It was John Wise’s great desire at one time to sail a balloon right across the Atlantic from America to Europe. Long study of the upper winds had convinced him that a regular current of air is always blowing steadily high aloft from west to east, and he believed that if an aeronaut could only keep his balloon in this upper current he might be carried across the ocean quicker, and with more ease and safety, than in the fastest steamship. Wise went so far as to work out all the details for this plan, the size of the balloon required, the ballast, provisions, and number of passengers; and only the want of sufficient money prevented him from actually making the attempt. Curiously enough, about the same time, Charles Green, in England, was, quite independently, working at the same idea, which he also believed, with proper equipment, to be quite feasible. CHAPTER IV THE BALLOON AS A SCIENTIFIC INSTRUMENT So far, in our history of aeronautics, we have referred to ballooning only as a sport or pastime for the amusement of spectators, and for the gratifying of a love of adventure. It is now time to speak of the practical uses of the balloon, and how it has been employed as a most valuable scientific instrument to teach us facts about the upper atmosphere, its nature and extent, the clouds, the winds and their ways, the travel of sounds, and many other things of which we should otherwise be ignorant. Before the invention of the balloon men were quite unaware of the nature of the air even a short distance above their heads. In those days high mountain climbing had not come into fashion, and when Pilâtre de Rozier made the first ascent, it was considered very doubtful whether he might be able to exist in the strange atmosphere aloft. Charles and Roberts were the first to make scientific observations from a balloon, for they took up a thermometer and barometer, and made certain rough records, as also did other early aeronauts. The most interesting purely scientific ascents of early days, however, were made in the autumn of 1804, from Paris, by Gay Lussac, a famous French philosopher. He took up with him all manner of instruments, among them a compass (to see if the needle behaved the same as on earth), an apparatus to test the electricity of the air, thermometers, barometers, and hygrometers, carefully exhausted flasks in which to bring down samples of the upper air, birds, and even insects and frogs, to see how great heights affected them. In his second voyage his balloon attained the enormous altitude of 23,000 feet, or more than four miles and a quarter, and nearly 2000 feet higher than the highest peaks of the Andes. At this tremendous height the temperature fell to far below freezing-point, and the aeronaut became extremely cold, though warmly clad; he also felt headache, a difficulty in breathing, and his throat became so parched that he could hardly swallow. Nevertheless, undismayed by the awfulness of his position, he continued making his