Benjamin Franklin Papers - To Sir Joseph Banks (unpublished)

On Wednesday the 27th. Instant, the new aerostatic Experiment, invented by Messrs. Mongolfier of Annonay, was repeated by Mr. Charles, Professor of experimental Philosophy at Paris.

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 Lintseed Oil, as is said. The Parts were sewed together while wet with the Gum, and some of it was afterwards passed over the Seams, to render it as tight as possible.

It was afterwards filled with the 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, 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 sometime 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 be 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 a Clock Notice was given to the Spectators 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 a Body of 12 feet Diameter, with a force only of 39 Pounds could be suppos’d to move 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 agreable Appearance. It dimi[nished] 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 and 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 heard of it till the next Day, when Information was receiv’d, that it fell a little after 6 a Clock at Gonesse, at Place about 4 Leagues Distance, and that it was [torn?] 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 compres’d by so heavy an Atmosphere.

One of 38 feet Diameter is preparing by Mr. Mongolfier himself, at the Expence of the Academy, which is to go up in a few Days. I am told it is constructed of Linen and Paper, and is to be filled with a 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 filled, the Ball was found to lose an eight 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.

I thought it my Duty, Sir, to send an early Account of this extraordinary Fact, to the Society which does me the honour to reckon me among its Members; and I will endeavour to make it more perfect, as I receive farther Information. With great Respect, I am, Sir, Your most obedient and most humble Servant

p. s. Since writing the above, I am favour’d with your kind Letter of the 25th. I am much obliged to you for the Care you have taken to forward the Transactions, as well as to the Council for so readily ordering them on Application. Please to accept and present my Thanks. I Just now learn, that some observers say, the Ball was 150 Seconds in rising, from the Cutting of the Cord [which] hid in the Clouds; that its height was then about 500 Toises; being moved out of the Perpendicular by the Wind, it had made a Slant so as to form a Triangle, whose Base on the Earth was about 200 Toises. It is said the Country People who saw it fall were frightned, conceiv’d from its bounding a little, when it touch’d the Ground, that there was some living Animal in it, and attack’d it with Stones and Knives, so that it was much mangled; but it is now brought to Town and will be rep[aired]. The great one of M. Mongolfier, is to go up, as said, from Versailles, in about 8 or 10 Days; It is not a Globe but of a different Form, more convenient for penetrating the Air. [It] contains 50,000 cubic Feet, and is supposed to have Force of Levity equal to 1500 pounds weight. A Philosopher here, Pilatre du Rozier has seriously apply’d to the Academy for leave to go up with it, in order to make some Experiments. He was complimented on his zeal and Courage for the Promotion of Science, but advis’d to wait till the Management of those Balls was made by Experience more certain and safe. They say the filling of it in M. Mongolfier’s Way will cost more than half a Crown. One is talk’d of to be feet Diameter. Several Gentlemen have ordered some ones to be made for their Amusement. One has ordered four of 15 feet Diameter each; I know not with which Purpose; But such is the present Enthusiasm for promoting and improving the Discovery, that probably we shall soon make considerable progress in the of constructing and using the Machines. Among the Pleasantries Conversation produces on this Subject, Some suppose Flying to be now invented, and that since Men may be supported in the Air, nothing is wanted but some light handy Instruments to give and direct Motion. Some think Progressive Motion on the Earth may be Advanc’d by it, and that a Running Footman or a Horse slung and suspended under such a Globe so as to have no more of Weight pressing the Earth with their Feet, than Perhaps 8 or 10 Pounds, might with a fair Wind run in a straight Line across Countries as fast as that Wind, and over Hedges, Ditches and even Waters. It has been even fancied that in time People will keep such Globes anchored in the Air, to which by Pullies they may draw up Game to be preferred in the Cool, and Water to be frozen when Ice is wanted. And that to get Money, it will be contrived to give People an extensive View of the Country, by running them up in an Elbow Chair a Mile high for a Guinea &c. &c.