[5] The writer has made hydrogen-inflated varnish bubbles a foot in diameter which ascended swiftly to the ceiling; also, air-inflated varnish bubbles a foot and a half in diameter which lasted an hour. These, if suitably heated, may be made to ascend; but this experiment is more difficult.
[6] Both had studied science in college. Stephen was an accomplished architect; Joseph, the author of many important inventions, among others the common lamp chimney, the hydraulic press, etc.
[7] A long patch on the balloon that can be ripped open for the sudden release of gas.
[8] The equator of such a balloon is its horizontal great circle.
[9] A similar suggestion was made by Thomas Jefferson in a letter to Prof. James Madison, and dated from Paris in 1785: “I went some time ago to see a machine which offers something new. A man had applied to a light boat a very large screw, the thread of which was a thin plate, two feet broad, applied by its edge spirally around a small axis. It somewhat resembled a bottle brush, if you will suppose the hairs of the bottle brush joining together, and forming a spiral plane. This, turned on its axis in the air, carried the vessel across the Seine. It is, in fact a screw which takes hold of the air and draws itself along by it; losing, indeed, much of its effort by the yielding nature of the body it lays hold of to pull itself on by. I think it may be applied in the water with much greater effect and to very useful purposes. Perhaps it may be used also for the balloon.”
[10] La Navigation Aerienne, Gaston Tissandier.
[11] The motive power equals the product of the speed and resistance. But in the assumed case, the speed is doubled and the resistance quadrupled; hence, the power required is eightfold.
[12] Santos-Dumont, My Airships.
[13] m3 signifies cubic meters. One cubic meter equals 35.3166 cubic feet.
[14] Hangar, an airship harbor, or garage.