In 1838 William Barnett took out a patent for an engine based on the same principle as that of Lebon. Two pumps compressed separately the combustible gas and the air and forced the mixture under pressure into the cylinder. The explosion was caused by a small gas-jet, communication between it and the cylinder being set up at the right moment by a revolving valve. The gas-jet was situated in the valve itself, and was so arranged that during half a revolution it was turned towards the outside, and was then lighted by a second jet, and during the remainder of the revolution it communicated with the interior of the cylinder and ignited the explosive mixture. This was the first gas motor in which the ignition was from the outside, and in which the explosive gases were at the same time under pressure. In most modern gases the same result is obtained, but the original and rather crude method of obtaining it has of course been much modified and improved. During the next few years several patents were taken out relating to the same subject. In 1844 John Reynolds suggested using a battery which should white-heat a platinum wire in order to ignite the gases, the ignition taking place at the required moment by means of an automatic switch closing the battery circuit.
In 1850 Stéphard recommended a magneto-electric machine driven by the engine itself instead of the primary battery.
Barsanti and Matteucci described in 1857 an atmospheric motor, their arrangement of the parts being afterwards adopted by Otto and Langen. A Bunsen cell supplied current to a De la Rive multiplier, causing a stream of sparks to pass between two fine points situated within the combustible mixture. In 1858 and 1859 Degrand explained in two patents a gas engine in which the gases were compressed in the cylinder itself. Owing to mechanical difficulties his machine was impracticable, but the idea forms an important step in the history of gas engines.
In 1860, when the Lenoir motor appeared, no other existed which was capable of regular and comparatively efficient work.
This machine, devised by Lenoir and constructed by Marinoni, had the appearance of a double-acting horizontal steam engine. The explosive mixture was ignited by an electric spark produced by a Ruhmkorff coil and a primary battery. The machine ran smoothly and regularly and its cost was moderate: among the advantages which it possessed at that time over other forms of motive power, were the absence of a cumbrous boiler and costly foundations, and the little care and attention necessary to keep it in working order. So great was its success at the time, that many people prophesied that the steam engine would soon become extinct.