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glass, and the outer or emptied side, being lessened by touching the hook or the conductor, the outer side can receive from the hand which touched it, and, by its receiving, the inner side cannot retain so much; and, for that reason, so much as it cannot contain electrizes the water, or filings, and conductor. For it seems to be a rule, that the one side must be emptied in the same proportion that the other is filled; though this from experiment appears evident, yet it is still a mystery not to be accounted for.
I am, in many places of the Abbe's book, surprised to find, that experiments have succeeded so differently at Paris, from what they did with Mr. Franklin, and as I have always observed them to do. The Abbe, in making experiments to find the difference between the two surfaces of a charged glass, will not have the phial placed on wax; "for," says he, "don't you know, that, being placed on a body originally electric, it quickly loses its virtue?" I cannot imagine what should have made the Abbe think so; it certainly is contradictory to the notions commonly received of electrics per se; and by experiment I find it entirely otherwise; for, having several times left a charged phial, for that purpose, standing on wax for hours, I found it to retain as much of its charge as another that stood at the same time on a table. I left one standing on wax from ten o'clock at night till eight the next morning, when I found it to retain a sufficient quantity of its charge to give me a sensible commotion in my arms, though the room in which the phial stood had been swept in that time, which must have raised much dust to facilitate the discharge of the phial.
I find that a cork ball suspended between two bottles, the one fully and the other but little charged, will not play between them, but is driven into a situation that makes a triangle with the hooks of the phials; though the Abbe has asserted the contrary of this, (p. 101,) in order to account for the playing of a cork ball between the wire thrust into the phial, and one that rises up from its coating. The phial which is least charged must have more electric matter given to it, in proportion to its bulk, than the cork ball receives from the hook of the full phial. before they will repel each other; which they will continue to do, for some time, after the tube is taken away.
The Abbe says, (p. 103,) "That a piece of metal leaf, hung to a silk thread and electrized, will be repelled by the bottom of a charged phial held by its hook in the air;" this I find constantly otherwise; it is with me always first attracted and then repelled. It is necessary, in charging the leaf, to be careful that it does not fly off to some non-electric body, and so discharge itself, when you think it is charged; it is difficult to keep it from flying to your,own wrist, or to some part of your body.
The Abbe (p. 108) says, "that it is not impossible, as Mr. Franklin says it is, to. charge a phial while there is a communipation formed between its coating and its hook." I have always found it impossible to charge such a phial so as to give a shock; indeed, if it hang on the conductor without a communication from it, you may draw a spark from it, as you may from any body that hangs there; but this is very different from being charged in such a manner as to give a shock. The Abbe, in order to account for the little quantity of electric matter that is to be found in the phial, says, " that it rather follows the metal than the glass, and that it spewed out into the air from the coating of the phial." I wonder how it comes not to do so too, when it sifts through the glass, and charges the exterior surface, according to the Abbe's system!
The Abbe's objections against Mr. Franklin's two last experiments, I think, have little weight in them; he
VOL. V. 42 BB*
seems, indeed, much at a loss what to say, wherefore he taxes Mr. Franklin with having concealed a material part of the experiment; a thing too mean for any gentleman to be charged with, who has not shown as great a partiality in relating experiments, as the Abbe has done.
As the balls in the first experiment are not insulated, they cannot properly be said to. be electrified; but when they hang within the atmosphere of the excited tube, they may attract and condense the electrical fluid round about them, and be separated by the repulsion of its particles. It is conjectured also, that the balls at this time contain less than their common share of the electrical fluid, on account of the repelling power of that which surrounds them; though some, perhaps, is continually entering and passing through the threads. And, if that be the case, the reason is plain why the balls hung by silk, in the second experiment, must be in a much more dense part of the atmosphere of the tube, before they will repel each other. At the approach of an excited stick of wax to the balls, in the first experiment, the electrical fire is supposed to come through the threads into the balls, and be condensed there, in its passage towards the wax; for, according to Mr. Franklin, excited glass emits the electrical fluid, but excited wax receives it.
Let a tin tube, of four or five feet in length, and about two inches in diameter, be insulated by silk; and from one end of it let the cork balls be suspended by linen threads. Electrify it, by bringing the excited glass tube near the other end, so as that the balls may stand an inch and a half, or two inches, apart; then, at the approach of the excited tube, they will, by degrees, lose their repelling power, and come into contact; and, as the tube is brought still nearer, they will separate again to as great a distance as before; in the