James Watt(1736 — 1819)

Often sickly as a child, James Watt spent much of his early years at home, where he entertained himself by taking apart and reassembling scientific instruments. Legend has it that he once watched steam lifting the lid of a kettle and drew from it the inspiration for his future inventions — but this story is most likely apocryphal. What is certain is that his early mechanical curiosity was remarkable.

In 1764, Watt was given a scale model of Newcomen's steam engine, belonging to the University of Glasgow, to repair. Rather than simply fixing it, he analyzed its fundamental inefficiencies and realized that the problem lay in the cylinder's alternating cooling and heating. This insight led him to invent the separate condenser — the single most decisive improvement in the history of the steam engine.

In 1775, Watt entered into partnership with manufacturer Matthew Boulton, forming the firm Boulton & Watt. Boulton reportedly declared enthusiastically to a visitor: 'I sell here, Sir, what all the world desires to have — Power.' This partnership proved essential, as Watt was a brilliant engineer but poor at business, while Boulton excelled at bringing products to market.

It was James Watt who coined the term 'horsepower' to help industrialists understand the output of his engines by comparing it to that of the horses they replaced. He calculated that a horse could lift roughly 33,000 foot-pounds per minute. The SI unit of power, the watt, was named in his honor in 1882 — more than sixty years after his death.

Watt suffered from migraines and depression throughout his life, which he referred to as his 'nerves.' Despite these hardships, he continued to invent well into old age. In retirement, he set up a workshop in the attic of his home at Heathfield and pursued his experiments with great enthusiasm, including work on mechanical sculpture. He died at the age of 83 in 1819, universally recognized as one of the greatest minds of his era.