The pole keel with its cross pieces, bicycle frame, and mechanism weighed heavy. Therefore, although the balloon was filled with hydrogen, I could not take up more than 50 kilogrammes (110 lbs.) of ballast.
I made almost daily experiments with this new air-ship during August and September 1900 at the Aéro Club's grounds at St Cloud, but my most memorable trial with it took place on 19th September in presence of the members of the International Congress of Aeronautics. Although an accident to my rudder at the last moment prevented me from making a free ascent before these men of science I, nevertheless, held my own against a very strong wind that was blowing at the time, and gave what they were good enough to proclaim a satisfying demonstration of the effectiveness of an aerial propeller driven by a petroleum motor.
A distinguished member of the Congress, Professor Langley, desired to be present a few days later at one of my usual trials, and from him I received the heartiest kind of encouragement.
The result of these trials was, nevertheless, to decide me to double the propeller's power by the adoption of the four-cylinder type of petroleum motor without water jacket--that is to say, the system of cooling _à ailettes_. The new motor was delivered to me very promptly, and I immediately set about adapting the air-ship to it. Its extra weight demanded either that I should construct a new balloon or else enlarge the old one. I tried the latter course. Cutting the balloon in half I had a piece put in it, as one puts a leaf in an extension table. This brought the balloon's length to 33 metres (109 feet). Then I found that the aerodrome was too short by 3 metres (10 feet) to receive it. In prevision of future needs I added 4 metres (13 feet) to its length.
Motor, balloon, and shed were all transformed in fifteen days. The Exposition was still open, but the autumn rains had set in. After waiting, with the balloon filled with hydrogen, through two weeks of the worst possible weather I let out the gas and began experimenting with the motor and propeller. It was not lost time, for, bringing the speed of the propeller up to 140 revolutions per minute, I realised, from a fixed point, a traction effort of 55 kilogrammes (120 lbs.). Indeed, the propeller turned with such force that I took pneumonia in its current of cold air.