Franklin also had all the inquisitiveness of a born philosopher. The winds, the birds, the fish, the celestial phenomena brought to his attention on his first voyage from England, the sluggish movement of his ship on his voyage to England in 1757, the temperature and movement of the Gulf Stream, the social and religious characteristics of the Moravians, Indian traits and habits, the still flies in their bath of Madeira wine—all excited his insatiable curiosity, and started him off on interesting trains of observation or reflection.
He was in the 78th year of his age, when, in the sight of fifty thousand people, one of the balloons recently invented by the Montgolfiers, and inflated with gas, produced by pouring oil of vitriol on iron filings, ascended from the Champs de Mars, shining brightly in the sun during the first stages of its ascent, then dwindling until it appeared scarcely larger than an orange, and then melting away in the clouds that had never before been invaded by such a visitant. But so fresh still was his interest in every triumph of human ingenuity, that it required a long letter to Sir Joseph Banks, the President of the Royal Society, supplemented by two postscripts, to disburthen his mind of the sensations and thoughts excited by the thrilling spectacle. Mingled in this letter with many precise details of size, weight and distance are the speculations of the Parisians with respect to the practical uses to which the toy might be put. Some believed that, now that men might be supported in the air, nothing was wanted but some light handy instruments to give and direct motion. Others believed that a running footman, or a horse, slung and suspended under such a globe, so as to diminish the weight of their feet on the ground to perhaps eight or ten pounds, might, with a fair wind, run in a straight line across country as fast as that wind, and over hedges, ditches and even waters. Still other fantasies were that in time such globes might be kept anchored in the air for the purpose of preserving game, or converting water into ice; or might be turned to pecuniary profit as a means of giving recreation-seekers a chance, at an altitude of a mile, to see far below them a vast stretch of the terrestrial surface. Already, said Franklin, one philosopher, M. Pilâtre de Rozier, had applied to the Academy for the privilege of ascending in a larger Montgolfier in order to make certain scientific experiments. The peasants at Gonesse, however, who had seen the balloon, cut adrift on the Champs de Mars, fall to the earth, had regarded it with very different feelings from the citizens of Paris. Frightened, and conceiving from its bounding a little, when it touched the ground, that there was some living animal in it, they had attacked it with stones and knives, so that it was much mangled.
With a subsequent letter to Dr. Price, Franklin enclosed a small balloon, which his grandson had filled with inflammable air the night before, and which, after mounting to the ceiling of Franklin's chamber, had remained rolling about there for some time. "If a Man," this letter suggestively asks, "should go up with one of the large ones, might there not be some mechanical Contrivance to compress the Globe at pleasure; and thereby incline it to descend, and let it expand when he inclines to rise again?" The same eager curiosity about the balloon was manifested by Franklin in many other later letters. Another great one, he informed Banks, had gone up from Versailles. It was supposed to have been inflated with air, heated by burning straw, and to have risen about two hundred toises; but did not continue long at that height, and, after being wafted in a horizontal direction by the wind, descended gently, as the air in it grew cooler. "So vast a Bulk," said Franklin, "when it began to rise so majestically in the Air, struck the Spectators with Surprise and Admiration. The Basket contain'd a Sheep, a Duck & a Cock, who except the Cock receiv'd no hurt by the fall." Another balloon of about five feet in diameter, the same letter stated, had been sent up about one o'clock in the morning with a large lanthorn under it by the Duke de Crillon at an entertainment, given by him, during the preceding week, in the Bois de Boulogne in honor of the birth of two Spanish princes. These were but a few of many recent ascensions. Most interesting of all, however, a new balloon, designed by Messieurs Charles and Robert, who were men of science and mechanical dexterity, was to carry up a man.
Another balloon, described by Franklin in one of his letters to Banks, was open at the bottom, and was fed with heated air from a grate, fixed in the middle of the opening, which was kept replenished with faggots and sheaves of straw by men, posted in a wicker gallery, attached to the outside of the lower part of the structure. By regulating the amount of fire in the grate, the balloon could be given an upward or downward direction at pleasure.
It was thought, Franklin said, that a balloon of this type, because of the rapidity and small expense, with which it could be inflated, might be made useful for military purposes.
Still another balloon described by Franklin in the same letter was one which was to be first filled with "permanently elastic inflammable air," and then closed. It was twenty-six feet in diameter, and made of gores of red and white silk, which presented a beautiful appearance. There was a very handsome triumphal car, to be suspended from it, in which two brothers, the Messrs. Robert, were to ascend with a table for convenience in jotting down their thermometric and other observations. There was no telling, Franklin declared, how far aeronautic improvements might be pushed. A few months before, the idea of witches riding through the air on a broomstick, and that of philosophers upon a bag of smoke would have appeared equally impossible and ridiculous. The machines, however, he believed, would always be subject to be driven by the winds, though perhaps mechanic art might find easy means of giving them progressive motion in a calm, and of slanting them a little in the wind. English philosophy was too bashful, and should be more emulous in this field of competition. If, in France, they did a foolish thing, they were the first to laugh at it themselves, and were almost as much pleased with a bon mot or a good chanson, that ridiculed well the disappointment of the project, as they might have been with its success.
The experiment might be attended with important consequences that no one could foresee.
Beings of a frank and—nature far superior to ours [the letter continued] have not disdained to amuse themselves with making and launching balloons, otherwise we should never have enjoyed the light of those glorious objects that rule our day and night, nor have had the pleasure of riding round the sun ourselves upon the balloon we now inhabit.
In due course, the Messrs. Robert, accompanied by M. Charles, a professor of experimental philosophy, and an enthusiastic student of aeronautics, made their perilous venture, which was likewise fully chronicled by Franklin. The spectators, he said, were infinite, crowding about the Tuileries, on the quays and bridges, in the fields and streets, and at the windows, and on the roofs, of houses. The device of stimulating flagging ascent by dropping sand bags from the car was one of the features of this incident, and so was the device of protecting the envelope of the balloon from rupture by covering it with a net, as well as that of lowering it by letting a part of its contents escape through a valve controlled by a cord.
Between one and two o'clock [Franklin's narrative states] all eyes were gratified with seeing it rise majestically from among the trees, and ascend gradually above the buildings, a most beautiful spectacle. When it was about two hundred feet high, the brave adventurers held out and waved a little white pennant, on both sides their car, to salute the spectators who returned loud claps of applause.