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Thus to me it appears, that the house and its inhabitants were saved by the rod, though the rod itself was unjointed by the stroke; and that, if it had been made of one piece, and sunk deeper in the earth, or had entered the earth at a greater distance from the foundation, the mentioned small damages (except the melting of the points) would not have happened.
To Miss MARY STEvenson.
Concerning the Leyden Bottle.
I Must retract the charge of idleness in your studies, when I find you have gone through the doubly difficult task of reading so big a book, on an abstruse subject, and in a foreign language.
In answer to your question concerning the Leyden phial. The hand that holds the bottle receives and conducts away the electric fluid that is driven out of the outside by the repulsive power of that which is forced into the inside of the bottle. As long as that power remains in the same situation, it must prevent the return of what it had expelled; though the hand would readily supply the quantity if it could be re
ceived. Your affectionate friend, B. FRANKLIN.
Electrical Experiments on Amber.
Saturday, 3 July, 1762.
To try, at the request of a friend, whether amber finely powdered might be melted and run together
again by means of the electric fluid, I took a piece of small glass tube, about two inches and a half long, the bore about one twelfth of an inch diameter, the glass itself about the same thickness. I introduced into this tube some powder of amber, and with two pieces of wire nearly fitting the bore, one inserted at one end, the other at the other, I rammed the powder hard between them in the middle of the tube, where it stuck fast, and was in length about half an inch. Then, leaving the wires in the tube, I made them part of the electric circuit, and discharged through them three rows of my case of bottles. The event was, that the glass was broke into very small pieces and those dispersed with violence in all directions. As I did not expect this, I had not, as in other experiments, laid thick paper over the glass to save my eyes, so several of the pieces struck my face smartly, and one of them cut my lip a little, so as to make it bleed. I could find no part of the amber; but the table where the tube lay was stained very black in spots, such as might be made by a thick smoke forced on it by a blast, and the air was filled with a strong smell, somewhat like that from burnt gunpowder. Whence I imagined, that the amber was burnt, and had exploded as gunpowder would have done in the same circumstances.
That I might better see the effect on the amber, I made the next experiment in a tube formed of a card rolled up and bound strongly with packthread. Its bore was about one eighth of an inch diameter. I rammed powder of amber into this as I had done into the other, and, as the quantity of amber was greater, I increased the quantity of electric fluid, by discharging through it at once five rows of my bottles. On opening the tube, I found that some of the powder had exploded; an impression was made on the tube, though
it was not hurt, and most of the powder remaining was turned black, which I suppose might be by the smoke forced through it from the burned part; some of it was hard; but, as it powdered again when pressed by the fingers, I suppose that hardness not to arise from melting any parts in it, but merely from my ramming the powder when I charged the tube.
about by a high wind at west or northwest, the bells rung for several hours (though with little intermissions) as briskly as ever I knew them, and I drew considerable sparks from the wire. This phenomenon I never observed but twice; viz. on the 31st of January, 1760, and the 3d of March, 1762. I am, Sir, &c. J. WINTHRoP.
FROM ALEXANDER SMALL TO BENJAMIN FRANKLIN. Flash of Lightning that struck St. Bride's Steeple.
I Have just recollected, that, in one of our great storms of lightning, I saw an appearance, which I never observed before, nor ever heard described. I am persuaded that I saw the flash which struck St. Bride's steeple. Sitting at my window, and looking to the north, I saw what appeared to me a solid straight rod of fire, moving at a very sharp angle with the horizon. It appeared to my eye as about two inches diameter, and had nothing of the zigzag lightning motion... I instantly told a person sitting with me, that some place must be struck at that instant. I was so much surprised at the vivid, distinct appearance of the fire, that I did not hear the clap of thunder, which stunned every one besides. Considering how low it moved, I could not have thought it had gone so far, having St. Martin's, the New Church, and St. Clement's steeples in its way. It struck the steeple a good way from the top, and the first impression it made in the side is in the same direction I saw it move in. It was succeeded by two flashes, almost united, moving in a pointed direction. There were two distinct houses struck in Essex Street. I should have thought the rod would have fallen in Covent Garden, it was so low. Perhaps the appearance is frequent, though never before seen by
To M.R. PETER FRANKLIN, AT NEWPort.
Best Method of securing a Powder JMagazine from Lightning.
. . . . . You may acquaint the gentleman that desired you to inquire my opinion of the best method of securing a powder magazine from lightning, that I think they cannot do better than to erect a mast not far from it, which may reach fifteen or twenty feet above the top of it, with a thick iron rod in one piece fastened to it, pointed at the highest end, and reaching down through the earth till it comes to water. Iron is a cheap metal; but, if it were dearer, as this is a public thing, the expense is insignificant; therefore I would have, the rod at least an inch thick, to allow for its gradually wasting by rust; it will last as long as the mast, and may be renewed with it. The sharp point for five or six inches should be gilt.
But there is another circumstance of importance to the strength, goodness, and usefulness of the powder, which does not seem to have been enough attended to; I mean the keeping it perfectly dry. For want of a method of doing this, much is spoiled in damp magazines, and much so damaged as to become of little value. If, instead of barrels, it were kept in cases of bottles well corked; or in large tin canisters, with small covers