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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 Abbé has done.
With an Attempt to account for their several Phenome
Together with some Observations on Thunderclouds, in further Confirmation of Mr. Franklin's Observations on the Positive and Negative Electrical State of the Clouds. By John Canton, M. A., F. R. S.
6 December, 1753.
From the ceiling, or any convenient part of a room, let two cork balls, each about the bigness of a small pea, be suspended by linen threads of eight or nine inches in length, so as to be in contact with each other. Bring the excited glass tube under the balls, and they will be separated by it, when held at the distance of three or four feet; let it be brought nearer, and they will stand farther apart; entirely withdraw it, and they will immediately come together. This experiment may be made with very small brass balls hung by silver wire; and will succeed as well with sealing-wax made electrical, as with glass.
If two cork balls be suspended by dry silk threads, the excited tube must be brought within eighteen inches
before they will repel each other; which they will continue to do, for some time, after the tube is taken away.
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 return of the tube, they will approach each other till they touch, and then repel as at first. If the tin tube be electrified by wax, or the wire of a charged phial, the balls will be affected in the same manner at the approach of excited wax, or the wire of the phial.
Electrify the cork balls, as in the last experiment, by glass, and at the approach of an excited stick of wax their repulsion will be increased. The effect will be the same, if the excited glass be brought towards them, when they have been electrified by wax.
The bringing the excited glass to the end or edge of the tin tube, in the third experiment, is supposed to electrify it positively, or to add to the electrical fire it before contained; and therefore some will be running off through the balls, and they will repel each other. But, at the approach of excited glass, which likewise emits the electrical fluid, the discharge of it from the balls will be diminished; or part will be driven back, by a force acting in a contrary direction; and they will come nearer together. If the tube be held at such a distance from the balls, that the excess of the density of the fluid round about them, above the common quantity in air, be equal to the excess of the density of that within them, above the common quantity contained in cork, their repulsion will be quite destroyed. But, if the tube be brought nearer, the fluid without being more dense than that within the balls, it will be attracted by them, and they will recede from each other again.
When the apparatus has lost part of its natural share of this fluid, by the approach of excited wax to one end of it, or is electrified negatively, the electrical fire is attracted and imbibed by the balls to supply the deficiency; and that more plentifully at the approach of excited glass, or a body positively electrified, than before ; whence the distance between the balls will be increased, as the fluid surrounding them is augmented. And, in general, whether by the approach or recess of any body, if the difference between the density of the internal and external fluid be increased, or diminished, the repulsion of the balls will be increased, or diminished, accordingly.
When the insulated tin tube is not electrified, bring the excited glass tube towards the middle of it, so as to be nearly at right angles with it, and the balls at the end will repel each other; and the more so, as the excited tube is brought nearer. When it has been held a few seconds, at the distance of about six inches, withdraw it, and the balls will approach each other till they touch; and then, separating again, as the tube is moved farther off, will continue to repel when it is taken quite away. And this repulsion between the balls will be increased by the approach of excited glass, but diminished by excited wax; just as if the apparatus had been electrified by wax, after the manner described in the third experiment.
Insulate two tin tubes, distinguished by A and B, so as to be in a line with each other, and about half an inch apart; and, at the remote end of each, let a pair of cork balls be suspended. Towards the middle of A, bring the excited glass tube, and holding it a short time, at the distance of a few inches, each pair of balls will be observed to separate ; withdraw the tube, and the balls of A will come together, and then repel each other again ; but those of B will hardly be affected. By the approach of the excited glass tube, held under the balls of A, their repulsion will be increased; but if the tube be brought, in the same manner, towards the balls of B, their repulsion will be diminished.
In the fifth experiment, the common stock of electrical matter in the tin tube is supposed to be attenuated about the middle, and to be condensed at the ends, by the repelling power of the atmosphere of the excited glass tube, when held near it. And perhaps the tin tube may lose some of its natural quantity of the electrical fluid, before it receives any from the glass; as that fluid will more readily run off from the ends and edges of it, than enter at the middle ;' and accordingly, when the glass tube is withdrawn, and the fluid is again equally diffused through the apparatus, it is found to be electrified negatively; for excited glass brought under the balls will increase their repulsion.
In the sixth experiment, part of the fluid driven out of one tin tube enters the other; which is found to be electrified positively, by the decreasing of the repulsion of its balls at the approach of excited glass.
Let the tin tube, with a pair of balls at one end, be placed three feet at least from any part of the room, and the air rendered very dry by means of a fire; electrify the apparatus to a considerable degree; then touch the tin tube with a finger, or any other conductor, and the balls will, notwithstanding, continue to repel each other, though not at so great a distance as before.
The air surrounding the apparatus, to the distance of two or three feet, is supposed to contain more or less of the electrical fire, than its common share, as the tin tube is electrified positively or negatively; and, when