James Watt

• 1. Introduction

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  "I can think of nothing else but this machine." Those words belong to James Watt, the Scottish inventor, engineer and chemist born in Greenock on the 19th of January 1736. He did not invent the steam engine. Thomas Newcomen had built one in 1712, and it had pumped water from mines for almost 50 years before Watt touched it. Yet the unit of power we measure today, the watt, carries his name. So does a £50 note, where he stands beside his business partner. How did a man who repaired telescopes and barometers at a university workshop become the figure historians tie to the Industrial Revolution? What did he see in a broken model engine that John Smeaton and other clever engineers had missed? And why did the man behind a world-changing machine confess that he would rather face a loaded cannon than make a bargain?

• 2. The Separate Condenser

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  In 1763, the University of Glasgow handed Watt a model Newcomen engine to repair. Even after he fixed it, the engine barely worked. After much experimentation, he discovered the reason. About three-quarters of the steam's thermal energy was being burned just heating the cylinder on every single cycle. The waste came from the machine's basic rhythm. Cold water was injected into the cylinder to condense the steam, then the whole cylinder had to be reheated again, over and over.

  Watt's answer arrived in May 1765, as he crossed Glasgow Green park. Let the steam condense in a separate chamber, away from the piston. Keep the cylinder itself hot by wrapping it in what he called a "steam jacket". Almost no energy would be lost to reheating, leaving far more to do useful work. He had a working model later that same year. This separate condenser became his first and most important patent, accepted on the 5th of January 1769. Behind the insight lay groundwork from a friend. Watt grasped the importance of latent heat, the thermal energy released or absorbed at constant temperature, though Joseph Black had discovered it years earlier, unknown to Watt at the time.

• 3. The Glasgow Workshop

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  Astronomical instruments bequeathed by Alexander MacFarlane arrived from Jamaica, and they needed expert attention. Watt restored them and was paid, and they were eventually installed in the Macfarlane Observatory. That repair job opened a door. Three professors offered him space for a small workshop within the University of Glasgow, set up in 1757. Two of them, the physicist and chemist Joseph Black and the economist Adam Smith, became his friends.

  The work was modest at first. Watt maintained and repaired scientific instruments, helped with demonstrations, and made brass reflecting quadrants, parallel rulers, scales, parts for telescopes, and barometers. He had reached this point the hard way. When he was 18, his mother died and his father's health began to fail, and he travelled to London for a single year of training as an instrument maker between 1755 and 1756. Without a full apprenticeship, he lacked the usual connections to set himself up as a journeyman. In 1759 he formed a partnership with John Craig to make musical instruments and toys, a venture that employed up to 16 workers and lasted six years until Craig died in 1765.

• 4. Boulton And Watt

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  John Roebuck, founder of the Carron Iron Works near Falkirk, was Watt's first major backer. Watt perfected his engine in a cottage beside Roebuck's home, Kinneil House in Bo'ness. The shell of that cottage still exists. But the real obstacle was metal. Watt needed a piston that was air tight, where a Newcomen engine only needed a water-tight seal, and the cylinders he could buy were not good enough. Strapped for resources, he was forced into other work, first as a surveyor and then as a civil engineer, for eight years.

  Roebuck went bankrupt, and Matthew Boulton, owner of the Soho Manufactory near Birmingham, acquired the patent rights. The partnership Boulton and Watt began in 1775 and lasted 25 years. Through Boulton, Watt finally reached the best iron workers in the world. John Wilkinson, who had developed precision boring for cannon at Bersham near Wrexham, solved the problem of a large cylinder with a tightly fitting piston. By 1776 the first engines were installed in commercial enterprises, pumping water out of mines, mostly in Cornwall. The firm did not even own a foundry until the Soho Foundry opened in 1796, so the great castings were made by others to Watt's drawings.

• 5. Beyond Pumping Water

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  Boulton urged Watt to make the engine do more than move pump rods up and down. The challenge was turning the piston's back-and-forth motion into rotation for grinding, weaving and milling. A crank was the obvious solution, but James Pickard held the patent for it. Watt refused to cross-license his condenser in exchange, and instead the firm circumvented the problem with the sun and planet gear in 1781.

  Over the next six years the improvements piled up. A double-acting engine let steam push on both sides of the piston. Watt described working steam "expansively" at higher pressures, and a compound engine that linked two or more engines together. The invention he was most proud of was the parallel motion linkage, patented in 1784, which produced straight-line motion from the arc of a rocking beam. A centrifugal governor, patented in 1788, kept an engine from running away. Together these made an engine up to five times as fuel efficient as Newcomen's. One device Watt kept as a trade secret was the steam indicator, which plotted pressure against volume inside the cylinder. For all this ambition, the danger of exploding boilers kept him cautious, and every one of his engines ran on steam at near atmospheric pressure.

• 6. Defending The Patent

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  By 1792, Edward Bull was building engines of his own design with a separate condenser, infringing Watt's patents. The Hornblower brothers, Jabez Carter and Jonathan Junior, began building engines around the same time. Mine owners in Cornwall grew convinced the patent could not be enforced and started withholding payments. By 1795 the firm had fallen on hard times. Of the total £21,000 owed, only £2,500 had been received.

  Watt went to court. He first sued Bull in 1793, and the jury found for him, though the validity of the patent's specification was left for another trial. Injunctions forced the infringers to place royalties in escrow, and most began to settle. Jonathan Hornblower held out and was brought to trial in 1799, where the verdict of the four judges went decisively in Watt's favour. The most painful case was John Wilkinson, the very man whose boring solved the cylinder problem. He had erected about 20 engines without Boulton and Watt's knowledge, and settled in 1796. The trials cost enormous money and time, yet ended in success for the firm.

• 7. Ink, Chlorine And Sculpture

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  Before 1780, there was no good way to copy a letter or a drawing. Watt's solution, developed from 1779, was to transfer ink physically from the original onto a thin moistened sheet pressed against it, so the writing could be read through the back when held to the light. He patented the process a year later and formed a new firm, James Watt and Co, with Boulton providing financing and James Keir managing the business. The copying machine became a commercial success and was used in offices into the 20th century.

  Chemistry pulled at Watt from an early age. In late 1786 in Paris, he watched Claude Louis Berthollet react hydrochloric acid with manganese dioxide to make chlorine. Watt had already found that chlorine in solution could bleach textiles. Back in Britain he tried a mixture of salt, manganese dioxide and sulphuric acid, then passed the chlorine into weak alkali, and shared his results with his father-in-law James McGrigor, a Glasgow bleacher. In March 1788, McGrigor bleached 1500 yards of cloth. But Berthollet published a similar process, rivals overtook Watt, and he dropped out. In his retirement at Handsworth, Watt turned to a garret-room workshop, building machines that copied sculptures and medallions. One of the first heads he produced was of his old friend Adam Smith.

• 8. The Measure Of The Man

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  "Those who consider James Watt only as a great practical mechanic form a very erroneous idea of his character." So said the chemist Humphry Davy, who praised Watt as a natural philosopher and chemist whose genius lay in uniting the sciences for practical use. Watt was an important member of the Lunar Society of Birmingham and a sought-after companion, with friendships and partnerships that lasted. Lord Liverpool, the Prime Minister, called him "A more excellent and amiable man in all the relations of life I believe never existed."

  Watt retired in 1800, the year his fundamental patent and partnership with Boulton expired, and the firm passed to their sons. In 1816 he took a trip on the paddle-steamer Comet, itself a product of his inventions, to revisit Greenock. He died on the 25th of August 1819 at his home, Heathfield Hall near Handsworth, at the age of 83, and was buried on the 2nd of September at St Mary's Church. His garret workshop was left locked and untouched as a kind of shrine until his biographer J. P. Muirhead first viewed it in 1853. When the house faced demolition in 1924, the entire room and its contents were given to the Science Museum, where the workshop that held his last inventions can still be seen.