Editing James Watt

{{Short description|Scottish inventor, mechanical engineer and chemist (1736–1819)}}
{{About|the inventor and mechanical engineer|the college|James Watt College|the award|James Watt International Medal|other people with similar names|James Watt (disambiguation)}}
{{pp-vandalism|small=yes}}
{{Use British English|date=February 2018}}
{{Use dmy dates|date=December 2019}}
{{Infobox scientist
| name              = James Watt
| honorific_suffix  = {{post-nominals|country=GBR|FRS|FRSE|size=100%}}
| image             = Watt James von Breda.jpg
| caption           = Portrait by [[Carl Frederik von Breda]], 1792 
| birth_date        = {{birth date|1736|1|19|df=y}}
| birth_place       = [[Greenock]], [[Renfrewshire (historic)|Renfrewshire]], Scotland
| death_date        = {{Death date and age|1819|8|25|1736|1|19|df=y}}{{efn|name=deathdate|Although some otherwise reputable sources give his date of death as 19 August 1819, all contemporary accounts report him dying on 25 August and being buried on 2 September. The date 19 August originates from the biography ''The Life of James Watt'' (1858, p. 521) by [[James Patrick Muirhead]]. It draws its (supposed) legitimacy from the fact that Muirhead was a nephew of Watt and therefore should have been well-informed. In the Muirhead papers, 25 August date is mentioned elsewhere. The latter date is also given in contemporary newspaper reports (for example, page 3 of ''[[The Times]]'' of 28 August) as well as by an abstract of and codicil to Watt's last will. (In the pertinent burial register of St. Mary's Church (Birmingham-Handsworth) Watt's date of death is not mentioned.)}}
| death_place       = [[Handsworth, West Midlands|Handsworth]], Birmingham, England
| fields            = [[Mechanical engineering]]
| workplaces        = [[University of Glasgow]]<br />[[Boulton and Watt]]
| known_for         = [[Watt steam engine]] <br /> [[Watt's linkage]] <br /> [[Watt's curve]]<br />[[Watt steam engine#Separate condenser|Separate condenser]] <br>[[Centrifugal governor]]<br/>[[Horsepower]]<br>[[Pressure volume diagram|Indicator diagram]]<br>[[Duplicating machines#Letter copying presses|Letter copying press]]<br>[[Sun and planet gear]]
| author_abbrev_bot =
| author_abbrev_zoo = 
| signature         = James Watt Signature.svg
| spouse            = Margaret Miller (m. 1764–1773 her death)<br />{{marriage|Anne McGrigor|1776}}
| children          = 4
| resting_place     = [[St. Mary's Church, Handsworth]] 
}}
[[File:James Watt by Francis Chantrey, Hunterian Museum, Glasgow.jpg|thumb|265px|<div style="text-align: center">Statue of Watt</div><br> <small>([[Hunterian Museum and Art Gallery|Hunterian Museum, Glasgow]], by [[Francis Chantrey]])</small>]]

'''James Watt''' {{post-nominals|country=GBR|FRS|FRSE}} ({{IPAc-en|w|ɒ|t}}; 30 January 1736 <small>(19 January 1736 [[Old Style and New Style dates|OS]])</small> – 25 August 1819){{efn|name=deathdate}} was a Scottish [[invention|inventor]], [[mechanical engineer]], and [[chemist]] who improved on [[Thomas Newcomen]]'s 1712 [[Newcomen steam engine]] with his [[Watt steam engine]] in 1776, which was fundamental to the changes brought by the [[Industrial Revolution]] in both his native Great Britain and the rest of the world. 

While working as an instrument maker at the [[University of Glasgow]], Watt became interested in the technology of [[steam engine]]s. At the time engineers such as [[John Smeaton]] were aware of the inefficiencies of Newcomen's engine and aimed to improve it.<ref name = "ODNBSmeaton">{{Cite ODNB|url=https://www.oxforddnb.com/display/10.1093/ref:odnb/9780198614128.001.0001/odnb-9780198614128-e-25746 |doi=10.1093/ref:odnb/25746 |title=Smeaton, John |last=Skempton |first=A. W. |author-link = A. W. Skempton |url-access=registration}}</ref> Watt's insight was to realise that contemporary engine designs wasted a great deal of energy by repeatedly cooling and reheating the [[cylinder (engine)|cylinder]]. Watt introduced a design enhancement, the [[Watt steam engine#Separate condenser|separate condenser]], which avoided this waste of energy and radically improved the power, efficiency, and cost-effectiveness of steam engines. Eventually, he [[rotative beam engine|adapted his engine]] to produce rotary motion, greatly broadening its use beyond pumping water.

Watt attempted to commercialise his invention, but experienced great financial difficulties until he entered a partnership with [[Matthew Boulton]] in 1775. The new firm of [[Boulton and Watt]] was eventually highly successful and Watt became a wealthy man. In his retirement, Watt continued to develop new inventions though none was as significant as his steam engine work.

As Watt developed the concept of [[horsepower]],<ref>{{cite web|url=http://www.egr.msu.edu/~lira/supp/steam/wattbio.html|title=Biography of James Watt|last=Lira|first=Carl|year=2001|publisher=egr.msu.edu|access-date=5 July 2010}}</ref> the [[SI]] unit of power, the [[watt]], was named after him.

== Biography ==

=== Early life and education ===
James Watt was born on 19 January 1736 in [[Greenock]], [[Renfrewshire (historic)|Renfrewshire]], the eldest of the five surviving children of Agnes Muirhead (1703–1755) and James Watt (1698–1782).<ref name=":0">{{cite ODNB|id=28880|title=Watt, James (1736–1819)|orig-year=2004|year=2013|last=Tann|first=Jennifer}}</ref> Watt was baptised on 25 January 1736 at [[Old West Kirk]], in Greenock.<ref name=nrs>{{cite web|url=https://www.nrscotland.gov.uk/research/learning/hall-of-fame/hall-of-fame-a-z/watt-james |title=Hall of Fame A-Z: James Watt (1736-1819) |website=National Records of Scotland |date=31 May 2013 |access-date=17 September 2024}}</ref>  His mother came from a distinguished family, was well educated and said to be of forceful character, while his father was a [[shipwright]], ship owner and contractor, and served as the Greenock's [[Baillie|chief baillie]] in 1751.<ref name=":0" /><ref>{{cite book|url=https://archive.org/details/in.ernet.dli.2015.24829|title=The life of James Watt: with selections from his correspondence|last=Muirhead|first=James Patrick|publisher=John Murray|year=1859|edition=2|page=[https://archive.org/details/in.ernet.dli.2015.24829/page/n35 10]}}</ref> The Watt family's wealth came in part from Watt's father's trading in slaves and slave-produced goods.<ref>Lisa Williams, [https://www.nationalgalleries.org/art-and-artists/features/remaking-our-histories-scotland-slavery-and-empire "Scotland and Slavery"], National Galleries Scotland, 9 October 2020. Retrieved 1 December 2021.</ref> 
Watt's parents were [[Presbyterian]]s and strong [[Covenanters]],<ref>{{cite book|url=https://books.google.com/books?id=WKuG-VIwID8C|title=Icons of invention: the makers of the modern world from Gutenberg to Gates|last=Klooster|first=John W.|publisher=ABC-CLIO|year=2009|isbn=978-0-313-34743-6|volume=1|page=30}}</ref> but despite his religious upbringing he later became a [[deist]].<ref>{{cite book|title=James Watt and the steam engine: the memorial volume prepared for the Committee of the Watt centenary commemoration at Birmingham 1919|last1=Dickinson|first1=Henry Winram|author-link1=Henry Winram Dickinson|last2=Jenkins|first2=Rhys|last3=Committee of the Watt Centenary Commemoration|publisher=Clarendon press|year=1927|page=78|quote=It is difficult to say anything as to Watt's religious belief, further than that he was a Deist.}}</ref><ref>{{cite web|url=http://www.infidels.org/library/historical/joseph_mccabe/dictionary.html|title=A Biographical Dictionary of Ancient, Medieval, and Modern Freethinkers|last=McCabe|first=Joseph|year=1945|publisher=Haldeman-Julius Publications|access-date=17 August 2012|quote=He made such improvement in the crude steam-engine that had been invented before his time that he is usually described as the inventor. "His many and most valuable inventions must always place him among the leading benefactors of mankind," says the account of him in the ''Dictionary of National Biography''. He was an accomplished man. He knew Greek, Latin, French, German and Italian and was very friendly with the great freethinking French scientists. Andrew Carnegie has written a life of him and describes him as a deist who never went to church.}}</ref> Watt's grandfather, Thomas Watt (1642–1734), was a teacher of mathematics, surveying and navigation<ref name=":0" /> and [[baillie]] to the [[Baron of Cartsburn]].<ref>{{cite book|url=https://archive.org/details/in.ernet.dli.2015.24829|title=The life of James Watt: with selections from his correspondence|last=Muirhead|first=James Patrick|publisher=John Murray|year=1859|edition=2|page=[https://archive.org/details/in.ernet.dli.2015.24829/page/n29 4], 7}}</ref>

Initially, Watt was [[Homeschooling|educated at home]] by his mother, later going on to attend Greenock Grammar School. There he exhibited an aptitude for [[mathematics]], while [[Latin]] and [[Ancient Greek|Greek]] failed to interest him.

Watt is said to have suffered prolonged bouts of ill-health as a child and from frequent headaches all his life.<ref name=":0" /><ref>{{cite book|url=https://archive.org/stream/in.ernet.dli.2015.173811/2015.173811.Lives-Of-The-Engineers#page/n21/mode/2up|title=Lives of the Engineers|last1=Smiles|first1=Samuel|date=1904|publisher=John Murray|edition=Popular|location=London|page=12|access-date=9 December 2017}}</ref>

After leaving school, Watt worked in the workshops of his father's businesses, demonstrating considerable dexterity and skill in creating engineering models. After his father suffered unsuccessful business ventures, Watt left Greenock to seek employment in [[Glasgow]] as a [[Measuring instrument|mathematical instrument maker]].<ref name=":0" />

[[File:James-watt-1736-1819-engineer-inventor-of-the-stea.jpg|thumb|James Watt by [[John Partridge (artist)|John Partridge]], after Sir [[William Beechey]] (1806)<ref>{{cite book|last1=Annan|first1=Thomas|title=Illustrated catalogue of the exhibition of portraits on loan in the new galleries of art, Corporation buildings, Sauchiehall Street|date=1868|publisher=Glasgow Art Gallery and Museum|location=Glasgow|page=90|url=https://archive.org/stream/illustratedcatal00anna#page/90/mode/2up/search/watt|access-date=4 December 2017}}</ref><ref>{{cite web|title=James Watt, 1736 – 1819. Engineer, inventor of the steam engine|url=https://www.nationalgalleries.org/art-and-artists/4074/james-watt-1736-1819-engineer-inventor-steam-engine|website=Scottish National Portrait Gallery|access-date=5 December 2017}}</ref>]]
[[File:Bust of James Watt.JPG|thumb|Bust of Watt in the [[Scottish National Portrait Gallery]]]]

When he was 18, Watt's mother died and his father's health began to fail. Watt travelled to [[London]] and was able to obtain a period of training as an instrument maker for a year (1755–56), then returned to Scotland, settling in the major commercial city of [[Glasgow]], intent on setting up his own instrument-making business. He was still very young and, having not had a full [[apprenticeship]], did not have the usual connections via a former master to establish himself as a [[journeyman]] instrument maker.

Watt was saved from this impasse by the arrival from Jamaica of [[List of astronomical instruments|astronomical instruments]] bequeathed by [[Alexander MacFarlane (judge)|Alexander MacFarlane]] to the [[University of Glasgow]] – instruments that required expert attention.<ref>Marshall (1925), Chapter 3.</ref> Watt restored them to working order and was [[Remuneration|remunerated]]. These instruments were eventually installed in the [[Macfarlane Observatory]]. Subsequently, three professors offered him the opportunity to set up a small workshop within the university. It was initiated in 1757 and two of the professors, the [[physicist]] and [[chemist]] [[Joseph Black]] as well as the famed economist [[Adam Smith]], became Watt's friends.<ref>
{{cite book
|title=Partners in Science: Letters of James Watt and Joseph Black
 |year=1970
 |url=https://archive.org/details/partnersinscienc0000robi
 |url-access=registration
 |last1=Robinson
 |first1= Eric
|last2=McKie
 |first2= Doublas
|location= Cambridge, Massachusetts
}}
</ref>

At first, he worked on maintaining and repairing scientific instruments used in the university, helping with demonstrations, and expanding the production of [[quadrant (instrument)|quadrants]]. He made and repaired brass [[octant (instrument)|reflecting quadrants]], [[parallel rulers]], [[Weighing scale|scales]], parts for [[telescope]]s, and [[barometer]]s, among other things.

Biographers such as [[Samuel Smiles]] assert that Watt struggled to establish himself in Glasgow due to opposition from the [[Trades House]], but this has been disputed by other historians, such as [[iarchive:historyofhammerm00lums/page/n8|Harry Lumsden]]. The records from this period are fragmentary, but while it is clear that Watt encountered opposition, he was nevertheless able to work and trade as a skilled [[Metalworking|metal worker]], suggesting that the [[Incorporated Trades of Edinburgh|Incorporation of Hammermen]] were satisfied that he met their requirements for membership, or that Watt managed to avoid their outright opposition.<ref>{{Cite book|url=https://archive.org/details/historyofhammerm00lums|title=History of the Hammermen of Glasgow; a study typical of Scottish craft life and organisation|last=Lumsden|first=Harry|publisher=A. Gardner|year=1912|location=Paisley|pages=[https://archive.org/details/historyofhammerm00lums/page/394 394]–404}}</ref>

In 1759, he formed a partnership with John Craig, an architect and businessman, to manufacture and sell a line of products including musical instruments and toys. This partnership lasted for the next six years, and employed up to 16 workers. Craig died in 1765. One employee, Alex Gardner, eventually took over the business, which lasted into the 20th century.<ref>Hills, vol. 1, pp. 103–15.</ref>

In 1764, Watt married his cousin Margaret (Peggy) Miller, with whom he had 5 children, 2 of whom lived to adulthood: [[James Watt Jr.|James Jr.]] (1769–1848) and Margaret (1767–1796). His wife died in childbirth in 1773. In 1777, he married again, to Ann MacGregor, daughter of a Glasgow [[dye]]-maker, with whom he had 2 children: Gregory (1777–1804), who became a geologist and mineralogist,<ref>{{Cite book | last1 = Torrens | first1 = H. S. | chapter = The geological work of Gregory Watt, his travels with William Maclure in Italy (1801–1802), and Watt's "proto-geological" map of Italy (1804) | doi = 10.1130/2006.2411(11) |title=The Origins of Geology in Italy |series=Geological Society of America | volume = 411 | pages = 179–197 | year = 2006 | isbn = 0-8137-2411-2 }}</ref> and Janet (1779–1794). Ann died in 1832.<ref>{{Cite book|url=https://books.google.com/books?id=kZcsXTQntrkC&pg=PA1045|title=The Lunar Men: The Inventors of the Modern World 1730–1810|last=Uglow|first=Jenny|date=2011|publisher=Faber & Faber|isbn=978-0-571-26667-8|language=en}}</ref> Between 1777 and 1790 he lived in Regent Place, [[Birmingham]].

== Scientific studies and inventions ==

===Watt and the kettle===
There is a popular story that Watt was inspired to invent the steam engine by seeing a kettle boiling, the steam forcing the lid to rise and thus showing Watt the power of steam. This story is told in many forms; in some Watt is a young lad, in others he is older, sometimes it's his mother's kettle, sometimes his aunt's, suggesting that it may be apocryphal. In any event, Watt did not ''invent'' the steam engine, but significantly ''improved the efficiency'' of the existing [[Newcomen atmospheric engine|Newcomen engine]] by adding a [[Watt steam engine#Separate condenser|separate condenser]], consistent with the now-familiar principles of [[thermal efficiency]]. The story was possibly created by Watt's son, [[James Watt junior|James Watt, Jr.]], who was determined to preserve and embellish his father's legacy.<ref>{{cite journal |title=True Myths: James Watt's Kettle, His Condenser, and His Chemistry |last=Miller |first=D. P. |journal=[[History of Science (journal)|History of Science]] |year=2004 |volume=42 |issue=3 |pages=333–360 [p. 334] |doi=10.1177/007327530404200304 |bibcode=2004HisSc..42..333M |s2cid=161722497 }}</ref> In this light, it can be seen as akin to the story of [[Isaac Newton#Apple incident|Isaac Newton and the falling apple]] and his discovery of [[gravity]].

Although likely a myth, the story of Watt and the kettle has a basis in fact. In trying to understand the [[thermodynamics]] of heat and steam, James Watt carried out many laboratory experiments and his diaries record that in conducting these, he used a kettle as a [[boiler]] to generate steam.<ref>{{cite book |title=Science and Technology in the Industrial Revolution |first1=A. E. |last1=Musson |first2=Eric |last2=Robinson |publisher=Manchester University Press |year=1969 |page=80 }}</ref>

===Early experiments with steam===
[[File:James Eckford Lauder - James Watt and the Steam Engine- the Dawn of the Nineteenth Century - Google Art Project.jpg|thumb|left|[[James Eckford Lauder]]: ''James Watt and the Steam Engine: the Dawn of the Nineteenth Century'', 1855]]
[[File:Watts First Condenser.jpg|thumb|[[Watt's separate condenser|Original condenser]] by Watt ([[Science Museum (London)|Science Museum]])]]

In 1759 Watt's friend [[John Robison (physicist)|John Robison]] called his attention to the use of steam as a source of [[Power (physics)|motive power]].<ref name="Muirhead1858">{{cite book|last=Muirhead|first=James Patrick|title=The life of James Watt: with selections from his correspondence|url=https://archive.org/details/lifejameswattwi03muirgoog|access-date=17 August 2011|year=1858|publisher=J. Murray|pages=[https://archive.org/details/lifejameswattwi03muirgoog/page/n99 74]–83}}</ref> The design of the Newcomen engine, in use for almost 50 years for pumping water from mines, had hardly changed from its first implementation. Watt began to experiment with steam, though he had never seen an operating steam engine. He tried constructing a model; it failed to work satisfactorily, but he continued his experiments and began to read everything he could about the subject. He came to realise the importance of [[latent heat]]—the [[thermal energy]] released or absorbed during a constant-temperature process—in understanding the engine, which, unknown to Watt, his friend [[Joseph Black]] had previously discovered years before. Understanding of the steam engine was in a very primitive state, for the science of [[thermodynamics]] would not be formalised for nearly another 100 years.

In 1763, Watt was asked to repair a model Newcomen engine belonging to the university.<ref name="Muirhead1858"/> Even after repair, the engine barely worked. After much experimentation, Watt demonstrated that about three-quarters of the thermal energy of the steam was being consumed in heating the [[Cylinder (engine)|engine cylinder]] on every cycle.<ref name="FrazerPa1859">{{cite book|last=Frazer|first=Persifor|title=Journal of the Franklin Institute|url=https://books.google.com/books?id=o3oqAQAAIAAJ&pg=PA296|access-date=17 August 2011|year=1859|pages=296–297}}</ref> This energy was wasted because, later in the cycle, cold water was injected into the cylinder to [[condense]] the steam to reduce its pressure. Thus, by repeatedly heating and cooling the cylinder, the engine wasted most of its thermal energy rather than converting it into [[mechanical energy]].

Watt's critical insight, arrived at in May 1765 as he crossed [[Glasgow Green]] park,<ref>Dickinson, p. 36.</ref> was to cause the steam to condense in a separate chamber apart from the [[piston]], and to maintain the temperature of the cylinder at the same temperature as the injected steam by surrounding it with a "steam jacket".<ref name="FrazerPa1859"/> Thus, very little energy was absorbed by the cylinder on each cycle, making more available to perform useful work. Watt had a working model later that same year.

[[File:James Watt Cottage ruin, Kinneil House, Bo'ness.JPG|thumb|left|The ruin of Watt's cottage workshop at [[Kinneil House]]<ref>{{cite web|title=OS 25-inch 1892–1949|url=http://maps.nls.uk/geo/explore/#zoom=17&lat=56.0081&lon=-3.6337&layers=168&b=1|website=National Library of Scotland|publisher=Ordnance Survey|access-date=26 October 2017}}</ref>]]
[[File:James Watt steam engine relic at the Carron Works.JPG|thumb|[[Cylinder (engine)|Cylinder]] fragment of Watt's first operational engine at the [[Carron Works]], Falkirk]]

Despite a potentially workable design, there were still substantial difficulties in constructing a full-scale engine. This required more [[Financial capital|capital]], some of which came from Black. More substantial backing came from [[John Roebuck]], the founder of the celebrated [[Carron Iron Works]] near [[Falkirk]], with whom he now formed a partnership. Roebuck lived at [[Kinneil House]] in [[Bo'ness]], during which time Watt worked at perfecting his steam engine in a cottage adjacent to the house.<ref>{{cite book|last1=Salmon|first1=Thomas James|title=Borrowstounness and district, being historical sketches of Kinneil, Carriden, and Bo'ness, c. 1550–1850|date=1913|publisher=William Hodge and Co.|location=Edinburgh|pages=372–376|url=https://archive.org/stream/borrowstounnessd00salmrich#page/270/mode/2up|access-date=9 December 2017}}</ref> The shell of the cottage, and a very large part of one of his projects, still exist to the rear.<ref>"James Watt's Cottage", CANMORE. Royal Commission on the Ancient and Historical Monuments of Scotland. Retrieved 13 May 2010.</ref>

The principal difficulty was in machining the piston and cylinder. [[Iron (material)|Iron]] workers of the day were more like [[blacksmith]]s than modern [[machinist]]s, and were unable to produce the components with sufficient precision. Much capital was spent in pursuing a [[patent]] on Watt's invention. Strapped for resources, Watt was forced to take up employment—first as a [[surveyor (surveying)|surveyor]], then as a [[civil engineer]]—for 8 years.<ref>Hills, vol. I, pp. 180–293.</ref>

{{anchor|James Watt's Fire Engines Patent Act 1775}}
Roebuck went [[Bankruptcy in the United Kingdom|bankrupt]], and [[Matthew Boulton]], who owned the [[Soho Manufactory]] works near [[Birmingham]], acquired his patent rights. An [[Patent extensions|extension]] of the patent to 1800 was successfully obtained in 1775.{{efn|James Watt's Fire Engines Patent Act 1775 ([[15 Geo. 3]]. c. 61). At the time, an [[Act of Parliament]] was required to extend a patent.}}

Through Boulton, Watt finally had access to some of the best iron workers in the world. The difficulty of the manufacture of a large cylinder with a tightly fitting piston was solved by [[John Wilkinson (industrialist)|John Wilkinson]], who had developed precision boring techniques for [[cannon]] making at [[Bersham Ironworks|Bersham]], near [[Wrexham]], [[North Wales]]. Watt and Boulton formed a hugely successful partnership, [[Boulton and Watt]], which lasted for the next 25 years.

===First engines===
[[File:SteamEngine Boulton&Watt 1784.png|thumb|left|Engraving of a 1784 [[Watt steam engine|steam engine]] designed by [[Boulton and Watt]]]]
{{Main|Watt steam engine|Watt's linkage|Watt's curve}}
In 1776, the first engines were installed and working in commercial enterprises. These first engines were used to power pumps and produced only [[reciprocating motion]] to move the pump rods at the bottom of the shaft. The design was commercially successful, and for the next five years, Watt was very busy installing more engines, mostly in [[Cornwall]], for pumping water out of mines.

These early engines were not manufactured by Boulton and Watt, but were made by others according to drawings made by Watt, who served in the role of [[consulting engineer]]. The erection of the engine and its [[shakedown (testing)|shakedown]] was supervised by Watt, at first, and then by men in the firm's employ, with the actual work being accomplished by the purchaser of the engine. Supervising erectors included at various times [[William Murdoch]], [[John Rennie the Elder|John Rennie]], [[William Playfair]], [[John Southern (engineer)|John Southern]], [[Logan Henderson (engineer)|Logan Henderson]], [[James Lawson (engineer)|James Lawson]], [[William Brunton]], [[Isaac Perrins]], and others.

These were large machines. The first, for example, had a cylinder with a diameter of 50&nbsp;inches and an overall height of about 24 feet, and required the construction of a dedicated building to house it. Boulton and Watt charged an annual payment, equal to one-third of the value of the coal saved in comparison to a Newcomen engine performing the same work.

The field of application for the invention was greatly widened when Boulton urged Watt to convert the reciprocating motion of the piston to produce [[Rotational energy|rotational power]] for grinding, weaving and milling. Although a [[crank (mechanism)|crank]] seemed the obvious solution to the conversion, Watt and Boulton were stymied by a patent for this, whose holder, [[James Pickard]] and his associates proposed to cross-license the external condenser. Watt adamantly opposed this and they circumvented the patent by their [[sun and planet gear]] in 1781.

Over the next six years, he made other improvements and modifications to the steam engine. A double-acting engine, in which the steam acted alternately on both sides of the piston, was one. He described methods for working the steam "expansively" (i.e., using steam at pressures well above atmospheric). A [[compound engine]], which connected two or more engines, was described. Two more patents were granted for these in 1781 and 1782. Numerous other improvements that made for easier manufacture and installation were continually implemented. One of these included the use of the steam [[indicator diagram|indicator]] which produced an informative plot of the pressure in the cylinder against its volume, which he kept as a [[trade secret]]. Another important invention, one which Watt was most proud of, was the [[parallel motion|parallel motion linkage]], which was essential in double-acting engines as it produced the straight line motion required for the cylinder rod and pump, from the connected rocking beam, whose end moves in a [[circular arc]]. This was patented in 1784. A [[throttle]] valve to control the power of the engine, and a [[centrifugal governor]], patented in 1788,<ref>{{cite book|last=Brown|first=Richard|title=Society and Economy in Modern Britain 1700–1850|url=https://archive.org/details/societyeconomymo00brow|url-access=limited|publisher=Routledge|location=London|year=1991|page=[https://archive.org/details/societyeconomymo00brow/page/n74 60]|isbn=978-0-203-40252-8}}</ref> to keep it from "running away" were very important. These improvements taken together produced an engine which was up to five times as [[Fuel efficiency|fuel efficient]] as the Newcomen engine.

Because of the danger of exploding boilers, which were in a very primitive stage of development, and the ongoing issues with leaks, Watt restricted his use of high pressure steam&nbsp;– all of his engines used steam at near atmospheric pressure.

===Patent trials===
[[File:20070616 Dampfmaschine.jpg|thumb|A steam engine built to James Watt's patent in 1848 at [[Freiberg, Saxony|Freiberg]] in Germany]]
[[Edward Bull]] started constructing engines for Boulton and Watt in Cornwall in 1781. By 1792, he had started making engines of his own design, but which contained a separate condenser, and so infringed Watt's patents. Two brothers, [[Jabez Carter Hornblower]] and [[Jonathan Hornblower]] Jnr also started to build engines about the same time. Others began to modify Newcomen engines by adding a condenser, and the mine owners in Cornwall became convinced that Watt's patent could not be enforced. They started to withhold payments to Boulton and Watt, which by 1795 had fallen on hard times. Of the total £21,000 (equivalent to £{{formatnum:{{Inflation|UK|21000|1795|{{Inflation-year|UK}}|r=-4}}}} as of {{Inflation-year|UK}}) owed, only £2,500 had been received. Watt was forced to go to court to enforce his claims.<ref>Hills, vol. 3, ch. 5 and 6.</ref>

He first sued Bull in 1793. The jury found for Watt, but the question of whether or not the original specification of the patent was valid was left to another trial. In the meantime, injunctions were issued against the [[Patent infringement|infringers]], forcing their payments of the [[Royalty payment|royalties]] to be placed in [[escrow]]. The trial on determining the validity of the specifications which was held in the following year was inconclusive, but the injunctions remained in force and the infringers, except for Jonathan Hornblower, all began to settle their cases. Hornblower was soon brought to trial in 1799, and the verdict of the four was decisively in favour of Watt. Their friend John Wilkinson, who had solved the problem of boring an accurate cylinder, was a particularly grievous case. He had erected about 20 engines without Boulton's and Watts' knowledge. They finally agreed to settle the infringement in 1796.<ref>Roll, p. 158.</ref> Boulton and Watt never collected all that was owed them, but the disputes were all settled directly between the parties or through [[arbitration]]. These trials were extremely costly in both money and time, but ultimately were successful for the firm.

===Copying machine===
[[File:Portable Copying Machine by James Watt & Co.jpg|thumb|Portable Copying Machine by James Watt & Co. Circa 1795]]
Before 1780, there was no good method for making copies of letters or drawings. The only method sometimes used was a mechanical one using multiple linked pens. Watt at first experimented with improving this method, but soon gave up on this approach because it was so cumbersome. He instead decided to try to physically transfer ink from the front of the original to the back of another sheet, moistened with a solvent, and pressed to the original. The second sheet had to be thin, so that the ink could be seen through it when the copy was held up to the light, thus reproducing the original exactly.<ref>Hills, Vol. 2, pp. 190–211.</ref><ref>W. B. Proudfoot, ''Origin of Stencil Duplicating'', p. 21, as quoted at Quaritch.com, 12 October 13.</ref>

Watt started to develop the process in 1779, and made many experiments to formulate the ink, select the thin paper, to devise a method for wetting the special thin paper, and to make a press suitable for applying the correct pressure to effect the transfer. All of these required much experimentation, but he soon had enough success to patent the process a year later. Watt formed another partnership with Boulton (who provided financing) and [[James Keir]] (to manage the business) in a firm called James Watt and Co. The perfection of the invention required much more development work before it could be routinely used by others, but this was carried out over the next few years. Boulton and Watt gave up their shares to their sons in 1794.<ref>Hills, vol. 3, p. 116.</ref> It became a commercial success and was widely used in offices even into the 20th century.

===Chemical experiments===
From an early age, Watt was very interested in chemistry. In late 1786, while in Paris, he witnessed an experiment by [[Claude Louis Berthollet]] in which he reacted [[hydrochloric acid]] with [[manganese dioxide]] to produce [[chlorine]]. He had already found that an [[aqueous solution]] of chlorine could [[bleach]] textiles, and had published his findings, which aroused great interest among many potential rivals. When Watt returned to Britain, he began experiments along these lines with hopes of finding a commercially viable process. He discovered that a mixture of salt, manganese dioxide and [[sulphuric acid]] could produce chlorine, which Watt believed might be a cheaper method. He passed the chlorine into a weak solution of [[alkali]], and obtained a [[Turbidity|turbid]] solution that appeared to have good bleaching properties. He soon communicated these results to James McGrigor, his father-in-law, who was a bleacher in Glasgow. Otherwise, he tried to keep his method a secret.<ref>Hills, vol. 3, ch. 4.</ref>

With McGrigor and his wife Annie, he started to scale up the process, and in March 1788, McGrigor was able to bleach {{Convert|1500|yd|ft|abbr=off}} of cloth to his satisfaction. About this time, Berthollet discovered the salt and sulphuric acid process, and published it, so it became public knowledge. Many others began to experiment with improving the process, which still had many shortcomings, not the least of which was the problem of transporting the liquid product. Watt's rivals soon overtook him in developing the process, and he dropped out of the race. It was not until 1799, when [[Charles Tennant]] patented a process for producing solid bleaching powder ([[calcium hypochlorite]]) that it became a commercial success.

By 1794, Watt had been chosen by [[Thomas Beddoes]] to manufacture apparatuses to produce, clean and store gases for use in the new [[Pneumatic Institution]] at [[Hotwells]] in [[Bristol]]. Watt continued to experiment with various gases, but by 1797, the medical uses for the "[[factitious airs]]" (artificial gases) had come to a dead end.<ref>Hills, vol. 3, pp. 152–58.</ref>[[File:Watt apparatus 3.JPG|thumb|Scientific apparatus designed by [[Boulton and Watt]] in preparation of the [[Pneumatic Institution]] in Bristol]]

===Personality===
Watt combined theoretical knowledge of science with the ability to apply it practically. The chemist [[Humphry Davy]] said of him, "Those who consider James Watt only as a great practical mechanic form a very erroneous idea of his character; he was equally distinguished as a [[natural philosopher]] and a chemist, and his inventions demonstrate his profound knowledge of those sciences, and that peculiar characteristic of genius, the union of them for practical application".<ref>{{cite book|last=Carnegie|first=Andrew|title=James Watt|url=http://www.history.rochester.edu/steam/carnegie/ch10.html|year=1905|publisher=Doubleday, Page and Company|chapter=10|url-status=dead|archive-url=http://arquivo.pt/wayback/20090708035219/http://www.history.rochester.edu/steam/carnegie/ch10.html|archive-date=8 July 2009}}</ref>

He was greatly respected by other prominent men of the [[Industrial Revolution]].<ref>Carnegie, chap. XI: ''Watt, the Man''.</ref> He was an important member of the [[Lunar Society of Birmingham]], and was a much sought-after conversationalist and companion, always interested in expanding his horizons.<ref>Hills, vol I, pp. 42–43.</ref> His personal relationships with his friends and business partners were always congenial and long-lasting.

According to Lord Liverpool (Prime Minister of the UK),<ref>{{cite book|last1=Laidler|first1=Keith J.|title=To Light such a Candle|date=1993|publisher=Oxford University Press|page=18}}
</ref>
<blockquote>A more excllent and amikable man in all the relations of life I believe never existed.</blockquote>

Watt was a prolific correspondent. During his years in [[Cornwall]], he wrote long letters to Boulton several times per week. He was averse to publishing his results in, for example, the ''[[Philosophical Transactions of the Royal Society]]'' however, and instead preferred to communicate his ideas in [[patents]].<ref>{{Cite book| last=Smiles| first=Samuel| title=Lives of Boulton and Watt: A History of the Invention and Introduction of the Steam Engine| url=https://archive.org/stream/livesofengineers04smiluoft#page/286/mode/2up | publisher=John Murray| place=London| year=1865 | page=286}}</ref> He was an excellent [[Drafter|draughtsman]].

[[File:James Watt's letters from the Science Museum Library & Archives in Wroughton.jpg|thumb|James Watt's letters from the [[Science Museum at Wroughton|Science Museum Library & Archives in Wroughton]], near Swindon]]

He was a rather poor businessman, and especially hated bargaining and negotiating terms with those who sought to use the steam engine. In a letter to [[William Small]] in 1772, Watt confessed that "he would rather face a loaded cannon than settle an account or make a bargain."<ref>Roll, p. 20</ref> Until he retired, he was always very concerned about his financial affairs, and was something of a worrier. His health was often poor and he suffered frequent nervous headaches and depression. When he retired in 1800, he became a rich enough man to pass the business on to his sons.

===Soho Foundry===
At first, the partnership made the drawings and specifications for the engines, and supervised the work to erect them on the customers' property. They produced almost none of the parts themselves. Watt did most of his work at his home in Harper's Hill in Birmingham, while Boulton worked at the [[Soho Manufactory]]. Gradually, the partners began to actually manufacture more and more of the parts, and by 1795, they purchased a property about a mile away from the Soho Manufactory, on the banks of the [[BCN Main Line|Birmingham Canal]], to establish a new foundry for the manufacture of the engines. The [[Soho Foundry]] formally opened in 1796 at a time when Watt's sons, Gregory and James Jr. were heavily involved in the management of the enterprise. In 1800, the year of Watt's retirement, the firm made a total of 41 engines.<ref>Roll, p. 280.</ref>

===Later years===
[[File:Heathfield Hall, Handsworth by Allen Edward Everitt.jpg|thumb|An 1835 painting of "[[Heathfield Hall|Heathfield]]", Watt's house in [[Handsworth, West Midlands|Handsworth]], by [[Allen Edward Everitt]] ]]
[[File:James Watt's Workshop.jpg|thumb|upright|James Watt's workshop]]
Watt retired in 1800, the same year that his fundamental patent and partnership with Boulton expired. The famous partnership was transferred to the men's sons, [[Matthew Robinson Boulton]] and [[James Watt junior|James Watt, Junior]]. The long-time firm engineer [[William Murdoch]] was soon made a partner and the firm prospered.

Watt continued to invent other things before and during his semi-retirement. Within his home in [[Handsworth, West Midlands|Handsworth]], Staffordshire, Watt made use of a [[garret]] room as a workshop, and it was here that he worked on many of his inventions.<ref>Dickinson, ch. VII.</ref> Among other things, he invented and constructed machines for copying sculptures and medallions which worked very well, but which he never patented.<ref>Hills, vol. 3, pp. 234–37.</ref> One of the first sculptures he produced with the machine was a small [[Bust (sculpture)|head]] of his old professor friend [[Adam Smith]]. He maintained his interest in civil engineering and was a consultant on several significant projects. He proposed, for example, a method for constructing a flexible pipe to be used for pumping water under the [[River Clyde]] at Glasgow.<ref>Hills, vol 3, pp. 230–31</ref>

He and his second wife travelled to France and Germany, and he purchased an estate in mid-Wales at Doldowlod House, one mile south of [[Llanwrthwl]], which he much improved.

In 1816, he took a trip on the [[Paddle steamer|paddle-steamer]] ''[[PS Comet|Comet]]'', a product of his inventions, to revisit his home town of Greenock.<ref>Robert Chambers' Book of Days.</ref>

He died on 25 August 1819 at his home "[[Heathfield Hall]]" near Handsworth in Staffordshire (now part of Birmingham) at the age of 83.<ref>{{cite news |url=https://www.britishnewspaperarchive.co.uk/viewer/bl/0002762/18190829/024/0008 |title=Deaths. |newspaper=Wooler's British Gazette |date=29 August 1819 |page=8 |via=British Newspaper Archive |access-date=18 September 2024}}</ref><ref>{{cite news |url=https://www.britishnewspaperarchive.co.uk/viewer/bl/0002644/18190830/019/0008 |title=Died. |newspaper=The National Register |date=30 August 1819 |page=8 |via=British Newspaper Archive |access-date=18 September 2024}}</ref> He was buried on 2 September in the graveyard of [[St Mary's Church, Handsworth]].<ref>{{Cite web|url=https://www.freereg.org.uk/search_records/5818e459e93790de6a311110|title=FreeREG database: Handsworth St Mary burial, 2 September 1819: James Watt Esq, of Heathfield, age 83. |access-date=18 Sep 2024 |work=FreeREG |publisher=Free UK Genealogy}}</ref> The church has since been extended and his grave is now inside the church.

==Family==

On 14 July 1764, Watt married his cousin Margaret Miller (d. 1773).<ref name=nrs /> They had two children, Margaret (1767–1796) and James (1769–1848). In 1791, their daughter married James Miller. In September 1773, while Watt was working in the [[Scottish Highlands]], he learned that his wife, who was pregnant with their third child, was seriously ill. He immediately returned home but found that she had died and their child was [[stillborn]].<ref name=":0" /><ref name=":1" />

On 29 July 1776, he married Ann MacGregor (d. 1832).<ref name=nrs /><ref name=":1">{{cite book|title=Biographical Index of Former Fellows of the Royal Society of Edinburgh 1783–2002|date=July 2006|publisher=The Royal Society of Edinburgh|isbn=978-0-902198-84-5|url=https://rse.org.uk/wp-content/uploads/2021/07/RSE-Fellows-BiographicalIndex-2.pdf}}</ref>

==Freemasonry==
He was Initiated into [[Freemasonry in Scotland|Scottish Freemasonry]] in The Glasgow Royal Arch Lodge, No. 77, in 1763. The Lodge ceased to exist in 1810. A [[Masonic Lodge]] was named after him in his home town of Glasgow – Lodge James Watt, No. 1215.<ref>Famous Scottish Freemasons. The Grand Lodge of Antient Free and Accepted Masons of Scotland. 2010. Pp.72–73. {{ISBN|978-0-9560933-8-7}}</ref>

==Murdoch's contributions==
William Murdoch joined Boulton and Watt in 1777. At first, he worked in the [[Pattern (casting)|pattern]] shop in Soho, but soon he was erecting engines in Cornwall. He became an important part of the firm and made many contributions to its success including important inventions of his own.

John Griffiths, who wrote a biography<ref>John Griffiths; ''The Third Man, The Life and Times of William Murdoch 1754–1839'' Illustrated with Black-and-white photographic plates and diagrams with Bibliography and Index; Andre Deutsch; 1992; {{ISBN|0-233-98778-9}}</ref> of him in 1992, has argued that Watt's discouragement of Murdoch's work with high-pressure steam on his steam road locomotive experiments delayed its development: Watt rightly believed that boilers of the time would be unsafe at higher pressures.<ref>{{cite book|last=Jarvis|first=Adrian|title=Samuel Smiles and the construction of Victorian values|year=1997|publisher=Sutton|isbn=978-0-7509-1128-3|page=82}}</ref>

Watt patented the application of the [[sun and planet gear]] to steam in 1781 and a [[steam locomotive]] in 1784, both of which have strong claims to have been invented by Murdoch.<ref>{{cite book|last1=Day|first1=Lance|last2=McNeil|first2=Ian|title=Biographical Dictionary of the History of Technology|url=https://books.google.com/books?id=FrGwIIvKSxUC&pg=PA878|year=2003|publisher=Routledge|isbn=978-0-203-02829-2|page=878}}</ref> The patent was never contested by Murdoch, however, and Boulton and Watt's firm continued to use the sun and planet gear in their [[rotative engine]]s, even long after the patent for the crank expired in 1794. Murdoch was made a partner of the firm in 1810, where he remained until his retirement 20 years later at the age of 76.

==Legacy==
[[File:Loughborough Beam Engine - geograph.org.uk - 2734519.jpg|right|thumb|A preserved [[Watt steam engine|Watt beam engine]] at [[Loughborough University]]]]
{{further|Industrial Revolution}}

As one author states, Watt's improvements to the steam engine "converted it from a prime mover of marginal efficiency into the mechanical workhorse of the Industrial Revolution".<ref>{{cite journal|last=Anderson|first=Anthony|date=3 December 1981|title=Review: James Watt and the steam engine|journal=New Scientist|page=685|url=https://books.google.com/books?id=FPxItYa5rgUC&q=james-watt%20%22industrial%20revolution%22&pg=PA685|access-date=26 October 2020|archive-date=2 February 2021|archive-url=https://web.archive.org/web/20210202171006/https://books.google.com/books?id=FPxItYa5rgUC&q=james-watt%20%22industrial%20revolution%22&pg=PA685|url-status=dead}}</ref>

==Honours==
Watt was much honoured in his own time. In 1784, he was made a fellow of the [[Royal Society of Edinburgh]], and was elected as a member of the [[Batavian Society for Experimental Philosophy]], of [[Rotterdam]], the Netherlands, in 1787. In 1789, he was elected to the elite group, the [[Smeatonian Society of Civil Engineers]].<ref>{{cite book | last = Watson | first = Garth | title = The Smeatonians: The Society of Civil Engineers | publisher=Thomas Telford | year = 1989 | isbn = 0-7277-1526-7}}</ref> In 1806, he was conferred the honorary [[Doctor of Law]]s by the [[University of Glasgow]]. The [[French Academy]] elected him a Corresponding Member and he was made a Foreign Associate in 1814.<ref>Dickinson, pp. 197–98.</ref>

The [[watt]] is named after James Watt for his contributions to the development of the [[steam engine]], and was adopted by the Second Congress of the [[British Science Association|British Association for the Advancement of Science]] in 1889 and by the 11th [[General Conference on Weights and Measures]] in 1960 as the unit of [[Power (physics)|power]] incorporated in the [[International System of Units]] (or "SI").

On 29 May 2009, the [[Bank of England]] announced that Boulton and Watt would appear on a new [[Banknotes of the pound sterling#Historical figures|£50 note]]. The design is the first to feature a dual portrait on a Bank of England note, and presents the two industrialists side by side with images of Watt's steam engine and Boulton's Soho Manufactory. Quotations attributed to each of the men are inscribed on the note: "I sell here, sir, what all the world desires to have—POWER" (Boulton) and "I can think of nothing else but this machine" (Watt). The inclusion of Watt is the second time that a Scot has featured on a Bank of England note (the first was [[Adam Smith]] on the 2007 issue £20 note).<ref>{{citation|url=http://news.bbc.co.uk/1/hi/scotland/glasgow_and_west/8075130.stm|title=Steam giants on new £50 banknote|publisher=BBC|date= 30 May 2009|access-date= 22 June 2009}}</ref> In September 2011, it was announced that the notes would enter circulation on 2 November.<ref>{{cite web|url=https://www.theguardian.com/business/2011/sep/30/bank-england-new-50-pound-note?newsfeed=true|title=Bank of England to launch new £50 note|author=Heather Stewart|work=The Guardian|date=30 September 2011}}</ref>

In 2011, he was one of seven inaugural inductees to the [[Scottish Engineering Hall of Fame]].<ref>{{cite web |url= http://www.engineeringhalloffame.org/index.html |title=Scottish Engineering Hall of Fame |work=engineeringhalloffame.org |year=2012 |access-date=27 August 2012}}</ref>

==Memorials==
[[File:James Watt Memorial College.jpg|thumb|upright|left|The [[James Watt College|James Watt Memorial College]] in [[Greenock]]]]

Watt was buried in the grounds of [[St. Mary's Church, Handsworth]], in Birmingham. Later expansion of the church, over his grave, means that his tomb is now buried ''inside'' the church.<ref>{{cite book|last=Kelly|first=E. R.|title=The Post Office Directory of Birmingham|url=https://books.google.com/books?id=dO8NAAAAQAAJ&q=%22james%20watt%22%20buried%20handsworth%20chapel&pg=PA176|year=1878|publisher=Kelly and co.|location=London|page=176}}</ref>

The [[attic|garret]] room workshop that Watt used in his retirement was left, locked and untouched, until 1853, when it was first viewed by his biographer [[James Patrick Muirhead|J. P. Muirhead]]. Thereafter, it was occasionally visited, but left untouched, as a kind of shrine. A proposal to have it transferred to the [[Intellectual Property Office (United Kingdom)|Patent Office]] came to nothing. When the house was due to be demolished in 1924, the room and all its contents were presented to the [[Science Museum (London)|Science Museum]], where it was recreated in its entirety.<ref>{{cite web|url=http://www.makingthemodernworld.org.uk/stories/the_age_of_the_engineer/03.ST.03/?scene=5&tv=true |title=Garret workshop of James Watt |publisher=Makingthemodernworld.org.uk |access-date=12 March 2011}}</ref> It remained on display for visitors for many years, but was walled-off when the gallery it was housed in closed. The workshop remained intact, and preserved, and in March 2011 was put on public display as part of a new permanent Science Museum exhibition, "James Watt and our world".<ref>{{cite web |title=James Watt's legendary 'magical retreat' to be revealed at Science Museum |url=http://www.sciencemuseum.org.uk/about_us/press_and_media/press_releases/2011/03/watt.aspx |work=(Press Release) |publisher=[[Science Museum (London)|Science Museum]] |access-date=25 March 2011 |archive-url=https://web.archive.org/web/20110317132223/http://www.sciencemuseum.org.uk/about_us/press_and_media/press_releases/2011/03/watt.aspx |archive-date=17 March 2011 |date=1 March 2011 |url-status=dead }}</ref>

The approximate location of James Watt's birth in Greenock is commemorated by a statue. Other memorials in Greenock include street names and the Watt Memorial Library, which was begun in 1816 with Watt's donation of scientific books, and developed as part of the Watt Institution by his son (which ultimately became the [[James Watt College]]). Taken over by the local authority in 1974, the library now also houses the local history collection and archives of [[Inverclyde]], and is dominated by a large seated statue in the [[Vestibule (architecture)|vestibule]]. Watt is additionally commemorated by statuary in [[George Square]], Glasgow and [[Princes Street]], Edinburgh, as well as others in [[Birmingham]], where he is also remembered by the [[Lunar Society Moonstones|Moonstones]] and a school is named in his honour.

The James Watt College has expanded from its original location to include campuses in [[Kilwinning]] (North Ayrshire), Finnart Street and The Waterfront in Greenock, and the Sports campus in [[Largs]]. [[Heriot-Watt University]] near [[Edinburgh]] was at one time the School of Arts of Edinburgh, founded in 1821 as the world's first [[Mechanics Institute]], but to commemorate George Heriot, the 16th-century financier to [[James VI and I|King James VI and I]], and James Watt, after [[Royal charter|Royal Charter]] the name was changed to Heriot-Watt University. Dozens of university and college buildings (chiefly of science and technology) are named after him. Matthew Boulton's home, [[Soho House]], is now a museum, commemorating the work of both men. The [[University of Glasgow]]'s Faculty of Engineering has its headquarters in the James Watt Building, which also houses the department of Mechanical Engineering and the department of Aerospace Engineering. The huge painting ''James Watt contemplating the steam engine'' by [[James Eckford Lauder]] is now owned by the [[National Gallery of Scotland]].

[[File:Watt James Chantrey.jpg|thumb|right|[[Francis Legatt Chantrey|Chantrey]]'s statue of James Watt]]

There is a statue of James Watt in [[Piccadilly Gardens]], Manchester and [[City Square, Leeds]].

A colossal statue of Watt by [[Francis Legatt Chantrey]] was placed in [[Westminster Abbey]],<ref>Hall, A. R. ''The Abbey Scientists'', p. 35: London; Roger & Robert Nicholson; 1966.</ref> and later was moved to [[St. Paul's Cathedral]]. On the [[cenotaph]], the inscription reads, in part, "JAMES WATT ... ENLARGED THE RESOURCES OF HIS COUNTRY, INCREASED THE POWER OF MAN, AND ROSE TO AN EMINENT PLACE AMONG THE MOST ILLUSTRIOUS FOLLOWERS OF SCIENCE AND THE REAL BENEFACTORS OF THE WORLD".

A bust of Watt is in the Hall of Heroes of the [[National Wallace Monument]] in [[Stirling]], Scotland.

The [[French Navy]] [[submarine]] {{ship|French submarine|Watt||2}} was named for Watt.

==Patents==
Watt was the sole inventor listed on his six patents:<ref>Hills, vol. 3, p. 13.</ref>
* Patent 913: A method of lessening the consumption of steam in steam engines – the separate condenser. The specification was accepted on 5 January 1769; enrolled on 29 April 1769, and extended to June 1800 by an Act of Parliament in 1775.
* Patent 1,244: A new method of copying letters. The specification was accepted on 14 February 1780 and enrolled on 31 May 1780.
* Patent 1,306: New methods to produce a continued rotation motion&nbsp;– sun and planet. The specification was accepted on 25 October 1781 and enrolled on 23 February 1782.
* Patent 1,321: New improvements upon steam engines&nbsp;– expansive and double acting. The specification was accepted on 14 March 1782 and enrolled on 4 July 1782.
* Patent 1,432: New improvements upon steam engines&nbsp;– three bar motion and steam carriage. The specification was accepted on 28 April 1782 and enrolled on 25 August 1782.
* Patent 1,485: Newly improved methods of constructing furnaces. The specification was accepted on 14 June 1785 and enrolled on 9 July 1785.

{{Clear}}

==Notes==
{{notelist}}

==References==
{{Reflist}}

===Sources===
* {{cite journal |title=Some Unpublished Letters of James Watt |journal=Journal of Institution of Mechanical Engineers |location=London |date=1915}}
* [[Andrew Carnegie|Carnegie, Andrew]], ''James Watt'' University Press of the Pacific (2001) (Reprinted from the 1913 ed.), {{ISBN|0-89875-578-6}}.
* {{cite book |last=Dickinson |first=H. W. |title=James Watt: Craftsman and Engineer |url=https://archive.org/details/jameswattcraftsm0000dick |url-access=registration |year=1935 |publisher=Cambridge University Press}}
* {{cite book |last1=Dickinson |first1=H. W. |last2=Vowles |first2=Hugh Pembroke |author-link2=Hugh Pembroke Vowles |title=James Watt and the Industrial Revolution |orig-date=1943 |date=1949}}
* [[Richard L. Hills|Hills, Rev. Dr. Richard L.]], ''James Watt, Vol 1, His time in Scotland, 1736–1774'' (2002); Vol 2, ''The years of toil, 1775–1785''; Vol 3 ''Triumph through adversity 1785–1819.'' Landmark Publishing Ltd, {{ISBN|1-84306-045-0}}.
* {{cite book | author = Hulse David K. | title = The early development of the steam engine | year = 1999 | publisher = TEE Publishing | location = Leamington Spa, UK | isbn = 1-85761-107-1 | pages = 127–152}}
* {{cite book | author = Hulse David K. | title = The development of rotary motion by steam power | publisher = TEE Publishing Ltd. | location = Leamington, UK | year = 2001 | isbn = 1-85761-119-5}}
* Marsden, Ben. ''Watt's Perfect Engine'' Columbia University Press (New York, 2002), {{ISBN|0-231-13172-0}}.
* Marshall, Thomas H. (1925), ''James Watt'', [https://web.archive.org/web/20100615081524/http://www.history.rochester.edu/steam/marshall/chapter3.html Chapter 3: Mathematical Instrument Maker], from [https://web.archive.org/web/20051212142412/http://www.history.rochester.edu/steam/ Steam Engine Library] of [[University of Rochester]] Department of History.
* Marshall, Thomas H. (1925) [https://web.archive.org/web/20051221105312/http://www.history.rochester.edu/steam/marshall/ ''James Watt''], [[University of Rochester]] Department of History.
* {{cite book |last=Muirhead |first=James Patrick |title=Origin and Progress of the Mechanical Inventions of James Watt |publisher =John Murray |location=London |year=1854 |url=https://books.google.com/books?id=9lspAAAAYAAJ&q=Origin+and+Progress+of+the+Mechanical+Inventions+of+James+Watt.}}
* {{cite book |last=Muirhead |first=James Patrick |title=The Life of James Watt |publisher=John Murray |location=London |year=1858 |url = https://archive.org/details/in.ernet.dli.2015.24829 |quote=The life of James Watt with selections from his correspondence.}}
* Roll, Erich (1930). ''An Early Experiment in Industrial Organisation : being a History of the Firm of Boulton & Watt.'' 1775–1805. Longmans, Green and Co.
* [[Samuel Smiles|Smiles, Samuel]], ''Lives of the Engineers'', (London, 1861–62, new edition, five volumes, 1905).

;Related topics
* {{cite book |last=Schofield |first=Robert E. |title=The Lunar Society, A Social History of Provincial Science and Industry in Eighteenth Century England |year = 1963 |publisher = Clarendon Press }}
* {{cite book |last=Uglow |first=Jenny |author-link=Jenny Uglow |title = The Lunar Men |url=https://archive.org/details/lunarmenfivefrie00uglo |url-access = registration |year = 2002 |location = London |publisher = Farrar, Straus and Giroux |isbn=9780374194406}}

==External links==
{{wikiquote}}
{{Commons category}}
{{wikisource author}}
* [https://archive.org/stream/jameswatt00carniala#page/n9/mode/2up James Watt by Andrew Carnegie (1905)]
* [https://archive.org/details/james_watt_bb_librivox Librivox audiobook: James Watt by Andrew Carnegie (1905)]
* [https://web.archive.org/web/20051221105312/http://www.history.rochester.edu/steam/marshall/ James Watt by Thomas H. Marshall (1925)]
* [http://www.birmingham.gov.uk/cs/Satellite?c=Page&childpagename=Lib-Central-Archives-and-Heritage%2FPageLayout&cid=1223092751138&pagename=BCC%2FCommon%2FWrapper%2FWrapper Archives of Soho] {{Webarchive|url=https://web.archive.org/web/20111031120629/http://birmingham.gov.uk/cs/Satellite?c=Page&childpagename=Lib-Central-Archives-and-Heritage%2FPageLayout&cid=1223092751138&pagename=BCC%2FCommon%2FWrapper%2FWrapper |date=31 October 2011 }} at Birmingham Central Library.
* [https://www.bbc.co.uk/history/historic_figures/watt_james.shtml BBC History: James Watt]
* [http://www.engineeringhalloffame.org/profile-watt.html Scottish Engineering Hall of Fame – James Watt]
* [https://web.archive.org/web/20060308154827/http://www.revolutionaryplayers.org.uk/home.stm Revolutionary Players website]
* [https://web.archive.org/web/20171106174825/http://crocat.cornwall.gov.uk/dserve/dserve.exe?dsqIni=Dserve.ini&dsqApp=Archive&dsqDb=Catalog&dsqCmd=Overview.tcl&dsqSearch=(RefNo='ad1583') Cornwall Record Office Boulton and Watt letters]
* [http://www.electricscotland.com/history/men/james_watt.htm Significant Scots – James Watt]
* {{cite web|url=http://www.history.rochester.edu/steam/carnegie/ch8.html |title=Chapter 8: The Record of the Steam Engine |publisher=history.rochester.edu |access-date=6 July 2009 |url-status=dead |archive-url=https://web.archive.org/web/20090708035056/http://www.history.rochester.edu/steam/carnegie/ch8.html |archive-date= 8 July 2009 }}

{{Scientists whose names are used as SI units}}
{{Authority control}}

{{DEFAULTSORT:Watt, James}}
[[Category:James Watt| ]]
[[Category:18th-century Scottish engineers]]
[[Category:18th-century British scientists]]
[[Category:18th-century Scottish people]]
[[Category:1736 births]]
[[Category:1819 deaths]]
[[Category:Alumni of the University of Glasgow]]
[[Category:Astronomical instrument makers]]
[[Category:Fellows of the Royal Society]]
[[Category:Fellows of the Royal Society of Edinburgh]]
[[Category:Industrial Revolution in England]]
[[Category:Industrial Revolution in Scotland]]
[[Category:Members of the Lunar Society of Birmingham]]
[[Category:People associated with energy]]
[[Category:People associated with Heriot-Watt University]]
[[Category:People from Greenock]]
[[Category:People of the Scottish Enlightenment]]
[[Category:Scottish businesspeople]]
[[Category:Scottish business theorists]]
[[Category:Scottish chemists]]
[[Category:Scottish deists]]
[[Category:Scottish Engineering Hall of Fame inductees]]
[[Category:Scottish inventors]]
[[Category:Scottish Presbyterians]]
[[Category:Scottish surveyors]]