Up in the Clouds: Balloon Voyages. Robert Michael Ballantyne

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СКАЧАТЬ each globe, fitted with a stop-cock, to a tube of at least thirty-five feet long; the whole being filled with water; when raised to the vertical position the water would run out, the stop-cocks would be closed at the proper time, and the vacuum secured. It does not seem to have entered the head of this philosopher that the weight of the surrounding atmosphere would crush and destroy his thin exhausted receivers, but he seems to have been alarmed at the idea of his supposed discovery being applied to improper uses, such as the passing of desperadoes over fortified cities, on which they might rain down fire and destruction from the clouds!

      Perhaps the grandest of all the fanciful ideas that have been promulgated on this subject was that of Galien, a Dominican friar, who proposed to collect the fine diffused air of the higher regions, where hail is formed, above the summit of the loftiest mountains, and to enclose it in a cubical bag of enormous dimensions—extending more than a mile every way! This vast machine was to be composed of the thickest and strongest sail-cloth, and was expected to be capable of transporting through the air a whole army with all their munitions of war!

      There were many other devices which men hit upon, some of which embraced a certain modicum of truth mixed with a large proportion of fallacy. Ignorance, more or less complete, as to the principles and powers with which they dealt, was, in days gone by, the cause of many of the errors and absurdities into which men were led in their efforts to mount the atmosphere. Our space, however, forbids further consideration of this subject, which is undoubtedly one of considerable interest, and encircled with a good deal of romance.

      Turning away from all those early and fanciful speculations, we now come to that period in the history of balloon voyaging, or aeronautics, when true theories began to be philosophically applied, and ascending into the skies became an accomplished fact.

      Chapter Two.

      The First Balloons

      The germ of the invention of the balloon lies in the discovery of Mr Cavendish, made in 1766, that hydrogen gas, called inflammable air, is at least seven times lighter than atmospheric air. Founding on this fact, Dr Black of Edinburgh proved by experiment that a very thin bag, filled with this gas, would rise to the ceiling of a room.

      In Dr Thomson’s History of Chemistry, an anecdote, related by Mr Benjamin Bell, refers to this as follows:—

      “Soon after the appearance of Mr Cavendish’s paper on hydrogen gas, in which he made an approximation to the specific gravity of that body, showing that it was at least ten times lighter than common air, Dr Black invited a party of friends to supper, informing them that he had a curiosity to show them. Dr Hutton, Mr Clerk of Eldin, and Sir George Clerk of Penicuik, were of the number. When the company invited had arrived, he took them into a room where he had the allantois of a calf filled with hydrogen gas, and, upon setting it at liberty, it immediately ascended and adhered to the ceiling. The phenomenon was easily accounted for; it was taken for granted that a small black thread had been attached to the allantois, that the thread passed through the ceiling, and that some one in the apartment above, by pulling the thread, elevated it to the ceiling, and kept it in its position! This explanation was so plausible, that it was agreed to by the whole company, though, like many other plausible theories, it turned out wholly fallacious, for, when the allantois was brought down, no thread whatever was found attached to it. Dr Black explained the cause of the ascent to his admiring friends; but such was his carelessness of his own reputation, that he never gave the least account of this curious experiment even to his class, and several years elapsed before this obvious property of hydrogen gas was applied to the elevation of balloons.”

      Cavallo made the first practical attempts with hydrogen gas six years later, but he only succeeded in causing soap-bubbles to ascend.

      At last the art of aerial navigation was discovered in France, and in 1782 the first ascent was made. The triumph was achieved by Stephen and Joseph Montgolfier, sons of a wealthy paper-maker who dwelt at Annonay, on the banks of a rivulet which flows into the Rhone, not far from Lyons.

      These brothers were remarkable men. Although bred in a remote provincial town, and without the benefit of a liberal education, they were possessed in a high degree of ingenuity and the spirit of observation. They educated themselves, and acquired an unusually large stock of information, which their inventive and original minds led them to apply in new fields of speculation. They were associated in business with their father, a man who passed his quiet days like a patriarch amidst a large family and a numerous body of dependants, until he reached the advanced age of ninety-three.

      Stephen devoted himself chiefly to the study of mathematics, Joseph to chemistry; and they were accustomed to form their plans in concert. It appears that they had long contemplated, with philosophical interest, the floating and ascent of clouds in the air, and when they heard of or read Cavendish’s theories in regard to different kinds of air, it at once struck them that by enclosing some gas lighter than the atmosphere in a bag, a weight might be raised from the earth into the air.

      The brothers Montgolfier were men of that vigorous stamp who act promptly on receiving their convictions. At once they set about experimenting, and constructed large bags of paper,—the substance which naturally came readiest to their hands, and which appeared to them to be best suited to their purpose. These were filled with hydrogen gas, which raised them to the ceiling; but, owing to the escape of the gas through the pores and cracks of the case, those embryo balloons descended in a few minutes. Instead of varnishing the paper to prevent the escape of the gas, and supposing, erroneously, that the fault lay in the latter, they sought about for a new gas more suitable to the paper. This they found, as they supposed, in the gas which resulted from the combustion of wet straw and wool, which had an upward tendency, they thought, on account of its electrical properties, which caused it to be repelled from the ground. It is scarcely necessary now to point out that the true cause of the upward tendency lay in the rarefaction of the air by the heat of the fire, and that hot air has a tendency to rise because its bulk is greatly increased beyond the same quantity of the surrounding cold air.

      Although wrong in assigning the cause of the result, they were right in the application of it. While on a visit to Avignon Joseph Montgolfier procured a silk bag having a small opening at its lower end, and a capacity of about fifty cubic feet. Under the orifice some paper was burnt; the air inside was heated and expanded so as to fill the bag, which, when let go, soared rapidly up to the height of seventy or eighty feet, where it remained until the air cooled and allowed it to descend. Thus did the first balloon ascend in the month of November 1782.

      Delighted with their success, the indefatigable brothers resolved to make further experiment on a larger scale. They procured a quantity of packcloth or coarse linen, formed it into a globe about ninety feet in circumference, lined it with paper, and lighted a fire under it in an iron choffer. This balloon went up with a force which they estimated as equivalent to 500 pounds.

      After this the Montgolfiers appeared to have become ambitious of accomplishing greater things, and giving to their discoveries publicity; for we are told that, “they invited the members of the provincial meeting of the states of the Vivarais, then assembled at Annonay, to witness the first public aerial ascent. On the 5th June 1783, amidst a very large concourse of spectators, the spherical bag or balloon, consisting of different pieces of linen, merely buttoned together, was suspended from cross poles. Two men kindled a fire under it, and kept feeding the flame with small bundles of chopped straw. The loose bag gradually swelled, assuming a graceful form, and in the space of five minutes it was completely distended, and made such an effort to escape that eight men were required to hold it down.

      “On a signal being given the stays were slipped, and the balloon instantly rose with an accelerating motion till it reached some height, when its velocity continued uniform, and carried it to an elevation of more than a mile. All was admiration and transport. Amidst the shouts of unbounded applause, the progress of the artificial cloud retiring from sight arrested every eye. It was hurried along by the wind; СКАЧАТЬ