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460 and inflated. The new balloon had the shape of an elongated ellipsoid, 32 meters(105 feet) on its great axis, and 6 meters (20 feet) on its short axis, terminated fore and aft by cones. Its capacity was 605 cubic meters (21,362 cubic feet), giving it a lifting-power of 620 kilos (1,362 pounds). Of this, 1,100 pounds were represented by keel, machinery, and my own weight, leaving a net lifting-power of 120 kilos (261 pounds). I eliminated every pound of this with ballast, so that while the system belongs to the category of aërial machines lighter than the air (because it can be made to rise by throwing out ballast), it at the same time resembles flying-machines heavier than the air (because it is regularly raised by its propeller, and descends as soon as its propeller stops). The propeller was moved by an 18-horse-power Buchet motor, cooled automatically by the circulation of water round its cylinders. This arrangement would permit me to utilize, without fear of over-heating or jamming en route, the full power of the motor, which communicated to the propeller (when the bow of the balloon was pointed upward) an added ascensional force of 30 kilos (66 pounds).

Among the peculiarities of the air-ships which I built in 1901, were the steel piano wires $$\frac{8}{10}$$ of a millimeter in diameter, to sustain the keel. Possessed of a high coëfficient of rupture and slight surface, they advantageouslyreplace the hempen cords of all previous dirigible balloons. The resistance of such cords to movement through the air might be compared to the resistance of the balloon-envelope itself.

For the first time, also, I made use of liquid ballast—two brass reservoirs, very thin and holding together 54 liters (60 quarts), placed between the motor and propeller, and provided with two spigots, which can be opened or closed from my basket by means of two steel wires.

Inside the balloon, sewed to the middle of the lower part of its envelope, was an air-balloon holding 60 cubic meters (2,118 cubic feet), fed with air by an aluminium ventilator. This air-balloon had a valve underneath opening into the balloon, while the balloon proper had two such valves communicating with the outer air. These valves were automatic, opening outward from within under pressure from either the air or the hydrogen, as the case might be. Their springs were regulated so that the valves of the air-balloon always opened first, to allow the air in it to escape, while the valves of the balloon could lose their hydrogen only afterward, if the pressure demanded it.

One of the hypotheses to account for the terrible accident to the unhappy Severo’s dirigible ‘‘Pax,’’ is concerned with this very delicate problem of valves. I have three valves, including the manœuver-valve; the ‘‘Pax’’ as originally constructed by M. Lachambre, had two. M. Severo, who was a theoretical but certainly not a practical aëronaut, actually stopped up one of these valves with wax before starting on his first and last voyage. In view of the decreasing pressure of the air as one goes higher, the ascent of a dirigible balloon should always be slow; gas will expand on the rise of a few yards. It is quite different from a spherical balloon in which there is no pressure. A dirigible, whose envelope is held as tight as a drum-head, depends entirely on these valves not to burst by reason of mere gas-expansion. With one of its valves stopped with wax, the ‘‘Pax’’ was allowed to shoot up from the earth; and immediately its occupants seem to have lost their heads. Instead of checking the rise of the balloon, one or other of them threw out ballast. Think of it—a handful of sand will send a great spherical balloon up perceptibly. Severo’s mechanician, in his excitement, is said to have thrown out a whole bag. Up shot the air-ship higher and higher—and the expansion, the explosion, and the awful fall, came as the consequence.

On September 6, 1901, a series of successful evolutions over Longchamps were ended by an accident of my own. The balloon was reinflated by September 15th; and four days later it crashed against a tree. Such slight accidents I have always regarded as, in a way, a kind of insurance against more terrible ones. Were I to give a single word of caution to all dirigible balloonists, it would be: ‘‘Keep close to earth!’’ The place of the air-ship is not in high altitudes.

On October 19, 1901, I was prepared to make another trial—which this time proved successful. The day before, I sent out the necessary telegrams convoking the Committee, but at 2 p.m., the hour announced for the trial, the atmospheric conditions were so unfavorable that, of the twenty-five members, only five were present. A southeast wind was blowing at at a speed of 6 meters (20 feet)