James Watt

James Watt was born in 1736 in Greenock, Scotland. James was a thin, weakly child who suffered from migraines and toothaches. He enjoyed mathematics in grammar school, and also learned carpentry from his father. His father was a carpenter by training, and built anything from furniture to ships, but primarily worked in shipbuilding. Watt learned about the navigational aids on ships: quadrants, compasses, telescopes. By his midteens he knew he wanted to become an instrument maker. Watt's father had just lost a substantial investment due to a shipwreck, and he could see the benefits of another occupation, so was supportive of Watt's ambitions. Unfortunately, there were no opportunities for instrument training in Greenock.

In 1754 Watt went to Glasgow, Scotland and became acquainted with Robert Dick through a relative who worked at the University of Glasgow. Robert Dick, a University scientist, was impressed with Watt's basic skills at instrument making, but recognized the need for special training. Dick encouraged Watt to go to London for training. Watt spent two weeks in London looking for an apprenticeship opportunity. However the instrument makers protected their trade by rules of a body known as the Worshipful Company of Clock-makers. The only employment was for fully-trained instrument makers or trainees serving seven-year apprenticeships!

John Morgan, an instrument maker in the heart of London, did not always follow the rules, and agreed to take Watt as an apprentice on the conditions of little pay! Morgan recognized the capabilities of Watt, and agreed to shorten the apprenticeship to a period of one year. Watt took the offer in 1755. Within two months, Watt's abilities surpassed those of Morgan's official apprentice, who had been there two years. Watt was eager to cram several years of training into one, and worked 10 hour days in the cold workshop. After hours, he worked for a small amount of cash, and his father sent him a little, but he maintained long hours on little food, and his health declined. During this time, Britain was at war with France, and the military would force into service any able-bodied man. Watt avoided the streets for this reason, which may have affected his health further. Watt finished his apprenticeship year successfully, but his health collapsed almost immediately afterwards.

Watt returned to Glasgow in 1756, now a trained instrument maker. His University of Glasgow acquaintances learned of his return, and gave him some work. Watt set up his shop, but found that other instrument makers shunned his credentials and training. He was an outsider in Glasgow, after being trained in London. The University professors recognized his abilities, and did not need to abide by the traditions of the instrument makers. They arranged for permission to set up a shop for Watt on University grounds and created the position "Mathematical Instrument Maker to the University".

Even with the new position, Watt still had trouble finding enough work since the other instrument makers were somewhat hostile. He started making musical instruments to avoid competition. His musical instruments were improvements over existing models and business began to grow. In 1758, an architect gave him backing to open a new shop in the heart of Glasgow. His business and reputation grew steadily and by 1763 he had apprentices of his own, but he was not out of debt.

The job that make revolution

Watt always had work from the University scientists, so he maintained through the years his shop on the University property. Professor John Anderson was the older brother of a grammar school companion, Andrew. One day in 1763, Professor John Anderson brought Watt a new problem. The University had a lab-scale model of the Newcomen pump to investigate why the full-scale pumps required so much steam. The model suffered a problem. It would stall after a few strokes. Watt recognized that the flaw was due to an undersized boiler that couldn't provide enough steam to reheat the cylinder after a few strokes.

During troubleshooting of the lab-scale model, Watt discovered the main reason the full-sized engines consumed such vast quantities of steam. However, implementation of the solution did not come easily. The Newcomen pumps required such vast quantities of steam since they were cooled during every stroke, then reheated. Watt needed a way to condense the steam without cooling the cylinder. Watt turned over the problem in his head for months and performed many experiments. He learned much about steam properties, and independently discovered latent heat of vaporization in his experiments. He also tabulated the vapor pressure of water at various temperatures before the work of Clapeyron. One of his University friends was Professor Black, who had discovered latent heat previously and had been lecturing on it without Watt's knowledge. They shared many interesting conversations after Watt told Professor Black of his "discovery". The concept for the breakthrough to improve the Newcomen engine came in May of 1765, over two years after Watt began to study the engine. Watt later described the moment of inspiration:

"I had gone to take a walk on a fine Sabbath afternoon, early in 1765. I had entered the green by the gate at the foot of Charlotte Street and had passed the old washing-house. I was thinking upon the engine at the time, and had gone as far as the herd's house, when the idea came into my mind that as steam was an elastic body it would rush into a vacuum, and if a communication were made between the cylinder and an exhausted vessel it would rush into it, and might be there condensed without cooling the cylinder. I then saw that I must get rid of the condensed steam and injection-water if I used a jet as in Newcomen's engine. Two ways of doing this occurred to me. First, the water might be run off by a descending pipe, if an offlet could be got at the depth of thirty-five or thirty-six feet, and any air might be extracted by a small pump. The second was to make the pump large enough to extract both water and air. . . . I had not walked farther than the golf-house when the whole thing was arranged in my mind."

With a separate condenser, the condensation process could take place constantly and the steam cylinder could be pulled to a vacuum while remaining hot. The vapor would rush into the condenser.

Watt would not work on the Sunday, as was the custom of the day. He controlled his impatience, but first thing Monday morning he was in his shop. He crafted a makeshift piston and condenser using a brass syringe. He filled the syringe with steam. He pumped the air out of his makeshift condenser, and cooled it. It worked!

Watt was 29 in 1765 when he discovered his idea would work. Yet it would be 11 years before he saw his invention in practice! He was modest, goodhearted, and shy. He once wrote to his business partner, Boulton, many years later, "I would rather face a loaded cannon than settle a disputed account or make a bargain." He also understood the significance of his development. "I can think of nothing but this engine", he said.

The waiting

Watt's University friends introduced him to John Roebuck, a industrialist who held leases on coal deposits. Roebuck agreed to back the development of a full-scale engine after he saw the model work. Watt devoted much time to troubleshooting and developing a full-scale model. Roebuck did not employ machinists with the experience that Watt's project required. Watt himself was a first rate instrument maker, but he was ill-suited to manage the work crew to operate the pump. Over the next four years, Watt was consumed with making an engine work. The experiments were slow and costly. The greatest difficulty was maintaining the seal on the large piston. In the Newcomen engine, the piston and cylinder were made up cast iron, and the fit was of very poor quality. However, since the entire cylinder was to be cooled, the piston was sealed by maintaining water on top of the piston in the open cylinder. Any leakage in the Newcomen engine simply sucked some water into the cylinder without defeating the driving force for the movement. Such a solution was unacceptable with Watt's design where the piston was to be maintained hot.

Although a full-scale working engine was constructed at Roebuck's coal mine, the effort was taxing on energy as well as finances. Andrew Carnegie writes in his biography of Watt:

The monster new engine, upon which so much depended, was ready for trial at last in September, 1769. About six months had been spent in its construction. Its success was indifferent. Watt had declared it to be a "clumsy job." The new pipe-condenser did not work well, the cylinder was almost useless, having been badly cast, and the old difficulty in keeping the piston-packing tight remained. Many things were tried for packing-cork, oiled rags, old hats (felt probably), paper, horse dung, etc., etc. Still the steam escaped, even after a thorough overhauling. The second experiment also failed. So great is the gap between the small toy model and the practical work-performing giant, a rock upon which many sanguine theoretical inventors have been wrecked! Had Watt been one of that class, he could never have succeeded. Here we have another proof of the soundness of the contention that Watt, the mechanic, was almost as important as Watt the inventor. (Carnegie, Andrew James Watt, New York: Doubleday, Page & Company, May, 1905.)

Roebuck was supportive of Watt and encouraged him to keep working on the pump. Watt was able to get a large engine to work well enough to apply for a patent, and Roebuck financed the engine patent that was granted in 1769. In exchange, Roebuck agreed to pay off all of Watt debts for his instrument shops but would take two-thirds of the money the invention made. Watt found this agreement acceptable because the large experiments were slow and costly. The invention was far from being ready for production. Then, Roebuck did another thing that helped Watt. He indirectly introduced Watt to Matthew Boulton of Birmingham, England. This last introduction was the one that helped the invention create the steam engine revolution -- but the revolution didn't come easily or fast!

Boulton recognized that the engine had potential applications for much more than pumping water! Boulton was an industrialist with an extraordinary vision to have all craftsmen work in a common building -- a "manufactory" (later shorted to "factory"). Previously, craftsmen had all maintained individual shops. Further, Boulton had the desire to furnish the manufactory with the best equipment and finest craftsmen. Boulton was certain that he could sell the engine.

Unfortunately, Boulton could not work out a deal with Roebuck who had majority control of the patent. Disheartened and in need of cash himself, Watt left the instrument making business in 1771, and took up surveying. In March 1773, Roebuck was in desperate need of cash. Boulton acquired Roebuck's rights to the engine in 1773, four years after the engine was patented, and nine years after Watt first discovered the separate condenser. Boulton was convinced the problems could be solved.

A Perfect Partnership

Boulton and Watt's personalities complemented each other and they got along well. Boulton's assembly of accomplished craftsmen provided the much-needed expertise that Watt had lacked in his collaboration with Roebuck. As soon as Watt finished his obligations for surveying, he moved to Birmingham to join Boulton's shop. Watt maintained work on the engine as well as other tasks. In November, 1774 he wrote to his father,

"The business I am here about has turned out rather successful; that is to say, the fire engine I have invented is now going, and answers much better than any other that has yet been made."

His letter was a modest statement of his true enthusiasm, for his concepts were developing into a fantastic engine. Boulton's desire to hire the best craftsmen had enabled the success.

Success at Last

In March 1776 the Bentley Mining Company started their newest piece of equipment, a Boulton-Watt engine. The Bentley Mining Company had taken a substantial risk by abandoning a half-built Newcomen engine and replacing it with the Boulton-Watt engine. The day the engine started a newspaper reporter was present:

"From the first Moment of its setting to Work, it made about 14 to 15 Strokes per Minute, and emptied the Engine Pit (which is about 90 Feet deep and stood 57 Feet high in Water) in less than an hour". From "Aris's Birmingham Gazette, March 11, 1776.

(Technical note: water can be drawn by suction less than 33 feet, so the pumps were placed within that distance of the bottom.)

This Bentley Mining Company engine used a cylinder crafted by the best ironmaster in Britain, John Wilkinson, who had recently developed a technique for boring cylinders (cannons) and had adopted the technique to the steam cylinder of the Boulton-Watt engine. The valves, piping, and fittings were manufactured at the Soho Manufactory - a factory 2 miles from Birmingham partnered by Boulton and Watt. The new engine used 1/4 of the steam that the Newcomen engines had required! 

The new Boulton-Watt engine was a great success. Watt became very busy maintaining business at Cornwall mines and setting up new pumps for the mines in the Cornwall region. 

More than Pumps

Boulton recognized the potential of the device for doing much more than pumping water. He also recognized the limited market for the device to drive pumps. In June 1781 he wrote to Watt:

"The people in London, Manchester and Birmingham are steam mill mad. I don't mean to hurry you, but I think in the course of a month or two, we should determine to take out a patent for certain methods of producing rotative motion…There is no other Cornwall to be found, and the most likely line for the consumption of our engines is the application of them to mills which is certainly an extensive field" (Sproule, Ann James Watt, Exley Publications, Herts, UK, 1992)

Watt answered this call, too. At age 45, Watt developed his next great invention -- a method to convert reciprocating motion of the piston to rotating motion. The invention was the sun and planet gear system. This invention was better than a crankshaft which was already patented (an idea Watt said was stolen from him). The sun and planet gear system permitted the rotative wheel to turn more than once per stroke of the piston! Since the piston moved slowly, this was an major improvement! An engine patented in 1782 by Boulton and Watt had another major improvement -- the steam cylinder used valves above and below the piston to connect independently to the boiler or the condenser; the piston performed work on both the upward and downward stroke! This evened out the stroking of the piston, performing equal work on each movement. Watt had another great improvement on this engine. He had devised a mechanism to match the rocking motion of the beam (which traces an arc) with the linear motion of the piston. This was known as the "parallel motion" device, and was necessary to enable the piston to push the beam on the upward stroke; the chains used in the previous single-acting engines didn't transfer work on the upward stroke. He once told his son that this was the invention of which he was most proud.

In 1782 a sawmill ordered an engine that was to replace 12 horses. Watt used data from a sawmill to determine that a horse could lift 33,000 pounds the distance of one foot in one minute -- and thus developed the units of hp.

Other major contributions developed by Watt include the steam throttling valve and the mechanism to connect the throttle to the engine governor. Used together, these devices regulated steam flow into the piston and kept a constant engine speed.

By 1800, 84 British cotton mills used Boulton and Watt engines. So did wool mills and flour mills! In his later years, Watt enjoyed the success and fame he deserved.

Today, it is appropriate to recognize Watt's contributions when we used the British (and American Engineering) units for power, hp, and the SI units for power, the Watt.

Author's note: I have found minor variations in the wording of quotes attributed to Watt by the various biographers, but for all the citations given here, the meaning is identical. The wording given here was provided by one of the biographers.