In 1891 Langley experimented with steam-engine powered Aerodromes, beginning the series which would lead to the human-carrying machine of 1903. The first of these was designated Aerodrome No. 0 and proved a failure. The second machine, Aerodrome No. 1, was powered by a carbonic acid gas and later by compressed air. Aerodrome No. 2, also built in 1891 was also a disappointment. Aerodrome No. 3 (1892) was of stronger construction and was modified a number of times. A better means of heating the steam was tested on Aerodrome No. 3 and was a decided improvement and was incorporated into Aerodrome No. 4. By the end of 1893 Aerodrome No. 4 was ready for testing and a launching device atop a house boat was built.