Benjamin Franklin Papers

From Benjamin Franklin to Jan Ingenhousz, 18 March 1774

To Jan Ingenhousz

ALS: Harvard University Library

London, March 18. 1774

Dear Friend,

I have lately been favoured with yours of the 24th past.3 I am very sensible of your Kindness in the Concern you express on Account of the late Attack on my Character before the Privy Council and in the Papers. Be assured, my good Friend, that I have done nothing unjustifiable, nothing but what is consistent with the Man of Honour, and with my Duty to my King and Country; and this will soon be as apparent to the Publick as it is now to all here who know me. I do not find that I have lost a single Friend on the Occasion. All have visited me repeatedly with affectionate Assurances of their unalterable Respect and Affection; and many of Distinction, with whom I had before but slight Acquaintance.4 You know that in England, there is every day in almost every Paper some Abuse on public Persons of all Parties, the King himself does not always escape; and the Populace, who are used to it, love to have a good Character cut up now and then for their Entertainment. On this occasion it suited the Purposes of the Ministry to have me abused, as it often suits the Purposes of their Opposers to abuse them. And having myself been long engag’d in Publick Business, this Treatment is not new to me, I am almost as much used to it as they are themselves, and perhaps can bear it better. So, my dear Friend, let it give you no more Uneasiness. I have indeed lost a little Place that was in their Power; but I can do very well without it. It will not be long before I publish my Vindication, which some Circumstances keep back at present. I shall send you a Copy of it, but had rather see you here. I hope your Intention of visiting us in the Spring still continues.

Sir John Pringle continues well. His Speech in giving the last Medal, on the Subject of the Discoveries relating to the Air, did him great Honour.5 I suppose you have seen it. Dr. Priestly goes on rapidly with new and curious Experiments on that Subject; too many to relate in a Letter. He is about printing a new 8vo Book full of them.6

Mr. Walsh, (one of whose Papers on the Torpedo I shall, to save Postage, send you thro’ the Hands of the Ambassador7) has just made a curious Discovery in Electricity. You know we find that in rarify’d Air it would pass more freely, and leap thro’ greater Spaces than in dense Air; and thence it was concluded that in a perfect Vacuum it would pass any distance without the least Obstruction. But having made a perfect Vacuum by means of boil’d Mercury in a long Torricellian bent Tube, its Ends immers’d in Cups full of Mercury, he finds that the Vacuum will not conduct at all, but resists the Passage of the Electric Fluid absolutely, as much as if it was Glass itself.8 This may lead to new Principles and new Views in the atmospheric Part of Philosophy. I am ever, my dear Friend, Yours most affectionately

B Franklin

M. Ingenhausz.

Addressed: To / Dr Ingenhauss / Physician of the Court / at Vienna / Austria

Notation: Opened on Account of the Postage not being paid.

[Note numbering follows the Franklin Papers source.]

3The letter survives only in the writer’s brief abstract.

4The public would presumably learn of BF’s innocence through his apologia, which he had begun a month before (to David Williams above, Feb. 21) and which is printed below at the end of the year. He never explained, as far as we know, what old friends stood by him and what new ones he made. Some of the old were deeply troubled; see the note on an extract of a letter above, Feb. 19. David Williams, seemingly a new friend, was not one of distinction.

5The speech by the President of the Royal Society, on the occasion of Priestley’s receiving the Copley Medal, was printed as a pamphlet: Sir John Pringle, A Discourse on the Different Kinds of Air … (London, 1774).

6Joseph Priestley’s Experiments and Observations on Different Kinds of Air (London, 1774) was advertised in the London Chron., June 4–7.

7The paper was the printed report to BF, we assume, and was sent via Count Lodovico Barbiano di Belgioioso: above, XX, 258–67; XIX, 305 n.

8We have found no other record of the experiment, and after discussing it with Prof. I. B. Cohen we can only assume that something was wrong with Walsh’s findings. The fact that French physicists found nothing novel in them (Dubourg to BF below, April 16) only deepens the mystery. Although the conductivity of a gas, as it approaches a vacuum, increases up to a point and then decreases, that point is far beyond what the technique described might have been expected to reach. Boiling replaced the air with mercury vapor, which as it cooled created a vacuum that could scarcely have been complete enough to decrease, let alone eliminate, the vapor’s conductivity.

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