than similarly sized conventional engines. The cylinders had good cooling airflow over them, even when the aircraft was at rest—which was important, as the low airspeed of aircraft of the time provided limited cooling airflow, and alloys of the day were less advanced. Balzer's early designs even dispensed with cooling fins, though subsequent rotaries did have this common feature of air-cooled engines. Balzer produced a 3-cylinder, rotary engined car in 1894, then later became involved in Langley's Aerodrome attempts, which bankrupted him while he tried to make much larger versions of his engines. Balzer's rotary engine was later converted to static radial operation by Langley's assistant, Charles M. Manly, creating the notable Manly–Balzer engine. De Dion-Bouton The famous De Dion-Bouton company produced an experimental 4-cylinder rotary engine in 1899. Though intended for aviation use, it was not fitted to any aircraft. Adams-Farwell The Adams-Farwell firm's automobiles, with the firm's first rolling prototypes using 3-cylinder rotary engines designed by Fay Oliver Farwell in 1898, led to production Adams-Farwell cars with first the 3-cylinder, then very shortly thereafter 5-cylinder rotary engines later in 1906, as another early American automaker utilizing rotary engines expressly manufactured for automotive use. Emil Berliner sponsored its development of the 5-cylinder Adams-Farwell rotary engine design concept as a lightweight power unit for his unsuccessful helicopter experiments. Adams-Farwell engines later powered fixed-wing aircraft in the US after 1910. It has also been asserted that the Gnôme design was derived from the Adams-Farwell, since an Adams-Farwell car is reported to have been demonstrated to the French Army in 1904. In contrast to the later Gnôme engines, and much like the later Clerget 9B and Bentley BR1 aviation rotaries, the Adams-Farwell rotaries had conventional exhaust and inlet valves mounted in the cylinder heads. Gnome The Gnome engine was the work of the three Seguin brothers, Louis, Laurent and Augustin. They were talented engineers and the grandsons of famous French engineer Marc Seguin. In 1906 the eldest brother, Louis, had formed the Société des Moteurs Gnome to build stationary engines for industrial use, having licensed production of the Gnom single-cylinder stationary engine from Motorenfabrik Oberursel—who, in turn, built licensed Gnome engines for German aircraft during World War I. Louis was joined by his brother Laurent who designed a rotary engine specifically for aircraft use, using Gnom engine cylinders. The brothers' first experimental engine is said to have been a 5-cylinder model that