Watt, James (1736–1819)

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WATT, JAMES (1736–1819)

Born fourth of five children to a merchant family in coastal Greenock, Scotland, on January 19, 1736, Watt was an ingenious modelmaker as a youth, being exposed to all the ship chandler's tackle and instruments, and was fascinated with natural philosopy, as science was called. His grandfather Watt was a very successful professor of mathematics in this remote locale. His mother's death when he was seventeen set his determination to pursue instrument making.

After nine years of some difficulty but considerable learning opportunity in London and at the University of Glasgow, while he was repairing a poorly built Newcomen engine for the university, he had the flash of inventive intuition that a separate condenser would greatly improve its efficiency. For this patented improvement, and its eventual technical and economic success, he is popularly credited with the invention of the steam engine. In 1765, while at the University of Glasgow, he married his cousin Margaret Miller.

At the age of thirty-three, Watt wrote, "Of all things in life, there is nothing more foolish than inventing." Just widowed with six children, he had put away his love of science, engineering and fine technical instrumentation to feed his family by contracting to survey for the Caledonian canal. Bankruptcy of his financial partner in steam development, John Roebuck, had derailed his efforts to improve the steam engine.

For some years previous, the successful Birmingham manufacturer Matthew Boulton had enjoyed an increasing correspondence in natural philosophy with such notables as Benjamin Franklin, Erasmus Darwin and Watt's partner, Roebuck, regarding practical uses of fuel and steam. Boulton's discussions with Watt in 1768 led him to discontinue his own developments, since Watt was clearly ahead technically and had obtained basic patents. With the bankruptcy of Roebuck, Boulton bought out Roebuck's interest, and Boulton's investment continued to fund Watt's demonstrations and developments. By then however, Watt's patent had nearly expired. With the leverage of Boulton's contacts in London, a Bill of Parliament extended the patent 24 years until 1800. The success of Watt's engine applications in the next few years brought Boulton and Watt together as partners, Boulton having two-thirds interest and managing the business, and Watt having one-third interest and managing the engineering and erection of engines.

While traveling on business, Watt met a Miss MacGregor who was connected with the University of Glasgow, and they married in 1776. Their two children did not live into adulthood.

The business acumen of Boulton provided profound industrial leverage to the technical creativity of Watt. The success of the steam engine for the rest of the century was substantially controlled by this part- nership. The partners initially obtained annual royalties based on the horsepower of their engines, then set the royalty at one-third the cost of fuel saved by the use of their engines over the Newcomen engine.

The engines were initially used in pumping and winding in the mines, then were extended to iron- rolling, spinning and weaving mills, and virtually any factory use of rotative power.

Retiring from their business just as the patents began to expire in 1800, the firm of Boulton & Watt was turned over to the junior Boulton and Watt as its industrial preeminence slipped away and royalties dwindled. Watt's friends and family aged and passed, and he settled into twilight development of three- dimensional replicating equipment for sculpture. His workshop from his home at Heathfield Hall, near Birmingham, is preserved at the Science Museum in South Kensington. The most famous engineer of his time, Watt died at home on August 19, 1819 at 82, and was buried alongside his partner Boulton in his country churchyard. A monument was erected in his memory in Westminster Abbey. Contemporary eulogies and biographies show Watt as a fine person with a brilliant mind, little business sense, and a tendency toward melancholy. It is clear that he valued Boulton as a friend as much as a business partner.

James Watt recognized the steam engine to be a heat engine, not a pressure engine, demanding the conservation and complete use of heat energy. His long acquaintance with scientists at the University of Glasgow, and his study of new information on heat and energy, gave him the intellectual tools to make these great steps, which he backed up with technical analysis. While many of the principles in Watt's 1769 patent had been previously described academically or constructed in other mechanical examples, Watt combined these principles and patented them just at the time when they could be technically applied to advantage. Coincidently, the quality of heavy machine work necessary for their success was at last becoming practical on a commercial basis. Previously, fine machine work was confined to technical, medical and other instruments.

To paraphrase the claims of Watt's 1769 patent: Keep the engine cylinder hot; condense the steam separately and keep the condenser cold; air in the steam system is defective to performance and must be removed by pumping as necessary; use the expansive energy in high-pressure steam without using a condenser; re-use the steam by compressing and reheating to avoid loss of the latent heat of evaporation. Additional patent claims were the concept of a rotary expansive engine and using materials other than cold water to seal and lubricate the engine to avoid loss of heat energy.

To more fully exploit the key patent claim for the separate condenser, the firm avoided the use of high- pressure steam since it did not absolutely require a condenser. The patent claim for expansive use of steam without a condenser was used only as ammunition to restrict development in that field, although high-pressure steam replaced low-pressure steam during Watt's lifetime, and noncondensing systems became the norm for railway locomotives and steam road vehicles.

Many of Watt's further innovations for the steam engine added to its utility, remaining in use long after patent protection expired, while some were merely stopgaps to avoid using the patents of other inventors. These include the double-acting engine in which the piston is powered in both directions with the rod passing through a seal, a parallel motion using links to guide the piston rod through a relatively straight path (Watt linkage), and the sun-and-planet gear method of driving a rotary shaft from a connecting rod, avoiding another's patent for the crank.

Watt also applied the flyball governor to the steam engine and invented the steam engine indicator, which gives a graphical representation of cylinder pressure versus displacement. In other fields, Watt invented the copying press for hand-written letters, which was in universal use for over a century, and a cloth drying machine using copper cylinders internally heated by steam.

Karl A. Petersen

See also: Trevithick, Richard.


Dickinson, H. W. (1936). James Watt, Craftsman & Engineer. Cambridge: The University Press.

Robinson, E., and Musson, A. E. (1969). James Watt and the Steam Revolution: A Documentary History. London: Adams & Dart.

Thurston, R. H. (1878). A History of the Growth of the Steam-Engine. New York: D. Appleton and Company.

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