Watt Steam Engine

A walk on Glasgow Green

James Watt was a humble instrument-maker at the University of Glasgow when he was asked to repair a model of Thomas Newcomen's atmospheric engine. The model worked — barely — but Watt was struck by how monstrously inefficient it was. The cylinder had to be heated and cooled with every stroke, wasting almost all of the steam's energy.

On a Sunday afternoon in 1765, walking across Glasgow Green, the answer arrived with the suddenness of a revelation: separate the condenser from the cylinder. Let the cylinder stay hot. Let the steam rush into a separate, cool vessel and condense there.

Boulton, Birmingham, and the world

It took years of experiment, debt, and grit before Watt's idea became a workable engine. In Matthew Boulton he found the perfect partner — a Birmingham industrialist with capital, ambition, and a manufactory that could machine cylinders to undreamt-of tolerances.

Together they built engines that pumped water from Cornish tin mines, drove the mills of Lancashire and the forges of the Black Country, and ultimately set in motion a transformation of human life so total we are still living inside it.

The unit of power

Long after Watt's death in 1819, the International System of Units chose his name for the SI unit of power. Every time you read a light-bulb's wattage, you are reading a small monument to a Greenock-born tinkerer who refused to let a bad engine stand.