compact high-speed circulation steam engine, for which he applied for a patent on 28 April 1876. The engine used very small pipes packed together "to obtain the highest possible contact surface for the smallest possible volume" "When he began with the aid of his brother, M. Louis du Temple, to experiment on a large scale, the inadequacy of all motors then known became apparent. They first tried steam at very high pressures, then a hot-air engine, and finally built and patented, in 1876 a very light steam boiler weighing from 39 to 44 lb. to the horse power, which appears to have been the prototype of some of the light boilers which have since been constructed. It consisted in a series of very thin tubes less than 1/8 inches in internal diameter, through which water circulated very rapidly, and was flashed into steam by the surrounding flame." Octave Chanute, Aeroplanes: Part III, August 1892 The "Monoplane" In 1874, the two brothers built the Monoplane, a large plane made of aluminium in Brest, France, with a wingspan of 13 meters and a weight of only 80 kilograms (without the pilot). Several trials were made with the plane, and it is generally recognized that it achieved lift off under its own power after a ski-jump run, glided for a short time and returned safely to the ground, possibly making it the first successful powered flight in history, depending on the definition — since the flight was only a short distance and a short time. The plane was displayed at the 1878 World Fair (Exposition Universelle (1878)) in Paris. High-circulation steam engine The plane's engine used a very compact, high-speed circulation steam boiler, the Du Temple boiler, for which Félix du Temple applied for a patent on 28 April 1876. The engine used very small pipes packed together "to obtain the highest possible contact surface for the smallest possible volume". The original steam engine which had been developed by Félix du Temple was later commercialized by him from a company he established in Cherbourg, "Générateur Du Temple S.A." and became highly successful. The design was adopted by the French Navy for the propulsion of the first French torpedo boats: "Officers and engineers have now made up their opinion regarding Du Temple's steam engine. Everybody proclaims the superiority of its qualities… orders are pouring in from our commercial harbours and from the French government."