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in making hypotheses and forming imaginary systems, which we are all too apt to please ourselves with, till some experiment comes and unluckily destroys them. Wishing you success in your inquiries, I have the honor to be, Sir, &c.



On his patent Electrical Machine, and the Effects of

Lightning on the Eyes of Animals killed by it.

Passy, 18 October, 1783. DEAR SIR, I received your favor of August 14th, by Mr. Sykes, with the book of directions for using your patent electric machine. The machine itself is also come to hand in good order, after some delay on the road; and I think it very ingeniously contrived indeed; I wish your success in the sale may be equal to its merits. The experiments in your pamphlet gave me pleasure, and I shall be glad to see the account you mention of the shortening of wires by lightning.

What you have heard of the eyes of sheep forced out by a stroke of lightning which killed them, puts me in mind of having formerly seen at Philadelphia six horses all killed by lightning in a stable, every one of whom appeared to have bled at the eyes, nose, and mouth; though I do not recollect that any of their eyes were out.

You are so good as to consider how much my time has been taken up, and to excuse on that account my being a bad correspondent. Near three years ago I began a letter to you on the subject of hygrometers.

I had written three folio pages of it, when I was interrupted by some business; and, before I had time to finish it, I had mislaid it. I have now found it, and, having added what I suppose I had intended to add, I enclose it. You can judge better than myself, whether my idea of such an instrument is practicable and may be useful.*

If you favor me with another line, let me know how Mrs. Nairne does, and your amiable children. With great esteem, &c.



Effect of an Electrical Shock.

Passy, 29 April, 1785. MY DEAR FRIEND, I believe my last letter to you was of May 16th, 1783. I am therefore much in your debt as a correspondent. I have now before me all your letters since received, and shall endeavour as well as I can to answer them. I confess that a man, who can leave so many letters so long unanswered, does not deserve so valuable a correspondence as yours. But I am grown very old, being now in my eightieth year; I am engaged in much business that must not be neglected, Writing becomes more and more irksome to me; I grow more indolent; philosophic discussions, not being urgent like business, are postponed from time to time till they are forgotten. Besides, I have been these twenty months past afflicted with the stone, which is always giving me more or less uneasiness, unless when I am laid in bed; and, when I would write, it interrupts my train of thinking, so that I lay down my pen, and seek some light amusement.

* The letter here mentioned is dated November 13th, 1780. It will be found among the PhilosoPHICAI PAPERS, under that date. - Editor.

I consent to your request concerning my paper on the weathercock struck by lightning. Dispose of it as you please.

You will find an account of the first great stroke I received, in pages 160, 161, of my book, fifth edition, 1774.* The second I will now give you. I had a paralytic patient in my chamber, whose friends brought him to receive some electric shocks. I made them join hands so as to receive the shock at the same time, and I charged two large jars to give it. By the number of those people, I was obliged to quit my usual standing, and placed myself inadvertently under an iron hook which hung from the ceiling down to within two inches of my head, and communicated by a wire with the outside of the jars. I attempted to discharge them, and in fact did so; but I did not perceive it, though the charge went through me, and not through the persons I intended it for. I neither saw the flash, heard the report, nor felt the stroke. When my senses returned, I found myself on the floor. I got up, not knowing how that had happened. I then again attempted to discharge the jars; but one of the company told me they were already discharged, which I could not at first believe, but on trial found it true. They told me they

* The passage here alluded to is a part of Mr. Watson's “ Account” of Franklin's “ Experiments and Observations on Electricity.” See Appendix, No, I., pp. 491, 492.

The incident mentioned is the same as that described in a letter to a gentleman in Boston, dated December 25th, 1750, and printed for the first time in the present edition. See above, p. 255. — EDITOR. VOL. v.


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had not felt it, but they saw I was knocked down by it, which had greatly surprised them. On recollecting myself, and examining my situation, I found the case clear. A small swelling rose on the top of my head, which continued sore for some days; but I do not remember any other effect, good or bad. The stroke you received, and its consequences, are much more curious. I communicated that part of your letter to an operator, encouraged by government here to electrify epileptic and other poor patients, and advised his trying the practice on mad people according to your opinion. I have not heard whether he has done it.



On the Utility of Electrical Conductors.

Philadelphia, 14 October, 1787.

I have received the excellent work, Upon the Utility of Electrical Conductors, which you had the goodness to send me. I read it with great pleasure, and beg you to accept my sincere thanks for it.

Upon my return to this country, I found the number of conductors much increased, many proofs of their efficacy in preserving buildings from lightning having demonstrated their utility. Among other instances, my own house was one day attacked by lightning, which occasioned the neighbours to run in to give assistance, in case of its being on fire. But no damage was done, and my family was only found a good deal frightened with the violence of the explosion.

Last year, my house being enlarged, the conductor was obliged to be taken down. I found, upon examination, that the pointed termination of copper, which was originally nine inches long, and about one third of an inch in diameter in its thickest part, had been almost entirely melted; and that its connexion with the rod of iron below was very slight. Thus, in the course of time, this invention has proved of use to the author of it, and has added this personal advantage to the pleasure he before received from having been useful to others. Mr. Rittenhouse, our astronomer, has informed me, that, having observed with his excellent telescope many conductors that are within the field of his view, he has remarked in various instances, that the points were melted in like manner. There is no example of a house, provided with a perfect conductor, which has suffered any considerable damage; and even those which are without them have suffered little, since conductors have become common in this city.


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