Jonathan Hornblower built this, the first compound steam engine. Hornblower patented compounding in 1781, but used steam pressures that were too low for it to work effectively.
Image: Science Museum/SSPL

Work with Boulton and Watt

Bigger factories needed more power. For steam engines this meant 'compounding' - a technique using high-pressure steam first in a small cylinder and then in a larger one to increase the amount of work done.

Arthur Woolf developed effective compounding in 1804. Woolf's engines did the same work as James Watt's, using only half the fuel. Those, like our engine, built by Hall of Dartford were described as 'the best specimens of that kind of engine which can be found'.