[1] Watt's insight was to realise that contemporary engine designs wasted a great deal of energy by repeatedly cooling and reheating the cylinder.

Watt introduced a design enhancement, the separate condenser, which avoided this waste of energy and radically improved the power, efficiency, and cost-effectiveness of steam engines.

[4] 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 chief baillie in 1751.

[3][11] 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 mathematical instrument maker.

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 made and repaired brass reflecting quadrants, parallel rulers, scales, parts for telescopes, and barometers, 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 Harry Lumsden.

[16] 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.

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.

After much experimentation, Watt demonstrated that about three-quarters of the thermal energy of the steam was being consumed in heating the engine cylinder on every cycle.

More substantial backing came from John Roebuck, the founder of the celebrated Carron Iron Works near Falkirk, with whom he now formed a partnership.

The difficulty of the manufacture of a large cylinder with a tightly fitting piston was solved by John Wilkinson, who had developed precision boring techniques for cannon making at Bersham, near Wrexham, North Wales.

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 power for grinding, weaving and milling.

Although a 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.

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.

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.

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.

He discovered that a mixture of salt, manganese dioxide and sulphuric acid could produce chlorine, which Watt believed might be a cheaper method.

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.

According to Lord Liverpool (Prime Minister of the UK),[40] A more excllent and amikable man in all the relations of life I believe never existed.Watt was a prolific correspondent.

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.

[46] 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.

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".

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".

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 Moonstones and a school is named in his honour.

A colossal statue of Watt by Francis Legatt Chantrey was placed in Westminster Abbey,[65] 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".