Abstract
III.
THE laws of the motion of a balloon, dependent on the change of level, appear to have been hitherto very little discussed from a scientific point of view. It is, however, a motion which can be procured very easily by throwing out a small quantity of sand, or of gas, if the balloon is properly constructed, and which is of great importance for any expedition in time cl war, more perhaps than even the attempt at guiding its direction. The number of minutes required for descending from a great altitude as well as for ascending to a certain level, being the most important consideration for the aëronaut endangered by the vicinity of some foreign force, this was analytically examined by M. Dupuy de Lome. It is the first instance that I know of such a disquisition since Euler worked his equations relating to the elevation of an aärostatic sphere supposed to be inextensible, and to be carried away in the atmosphere with a certain amount of motive power due to the small specific gravity of the included gas. That beautiful analytical disquisition is the last ever written by the old philosopher, who was totally blind at the time. It was icund written by him on the tableau noir where he was making his calculations on the very day before he died. He had received the intelligence of the great experiment tried by Mongolfier, and his excited brain had produced during the night that masterly piece of mathematical skill which was unhappily his last! This contribution to scientific ballooning is to be found in the “MémoiresdelAcadémiedes Sciences de Paris” for 1781, a date anterior to the experiment of Mongolfier, which is accounted for by the issue of the volumes being always later than the date inscribed on them. Another singularity is that Euler speaks of gas for filling the balloon, while Mongolfier's was merely heated air. We must not, however, give Euler the merit of having been the real inventor of Charliéres or gas balloon, as Mongolfier believed that he prepared gas by burning damp corn-straw! Before returning to the questions considered by Dupuy de Lome, we may be allowed to mention that the use of gas enclosed in a gasholder of any description, was suggested by Blake in his lectures at Edinburgh, and by an Italian philosopher transacting business in London. Carvalho tried to give to the idea of Blake the shape of an experiment, but uselessly, for the want of a proper varnish, which was invented by Charles a few months only after Mongolfier's great experiment.
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DE FONVIELLE, W. Balloon Ascents for Military Purposes . Nature 3, 175–176 (1870). https://doi.org/10.1038/003175a0
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DOI: https://doi.org/10.1038/003175a0