I have reason to be careful of the balloon of my "No. 7." In it the speed problem will be attacked definitely. It has two propellers, each 5 metres (16½" feet) in diameter. One will push, as usual, from the stern, while the other will pull from the stem, as in my "No. 4." Its 60 horse-power Clement motor will, if my expectations are fulfilled, give it a speed of between 70 and 80 kilometres (40 and 50 miles) per hour. In a word, the speed of my "No. 7" will bring us very close to practical, everyday aerial navigation, for as we seldom have a wind blowing as much even as 50 kilometres (30 miles) per hour such an air-ship will surely be able to go out daily during more than ten months in the twelve.
[CHAPTER XX]
AN ACCIDENT AND ITS LESSONS
At half-past two o'clock on the afternoon of the 14th of February 1902 the staunch air-ship which won the Deutsch prize left the aerodrome of La Condamine on what was destined to be its last voyage.
Immediately on quitting the aerodrome it began behaving badly, dipping heavily. It had left the balloon house imperfectly inflated, hence it lacked ascensional force. To keep my proper altitude I increased its diagonal pointing and kept the propeller pushing it on upward. The dipping, of course, was due to the counter effort of gravity.
In the shaded atmosphere of the aerodrome the air had been comparatively cool. The balloon was now out in the hot, open sunlight. As a consequence, the hydrogen nearest to the silk cover rarefied rapidly. As the balloon had left the aerodrome imperfectly inflated the rarefied hydrogen was able to rush to the highest possible point—the up-pointing stem. This exaggerated the inclination which I had made purposely. The balloon pointed higher and higher. Indeed, for a time, it seemed almost to be pointing perpendicularly.
Before I had time to correct this "rearing up" of my aerial steed many of the diagonal wires had begun to give way, as the slanting pressure on them was unusual, and others, including those of the rudder, caught in the propeller.
Should I leave the propeller to grind on the rigging the balloon envelope would be torn the next moment, the gas would leave the balloon in a mass, and I would be precipitated into the waves with violence.
I stopped the motor. I was now in the position of an ordinary spherical balloonist—at the mercy of the winds. These were taking me in shore, where I would be presently cast upon the telegraph wires, trees, and house corners of Monte Carlo.