James Watt: The Engineer Who Measured the Power of an Age

Few figures of the eighteenth century left a deeper or more durable mark upon the modern world than the soft-spoken Scottish instrument maker who, between 1763 and his patent of 1769, transformed the steam engine from a wheezing pumping device into the universal prime mover of industrial civilization. The image of James Watt as a daydreaming boy watching a tea kettle boil and intuiting from the dancing of its lid the principle of steam power is a charming Victorian invention with little historical foundation. The real story is more interesting and more revealing. Watt was a slow, patient, melancholic, and stubbornly methodical man, often laid low for weeks at a time by migraine and stomach trouble, given to spells of black depression that bordered on incapacity, and disposed by temperament toward an exacting perfectionism that drove him to spend years refining an idea that lesser engineers would have rushed into the marketplace half-formed. He was a working tradesman before he was an inventor, a mathematical instrument maker by craft, a chemist by avocation, a surveyor and civil engineer by necessity, and finally — after his decisive partnership with the Birmingham manufacturer Matthew Boulton — the most consequential mechanical engineer of his century. The unit of power that bears his name is fittingly the unit that quantifies the very thing he taught the modern world how to count: the rate at which a machine does work. Before Watt, work was the labor of arms and backs, of falling water and rising wind, of horses heaving against traces; after Watt, work was the controlled and metered output of engines fed by coal, and the wealth of nations could be measured in horsepower as surely as in gold.

He was born on 19 January 1736 in the modest port town of Greenock on the south bank of the River Clyde, the son of a Scottish shipbuilder, ship's chandler, town councilor, and treasurer of the burgh; he was reared in the dissenting Presbyterian tradition of the western Lowlands, learned the trade of mathematical instrument making in London and Glasgow, and at the age of twenty-one took up a small workshop and a sub-letter's pair of rooms in the precincts of the University of Glasgow, where Adam Smith, Joseph Black, and the philosopher Thomas Reid were teaching during the heroic decades of the Scottish Enlightenment. He read voraciously, taught himself French and German and Italian in order to consult the technical literature of continental Europe, befriended professors and students alike, and through his consultations with the chemist Joseph Black absorbed the new theory of latent heat that would later inform his fundamental analysis of the wasteful operation of the Newcomen pumping engine. The patent he obtained on 5 January 1769 for "A New Invented Method of Lessening the Consumption of Steam and Fuel in Fire Engines" was the single most important industrial patent of the eighteenth century. Through his partnership from 1775 with Matthew Boulton at the great Soho Manufactory on the outskirts of Birmingham, he supervised, over the following twenty-five years, the construction of nearly five hundred steam engines that drained the deepest tin mines of Cornwall, powered the cotton mills of Lancashire, drove the bellows and hammers of the ironworks of South Wales and the Black Country, and propelled the early commercial steamships that would soon shrink the Atlantic and open the rivers of America to the steam age. By the time his Soho patents expired in 1800, the steam engine had become the irreplaceable instrument of British industrial supremacy, and Britain had become the first nation in human history to transcend the ancient constraints of organic energy and to build its prosperity upon the controlled combustion of fossil fuel.

But the conventional story of Watt as solitary inventor obscures both the social texture of his achievement and the depth of his other contributions. He was, throughout his life, a member of a remarkable circle of natural philosophers and industrial improvers — the Lunar Society of Birmingham, which gathered around Boulton at the full moon on Mondays and which numbered among its dozen or so habitual members the potter Josiah Wedgwood, the physician and natural philosopher Erasmus Darwin (grandfather of Charles), the dissenting chemist and theologian Joseph Priestley, the geologist James Keir, the metallurgist John Roebuck, and a shifting penumbra of correspondents that reached from Benjamin Franklin in Philadelphia to Antoine Lavoisier in Paris. Through this circle Watt's engine drew its first capital, its skilled mechanics, its political friends in Parliament, and the cultural credit that allowed industrial improvers to be received as members of the Republic of Letters rather than merely as ingenious mechanics. Watt himself contributed to that circle's intellectual exchange far more than the steam engine. He invented (or shares the credit for inventing) the technique of letter-copying that became the standard office procedure throughout the English-speaking world until photocopying replaced it in the mid-twentieth century. He devised the first attachment for direct mechanical drawing of engine-indicator diagrams, by which the changing pressure of steam inside a cylinder could be plotted graphically against the position of the piston, giving engineers for the first time a precise and quantitative window into the thermodynamic operation of their machines. He played a substantial part in the chemical controversies of the 1780s, and was a serious contender (along with Henry Cavendish and Lavoisier) for the discovery of the composition of water. He participated in canal and harbor surveys across Scotland and northern England, designed the bleaching with chlorine that revolutionized the linen industry, and produced architectural drawings, hydraulic calculations, and improvements in pottery glazing that would be the work of a respectable career on their own. The slow, melancholy, depressive instrument maker of the rue d'Argyll in Glasgow turned out, when his temperament permitted, to be one of the most versatile minds of his century.

Yet for all the breadth of his accomplishments, it is the steam engine that defines him and that justifies the lavish memorials raised to his memory after his death — the statue in Westminster Abbey, the colossal seated bronze in St. George's Hall in Liverpool, the monumental column in Greenock, the dozens of schools and engineering institutes and public houses across the British Isles that bear his name. When the British Association for the Advancement of Science formalized the system of mechanical units that would become the international standard, the unit of power was named the watt by an act of conscious historical homage: a watt is the rate of doing work equal to one joule per second, and by that measure the worldwide electrical generating capacity of the early twenty-first century amounts to roughly six trillion watts, or six terawatts. The unit and the man are everywhere. Yet in his lifetime he was, by his own repeated description, an anxious tradesman, plagued by debt, by litigation against patent infringers, by family bereavement, by recurrent ill-health, by a wife (his first) who died in childbirth and a second wife who outlived him by a decade, by sons he loved and could not always shield from the consequences of their political enthusiasms. The portraits we have of him in middle age show a face of unmistakable gentleness, deeply lined, with high cheekbones, a delicate long nose, and large, melancholy gray-green eyes; in old age he appears in caricature and in dignified academic portraits as a benevolent patriarch, but the patriarchy was earned at the price of decades of patient struggle. The biography that follows traces that struggle in detail — the early years in Greenock, the apprenticeship in London, the long Glasgow phase, the decisive collaborations of the 1760s, the partnership with Boulton, the great expansion of the steam-engine business, the personal sorrows and friendships of his middle years, the chemical controversies and political crises through which he passed, the comfortable retirement at Heathfield outside Birmingham, and the worldwide diffusion of his ideas in the century after his death in 1819.

Birth and Family in Greenock

James Watt was born on the morning of 19 January 1736 in the family house on Dalrymple Street, Greenock, a busy port and ship-building town on the south bank of the Firth of Clyde some twenty-five miles down the river from Glasgow. Greenock in the 1730s was a place of perhaps three thousand inhabitants set between the steep wooded hills of the Renfrewshire shore and the broad, salty tide of the lower Clyde. Its prosperity depended on the herring fishery, on the building and repair of wooden trading vessels, on the importing of timber from the Baltic and tobacco from Virginia, and on the modest re-export trade through which Scottish merchants forwarded West Indian sugar, rum, and molasses to the markets of northern Europe. The town had grown rapidly in the half-century since the Union of 1707 had opened the protected colonial markets of the British Empire to Scottish enterprise, and James Watt was born into a family that had risen with the rising fortunes of the Clydeside burghs.

His grandfather Thomas Watt had been a teacher of mathematics, surveying, and navigation in the neighboring parish of Cartsburn, where he had run a small private school that prepared young men for the practical professions of an Atlantic port. Thomas Watt was a man of some local distinction — he had been a kirk elder, a member of the burgh council, a friend of professors at the University of Glasgow, and a survivor of the bitter sectarian struggles of the seventeenth century that had given the Lowlands their stern Presbyterian temper. He had taught his sons the rudiments of mathematics and the practical applications of geometry to surveying and navigation, and one of those sons, James Watt the elder (the inventor's father), had carried that combination of practical learning and mercantile ambition into the next generation.