Jonathan Hornblower (July 5, 1753 - February 23, 1815) was a British pioneer of steam power. He patented a double-cylinder compound reciprocating beam engine in 1781. He was prevented from developing it further by James Watt, who claimed his own patents were infringed. Compound steam engines use two or more cylinders to allow the steam to expand, beginning at the input pressure and ending at the exhaust pressure, in two or more stages. Compounds are referred to by the number of stages of expansions that the steam undergoes. Most common is the double compound simple referred to as a compound steam engine.