Benjamin Franklin to Joseph Banks 22-Nov-1783

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Franklin encloses Procès verbal of a hot-air balloon ascent of the previous day (21 November 1783) at "the Garden of the Queen's Palace la Muette, where the Dauphin now resides."

This Balloon was larger than that which went up from Versailles and carried the Sheep, &c. Its bottom was open, and in the middle of the Opening was fixed a kind of Basket Grate, in which Faggots and Sheaves of Straw were burnt. The Air rarefied in passing thro' this Flame rose in the Balloon, swell'd out its sides, and fill'd it.
The Persons who were plac'd in the Gallery made of Wicker, and attached to the outside near the Bottom, had each of them a Port thro' which they could pass Sheaves of Straw into the Grate to keep up the Flame, & thereby keep the Balloon full. When it went over our Heads, we could see the Fire which was very considerable. As the Flame slackens, the rarefied Air cools and condenses, the Bulk of the Balloon diminishes and it begins to descend. If those in the Gallery see it likely to descend in an improper Place, they can by throwing on more Straw, & renewing the Flame, make it rise again, and the Wind carries it farther. . . .

Applications:

This method of filling the Balloon with hot Air is cheap and expeditious, and it is supposed may be sufficient for certain purposes, such as elevating an Engineer to take a view of an Enemy's Army, Works, &c., conveying Intelligence into, or out of a besieged Town, giving Signals to distant Places, or the like.

He anticipates in a few days another balloon launch, this one by the Frères Roberts along with Jacques Charles, in a 26'-diameter balloon said to cost (with gas) 10,000 livres.

A comment on Progress:

But the Emulation between the two parties running high, the Improvement in the Construction and Management of the Balloons has already made a rapid Progress; and one cannot say how far it may go. A few Months since the Idea of Witches riding thro' the Air upon a Broomstick, and that of Philosophers upon a Bag of Smoke, would have appeared equally impossible and ridiculous.

And getting Philosophical indeed at the end of the letter:

Beings of a Rank and Nature far superior to ours 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 & Night, nor have had the Pleasure of riding round the Sun ourselves upon the Balloon we now inhabit.

Sources

Sender Benjamin Franklin
Recipient Joseph Banks
Date sent 22-Nov-1783
From location Passy, France
To location London?
Communication type
Language English
Refers to flight? 1
Tech fields balloon, LTA, military, reconnaissance, communications, instrument, barometer, thermometer, propulsion
Length (in words)
Full text available