery,” and one of the “most novel and beautiful improvements in his time.” Professor Gregory of Aberdeen characterized it as “the greatest improvement with which he was acquainted.” Mr. Jessop, an extensive English iron manufacturer, declared it to be “of as great advantage in the iron trade as Arkwright’s machinery was in the cotton-spinning trade; and Mr. Fairbairn, in his contribution on “Iron” in the Encyclopaedia Britannica, says that it “has effected an entire revolution in the iron industry of Great Britain, and forms the last era in the history of this material.” ]

The patent was secured in 1828 for a term of fourteen years; but, as Mr. Neilson did not himself possess the requisite capital to enable him to perfect the invention, or to defend it if attacked, he found it necessary to invite other gentlemen, able to support him in these respects, to share its profits; retaining for himself only three-tenths of the whole. His partners were Mr. Charles Macintosh, Mr. Colin Dunlop, and Mr.John Wilson of Dundyvan. The charge made by them was only a shilling a ton for all iron produced by the new process; this low rate being fixed in order to ensure the introduction of the patent into general use, as well as to reduce to a minimum the temptations of the ironmasters to infringe it.

The first trials of the process were made at the blast-furnaces of Clyde and Calder; from whence the use of the hot blast gradually extended to the other iron-mining districts. In the course of a few years every furnace in Scotland, with one exception (that at Carron), had adopted the improvement; while it was also employed in half the furnaces of England and Wales, and in many of the furnaces on the Continent and in America. In course of time, and with increasing experience, various improvements were introduced in the process, more particularly in the shape of the air-heating vessels; the last form adopted being that of a congeries of tubes, similar to the tubular arrangement in the boiler of the locomotive, by which the greatest extent of heating surface was provided for the thorough heating of the air. By these modifications the temperature of the air introduced into the furnace has been raised from 240 degrees to 600 degrees, or the temperature of melting lead. To protect the nozzle of the air-pipe as it entered the furnace against the action of the intense heat to which it was subjected, a spiral pipe for a stream of cold water constantly to play in has been introduced within the sides of the iron tuyere through which the nozzle passes; by which means the tuyere is kept comparatively cool, while the nozzle of the air-pipe is effectually protected.* [footnote… The invention of the tubular air-vessels and the water-tuyere belongs, we believe, to Mr. John Condie, sometime manager of the Blair Iron Works.]

This valuable invention did not escape the usual fate of successful patents, and it was on several occasions the subject of protracted litigation. The first action occurred in 1832; but the objectors shortly gave in, and renewed their licence. In 1839, when the process had become generally adopted throughout Scotland, and, indeed, was found absolutely essential for smelting the peculiar ores of that country–more especially Mushet’s Black Band–a powerful combination was formed amongst the ironmasters to resist the patent. The litigation which ensued extended over five years, during which period some twenty actions were proceeding in Scotland, and several in England. Three juries sat upon the subject at different times, and on three occasions appeals were carried to the House of Lords. One jury trial occupied ten days, during which a hundred and two witnesses were examined; the law costs on both sides amounting, it is supposed, to at least 40,000L. The result was, that the novelty and merit of Mr. Neilson’s invention were finally established, and he was secured in the enjoyment of the patent right.

We are gratified to add, that, though Mr. Neilson had to part with two-thirds of the profits of the invention to secure the capital and influence necessary to bring it into general use, he realized sufficient to enable him to enjoy the evening of his life in peace and comfort. He retired from active business to an estate which he purchased in 1851 in the Stewartry of Kirkcudbright, where he is found ready to lend a hand in every good work–whether in agricultural improvement, railway extension, or the moral and social good of those about him. Mindful of the success of his Workmen’s Institution at the Glasgow Gas-Works, he has, almost at his own door, erected a similar Institution for the use of the parish in which his property is situated, the beneficial effects of which have been very marked in the district. We may add that Mr. Neilson’s merits have been recognised by many eminent bodies–by the Institution of Civil Engineers, the Chemical Society, and others–the last honour conferred on him being his election as a Member of the Royal Society in 1846.

The invention of the hot blast, in conjunction with the discovery of the Black Band ironstone, has had an extra ordinary effect upon the development of the iron-manufacture of Scotland. The coals of that country are generally unfit for coking, and lose as much as 55 per cent. in the process. But by using the hot blast, the coal could be sent to the blast-furnace in its raw state, by which a large saving of fuel was effected.* [footnote… Mr. Mushet says, “The greatest produce in iron per furnace with the Black Band and cold blast never exceeded 60 tons a-week. The produce per furnace now averages 90 tons a-week. Ten tons of this I attribute to the use of raw pit-coal, and the other twenty tons to the use of hot blast.” [Papers on Iron and Steel, 127.] The produce per furnace is now 200 tons a-week and upwards. The hot blast process was afterwards applied to the making of iron with the anthracite or stone coal of Wales; for which a patent was taken out by George Crane in 1836. Before the hot blast was introduced, anthracite coal would not act as fuel in the blast-furnace. When put in, it merely had the effect of putting the fire out. With the aid of the hot blast, however, it now proves to be a most valuable fuel in smelting.]

Even coals of an inferior quality were by its means made available for the manufacture of iron. But one of the peculiar qualities of the Black Band ironstone is that in many cases it contains sufficient coaly matter for purposes of calcination, without any admixture of coal whatever. Before its discovery, all the iron manufactured in Scotland was made from clay-band; but the use of the latter has in a great measure been discontinued wherever a sufficient supply of Black Band can be obtained. And it is found to exist very extensively in most of the midland Scotch counties,–the coal and iron measures stretching in a broad belt from the Firth of Forth to the Irish Channel at the Firth of Clyde. At the time when the hot blast was invented, the fortunes of many of the older works were at a low ebb, and several of them had been discontinued; but they were speedily brought to life again wherever Black Band could be found. In 1829, the year after Neilson’s patent was taken out, the total make of Scotland was 29,000 tons. As fresh discoveries of the mineral were made, in Ayrshire and Lanarkshire, new works were erected, until, in 1845, we find the production of Scotch pig-iron had increased to 475,000 tons. It has since increased to upwards of a million of tons, nineteen-twentieths of which are made from Black Band ironstone.* [footnote… It is stated in the North British Review for Nov. 1845, that “As in Scotland every furnace–with the exception of one at Carron–now uses the hot blast the saving on our present produce of 400,000 tons of pig-iron is 2,000,000 tons of coals, 200,000 tons of limestone, and #650,000 sterling per annum.” But as the Scotch produce is now above a million tons of pig-iron a year, the above figures will have to be multiplied by 2 1/2 to give the present annual savings.]

Employment has thus been given to vast numbers of our industrial population, and the wealth and resources of the Scotch iron districts have been increased to an extraordinary extent. During the last year there were 125 furnaces in blast throughout Scotland, each employing about 400 men in making an average of 200 tons a week; and the money distributed amongst the workmen may readily be computed from the fact that, under the most favourable circumstances, the cost of making iron in wages alone amounts to 36s. a-ton.* [footnote… Papers read by Mr. Ralph Moore, Mining Engineer, Glasgow, before the Royal Scottish Society of Arts, Edin. 1861, pp. 13, 14.]

An immense additional value was given to all land in which the Black Band was found. Mr. Mushet mentions that in 1839 the proprietor of the Airdrie estate derived a royalty of 16,500L. from the mineral, which had not before its discovery yielded him one farthing. At the same time, many fortunes have been made by pushing and energetic men who have of late years entered upon this new branch of industry. Amongst these may be mentioned the Bairds of Gartsherrie, who vie with the Guests and Crawshays of South Wales, and have advanced themselves in the course of a very few years from the station of small farmers to that of great capitalists owning estates in many counties, holding the highest character commercial men, and ranking among the largest employers of labour in the kingdom.