The Lenoir gas engine was the first practical internal combustion engine, anticipating the design of later petrol and diesel engines. It was intended as a compact and more convenient alternative to the steam engine, which required a boiler, furnace and large quantities of coal and water. In the age before an electrical power supply was available, the gas engine appealed to the owners of smaller factories and workshops and ran on the gas supply then used widely in towns for lighting.

The engine drew in a mixture of coal gas and air through a valve. The gas mixture was then fired by an electric spark provided by a battery and induction coil.

The engine enjoyed commercial success for a decade. Unfortunately it proved troublesome to maintain and expensive to run. It was soon overtaken as better gas engines from many different makers came onto the market, most notably those of Otto & Langen. Fewer than 500 Lenoir engines were built before production stopped in 1869.

The engine shown here was initially loaned to the Patent Office Museum (the forerunner of the Science Museum) by the Lenoir company in 1865. It generated about 1 hp (0.75 kW) and was used successfully to run workshop machinery for more than three years.

Inv. 1865-21