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The patient experiments and inspired research work of James Watt have won him a unique position among engineers. His inventions were responsible for the discovery of a new world of engineering, and his fortunate partnership with the enterprising Matthew Boulton brought him success in his own lifetime



INTERIOR OF THE WORKSHOP in which James Watt, in his later years, worked at Heathfield, near Birmingham. With the expansion of that city, the site was required for other purposes, and the contents of the workshop were removed and installed, exactly as left by him, in a replica of the room at the Science Museum, South Kensington.

OF the two men who tower above all others as makers of engineering history, namely, Sir Charles Algernon Parsons and James Watt, the former lived in our own times and his record is therefore amply documented. James Watt, on the contrary, lived in what may be considered pre-newspaper days and therefore, until comparatively recently, his contributions to engineering were undervalued in some ways and exaggerated in others. The story that he invented the steam engine by watching the effect of steam in raising the lid of his mother’s kettle is, for instance, pure romance. The steam engine had been in existence in several forms long before Watt took up the study of it. On the other hand, the full extent of his genius has become apparent only from the painstaking investigations of present-day historians.

James Watt, born at Greenock, Renfrewshire, on January 19, 1736, seems to have been anything but a strong boy, but he was fortunate in having a careful, affectionate mother and a father whose abilities had raised him to responsible positions in the municipal government. Watt senior, though nominally a carpenter, built ships and erected houses, traded as a ship-chandler, repaired such apparatus as ships’ pumps and, in general, appears to have been a sort of “handy man”. The boy James, though distinguished in his school days neither at lessons nor at games, grew up in an environment in which he could make models of various sorts, and he was able to acquire a useful knowledge of the properties of materials.

Having left school, he apparently passed most of his time in his father’s workshop, not as an apprentice, but-engaged in his own hobbies and occasionally doing such work as was within his capacity. No doubt his mother tended to spoil her delicate son, but she died when he was seventeen. This may have led him to make up his mind as to his future career.

At all events we find Watt, in June 1754, setting out for Glasgow, then only a small University town, with the intention of learning to be a mathematical instrument maker. There soon proved to be no opportunities of the kind in Glasgow, but young Watt was advised that in London there was a decidedly better chance. And so, just a year after having left Greenock for the first time, he set out on horseback, with a companion, and arrived at the metropolis twelve days later.

At first London received Watt coldly. No one wanted a youth who was too old to serve a proper apprenticeship and who had had no regular instruction. Eventually, however, for the sum of twenty guineas and free service for a year, he was allowed to work in the shops of one John Morgan, near Cornhill. Living on eight shillings a week, Watt made surprising progress, perhaps because he had little time for anything but work. His working day ended at nine o’clock every night but Saturday. It is no wonder that his health was affected, particularly as he scarcely dared to leave the shop for fear of being kidnapped for shipment to the “plantations”, or of being captured by the pressgang. As an unlicensed workman, that is, neither a regular apprentice nor a freeman, Watt could not count on the City authorities for protection. The year ended, Watt, having become a first-rate workman, though he was not yet 21, set off for home with a store of materials and tools.

Arrived in the North, he eventually found his way again to Glasgow, where his friendly adviser, Professor Dick, gave him the job of reconditioning some astronomical instruments which had been presented to the University. Later, in 1757, Watt was allowed to set up a shop in the precincts and to style himself “Mathematical Instrument Maker to the University”. Watt opened a second shop in the city itself in 1759.

The shop in the University was kept up, but Watt took a partner for the other shop, which was in the principal street of the city. There lie sold, according to his newspaper advertisement, “all sorts of mathematical and musical instruments”.

Invention of the Condenser

WATT married in 1764, and set up house near a pottery works in which he was interested, in what is now known as James Watt Street. What concerns us here is, however, not the struggle of the young married man to keep up an establishment, but the way in which he became involved, to the nation’s advantage, in the manufacture of the steam engine.

The Natural Philosophy Class of the University, that is, the class for the study of what we should now call Physics, had, among its apparatus for demonstration, a working model of the Newcomen engine, a type of engine which was to be found in many places all over the country, pumping in mines and so forth. It was inefficient, it is true, but much better than the horse-driven pumps it had displaced. The model needed some repairs and was sent to London for the purpose - to be returned in little better condition. Professor John Anderson then turned to Watt for help. This was in the session 1763-64, and Watt gladly set to work, as he had been making some purposeless experiments with steam a year or two before. As Watt himself tells us, he “set about repairing the model as a mere mechanician”, but he could not finish the job in the same spirit. His intensely active mind led him to investigate the principles underlying the working of the engine.

The Newcomen engine is described on page 587. The model, though correct in principle, was wrong in its proportions. The boiler, for one thing, was too small. Watt made numerous experiments, in which he unwittingly confirmed the famous discovery of latent heat by Professor Joseph Black. The term “latent”, meaning “hidden”, embodies the fact that substances capable of changing their physical state absorb or give out a large quantity of heat in the change without showing any difference in temperature as measured by the thermometer. Water at normal boiling point, that is, at a temperature of 212° F., will change into steam at that temperature, but not unless it has been supplied with 996 heat units per lb, a heat unit, in British practice, being the amount required to raise one pound of water one degree Fahrenheit in temperature.

James WattThe essential feature of the working of the Newcomen engine was first to fill the cylinder under the piston with steam and then to condense that steam so that a vacuum was created under the piston. The weight of the air above the piston, not being opposed by any pressure, forced the piston down and raised the pump piston attached to the other end of the beam. But for the steam to be condensed it had to give up all its latent heat and the cylinder had to be cooled sufficiently to absorb that heat, a jet of cold water being used to effect the cooling. On the other hand, to fill the cylinder with steam, the cylinder walls had to be as hot as the entering steam, or condensation would take place too soon. It was this premature condensation that was the great defect of the Newcomen engine, an enormous quantity of steam, and therefore of coal, being wasted at each stroke in merely warming up the cylinder, which was as regularly cooled down again when the cold water was injected.

BORN ON JANUARY 19, 1736, at Greenock, Renfrewshire, James Watt spent much of his early years in his father’s workshop. In 1757 Watt became “Mathematical Instrument Maker to the University” in Glasgow. In partnership with Matthew Boulton, Watt spent an active and successful life. He died in 1819. in his eighty-fourth year.

The real problem, as it appeared to Watt, was to keep the cylinder always as hot as the steam. He pondered long over some means of attaining this end, but, seeing that condensation was always, and apparently could only be, effected by cooling the cylinder, it seemed as if the problem was not capable of any practical solution. Yet the solution came to him suddenly during a quiet Sunday afternoon stroll.

This solution was the use of a separate condenser which could be kept cool while the cylinder could remain hot. It seems simple enough to us now, but the invention of the separate condenser was an event of the greatest importance then. It turned the crude atmospheric engine of Newcomen into the real steam engine for which the industrial world was unknowingly waiting. The Newcomen engine was by that time well known. It was at work in more than one country. Smeaton and others had improved it and printed accounts of it were available. Yet no one had had the wit to see how its defects could be eliminated until the reasoned experiments of the genius Watt had shown the way.

Influential Friends

ON the Monday following the discovery a crude model of a condensing engine was made. This, it is believed, is the one now at the Science Museum, South Kensington. The way was not yet open, however, for the development of the engine in the manufact-uring sense, for Watt had had no experience whatever in this kind of construction and, moreover, he knew no one who had. Added to this, he had his family to provide for and had to find remunerative employment.

To condense into a sentence Watt’s means of livelihood from 1766 to 1774 is to say that as a surveyor he was engaged on a number of canal schemes in Scotland, ranging from Ayrshire to Inverness. This part of his life, though it might have led Watt to graduate into a distinguished civil engineer, has little reference to his contributions to mechanical engineering.

Experimental and even some constructional work was, however, being carried out at irregular intervals during the surveyorship period. About 1766, the Watt engine had been improved by the covering in of the cylinder top, the use of boiler steam instead of the atmosphere to press down the piston having been decided upon. This kept the cylinder hotter, but the piston rod had to be provided with a stuffing box where it passed through the cover. An air pump to remove air and water from the condenser had also been adopted.

The main lines of the Watt engine had thus been settled. It incorporated the beam of the Newcomen engine, though Watt had also designed a rotary engine without a beam. Such experimental parts as he had had made for the beam engine suffered from the inferior workmanship and defective materials of the period, and Watt was scarcely the man to take such discouragements in his stride. He was easily depressed, and despondent passages are frequent in his letters.

SINGLE-ACTING PUMPING ENGINE used for draining mines in CornwallIt was thus fortunate for Watt that certain of his friends realized the importance of his work and were at hand to encourage him in it. First of these friends was Dr. Black, who lent him money for experimental work and introduced him to an industrial magnate of Birmingham, Dr. John Roebuck. Through him Watt got to know two other leading Birmingham men, Dr. William Small and Matthew Boulton. Boulton was destined to have a profound influence on Watt’s career. Watt himself said “without him the invention could never have been carried by me to the length it has been.” While Watt was gaining a livelihood from civil engineering practice, therefore, the steam engine still occupied a large part of his thoughts and he continued to make experiments on fresh lines. The results he communicated to Dr. Roebuck, who, having realized that the improvements were practical and valuable, offered to finance Watt in return for an interest in the invention. This involved him in the payment of Watt’s debt to Dr. Black, a sum of nearly £1,000, and in the cost of taking out a patent, in those days about £120. A decisive step was taken when Dr. Roebuck, in July 1768. sent Watt to London in connexion with the latter business, the patent being sealed on January 5, 1769.

SINGLE-ACTING PUMPING ENGINE used for draining mines in Cornwall. This drawing shows the arrangement supplied by Boulton and Watt in 1788. The high economy of this type of engine is due to the fact that the piston and cylinder are never exposed to the low temperature of steam discharging into the condenser. The closed-top cylinder was first used in practice by Watt in 1774.

Watt, on his return journey, met Matthew Boulton at his factory at Soho, then outside Birmingham, now a part of that city. At the factory, undoubtedly one of the finest of its day, were manufactured such articles as metal buttons, sword hilts and steel buckles, and its power was derived from a waterwheel supplied by a somewhat unreliable stream Boulton had been considering using steam as an indirect motive power, that is, the use of a steam-driven pump to circulate water over the wheel in times of drought. He was keenly interested in the Watt engine, so keenly that he wanted to manufacture it at Soho.

Watt accordingly endeavoured to get Boulton admitted to the partnership between himself and Dr. Roebuck, but, when the doctor offered Boulton only a licence to manufacture for three counties, Boulton replied (February 1769) “It would not be worth my while to make for three counties only, but I find it very well worth while to make for all the world.” Truly the reply of a man of wide vision.

However, the years slipped by and nothing of moment was done to exploit the patent beyond the building of an engine for Dr. Roebuck, which gave constant trouble from defects in material and workmanship. Then dawned 1773, a fateful year for Watt, for in that year his wife died and Dr. Roebuck became bankrupt. Shortly afterwards Watt writes despondently to a friend, “I am heartsick of this cursed country.”

Trouble with Mine-Owners

IN such depressing circumstances a major change would not seem formidable and Watt finally decided to throw in his lot with Boulton, settling in Birmingham in the early summer of 1774, a widower of 39 years; with two children, and handicapped by ill-health. The way was paved by Boulton discharging Watt’s obligations to Dr. Roebuck, the trustees for whose estate, in return,

being willing to convey the patent which they did not “value at a farthing”.

The patent, however, secured in 1769, had only a further eight years to run, a state of affairs which did not suit the business-like Boulton, who, after a protracted struggle, managed to get it extended for a period of twenty-five years dating from May 22, 1775. The prospects of a successful career were now open to the two partners, the energetic courageous Boulton and the unenterprising diffident Watt. The first real start was made with a blowing engine having a cylinder of 38-in diameter and with a pumping engine having a cylinder of 50-in diameter. This was a big advance on the 18-in cylinder of Roebuck’s engine. Both engines were erected in 1776 and in that year Watt married a second time.

It was some years after this, however, before Boulton realized his ambition of manufacturing the engines, for the main castings and forgings had to be made by other firms and only some comparatively small parts were produced at Soho. There was no erection before delivery, as is the usual modern practice, the parts being assembled for the first time on the final site of the engine. This meant, until a staff of reliable men had been gathered together, constant attention on the part of the principals. Both Boulton and Watt were, in the early years, frequently in Cornwall, in which county there was a big demand for the new engine, largely because of its great economy of fuel compared with the old atmospheric engines then in use for pumping.

ROTATIVE BEAM ENGINE, built in 1797 by Boulton and WattIn spite of this personal attention, all was not smooth sailing. The mine owners alleged that the charges for the use of the new engines were too high. These were, however, based fairly on a calculation of the amount of coal saved, a matter with which the owners themselves should have been conversant. In an endeavour to get things on a more amicable basis, Watt invented the counter, a device for automatically counting the number of strokes made by an engine. The owners, however, maintained that as short strokes were registered as well as long ones they were penalized again and so the troubles continued. Added to them was the opposition from other engineers, which was attended in later years by competition and by a crop of lawsuits over patent infringement.

ROTATIVE BEAM ENGINE, built in 1797 by Boulton and Watt for a chemical works in London. The engine was working until 1885, when it was presented to the Science Museum. It is a low-pressure condensing engine with the sun and planet gear invented by Murdock. The cylinder diameter is 19¼-in and the nominal horse-power 12.

Altogether the business had not, according to Watt, paid its way up to the year 1780, though all the financial worry and burden was born by Boulton. But things began to brighten. William Murdock, engaged in 1777 (see page 428), proved a great help and in 1782 Watt was relieved of the major part of his drawing office work by the engagement of his first draughtsman, John Southern, a man of great talent who eventually became a partner in the firm.

In 1781 Boulton urged Watt to devise some means of adapting the steam engine to produce rotative motion. “There is no other Cornwall to be found,” he says. The allusion means that engines were used in Cornwall for pumping in mines, and that the demand for such engines was limited.

The pumping engine of the time was single-acting, that is, the steam acted on the downstroke of the piston, which was attached to one end of the beam by a chain passing over a quadrant on it at that end. The upstroke of the piston was an idle one, the beam being pulled down by the weight of the pump gear attached by quadrant and chain at its other end. To convert the reciprocating motion of the piston atone end of the oscillating beam to give a rotative action at the other end two major alterations to the pumping engine were necessary. The first of these was that the chain gear at the ends of the beam, which would transmit only a pull, should be replaced by a connexion which would allow alternate pushing and pulling.

World-Famous Designs

AS the ends of the beam did not move in a straight line but in an arc of a circle, it was clearly impossible to couple the piston rod to the beam directly. Watt accordingly devised his parallel motion, a highly ingenious mechanism enabling the piston to exert force in a straight line upwards and downwards while still using a beam. The second change was much more troublesome. To every one to-day it seems clear that all that is needed is a connecting rod coupling the beam to a crank, but to Watt, genius as he was, this simple gear did not seem practicable.

Watt spent a great deal of time and energy on scheming out other methods of connexion, all ingenious but all complicated. The result was that another engineer, adopting the crank as a sort of forlorn hope, found that it worked perfectly well and patented the arrangement. The patent blocked the way for Watt and forced him to adopt a clever invention of Murdock’s - the sun and planet motion.

MODEL OF A DOUBLE-ACTING PUMPING ENGINE built for a mine in CornwallThe creation of the rotative engine gave Watt scope for invention in other directions. The engine was double-acting, but it was not necessary to admit steam to the cylinder for the whole of each stroke. The valve gear was therefore redesigned so that the steam supply could be cut off at any point of the stroke, the steam being then allowed to expand during the remainder of the stroke. This expansive working, due to Watt, is used on all reciprocating steam engines to-day and is an economical method of working. The centrifugal governor, too, was invented for the rotative engine and was first fitted to the engine, which was used for driving certain of the machines at Soho. Another development arising from the rotative engine was Watt’s creation of that universally used unit, the horsepower. Still another was the indicator, also still in use though modified in detail; this is an instrument which draws a picture of the pressure changes taking place in the cylinder. In 1795 Boulton’s dream was realized. A proper engine factory and foundry were established at Smethwick, about a mile away from Soho, and from it for many years went engines which made the name of Boulton, Watt & Company famous throughout the world. The original partnership, which expired in 1800, had been extended to admit, among others, James Watt, Junior, and Matthew Boulton, Junior, and it was in the hands of these young men that the flourishing business was left when Watt, at the age of 64, and Boulton, then aged 72, retired.

Boulton died at the age of 81, in 1809, but Watt survived till 1819, when he had reached his eighty-fourth year. Both are buried at Handsworth Parish Church, Birmingham.

MODEL OF A DOUBLE-ACTING PUMPING ENGINE built for a mine in Cornwall. It was for Cornish mines that Boulton and Watt first built steam engines. This engine is fitted with the famous parallel motion.

[From part 43, published 21 December 1937]

You can read more on “John Smeaton”, “Origin of the Steam Engine” and “William Murdock” on this website.

James Watt, 1736-1819