188 AERONAUTICS [DISCOVERY OF ie Iro- a town about 40 miles from Lyons. The brothers had ers Mont- observed the Suspension of clouds in the atmosphere, and it occurred to them that if they could enclose any vapour of the nature of a cloud in a large and very light bag, it might rise and carry the bag with it into the air. They accordingly made experiments, inflating bags with smoke from a fire placed iinderneath, and found either that the smoke or some vapour emitted from the fire did ascend and carry the bag with it. Being thus assured of the cor rectness of their views, they determined to have a public ascent of a balloon on a large scale. They accordingly invited the States of Vivarais, then assembled at Annonay, to witness their aerostatic experiment; and on June 5, 1783, in the presence of a considerable concourse of spec tators, a linen globe of 105 feet in circumference was inflated over a fire fed with small bundles of chopped straw, and when released rapidly rose to a great height, and descended, at the expiration of ten minutes, at the distance of about 1 mile. This was the dis covery of the balloon. The brothers Montgolfier imagined that the bag rose because of the levity of the smoke or other vapour given forth by the burning straw; and it was not till some time later that it was recognised that the ascending power was due merely to the lightness of heated air compared to an equal volume of air at a lower temperature. Air, like all other fluids, expands by heat, and thereby becomes rarefied, so that any volume of hot air weighs less than the corresponding volume of air at a lower temperature. If, then, the air inside the balloon be so heated that it, together with the balloon, weighs less than the air displaced, the balloon will rise till it arrives at such a height that it and the enclosed air are equal in weight to that of the displaced air, when equilibrium will be ob tained. In Montgolfier s first balloon, no source of heat was taken up with it, so that the air in.side rapidly cooled, and the balloon soon descended. The news of the experiment at Annonay rapidly spread O ver Europe, and at Paris attracted so much attention that -jyjr Faujas d e Saint-Fond, a naturalist, set on foot a sub scription for paying the expense of repeating the experi ment. The balloon was constructed by two brothers of the name of Robert, under the superintendence of M. Charles, professor of natural philosophy in Paris, and afterwards a member of the Academy of Sciences. It had at first been suggested to copy the process of Montgolfier, but Charles proposed the application of hydrogen gas, which was adopted. The filling of the balloon, which was made of thin silk varnished with a solution of elastic gum, and was about 13 feet in diameter, was commenced on August 23, 1783, in the Place des Victoires. The hydrogen gas was obtained by the action of dilute sulphuric acid upon iron filings, and was introduced through leaden pipes; but as the gas was not passed through cold water, great difficulty was experi enced in filling the balloon completely; and altogether about 500 ft) of sulphuric acid and twice that amount of iron filings were used. Bulletins were issued daily of the progress of the inflation; and the crowd was so great that on the 26th the balloon was moved to the Champ de Mars, a distance of 2 miles. This was done secretly, in the middle of the night, to avoid the crowd; and the appearance of the balloon being thus removed, preceded by lighted torches and escorted by a detachment of soldiers, is described as having been very remarkable. On the next day, August 27, an immense concourse of people covered the Champ de Mars, and every spot from which a view could be obtained was crowded. About five o clock a cannon was discharged as the signal for the ascent, and the balloon when liberated rose to the height of about 3000 feet with great rapidity. A shower of rain which began to fall directly after the balloon had left the earth in no way checked its progress; and the excitement was so great, that thousands of well-dressed spectators, many of them ladies, stood exposed, watching it intently tho whole time it was in sight, and were drenched to the skin. The balloon, after remaining in the air for about three- quarters of an hour, fell in a field near Gonesse, about 15 miles off, and terrified the peasantry so much that it was torn into shreds by them. Hydrugen gas was at this time known by the name of inflammable air; and balloons inflated with gas have ever since been called by the people air-balloons, the kind invented by the Mont- golfiers being designated fire-balloons. French writers have also very frequently styled them after their inventors, Charlieres and Montgolfieres. On the 19th of September 1783 Joseph Montgolficr repeated the Annonay experiment at Versailles, in the pre sence of the king, the queen, the court, and an immense number of spectators. The inflation was commenced at one o clock, and completed in eleven minutes, when the balloon rose to the height of about 1500 feet, and descended after eight minutes, at a distance of about two miles, in the wood of Vaucresson. Suspended below the balloon, in a cage, had been placed a sheep, a cock, and a duck, which were thus the first aerial travellers. They were quite un injured, except the cock, which had its right wing hurt in consequence of a kick it had received from the sheep; but this took place before the ascent. The balloon, which was painted with ornaments in oil colours, had a very showy appearance. The first human being who ascended in a balloon was M. Franois Piltitre de Rozier, a young naturalist, who, two years afterwards, was killed in an attempt to cross the English Channel in a balloon. On October 15, 1783, and following days, he made several ascents (generally alone, but once with a companion, M. Girond de Villette), in a captive balloon (i.e., one attached by ropes to the ground), and demonstrated that there was no difficulty in taking up fuel and feeding the fire, which was kindled in a brazier suspended under the balloon, when in the air. The way being thus prepared for aerial navigation, on November 21, 1783, M. Pilatre de Rozier and the Marquis d Arlandes first trusted themselves to a free fire-balloon. The experi ment was made from the Jardin du Chateau de la Muette, in the Bois de Boulogne. The machine employed, which was a large fire-balloon, was inflated at about two o clock, and leaving the earth at this time, it rose to a height of about 500 feet, and passing over the Invalides and the Ecole Militaire, descended beyond the Boulevards, about OOOOyards from the place of ascent, having been between twenty and twenty-five minutes in the air. The result was completely successful; and it is scarcely necessary to add, the excite ment in Paris was very great. Only ten days later, viz., on December 1, 1783, MM. Charles and Robert ascended from Paris in a balloon in flated with hydrogen gas. The balloon, as in the case of the small one of the same kind previously launched from the Champ de Mars, was constructed by the brothers Robert. It was 27 feet in diameter, and the car was sus pended from a hoop surrounding the middle of the balloon, and fastened to a net which covered the upper hemisphere. The balloon ascended very gently from the Tuileries at a quarter to two o clock, and after remaining for some time at an elevation of about 2000 feet, it de scended in about two hours at Nesle, a small town about 27 miles from Paris, when M. Robert left the car, and M. Charles made a second ascent by him.self. He had intended to have replaced the weight of his companion by a nearly equivalent quantity of ballast; but not having any suitable means of obtaining such ready at the place of descent, and it being just upon sunset, he gave the word Ascent c sheep, a cock, an duck. See Plat Ascent ( M. Pilat tie Rozie ami the Marquis d Arlanii Ascent of MM. Charles and Hoi; in a ballt inflated with hy<" gen gas.
See Plat.
