(b Greenock, Scotland, 19 January 1736; d Heathfield, England, 19 August 1819), engineering, chemistry.
Although Watt’s achievements as an inventor and an engineer have been fully recognized and universally honored, the dependence of his technical work on contemporary science and his own scientific research have long provoked sharp differences of opnion.
Watt’s grandfather and father had both followed technical pursuits: the former, Thomas, as a teacher of surveying and navigation (“professor of the mathematicks”) and the latter, James, as a shipwright and maker and supplier of nautical instruents. His mother, Agnes Muirhead (or Muireheid), was descended from a family that had at one time been prominent in Scottish life. Owing to his fragile health Watt’s attendance at elementary school was somewhat irregular, but he nonetheless attained some proficiency in geometry (in which he showed great interest), Latin, and Greek. Schooling, however, composed only the lesser part of his education; the more consequential portion he received in his father’s shop, where he first gained the knowledge and skills of contemporary craftsmanship-woodworking, metalworking, smithing, instrument making, and model making.
At the age of eighteen, having decided to follow the career of scientific instrument maker, Watt left Greenock and took up residence in nearby Glasgow, which was then becoming a center of commerce and industry. In 1775 he went to London, where he spent a year as an apprentice, rapidly mastering the arts and crafts that entered into the making of navigational and scientific instruments. He found London both disagreeable and a strain on his health, however, and a year later he returned to Scotland. Watt hoped to establish himself in Glasgow as an instrument maker, but he was prevented from doing so by guild restrictions. It was only through the influence of friends on the faculty of the University of Glasgow that he was able in 1757 to evade the jurisdiction of the corporations of tradesmen through an appointment as “mathematical instrument maker to the university.” Watt thus found the setting that fostered much of his technical and scientific work. He soon became acquainted with John Robison (who first directed his attention to the steam engine) and Joseph Black; and it was in 1765, during his association with the university, that he made his first and most important invention, the separate condenser for the Newcomen engine. He patented it in 1769 and developed it commercially, first in partnership with John Roebuck and later with Matthew Boulton.
This initial success was followed over the next quarter-century by a remarkable sequence of additional inventions related to the steam engine-the sun-and-planet gearing system to translate the engine’s reciprocating motion into rotary motion without employing the common crank (which was entangled in patent claims); the application to the steam engine of the double-acting principle that was then commonly used in pumps; the “expansive principle” whereby Watt recognized that because of its expansive power, steam need not be admitted into the cylinder during the entire stroke; the “parallel motion” with which he connected a rigid piston rod to the overhead beam without causing the rod to wobble;and the “indicator” for determining the pressure in the cylinder during the cycle. Besides these signal contributions to the technology of the atmospheric steam engine, Watt also originated a perspective drawing machine, a letter-copying process, an indicator liquid for testing acidity, and a steam wheel (which he was unable to perfect) for producing rotary motion directly from steam pressure.
In 1766 Watt closed his shop at the university and opened a land surveying and civil engineering office in Glasgow, where he practiced as a civil engineer until 1774. In the latter year he moved to Birmingham and formed the partnership with Boulton whereby he successfully commercialized his improved steam engine design. During the 1790’s he was heavily preoccupied with the litigation through which he preserved his separate condenser patent against a series of challenges. And in 1800 both Watt and Boulton retired, turning their business enterprises over to their sons.
Watt became a fellow of the Royal Society of Edinburgh and of London, and was member of the Lunar Society of Birmingham. He married Margaret Miller, a cousin, and after her death in 1773, Ann MacGregor, the daughter of a Glasgow merchant. Of the children born from these marriages only a son, James, outlived the father.
Watt’s career as a scientist centered on his interest in chemistry. He performed numerous experiments, was in contact with several of the foremost chemists of the day (including Black, Priestley, and Berthollet), and occasionally ventured into the realm of theory. In 1783 he formed the opinion that water is a compound; but his designation of its components was ambiguous, inasmuch as he described them as “dephlogisticated and inflammable air, or phlogiston,” where “phlogiston,” as he often used the term, signified various gases. During the nineteenth century a spirited debate arose among the partisans of Watt, Cavendish, and Lavoisier over credit for priority in the discovery of the “composition of water” J.R. Partington, the historian of chemistry after closely evaluating the conflicting claims has lent his authority to the view that while Watt is entitled to credit for first stating that water is not elementary, it was Lavoisier who clearly specified what its components are.
Watt also did experiments during the 1780’s that contributed to the commercial application in Britain of the process, which Berthollet had discovered, of bleaching textiles with chlorine. In this case Watt’s role as a chemist must be heavily qualified. Unlike Berthollet, whose chemical research was part of a program of theoretical inquiry and who promptly published his discoveries even when they had commercial possibilites, Watt was more akin to what would presently be designed to render the process effective and economical on a commercial scale. Moreover, Watt’s father–inlaw, James MacGregror, was in the bleaching businees; and Watt hoped that by keeping their improvements secret, they would realize substantial profits. He was openly disappointed that Berthollet was conducting his research “earnestly” and was making “his discoveries on it publick,” When Watt proposed to Berthollet that, with MacGregor, they brushed aside the proposal with the remark “Quand on aime les sciences on a peu besoin de fortune …” These distinctions between the motivations and purposes of the engineer and the scientist are of great interest in attempting to reach an understanding of the development of modern science.
Twenty years earlier, during the 1760’s Watt had played a similar role in an attempt to commercialize a process for producing alkali using common salt and lime as ingredients. The “theory,” according to Watt’s own testimony, was formulated by Black; Watt’s contribution consisted of experiments designed to find a commercially feasible procedure. Watt unquestionably displayed considerable knowledge of the chemistry of bleaching, dyeing, and alkali production: but in these fields his contrubutions were to industrial chemistry, not to chemical theory. They were the chemical equivalents of his mechanical inventions (which likewise followed systematic experiments).
In one additional area of his involvement with chemistry, a misunderstanding continues to confound our appreciation of Watt’s career as a scientist. Both Robison and Black advanced the claim that the invention of the separate condenser rested upon Watt’s understanding of Black’s principle of latent heat. Although Watt denied these assertions and presented a convincing description of the events that led to his invention,1 some writers have not only repeated the claim but have gone further and asserted that Watt discovered or “rediscovered” the principle itself2 In fact, however, Watt only noticed the phenomenon (the apparent loss of heat when water is boiled) that is accounted for by the principle of latent heat. Upon describing his observations to Black, he was told of the principle, which Black had been teaching at the University of Glasgow for serveral years. Watt’s own claim was only that he had “stumbled upon one of the material facts by which that beautiful theory is supported”
If we confine our meaning of science to its theoretical dimensions, we must conclude that Watt’s inventions were made for the most part independently of science. But there can be no question that, conversely theoretical science owes much to his inventions. The steam revolution that Watt’s work as an inventor promoted, focused the attention of mathematicians and natural philosophers on problems that prompted important research in the theory of heat and in kinematics. Indeed, his “expansive principle” was embodied in the adiabatic expansion phase of Sadi Carnot’s heat cycle.3 And the parallel motion that Watt substituted for the chain and arch head connection stimulated considerable research in pure kinematics.4
If, however, we take a wider view of science, we can find still more meaning in Watt’s career. For despite the contrast between his modest achievements as a scientist and his extraordinary originality and inventive power as an engineer, his career displays one of the key developments in the history of science — the entrance by engineers into the world of research. During the eighteenth century the traditional affiliation between engineering and craftsmanship was being revised in favor of a merger of engineering with experimental and theoretical science; and in Watt’s work in chemistry, in his associations with chemists and natural philosophers, in his employment at the University of Glasgow, and in his membership in the foremost British scientific societies we have one of the earliest and clearest traces of that emerging pattern.
1. For a defense of Watt’s position, see Donlad Fleming, “Latent Heat and the Invention of the Watt Engine,” in Isis, 43 (1952), 3 – 5.
2. A. E. Musson and Eric Robinson, Science and Technology in the Industrial Revolution (Manchester, 1969), 80. These authors generally claim more for the theoretical content of Watt’s work than the present article allows.
I. Original Works. Watt wrote much but published little. His only publication on his inventions is his ed. of John Robison’s Encyclopaedia Britannica articles on steam and steam engines: Tit(,Articles Steam and Steam–Engines, Written for the Encyclopaedia Britannica, by the Late John Rohinson, LLD., F.R.S.L. & E. (Edinburgh, 1818); this material is reproduced in vol. II of the posthumous collection of Robinson’s articles, A System of Mechanical Philosophy, David Brewster, ed., 4 vols. (Edinburgh, 1822). Two letters by Watt setting forth his views on the composition of water were published by the Royal Society: “Thoughts on the Constituent Parts of Water and of Dephlogisticated Air; With an Account of Some Experiments on that Subject. In a Letter From Mr. James Watt, Engineer, to Mr. De Luc, F.R.S.,” in Philosophical Transactions of the Royal Society, 74 (1784), 329 – 353; and “Sequel to the Thoughts on the constituent Parts of Water and Dephlogisticated Air: In a Subsequent Letter From Mr. James Watt, Engineer, to Mr. De Luc, F.R.S.,” ibid., 354 – 357. Watt’s biographer, James Patrick Muirhead, later reprinted these letter with additional material relevant to the composition-of-water controversy: Correspondence of the Late James Watt on His Discovery of the Theory of the Composition of Water, James Patrick Muirhead, ed. (London, 1846).
Watt’s interest in the application of pneumatic chemistry to medicine resulted in his collaboration with Thomas Beddoes on the following works: Considerations on the Medicinal Use of Factitious Airs, and on the Manner of Obtaining Them in Large Quantities (Bristol, 1794; 2nd ed., 1795; 3rd ed., 1796); and Medical Cases and Speculations; Including Parts IV and V of Considerations on the Medicinal Powers, and the Production of Factitious Airs (Bristol, 1796) — Watt’s contribution to the first of these was also printed separately as Description of a Pneumatic Apparatus. With Directions for Procuring the Factitious Airs (Birmingham, 1795). He also published a note on his test for acidity: “On a New Method of Preparing a Test Liquor to Shew the Presence of Acids and Alkalies in Chemical Mixtures,” in Philosophical Transactions of the Royal Society, 74 (1784), 419 – 422.
Some of Watt’s multitudinous letters and unpublished papers have been reprinted: vol. II of James Patrick Muirhead. The Origin and Progress of the Mechanical Inventions of James Watt, 3 vols. (London, 1854), contains a selection of Watt’s correspondence; and recently two systematic collections that include much previously unpublished material have appeared: Eric Robinson and A. E. Musson, James Watt and the Steam Revlution. A Documentary History (London, 1969); and Eric Robinson and Douglas McKie, eds., Partners in Science. Letters of James Watt and Joseph Black (London, 1970). Many of Watt’s letters and notes are preserved among the family papers at Doldowlod, Radnorshire.
II. Secondary Literature. Writings on Watt’s life and work are voluminous, almost all of them on his engineering rather than his science. For his personal life and especially his family background, see George Williamson, Memorials of the Lineage, Early Life, Education, and Development of the Genius of James Watt (Edinburgh, 1856). James Patrick Muirhead’s 3–vol. work (see above) is the standard nineteenth-century biography; besides the volume of correspondence (II), vol. I contains a narrative of Watt’s life and vol. III patent specifications and information. The narrative is recapitulated in Muirhead’s The Life of James Watt (London, 1858). Among the more recent biographical works the most valuable is H. W. Dickinson and Rhys Jenkins, James Watt and the Steam Engine. The Memorial Volume Prepared for the Committee of the Watt Centenary Commemoration at Birmingham 1919 (Oxford, 1927); this work contains a narrative biography, descriptions of many of Watt’s technical achievements, reproductions of some of his drawings, and an extensive annotated bibliography. The composition-of-water controversy is summarized and the various claims evaluated in J. R. Partington. A History of Chemistry. III (London, 1962), 344 – 362. Partington’s History is also useful in connection with Watt’s other chemical endeavors. An important study of science in the industrial revolution that bears heavily on watt’s career is A. E. Musson and Eric Robinason. Science and Technology in the Industrial Revolution (Manchester, 1969).
The following publications are among those that have recently contributed to a fuller understanding of Watt’s place in science: Robert E. Schofield, The Lunar Society of Birmingham (Oxford, 1963), 60 – 82, passim: D. S. L. Cardwell, From Watt to Clausius (Ithaca, N. Y., 1971), 40 – 55, passim; W. A. Smeaton, “Some Comments on James Watt’s Published Account of His Work on Steam and Steam Engines,” in Notes and Records. Royal Society of London, 26 (1971), 35 – 42; David F. Larder, “An Unpublished Chemical Essay of James Watt,Engineer and Man of Science,” ibid.,24 (1969 – 1970) 221 – 232.
The British instrument maker and engineer James Watt developed an efficient steam engine that was a universal (covering everything) source of power and thereby provided one of the most essential technological parts of the early industrial revolution (a period of rapid economic growth that involved increased reliance on machines and large factories).
Watt's early years
James Watt was born on January 19, 1736, in Greenock, Scotland, the son of a shipwright (a carpenter who builds and fixes ships) and merchant of ships' goods. As a child James suffered from ill health. He attended an elementary school where he learned some geometry as well as Latin and Greek, but he was not well enough to attend regularly. For the most part he was educated by his parents at home. His father taught him writing and arithmetic, and his mother taught him reading.
Of much more interest to James was his father's store, where the boy had his own tools and forge (furnace to shape metals), and where he skillfully made models of the ship's gear that surrounded him. His father taught him how to craft things from wood and metal. He also taught James the skill of instrument making. As a youngster he played with a small carpentry set his father gave him, taking his toys apart, putting them back together, and making new ones.
In 1755 Watt was apprenticed (working for someone to learn a craft) to a London, England, mathematical instrument maker. At that time the trade primarily produced navigational (ship steering) and surveying (land measuring) instruments. Watt found London to be unpleasant, however. A year later he returned to Scotland.
Watt wanted to establish himself in Glasgow, Scotland, as an instrument maker. However, restrictions imposed by the tradesmen's guilds (associations of craftsmen) stood in his way. Friends at the University of Glasgow eventually arranged for him to be appointed as "mathematical instrument maker to the university" in late 1757. About this time Watt met Joseph Black, who had already laid the foundation (base) of modern chemistry and of the study of heat. Their friendship was of some importance in the early development of the steam engine.
Invention of the steam engine
At the University of Glasgow, Watt had become engaged in his first studies on the steam engine. During the winter of 1763–64 he was asked to repair the university's model of an earlier model of the steam engine made by Thomas Newcomen around the year 1711. After a few experiments, Watt recognized that the fault with the model rested not so much in the details of its construction as in its design. He found that a volume (amount of space taken up by an object or substance) of steam three or four times the volume of the piston cylinder (chamber with a moving object inside of it) was required to make the piston move to the end of the cylinder.
The solution Watt provided was to keep the piston at the temperature of the steam (by means of a jacket heated by steam) and to condense (make less dense) the steam in a separate vessel (chamber) rather than in the piston. Such a separate condenser avoided the large heat losses that resulted from repeatedly heating and cooling the body of the piston, and so engine efficiency was improved.
It took time for Watt to turn a good idea for a commercial invention into reality. A decade passed before Watt solved all the mechanical problems. Black lent him money and introduced him to John Roebuck of the Carron ironworks in Scotland. In 1765 Roebuck and Watt entered into a partnership.
Watt still had to earn his own living but his employment as surveyor of canal construction left little time for developing his invention. However, Watt did manage to prepare a patent application on his invention, and the patent was granted on January 5, 1769.
By 1773 Roebuck's financial difficulties brought not only Watt's work on the engine to a standstill but also Roebuck's own business. Matthew Boulton, an industrialist (someone who owns and operates a factory) of Birmingham, England, then became Watt's partner. Watt moved to Birmingham. He was now able to work full time on his invention. In 1775 Boulton accepted two orders to build Watt's steam engine. The two engines were set up in 1776 and their success led to many other orders.
Improvements in the steam engine
Between 1781 and 1788 Watt modified and further improved his engine. These changes combined to make as great an advance over his original engine as the latter was over the Newcomen engine. The most important modifications were a more efficient use of the steam, the use of a double-acting piston, the replacement of the flexible chain connection to the beam by the rigid three bar linkage, the provision of another mechanical device to change the reciprocating (back and forth) motion of the beam end to a rotary (circular) motion, and the provision of a device to regulate the speed.
Having devised a new rotary machine, the partners had next to determine the cost of constructing it. These rotary steam engines replaced animal power, and it was only natural that the new engine should be measured in terms of the number of horses it replaced. By using measurements that millwrights (people who build mills), who set up horse gins (animal-driven wheels), had determined, Watt found the value of one "horse power" to be equal to thirty-three thousand pounds lifted one foot high per minute. This value is still used as the standard for American and English horsepower. The charge of building the new type of steam engine was based upon its horsepower from that time forward.
On Watt's many business trips, there was always a good deal of correspondence (letters) that had to be copied. To avoid this tiresome task, he devised letter-press copying. This works by writing the original document with a special ink. Copies are then made by simply placing another sheet of paper on the freshly written sheet and then pressing the two together.
Watt's interests in applied (practical) chemistry led him to introduce chlorine bleaching into Great Britain and to devise a famous iron cement. In theoretical chemistry, he was one of the first to argue that water was not an element (basic substance of matter made up of only one kind of atom) but a compound (substance made up of two or more elements).
In 1794 Watt and Boulton turned over their flourishing business to their sons. Watt maintained a workshop where he continued his inventing activities until he died on August 25, 1819.
Watt's achievements in perfecting the steam engine have been recognized worldwide. The watt, a unit of electrical power, was named after him.
For More Information
Champion, Neil. James Watt. Chicago: Heinemann Library, 2001.
Robinson, Eric, and A. E. Musson. James Watt and the Steam Revolution. New York: A. M. Kelley, 1969.
Sproule, Anna. James Watt: Master of the Steam Engine. Woodbridge, CT: Blackbirch Press, 2001.
Scottish Inventor and Scientific Instrument Maker
Although James Watt did not invent the steam engine, he made improvements to already existing engines that greatly increased their power. Watt also developed several other important inventions: a rotary engine to drive machinery; a double-action engine; a steam indicator to measure pressure in an engine; and a centrifugal governor to automatically regulate engine speed. He developed the concept of horsepower to describe the operating strength of engines. Watt also made important surveys of several canal routes and invented a telescope attachment to measure distance. In 1882 the British Association named a unit of electrical power measurement after Watt.
James Watt was born on January 19, 1736, in the village of Greenock in Renfrewshire, Scotland. Watt's grandfather, Thomas, had been a teacher of mathematics, surveying, and navigation; and his father James, the treasurer and magistrate for Greenock, ran a successful business building ships, houses, and mathematical instruments. Early in his life Watt demonstrated both manual dexterity and an aptitude for mathematics, and he spent much time in his father's workshop building models of such things as cranes and barrel organs. At the age of about 18 he was sent to live in the city of Glasgow with his mother's relatives, one of whom taught at the university. Watt soon moved to London to apprentice himself to a mathematical instrument maker. Watt was a sickly young man who suffered severe headache attacks all his life, and London did not suit him. By the age of 21 he had returned to Glasgow.
Through the connections of Andrew Anderson, an old school friend, Watt received an appointment as mathematical instrument maker for the University of Glasgow in 1757 and was allowed to establish a workshop on its property. He met important professors at the university, including chemist Joseph Black (1728-1799), whose studies of the heat properties of steam led him to develop the concept of latent heat. Black and Watt remained friends and corresponded until Black's death in 1799.
In 1710 Thomas Newcomen (1663-1729) and John Calley had developed a "fire" or steam engine, examples of which were being used by the mid-1700s to pump water from mines. The university had a model of one of these Newcomen engines that needed repair, and Watt undertook the task. During the job Watt noticed that the design of this engine caused large amounts of steam to be wasted and began thinking about an engine with a separate condenser that would solve the problem. At about this time Watt met John Roebuck, founder of the Carron Works factories, who urged the young inventor to build an engine that incorporated his ideas. With the help of money from Black, Watt built a small engine to test his ideas and then entered into a partnership with Roebuck in 1768. The following year Watt obtained his most famous patent, "A New Invented Method of Lessening the Consumption of Steam and Fuel in Fire Engines."
Watt had begun his surveys for canal routes all over Scotland in 1766, and this work kept him from devoting much time to his engine. In 1772 Roebuck's went bankrupt, and Matthew Boulton (1728-1809), who had inherited the Soho Works silver factories in Birmingham from his father, assumed a share of Watt's patent. Two years later Watt left Scotland and moved to Birmingham. The partnership seemed perfect; Watt needed Boulton's financial help, and Boulton's factories needed power. The effort nearly bankrupted Boulton, but by the early 1780s Watt's engine was used in copper and tin mines in Cornwall.
During that decade, often at Boulton's suggestion, Watt continued improving his engine. In 1781 he developed a "sun-and-planet" or rotary gear that replaced the back-and-forth motion of his engine with a circular one. The following year Watt patented a double-action engine in which the pistons both pushed and pulled. Since this engine required a new method to connect the pistons, Watt created a parallel motion apparatus in which connected rods drove the pistons in perpendicular motion. In 1788 he added a centrifugal governor that controlled the engine speed, and two years later Watt invented an automatic pressure gauge. Thus, by 1790 Watt's series of improvements and inventions had moved far beyond the scope of the Newcomen engine and had created a device that powered the Industrial Revolution. In 1800 over 500 Watt engines were installed in mines and factories all over Great Britain. Watt's patents also meant that he was a very wealthy man.
Watt's interests extended beyond business and industry. In the early 1790s Watt's teenage daughter Jesse suffered from tuberculosis. His friend Erasmus Darwin (1731-1802), a physician and grandfather of Charles Darwin, attempted treatment that did not help the girl; Darwin then suggested another physician, Thomas Beddoes (1760-1808). Beddoes had a practice in the seaport of Bristol and was attempting to use inhalation of various gases to treat tuberculosis and other diseases. Despite the efforts of Beddoes, Jesse died, but he and Watt developed a partnership to further investigate the gases. The inventor designed a breathing apparatus that was manufactured briefly by Boulton's firm and distributed to various physicians around Britain who were willing to try Beddoes's treatments. In 1798 Beddoes opened the Pneumatic Medical Institute in Bristol; this facility included a clinic, classrooms, and research laboratory. In 1799 the first human experiments with nitrous oxide, or "laughing gas," were completed here; Watt, his second wife, and two of his sons all participated. Unfortunately, the experiments at Bristol were not effective in treating diseases and ended the following year.
In 1763 Watt married his cousin Margaret Miller of Glasgow; she bore him several children but died in childbirth in 1773. Two years later Watt married Ann Macgregor; she had two children by Watt and outlived him by 13 years. By 1800 Watt was essentially retired. He received numerous honors during his life, including selection as a fellow of the Royal Society in 1785 and an honorary degree from the University of Glasgow in 1806. He spent much time in his final years travelling the European continent. Watt died on August 25, 1819, at his residence Heathfield Hall outside Birmingham. Two years earlier his son James Watt, Jr., had purchased the ship Caledonia and replaced her engines, making the vessel the first steamship to leave an English port.
The British instrument maker and engineer James Watt (1736-1819) developed an efficient steam engine which was a universal source of power and thereby provided one of the most essential technological components of the early industrial revolution.
James Watt was born on Jan. 19, 1736, in Greenock, Scotland, the son of a shipwright and merchant of ship's stores. He received an elementary education in school, but of much more interest to him was his father's store, where the boy had his own tools and forge and where he skillfully made models of the ship's gear surrounding him. In 1755 he was apprenticed to a London mathematical instrument maker; at that time the trade primarily produced navigational and surveying instruments. A year later he returned to Scotland. By late 1757 Watt was established in Glasgow as "mathematical instrument maker to the university."
About this time Watt met Joseph Black, who had already laid the foundations of modern chemistry and of the study of heat. Their friendship was of some importance in the early development of the steam engine.
Invention of the Steam Engine
In the meantime, Watt had become engaged in his first studies on the steam engine. During the winter of 1763/ 1764 he was asked to repair the university's model of the Newcomen steam engine. After a few experiments, Watt recognized that the fault with the model rested not so much in the details of its construction or in its malfunctioning as in its design. He found that a volume of steam three or four times the volume of the piston cylinder was required to make the piston move to the end of the cylinder. The solution Watt provided was to keep the piston at the temperature of the steam (by means of a jacket heated by steam) and to condense the steam in a separate vessel rather than in the piston. Such a separate condenser avoided the large heat losses that resulted from repeatedly heating and cooling the body of the piston, and so engine efficiency was improved.
There is a considerable gap between having a good idea for a commercial invention and in reducing it to practice. It took a decade for Watt to solve all the mechanical problems. Black lent him money and introduced him to John Roebuck of the Carron ironworks in Stirlingshire, Scotland. In 1765 Roebuck and Watt entered into a partnership. However, Watt still had to earn his own living, and his employment as surveyor of canal construction left little time for developing his invention. However, Watt did manage to prepare a patent application on his invention, and the patent was granted on Jan. 5, 1769.
By 1773 Roebuck's financial difficulties brought not only Watt's work on the engine to a standstill but also Roebuck's own business. Matthew Boulton, an industrialist of Birmingham, England, then became Watt's partner, and Watt moved to Birmingham. He was now able to work full time on his invention. In 1775 Boulton accepted two orders to erect Watt's steam engine; the two engines were set up in 1776 and their success led to many other orders.
Improvements in the Steam Engine
Between 1781 and 1788 Watt modified and further improved his engine. These changes combined to make as great an advance over his original engine as the latter was over the Newcomen engine. The most important modifications were a more efficient utilization of the steam, the use of a double-acting piston, the replacement of the flexible chain connection to the beam by the rigid threebar linkage, the provision of another mechanical device to change the reciprocating motion of the beam end to a rotary motion, and the provision of a centrifugal governor to regulate the speed.
Having devised a new rotary machine, the partners had next to determine the cost of constructing it. These rotary steam engines replaced animal power, and it was only natural that the new engine should be measured in terms of the number of horses it replaced. By using measurements that millwrights, who set up horse gins (animal-driven wheels), had determined, Watt found the value of one "horse power" to be equal to 33, 000 pounds lifted one foot high per minute, a value which is still that of the standard American and English horsepower. The charge of erecting the new type of steam engine was accordingly based upon its horsepower.
On Watt's many business trips, there was always a good deal of correspondence that had to be copied. To avoid this irksome task, he devised letter-press copying, in which, by writing the original with a special ink, copies could be made by simply placing another sheet of paper on the freshly written sheet and then pressing the two together.
Watt's interests in applied chemistry led him to introduce chlorine bleaching into Great Britain and to devise a famous iron cement. In theoretical chemistry, he was one of the first to argue that water was not an element but a compound.
In 1794 Watt and Boulton turned over their flourishing business to their sons. Watt maintained a workshop where he continued his inventing activities until he died on Aug. 25, 1819.
Excellent biographies of Watt are H. W. Dickinson and Rhys Jenkins, James Watt and the Steam Engine (1927), and Dickinson's James Watt (1936). Eric Robinson and A. E. Musson, James Watt and the Steam Revolution (1969), is a documentary history that commemorates the bicentenary of Watt's patent for the separate condenser in his steam engine and includes extracts from Watt's personal letters and other documents not before published. For background material see H.W. Dickinson, A Short History of the Steam Engine (1939), and T. S. Ashton, The Industrial Revolution (1948). □
Early Years Born in Greenock, Scotland, James Watt was largely self–educated before he went to London in 1755 to learn the trade of mathematical–instrument manufacturing. Two years later he returned home to become instrument maker for the University of Glasgow. Watt became interested in steam power after he was called on to repair a Newcomen steam engine (steam used to pump water from mines). During the 1760s, with financial support from English inventor John Roebuck (1718–1794), Watt experimented with improving the efficiency of this steam engine, which operated on the negative pressure of a vacuum created when steam in a cylinder was cooled and condensed by the introduction of water. With his first engine (patented in 1769), Watt overcame the wasteful use of steam in the Newcomen design by employing a separate condensing chamber that eliminated the need to cool and reheat the cylinder for every stroke of the engine, thereby maximizing efficiency.
Businessman. A new phase in Watt’s career began in 1775, after Matthew Boulton (1728–1809) purchased Roebuck’s interest in Watt’s engine, and the two partners began to manufacture steam engines at the Soho Engineering Works in Birmingham. Their first engine, installed in 1776, pumped water from a coal mine. Highly trained metal craftsmen at the Soho Works also contributed to the improvement of Boulton and Watt’s engines. Their efficiency was greatly enhanced after 1776, when John Wilkinson (1728–1808) invented a new lathe that was capable of making pistons and cylinders with much greater precision than earlier machines. Over the next several years Watt developed and patented several other innovations, including the gears to convert the reciprocal, up–and–down movement of pistons into a continuous circular motion that could drive machines such as the loom. He also designed a system in which steam was admitted alternately to both ends of a cylinder, thus creating pressure on the piston in both strokes of the cycle and creating greater and more–continuous power. Finally, drawing on the design of a device used earlier to control windmill speed, Watt developed a steam governor that automatically regulated the speed of an engine by linking output to input, a concept fundamental to automation. Boulton and Watt also benefited from the powerful British patent system, which gave them a monopoly on their inventions. They guardedtheir rights fiercely.
Scientist. Boulton and Watt conceived of themselves as scientists, joining and participating faithfully in several different learned societies and indulging their interests in many subjects. This activity enhanced their national and international reputations as well as sales of their engines. In 1800 Boulton and Watt’s patent rights expired, and Watt retired from business, ostensibly to devote himself solely to science. At this time England had more than five hundred operational Boulton and Watt engines. Several dozen more had been sold on the Continent, and a significant number of copies had been made in places where English patent rights could not be protected. Watt’s designs and his willingness to oversee the quality of the machines he and Boulton built earned him a reputation as a scientist and inventor. Because of this renown, subsequent generations remembered him as the inventor of the steam engine, even though such engines had been in existence for generations before Watt took out his first patent. In fact, he vastly improved the efficiency of the steam engine, making it practical for use in industry, thus facilitating the mechanization so fundamental to the Industrial Revolution. Watt also originated the concept of horsepower as a measurement of energy output. As a sign of his importance to the study of efficiency and power, a unit of electrical measurement, the watt, was named after him.
Jennifer Tann, The Selected Papers of Boulton &Watt (Cambridge, Mass.: MIT Press, 1981).
Tann and M. J. Brecklin, “The International Diffusion of the Watt Engine, 1775-1825,” Economic History Review, 31 (1978): 541–564.
J. A. Chartres