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On an Electrical Experiment.

Passy, 16 May, 1783.

I AM glad you have made the experiments you mention, and with success. You will find that the holes are not made by the impulse of the fluid moving in certain directions, but by circumstances of explosion of parts of the matter; and I still think my explanation of the holes in the vane probable, viz. that it was the explosion of tin against parts of the copper plate that were almost in a state of fusion, and therefore easily burst through either on one side or the other, as it happened.* The bursting of the twelve bottles all at once, I take to be owing to small bubbles in the substance of the glass, or grains of sand, into which a quantity of the electric fluid had been forced and compressed while the bottles were charging; and when the pressure was suddenly taken off by discharging the bottles, that confined portion by its elastic force expanding caused the breach. My reasons for thinking, that the charge did not pass by those holes you will find in a former letter; † and I think you will always find, that the coating within and without is forced both ways by the explosion of these bubbles.


* See page 472.

See page 463.

On the Shock by the Electric Bottle, and the Density of Glass.*


Passy, 14 June, 1783.

I received some time since the letter you honored me with, containing your hypothesis for explaining the shock given by the electric bottle, on which you seem to desire my opinion. It is many years since I was engaged in those pleasing studies, and my mind is at present too much occupied with other and more important affairs to permit my returning to them. I cannot therefore examine your ingenious hypothesis with the attention it appears to merit. You will find in a letter of mine to Dr. Lining, dated March 18th, 1755, that I abandoned my hypothesis of the greater density of glass in the middle than near its surfaces, as contributing to produce the effect, because I found the effect to be the same after I had ground that part away.

And I think you might likewise try yours by an easy experiment. Take a plate of lead twelve inches square; cover one of its sides with a coat of bees' wax, about one line thick; upon that apply closely a thin plate of lead eight inches square, so as to leave a margin of two inches all round. Electrify this composition of lead and wax, and try if you can receive a shock from it; if not, you may draw thence a further argument to support your hypothesis, because the wax, though a non-conductor, is not elastic, any more than pure lead. I see you are endowed with a genius for the study of nature; and I would recommend it to you to employ your time rather in making experiments, than

It is not known to whom this letter was written. EDITOR.

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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.


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.

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

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

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


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.




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