I didn't lose sight of it for a moment, I heard the engine start up and [the machine] began to roll in a straight line. I was watching from a little to one side … It covered perhaps 100 metres and then it rose very slowly, gained height and I saw it clearly above the heads of the crowd. How high was it? 20 metres, perhaps 25. It was pitching quite heavily as it progressed and after 100 or 150 metres it changed direction slightly. I had the impression the pilot was having trouble with the steering. Then suddenly I saw it fall.' Ader subsequently claimed he had achieved flight; certainly, it skipped across the ground. But there were obvious problems with stability and steering, as well as the matter of the steam engine. And it was not sustained flight.
His most lasting contribution was the introduction of the word 'avion' into the French language, to mean 'aircraft'. It replaced 'aéroplane' in official usage in 1910 as a tribute to the inventor, and subsequently became the standard word.
Pictures: Ader in old age; Ader's engine; a painting showing the trial of Eole; Charles Freycinet, Minister of War; Aquilon, currently hanging in the Museum of Arts et Métiers in Paris; a contemporary reconstruction of his 'flight'; the pilot's compartment of Aquilon, showing the pilot had no forward view; the monument to Ader, appropriately enough situated in the Rue Clement Ader, Versailles.