58. TO WILLIAM STRAHAN PHILADELPHIA, Jan. 4, 1746, 7. SIR; I wrote a line to you some days since, via New York, enclosing a bill of £25 sterling; the second in a copy to go by some other vessel from that port; the third you have herein; together with a bill for £60 sterling, which I hope will be duly honoured. My wife wrote to you per Mesnard for 6 Nelson's Justice, 6 Dyche's Dictionaries, 12 Cole's English Ditto, 6 Female Fables, 6 Croxall's Ditto, and Mrs. Rowe's works complete. If not sent before, please add them to the within invoice, and send the whole per first ship; and also Lenery on Foods, and Dr. Moffat on Health. Please to deliver the enclosed procuration to Mr. Acworth with the bill. The books you sent per Mesnard turned out all right, and in good order, except that the Prayer-books had all wrong psalms, the old version. I do not know if they will ever sell. The paper should not have been cut at the edges, being to be bound in account books. Our friends Hall and Read continue well. My wife joins me in best respects to Mrs. Strahan and yourself. She will write per Seymour, as will Mr. Hall. The Life of Du Renty, charged at 6 s. per dozen, has Price, stitched, four pence, under the title-page. Is there not a mistake in the charge? I am, sir, your obliged humble servant B. FRANKLIN. Your government sent no fleet to protect us against the French under D'Anville. But they have been defeated by the hand of God. SIR, 59. TO PETER COLLINSON1 PHILADELPHIA, March 28, 1747. Your kind present of an electric tube, with directions for using it, has put several of us on making electrical experiments, in which we have observed some particular phænomena, that we look upon to be new. I shall therefore communicate them to you in my next, though possibly they may not be new to you, as among the numbers daily employed in those experiments on your side the water, 'tis probable some one or other has hit on the same observations. For my own part, I never was before engaged in any study that so totally engrossed my attention and my time as this has lately done; for what with making experiments when I can be alone, and repeating them to my Friends and Acquaintance, who, from the novelty of the thing, come continually in crouds to see them, I have, during some months past, had little leisure for any thing else. I am, &c. B. FRANKLIN. SIR, 60. TO PETER COLLINSON [PHILADELPHIA,] July 11, 1747. In my last I informed you that, in pursuing our electrical enquiries, we had observed some particular phænomena, which we looked upon to be new, and of which I promised 1 I have printed this letter and the subsequent letters dated July 11, 1747, September 1, 1747, from the "Experiments and Observations" (1769), pp. I-21.-ED. to give you some account, though I apprehended they might possibly not be new to you, as so many hands are daily employed in electrical experiments on your side the water, some or other of which would probably hit on the same observations. The first is the wonderful effect of pointed bodies, both in drawing off and throwing off the electrical fire. For example, Place an iron shot of three or four inches diameter on the mouth of a clean dry glass bottle. By a fine silken thread from the cieling, right over the mouth of the bottle, suspend a small cork ball, about the bigness of a marble; the thread of such a length, as that the cork ball may rest against the side of the shot. Electrify the shot, and the ball will be repelled to the distance of four or five inches, more or less, according to the quantity of Electricity. When in this state, if you present to the shot the point of a long slender sharp bodkin, at six or eight inches distance, the repellency is instantly destroy'd, and the cork flies to the shot. A blunt body must be brought within an inch, and draw a spark, to produce the same effect. To prove that the electrical fire is drawn off by the point, if you take the blade of the bodkin out of the wooden handle, and fix it in a stick of sealing-wax, and then present it at the distance aforesaid, or if you bring it very near, no such effect follows; but sliding one finger along the wax till you touch the blade, and the ball flies to the shot immediately. If you present the point in the dark, you will see, sometimes at a foot distance, and more, a light gather upon it, like that of a fire-fly, or glow-worm; the less sharp the point, the nearer you must bring it to observe the light; and, at whatever distance you see the light, you may draw off the electrical fire, and destroy the repellency. If a cork ball so suspended be repelled by the tube, and a point be presented quick to it, tho' at a considerable distance, 'tis surprizing to see how suddenly it flies back to the tube. Points of wood will do near as well as those of iron, provided the wood is not dry; for perfectly dry wood will no more conduct Electricity than sealing-wax. To shew that points will throw off1 as well as draw off the electrical fire; lay a long sharp needle upon the shot, and you cannot electrise the shot so as to make it repel the rock ball.' Or fix a needle to the end of a suspended gun-barrel, or iron rod, so as to point beyond it like a little bayonet; and while it remains there, the gun-barrel, or rod, cannot by applying the tube to the other end be electrised so as to give a spark, the fire continually running out silently at the point. In the dark you may see it make the same appearance as it does in the case before mentioned. The repellency between the cork ball and the shot is likewise destroyed. 1, by sifting fine sand on it; this does it gradually. 2, by breathing on it. 3, by making a smoke about it from burning wood. 4, by candle-light, even 1 This power of points to throw off the electrical fire, was first communicated to me by my ingenious friend, Mr. Thomas Hopkinson, since deceased, whose virtue and integrity, in every station of life, public and private, will ever make his Memory dear to those who knew him, and knew how to value him. 2 This was Mr. Hopkinson's experiment, made with an expectation of drawing a more sharp and powerful spark from the point, as from a kind of focus, and he was surprized to find little or none. 3 We suppose every particle of sand, moisture, or smoke, being first attracted and then repelled, carries off with it a portion of the electrical fire; but that the same still subsists in those particles, till they communicate it to something else, and that it is never really destroyed. So, when water is thrown on common fire, we do not imagine the element is thereby destroyed though the candle is at a foot distance: these do it suddenly. The light of a bright coal from a wood fire; and the light of red-hot iron do it likewise; but not at so great a distance. Smoke from dry rosin dropt on hot iron, does not destroy the repellency; but is attracted by both shot and cork ball, forming proportionable atmospheres round them, making them look beautifully, somewhat like some of the figures in Burnet's or Whiston's Theory of the Earth. N. B. This experiment should be made in a closet, where the air is very still, or it will be apt to fail. The light of the sun thrown strongly on both cork and shot by a looking-glass for a long time together, does not impair the repellency in the least. This difference between fire-light and sun-light is another thing that seems new and extraordinary to us.1 We had for some time been of opinion, that the electrical fire was not created by friction, but collected, being really an element diffus'd among, and attracted by other matter, particularly by water and metals. We had even discovered and demonstrated its afflux to the electrical sphere, as well as its efflux, by means of little light windmill-wheels made of stiff paper vanes, fixed obliquely and turning freely on fine wire axes; also by little wheels of the same matter, but formed like water-wheels. Of the disposition and application of which wheels, and the various phænomena resulting, or annihilated, but only dispersed, each particle of water carrying off in vapour its portion of the fire, which it had attracted and attached to itself. 1 This different Effect probably did not arise from any difference in the light, but rather from the particles separated from the candle, being first attracted and then repelled, carrying off the electric matter with them; and from the rarefying the air, between the glowing coal or red-hot iron, and the electrised shot, through which rarified air the electric fluid could more readily pass. VOL. II-X |