AEROLITHS, from rile, the air, and Ar905, a stone, a name recently and very improperly given to the mine ral substances which have fallen from the atmosphere.
See METEORIC STONES. (w) co:fp the air, and yuvroo7, the art ror is the science of navigating the air by of balloons.
This science, however extravagant it might at first appear as an object either of philosophical speculation or probable success, has been prosecuted with increasieg interest and attention fir a considerable period of time. While the art of traversing the air was unknown, man kind, guided by those superstitious notions which ac company the infancy of knowledge, regarded it as the exclusive privilege of those supernatural agents, who by their power over the elements, were permitted to penetrate into regions, which nature had prohibited to man. But though such opinions prevailed from periods of the remotest antiquity, they began, even during the darker ages, to yield to more rational conceptions. Ro ger Bacon was among the first philosophers who sug gested the possibility of traversing the air by means of mechanical contrivances : He mentions a machine for flying, as in his time certainly known, " not that he him self had seen it, or was acquainted with any person who had done so, but he knew an ingenious person who had contrived one." It is evident, however, that he alludes to some method of putting artificial wings in motion. In later times, John Wilkins, bishop of Chester, an in genious mechanic, who died in 1672, published a trea tise Concerning a li"orld, in which lie maintains the possibility of reaching the moon, provided he could be conveyed beyond the earth's attraction. He supposes the different strata of the atmosphere to be of different densities; and concludes, that a vessel filled with lighter air, will float on heavier air, just as a ship is buoyed up by the water. In the same work he asserts, that a fly ing chariot might be constructed on mechanical princi ples; and in his Mathematical Magic, which was a sub sequent publication, after specifying various artificial methods of flying, he gives the preference to the flying chariot, on account both of its superior utility, and the greater probability of its success.
Nearly about the same period, Francis Lana, a Jesuit, suggested a method of traversing the air, founded on the same principles as those which are at present adopted. He proposed to provide four hollow spheres of copper, each 20 feet in diameter, and so thin, that on exhausting the included air, they would float in the atmosphere, and be capable of supporting a vessel or any other load. This plan, though founded on strict philosophical prin ciples, was abandoned on account of its practical defects : Not only was Lana's method of procuring a vacuum im perfect, but the thickness of the metal being necessarily reduced to A of a line, it was found insufficient to resist the external pressure of the surrounding air. This con
trivance is described in a work, intitled, Prodrcano dell' Arte Maestra Brescia, 1670.
It has been said, that a basket of wicker work, of se ven or eight feet diameter, which was constructed at Lisbon, was exhibited in 1736, and upon trial ascended to the height of 200 feet. But we have been able to ob tain no satisfactory accounts of the experiment.
In the year 1755, there was published at Avignon, by Joseph Galien, a small work, intitled, "L'art de naviguer Mans les airs," in which the author asserts, that a bag of cloth or leather, filled with an air lighter than that of the atmosphere, might be employed with perfect seeurity fir the purpose of aerial voyages. But though Galten was correct in the principle which he assumed, he seems to have been ignorant of the existence of any lighter spe cies of air, except what is to be found in the higher re gions of the atmosphere.
In the year 1782, the science of aeronautics was car ried in France to an unexampled degree 01 It was already known, that air was an elastic fluid, pos sessing the same general properties as other fluids ; and that it a certain bulk of it was displaced by another body of the same bulk, but of less specific gravity, that body would float. From these data, Stephen and Joseph Muntgollier, two brothers, w ho were proprietors of a paper manufactory at Annonai, were first led to the con struction of balloons. Observing the natural tendency of smoke and clouds to ascend in the air, they conceived it practicable to confine an artificial cloud, which would also rise and carry along with it the inclosing substance. The first experiment which they made was at Avignon. They prepared a bag of silk, of the form of a parallelo piped, containing about 4.0 feet when inflated. In the lower part was formed an aperture, and when burning paper was applied to it, the bag expanded by the rare faction of the internal air, rose rapidly, and struck the ceiling of the apartment where the experiment was made. In tile next experiment, it ascended 70 feet in the open Encouraged by this success, the inventors enlarged the scale of their experiments. A bag containing 650 cubic feet of air, rose 600 feet high. A spherical bal loon, 35 feet in diameter, was next prepared. It con tained '23,000 feet of air, and was capable of raising a weight of 500 pounds. It was filled with rarefit d air, produced by the combustion of chopped straw and wool placed below the aperture. On the 5th June. 1783, when the experiment was made, a crowd of spectators assem bled to witness this new and interesting invention, and the result justified their most sanguine expectations. The bag ascended 6003 feet into the atmosphere, and fell at the distance of 7665 feet from the place of ascent.