Benjamin Franklin Papers
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From Benjamin Franklin to Ingenhousz, 16 January 1784

To Ingenhousz

ALS: New York Public Library; copy: Library of Congress

Passy, Jan. 16. 1784

Dear Friend,

I have this Day received your Favour of the 2d Instant. Every Information in my Power respecting the Balloons I sent you just before Christmas,7 contain’d in Copies of my Letters to Sir Joseph Banks. There is no Secret in the Affair, and I make no doubt that a Person coming from you would easily obtain a Sight of the different Balloons of Mongolfier & Charles, with all the Instructions wanted; and if you undertake to make one, I think it extreamly proper and necessary to send an ingenious Man here for that purpose. Otherwise for want of Attention to some particular Circumstance, or of being acquainted with it, the Experiment might miscarry, which being in an Affair of so much public Expectation, would have bad Consequences, draw upon you a great deal of Censure, and affect your Reputation. It is a serious thing to draw out from their Affairs all the Inhabitants of a great City & its Environs, and a Disappointment makes them angry. At Bourdeaux lately, a Person who pretended to send up a Balloon & had received Money of many People, not being able to make it rise, the Populace were so exasperated that they pull’d down his House, and had like to have kill’d him.—

It appears as you observe, to be a Discovery of great Importance; and what may possibly give a new Turn to human Affairs. Convincing Sovereigns of the Folly of Wars, may perhaps be one Effect of it: since it will be impracticable for the most potent of them to guard his Dominions. Five Thousand Balloons capable of raising two Men each, would not cost more than Five Ships of the Line: And where is the Prince who can afford so to cover his Country with Troops for its Defense, as that Ten Thousand Men descending from the Clouds, might not in many Places do an infinite deal of Mischief, before a Force could be brought together to repel them?— It is a pity that any national Jealousy, should, as you imagine it may, have prevented the English from prosecuting the Experiment, since they are such ingenious Mechanicians, that in their Hands it might have made a more rapid Progress towards Perfection, & all the Utility it is capable of affording. The Balloon of Messrs Charles & Robert, was really fill’d with inflammable Air. The Quantity being great it was expensive, & tedious in filling, requiring two or three Days & Nights constant Labour. It had a Soupape near the Top, which they could open by pulling a String and thereby let out some Air when they had a mind to descend; and they discharg’d some of their Ballast of Sand, when they would rise again. A great deal of Air must have been let out when they landed, so that the loose Part might envelope one of them; yet the Car being lightned by that one getting out of it, there was enough left to carry up the other rapidly. They had no Fire with them. That is us’d only in Messrs Mongolfier’s Globe, which is open at Bottom, and Straw constantly burnt to keep it up. This kind is sooner & cheaper fill’d; but must be much bigger to carry up the same Weight; since Air rarify’d by Heat is only twice as light as common Air, & inflammable Air ten times lighter. M. de Morveau a famous Chemist at Dijon, has found an inflammable Air that will cost only a 25th part of the Price of what is made by Oil of Vitriol pour’d on Iron Filings. They say it is made from Sea Coal. Its comparative Weight is not mentioned.—8

I dispatch’d your Letters by the petit Poste to day as soon as I receiv’d them.—9

As the Pacquet of German Papers & Almanacs were 18 Months in getting to your hands,1 I begin to fear for my last Packet, since it was trusted to the same Conveyance, being sent to the Ambassadors, who promis’d to take care of it. I therefore send a Copy of my Letter with this per Post, but I cannot copy the other Papers (they being too long) so as to go by this Courier.— Nor can I now add farther but that I am, as ever, my dear Friend, Yours most affectionately

B Franklin

I have still some Letters of yours to answer.—

Dr. Ingenhausz

Addressed:2 A Monsieur / Monsieur Le Dr. Ingenhauss / Medecin de Sa Majesté Imperiale / à Vienne / en Autriche.

[Note numbering follows the Franklin Papers source.]

7BF to Ingenhousz, Dec. 24.

8In the Jour. de Paris of Jan. 7, 1784, Louis-Bernard Guyton, dit Guyton-Morveau, announced the opening of a subscription in Dijon for the construction and launch of a balloon, to be elevated by an unspecified and inexpensive type of inflammable gas. He later revealed that the substance was hydrogen distilled from potatoes: DBF; Barthélemy Faujas de Saint-Fond, Premiere suite de la description des expériences aérostatiques de MM. de Montgolfier … (Paris, 1784), pp. 246–7.

9BF’S account of postage shows payments on Jan. 17 and 18 for sending a letter and a packet, respectively, for Ingenhousz: Account XXV (XXXII, 3).

1As Ingenhousz complained in his letter of Jan. 2.

2The address was added by L’Air de Lamotte.

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