Watt began his career as a home-schooled tool and instrument maker. At the University of Glasgow, where he had set up a shop when the local guild rejected his membership, Watt discovered a Newcomen Engine, a basic forerunner of his steam engine. After years of experimentation and tinkering, Watt perfected his engine and then spent massive sums securing a patent before teaming up with Matthew Boulton to manufacture them.
Watt had helped to unleash new forces on the world, revolutionizing the weaving, milling, grinding, and sawing industries. Between 1794 and 1824, Boulton & Watt made over 1,000 engines with a capacity of over 26,000 total horsepower. Eventually, the steam engine transformed not only the manufacturing industries, but it also sparked the Transportation Revolution with the advent first of steamboats and then railroads. A whole new approach to work spread across the globe as men suddenly could harness the power and energy of steam instead of relying on their own muscles—in effect, Watt helped unleash brain power to conquer muscle power for good.
How Stuff Works Steam Engine
Full text of Andrew Carnegie's biography of Watt