from a variety of causes, will not keep at that altitude. The great changes which are constantly taking place in the weight of the atmosphere, the deposition of humidity on the surface of the balloon, and its subsequent evaporation by the rise of temperature, the alternate heating and cooling of the gaseous contents of the balloon, according as it may be exposed to the action of the solar rays or screened from them by the interposition of clouds, not to advert to other agencies, less known though not less powerful, all combine in making the machine at one time to ascend and at another to descend. Thus it may be removed out of a favorable into an adverse current. To overcome this difficulty, and enable the aeronaut to keep the balloon at the same level without expending its power, by discharging gas from the valve to lower it, or by casting out a portion of the ballast to raise it – processes which must in time waste the whole power of the largest balloon, and bring it to the earth – Mr. Green suggested the contrivance of a rope of sufficient length and material trailing on the ground beneath, and if over the sea, the rope is to be tied to a vessel filled with liquid ballast, which floats on the surface. This rope will act as a drag on the balloon, when, from any of the causes we have referred to, it tends to rise, for, in that case, it will draw up a portion of the rope, and, by thus adding to its weight, will be impeded in its upward course; and, on the other hand, when, from opposite causes, it tends to descend, it will, during every foot of its descent, have its weight, and consequently its descending tendency, diminished, by throwing on the earth the labor of supporting an additional portion of the rope. This, however, at best, is a clumsy contrivance, and there are various objections to its practical utility. It could hardly be practicable on land, on account of the damage and danger that would be occasioned by the entanglement of the rope in trees and buildings; and at great elevations above the earth, the weight of the rope would become so considerable as to require for its support a large portion of the ascending power of any balloon.
In the United States, many aerial voyages have been performed. The first of these was made by a Frenchman, M. Blanchard, in Jan., 1793, from Philadelphia, at which General Washington was a spectator. Gillio and Robertson, both Europeans, were the next after Blanchard. No Americans were engaged in the business until Mr. Durant, an ingenious citizen of New York, took it up after Robertson. He made a number of aerial excursions, and was shortly followed by new adventurers in the art, among whom the most celebrated is Mr. Wise, a piano-forte maker in Philadelphia, who in 1835 betook himself to the trade of ascending in balloons, and who up to this date has made upward of a hundred ascents.
Mr. Wise is entitled to the merit of having carefully studied and mastered the scientific principles of aeronautics, and he is among the most enthusiastic of his profession. While admitting that the art has advanced but little since its first discovery, compared with other sciences, he anticipates from it, if perseveringly cultivated by men of genius, the most splendid results, adopting, as the motto on the title-page of his work, the couplet from Shakspeare:
"There are more things in heaven and earth, Horatio,
Than are dreamt of in your philosophy."
Some of his feats have been daring enough, and others still more perilous he is willing to undertake.
Not long after commencing the practice of his new profession, Mr. Wise resolved to test the practicability of descending in safety with the balloon, after it had burst, at the elevation of a mile or two. It would then, he conceived, form a parachute, and, from the resistance it would meet with from the atmosphere in its descent, would gently let him down to the earth. Having prepared a balloon of cambric muslin, which he coated with his newly-invented varnish, he ascended, as had been advertised, from Easton, in Pennsylvania, on the 11th of August, 1838, at a few minutes before two o'clock, afternoon, with the full determination of making the experiment, though he had concealed his intention both from the public and from his personal friends. He carried up with him two parachutes, the one containing a cat, and the other a dog. As the balloon approached a dense body of black thunder-clouds, some vivid flashes of lightning, accompanied by violent peals of thunder, greeted his upward course. This gave the first part of his voyage a terrific but grand and imposing appearance. It seemed to him as if heaven's artillery were celebrating these efforts of the new-born science, and, acting on his imagination, this inspired him with a fresh determination to explode the balloon. At different elevations, he detached first one and then another of the parachutes, with their occupants, which landed in safety. At the altitude of about 13,000 feet, the gas became expanded to its utmost tension, and the balloon was still rising, making it evident that, unless the safety-valve were speedily opened to allow a portion of the gas to escape, an explosion would speedily ensue. At this critical moment he became somewhat excited, and looking over the side of his car, he observed the sparkling coruscations of lightning springing from cloud to cloud, a mile beneath him, as the thunder-storm was passing, in its last remnants, below. He took out his watch, noted on his log-book the time – twenty minutes past two – and as he was about returning it to his pocket, thinking at the time whether it were not best, by opening the valve, to abandon, for the present, his favorite idea, the balloon exploded. His confidence in the success of the experiment never forsook him, and yet he admits that this was a moment of awful suspense. The gas rushed with a tempestuous noise from the rupture in the top, and in less than ten seconds, the balloon was emptied of every particle of hydrogen. The descent at first was rapid, and in a moment or two, on looking up, he discovered that the balloon was canting over, but the weight of the car counteracted its tilting tendency, giving it an oscillating motion, which it retained until it reached the earth, which it struck with a violent concussion, and the car striking the earth obliquely, Mr. Wise was thrown forward from it about ten feet. The landing was made on a farm about ten miles from Easton, and many minutes had not elapsed before he had resolved in his mind to repeat the experiment in Philadelphia on the first opportunity.
Having arrived in Philadelphia in the month of September immediately following, he consulted several scientific gentlemen as to his intention. Doubtful of the safety of the experiment, though neither questioning the philosophy of atmospheric resistance, nor the theory of converting the balloon into a parachute, they earnestly endeavored to dissuade him from his purpose. But confident of the perfect safety with which, on scientific principles, he would descend, he publicly announced that he would ascend on the first of October, and explode the balloon at the height of upward of a mile. On the day advertised, at twenty minutes before five o'clock, afternoon, he left the earth in the presence of assembled thousands, and rose almost perpendicularly, in a perfectly clear sky. When the explosion took place, the lower part of the balloon did not immediately invert, as in the former experiment, for in this case the balloon burst open from top to bottom, and caved sideways. At the first discovery of this, he was somewhat alarmed, fearing that it might come down with a continuous accelerated velocity; but from this anxiety he was soon relieved, for it caught the wind like the mainsail of a ship, and slid down upon the atmosphere in a spiral course with a uniform velocity. The concussion, though from the apparent rapidity of the descent it threatened to be violent, was not harder than that which would follow the jumping from an elevation of ten feet to the ground.
From the experience of his numerous aerial excursions, Mr. Wise is of opinion, that, at a considerable elevation, there is a constant and regular current of wind blowing at all times, from west to east, with a velocity of from twenty to forty, and even sixty miles per hour, according to its height from the earth. On the strength of this conviction, he believes it to be perfectly practicable and safe, not only to cross the Atlantic, but even to circumnavigate the globe, in a balloon; and he has expressed his readiness to undertake either of these voyages. About the beginning of the year 1843, he actually proposed to some gentlemen of the city of Philadelphia, the project of making an aerial trip across the Atlantic, in undertaking which, he assured them, he would have as little hesitation as about embarking in the most approved steam-vessel that plied between the ports of New York and Liverpool. At first, supposing him to be in jest, they expressed their willingness to promote the design, but finding that he was in sober earnest, they began to evince conscientious scruples as to the responsibility they would incur, if by any chance his life should fall a sacrifice to the bold adventure. He next determined to petition the Congress of the United States, at their ensuing session, for the necessary pecuniary
