A hollow Globe 12 feet Diameter was formed of what is called in England Oiled Silk, here Taffetas gommé, the Silk being impregnated with a Solution of Gum elastic in Linseed Oil, as he said. The Parts were sewed together while wet with the Gum, and some of it was afterwards passed over the Seam, to render it as tight as possible.
It was afterwards filled with inflammable Air that is produced by pouring Oil of Vitriol upon Filings of Iron, when it was found to have a tendency upwards so strong as to be capable of lifting a Weight of 39 Pounds, exclusive of its own Weight which was 25 lbs and the Weight of the Air contain’d.
It was brought early in the morning to the Champ de Mars, a Field in which Reviews are sometimes made, lying between the military School and the River. There it was held down by a Cord till 5 in the afternoon, when it was to let loose. Care was taken before the Hour to replace what Portion had been lost, of the inflammable Air, or of its Force, by injecting more.
It is supposed that not less than 50,000 People were assembled to see the Experiment, The Champ de Mars being surrounded by multitudes, and vast Numbers on the opposite Side of the River.
At 5 O’clock Notice was given to the Spectators by the Firing of two Cannon, that the Cord was about to be cut. And presently the Globe was seen to rise, and that as fast as a Body of 12 feet Diameter, with a force only of 39 Pounds, could be suppos’d to remove the resisting Air out of its Way. There was some Wind, but not very strong. A little Rain had wet it, so that it shone, and made an agreeable appearance. It diminished in Apparent Magnitude as it rose, till it enter’d the Clouds, when it seem’d to me scarce bigger than an Orange, and soon after became invisible, the Clouds concealing it.
The multitude separated, all well satisfied and delighted with the Success of the Experiment, and amusing one another with discourses of the various uses it may possibly be apply’d to, among which many were very extravagant. But possibly it may pave the Way to some Discoveries in Natural Philosophy of which at present we have no conception.
A Note secur’d from the Weather had been affix’d to the Globe, signifying the Time & Place of its Departure, and praying those who might happen to find it, to send an account of its state to certain Persons at Paris. No News was learned of it till the next Day, when information was received that it fell a little after 6 o’clock, at Gonesse, a Place about four Leagues Distance, and that it was rent open, and some say had ice in it. It is suppos’d to have burst by the Elasticity of the contain’d Air when no longer compress’d by so heavy an Atmosphere.
One of 38 feet Diameter is preparing by Mr. Montgolfier himself, at the Expence of the Academy, which is to go up in a few days. I am told it is constructed of Linen & Paper, and is to be filled with different Air, not yet made public, but cheaper than that produc’d by the Oil of Vitriol, of which 200 Paris Pints were consum’d in filling the other.
It is said that for some Days after its being fill’d the Ball was found to lose an eighth Part of its Force of Levity in 24 Hours; Whether this was from Imperfection in the Tightness of the Ball, or a Change in the Nature of the Air, Experiments may easily discover....
M. Montgolfier’s Air to fill the Globe has hitherto been kept secret; some suppose it to be only common Air heated by passing thro’ the Flame of burning Straw, and thereby extreamly rarefied. If so, its Levity will soon be deminish’d by Condensation, when it comes into the cooler Region above....