The Marquis de Dion and his mechanic, Georges Bouton, invented this single-cylinder, four-stroke (admission, compression, release and exhaust), 1.5-horsepower, 25-kilogram petrol engine in 1895. The exhaust valve was controlled, but petrol was admitted automatically by means of an valve that opened when the piston's downward stroke exerted pressure. Ignition was high voltage: when a circuit-breaker* was opened, a Ruhmkorff coil charged by a battery released electromagnetic energy to produce an arc between the spark plug's electrodes. Air coming in through wide vents along the entire height of the cylinder and its head* cooled the engine, whose exterior appearance and internal design were technical achievements. This invention heralded the reign of the reliable, sturdy, small, light and powerful internal combustion engine. Immediately successful, it was used in tricycles, motorcycles, automobiles, motorboats and even Santos-Dumont's dirigible.