McNaught, William (1813–1881)

Scottish mechanical engineer who developed a compound steam engine in 1845. This type of engine extracts the maximum energy from the hot steam by effectively using it twice – once in a high-pressure cylinder (or cylinders) and then, when exhausted from this, in a second, low-pressure cylinder.

McNaught was born in Paisley and joined his father's steam-engine firm. In 1849 he moved to Manchester. The firm of J and W McNaught was established in 1860, manufacturing steam engines until 1914.

By 1845, the cotton and wool mill owners in the north of England thought that they would have to replace their steam engines with bigger ones to keep up with the demand for more power. McNaught's conversion to compound action saved them this financial outlay. His method became known as ‘McNaughting’, and was to be a valuable energy-saving system for many years to come.

Three types of new engine were to emerge using McNaught's principle. The first used cylinders mounted side by side, the second had cylinders in a line (a tandem compound), and the third and rarest type had the high-pressure cylinder enclosed by the low-pressure one.