Stephen Alontgolfier arriving soon afterwards in Pa ris, the Royal Academy of Sciences, with a laudable libe rality, invited him to repeat the experiment at their ex pense. Ile accordingly constructed a large balloon of an elliptical form, 72 feet in height, and 41 in diameter. It weighed 1000 pounds, and was superbly ornamented. In a preliminary experiment, it raised eight men hom the ground ; and on the 12th September, 1783, in pre sence of the members of the Academy, it bore up a load of between 400 and 500 pounds, but was accidentally damaged by a violent blast of wind. A new balloon, of nearly the same dimensions, was therefore constructed; three lit ing animals in a wicker basket were attached to it, and it ascended in presence of the royal family. An accident similar to the former unfortunately affected the success of this experiment, and the balloon did not rise above 1440 feet. It fell at the distance of 10,200 feet. from the place of ascent, without any injury to the ani mals.
Another balloon was prepared, 74 feet high and 48 in diameter, w ith w hich 11. Pilatre de Rozier offered to make an aerial voyage. To the lower part of it was suspended a gallery ul wicker work, three feet broad, with a balustrade of the same height. The interior di ameter was about 16 feet, and the aperture of the bal loon nearly the same. Below the aperture was an iron grate, hung by chains from the sides oldie balloon, which the aeronaut could easily supply with fuel. M. Pilatre de Rozicr, alter making several successful trials with this balloon, while restrained by ropes, resolved to ven ture on an aerial voyage. On the 21st November, lie took his place on one side of the gallery, and the marquis d'Arlandes occupied the other side, to preserve an equi librium. The whole, when thus loaded, weighed up wards of 1600 pounds. The balloon rose majestically before the wondering spectators, above 3000 feet in the .air; and in 25 minutes descended above live miles from the place of its outset.* In the beginning of the year 1784, a balloon of prodi gious size was constructed at Lyons, being nearly 130 feet high, above 105 in diameter, and containing 540,000 cubic feet of rarefied air. This immense machine re quired more than 50 men to retain it when inflated ; and it was capable of raising from the ground six persons, and 3200 pounds of ballast. On the 19th January, 1784, after being filled in only 17 minutes, it ascended up wards of 3200 feet, with seven aeronauts in the gallery. But a rent of 50 feet, in consequence of the badness of the materials, brought it to the ground, in 15 minutes front the beginning of its ascent ; the aeronauts, how ever, suffered no injury from the accident.
In February 1731, an aerial voyage, made from Milan by three Italian gentlemen, in a balloon 68 feet in di ameter, was attended w ith a degree of success which contributed to inspire still confidence in this sin gular mode of conveyance.
Such were the leading experiments made with bal loons filled with rarefied air ; but the science was des tined to undergo still greater improvements.
An aeriform fluid, now denominated hydrogen gas, had been long known ; but till the year 1766, its pro perties had not been ascertained. :‘.Ir Henry Cavendish then instituted a series of experiments for that purpose, and found, among other properties, that it was only one-seventh of the w eight of common atmospherical air. It immediately occurred to philosophers, that if a quan tity of hydrogen gas could be confined within any light substance, that substance would rise in the atmosphere. Dr Black, about 1767 or 1768, suggested, that the allan tois of a calf filled with this gaseous substance, would rise from the earth ; but it was not till the year 1782, that hydrogen gas was actually employed to support bodies floating in the atmosphere. Mr Tiberius Cavallo raised soap bubbles in the air, by filling them with this gas ; but he failed in his application of the gas to every other substance.
Since balloons filled with rarefied air had ascended, it was evident that the substitution of hydrogen gas, ‘•ose specific gravity was much less, would insure still gi cater success. Two brothers, accordingly, Messrs Roberts, and Mr Charles, professor of experimental phi losophy, constructed a balloon at Paris, of a spherical Form, and 13 feet in diameter. It was made of silk ; and in order to render it impermeable to the inflamma ble air, which they procured from sulphuric acid and iron filings, they varnished it with a solution of elastic gum. After experiencing much difficulty in filling it, they found its ascensive power to be 35 pounds. On the 27th August, 1783, it was tried, and ascended up wards of 3000 feet, an the short space of two minutes. After traversing a space of 15 miles, it was brought to the ground by a rupture, which was probably effected in the higher regions of the air, by the expansion of the gas. In November 1783, a balloon, 10 feet diame ter, constructed by count Zambeccari, ascended from London, and after two hours and a half, came down at the distance of 48 miles Irons the place of ascent.