Scottish-born James Watt is remembered for designing the steam engine that powered Britain’s Industrial Revolution. Even during his lifetime, Watt had a reputation for being a leading mind in engine technology.
Yet Watt’s contribution to the efficiency of industry was not limited to Britain’s great steam-powered beasts. His best-known work on steam engines inspired a host of contributions to the world of science.
From a young boy making models in his father’s workshop to a man who engineered an industrial revolution, here’s the fascinating life and legacy of James Watt. 
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From Greenock to Glasgow
On 19 January 1736, in the Scottish town of Greenock, Agnes Muirhead and James Watt’s first child was born. They named their newborn son James after his father, a shipwright who acquired most of his wealth from the Atlantic slave trade.
Because he was often ill, Watt’s early childhood was spent at home being taught by his mother. But it was in his father’s workshop, sat at his own bench making models and repairing nautical instruments, that Watt’s education in engineering began.
In 1755, aged just 18, he left for London to train as a journeyman instrument-maker. Yet it wasn’t long before Watt was drawn back to his homeland. A year after leaving Scotland he returned to settle in Glasgow, a city bursting with trade and opportunity.
Portrait of Scottish inventor and mechanical engineer James Watt
Image Credit: Carl Frederik von Breda, Public domain, via Wikimedia Commons
Despite not having finished his apprenticeship, Watt’s arrival in the bustling port coincided with a delivery of astronomical instruments given by the physicist Alexander MacFarlane to the University of Glasgow. The instruments were in terrible condition and needed repairing; Watt was just the man for the job.
Now with some experience and money in his pocket, Watt was offered the chance to set up a workshop at the university. Among a myriad of other objects, his time was spent making and repairing parts for telescopes, rulers, scales and barometers.
Did James Watt invent the steam engine?
Although often dismissed as a myth and told in many forms, popular stories claim Watt was inspired to invent the steam engine after seeing a kettle boil, lifting the lid and showing him the power of steam.
Watt did not invent the first steam engine. Thomas Newcomen’s engine had been in use pumping water from mines for almost 50 years by the time Watt began experimenting in 1759. Even Newcomen was inspired by Thomas Savey’s 1698 invention.
However, the stories of Watt and the kettle are based in fact. In his diaries, Watt describes that in trying to understand the thermodynamics of heat and steam, he used a kettle to generate steam.
Powering the revolution
In 1763, Watt was asked to repair a model Newcomen engine belonging to Glasgow University. After considerable experimentation, he discovered most of the energy was wasted on repeatedly heating and cooling the engine cylinders.
The solution came to Watt 2 years later whilst strolling through Glasgow’s Green Park: by creating a separate cylinder to cool the steam, you could maintain the rest of the engine piston’s temperature.
Matthew Boulton, an engineer and owner of the Soho Manufactory works near Birmingham, saw the genius in Watt’s design and bought a share of his patent in 1776. Boulton’s support gave Watt access to some of the world’s finest ironworks to perfect his engine. Watt then spent long periods in Cornwall installing pumping engines for copper and tin mines, whose managers wanted to reduce fuel costs. But he was no businessman.
Engraving of a 1784 steam engine designed by Boulton and Watt (left) / James Watt. Stipple engraving by H. Adlard after H. Corbould after Sir F. Chantrey (right)
Image Credit: Robert Henry Thurston (1839–1903), Public domain, via Wikimedia Commons (left) / H. Adlard, CC BY 4.0
Instead, it was Boulton who raised the capital for their company and foresaw a new market in corn and cotton mills. He urged Watt to improve his earlier engine to suit the different industries. The result was Watt’s ‘double-acting engine’, which let steam condense on both sides of the piston, effectively doubling an engine’s power.
Boulton and Watt’s partnership was hugely successful and lasted some 25 years, only to be continued by their sons Matthew Robinson Boulton and James Watt Jr. 
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What was James Watt’s legacy?
Watt needed a way of describing and accurately measuring the output of his steam engines. Comparing the power output of steam engines to the power output of draft horses, the living engines of the pre-industrial world, Watt coined the term ‘horsepower’ which is still used today to describe pulling power.
Modern workplaces are also indebted to Watt’s creativity. In the 1780s he developed a way of making precise copies of drawings without having to trace them by hand, inventing the first copying machine.
Carl Frederik von Breda, Public domain, via Wikimedia Commons
Image Credit: Andrew Gray, CC BY-SA 3.0
James Watt died on 25 August 1819 at his home in Staffordshire, near Birmingham. By the time of his death, he was a wealthy man, his engines in use at paper, flour, cotton and iron mills, as well as distilleries, waterworks and canals.
In 1960, at the 11th General Conference on Weights and Measures, the ‘watt’ was made a universally recognised unit of power. Today, most of the electrical devices in our homes are measured in watts, named for the ingenious Scottish engineer.
