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who has an over quantity; but gives one to A, who has an under quantity. If A and B approach to touch each other, the spark is stronger, because the difference between them is greater. After such touch there is no spark between either of them and C, because the electrical fire in all is reduced to the original equality. If they touch while electrizing, the equality is never destroyed, the fire only circulating. Hence have arisen some new terms among us; we say B (and bodies like circumstanced) is electrized positively; A, negatively. Or rather, B is electrized plus; A, minus. And we daily in our experiments electrize bodies plus or minus, as we think proper. To electrize plus or minus, no more needs to be known than this, that the parts of the tube or sphere that are rubbed, do, in the instant of the friction, attract the electrical fire, and therefore take it from the thing rubbing; the same parts immediately, as the friction upon them ceases, are disposed to give the fire they have received to any body that has less. Thus you may circulate it, as Mr. Watson has shown; you may also accumulate or subtract it, upon or from any body, as you connect that body with the rubber, or with the receiver, the communication with the common stock being cut off. We think that ingenious gentleman was deceived, when he imagined (in his Sequel), that the electrical fire came down the wire from the ceiling to the gun-barrel, thence to the sphere, and so electrized the machine and the man turning the wheel, &c. We suppose it was driven off, and not brought on through that wire; and that the machine and man, &c., were electrized minus, that is, had less electrical fire in them than things in common.
As the vessel is just upon sailing, I cannot give you so large an account of American electricity as I intended; I shall only mention a few particulars more. We
find granulated lead better to fill the phial with, than water, being easily warmed, and keeping warm and dry in damp air. We fire spirits with the wire of the phial. We light candles, just blown out, by drawing a spark among the smoke, between the wire and snuffers. We represent lightning, by passing the wire in the dark, over a China plate, that has gilt flowers, or applying it to gilt frames of looking-glasses, &c. We electrize a person twenty or more times running, with a touch of the finger on the wire, thus; He stands on wax. Give him the electrized bottle in his hand. Touch the wire with your finger, and then touch his hand or face; there are sparks every time.* We increase the force of the electrical kiss vastly, thus; Let A and B stand on wax; or A on wax, and B on the floor; give one of them the electrized phial in hand; let the other take hold of the wire; there will be a small spark; but when their lips approach, they will be struck and shocked. The same, if another gentleman and lady, C and D, standing also on wax, and joining hands with A and B, salute or shake hands. We suspend by fine silk thread a counterfeit spider, made of a small piece of burnt cork, with legs of linen thread, and a grain or two of lead stuck in him, to give him more weight. Upon the table, over which he hangs, we stick a wire upright, as high as the phial and wire, four or five inches from the spider; then we animate him, by setting the electrified phial at the same distance on the other side of him; he will immediately fly to the wire of the phial, bend his legs in touching it, then spring off, and fly to the wire in the table, thence again to the wire of the
* By taking a spark from the wire, the electricity within the bottle is diminished; the outside of the bottle then draws some from the person holding it, and leaves him in the negative state. Then when his hand or face is touched, an equal quantity is restored to him from the person touching.
phial, playing with his legs against both, in a very entertaining manner, appearing perfectly alive to persons unacquainted. He will continue this motion an hour or more in dry weather. We electrify, upon wax in the dark, a book that has a double line of gold round upon the covers, and then apply a knuckle to the gilding; the fire appears everywhere upon the gold like a flash of lightning; not upon the leather, nor if you touch the leather instead of the gold. We rub our tubes with buckskin, and observe always to keep the same side to the tube, and never to sully the tube by handling; thus they work readily and easily, without the least fatigue, especially if kept in tight pasteboard cases, lined with flannel, and sitting close to the tube.* This I mention, because the European papers on electricity frequently speak of rubbing the tube as a fatiguing exercise. Our spheres are fixed on iron axes, which pass through them. At one end of the axis there is a small handle, with which you turn the sphere like a common grindstone. This we find very commodious, as the machine takes up but little room, is portable, and may be enclosed in a tight box, when not in use. It is true, the sphere does not turn so swift as when the great wheel is used; but swiftness we think of little importance, since a few turns will charge the phial, &c., sufficiently.†
I am, &c.
Our tubes are made here of green glass, twenty-seven or thirty inches long, as big as can be grasped.
This simple, easily-made machine was a contrivance of Mr. Syng's.
TO PETER COLLINSON.
Observations on the Leyden Bottle, with Experiments proving the different Electrical State of its different Surfaces.
Philadelphia, 1 September, 1747.
The necessary trouble of copying long letters, which perhaps, when they come to your hands, may contain nothing new, or worth your reading, (so quick is the progress made with you in electricity,) half discourages me from writing any more on that subject. Yet I cannot forbear adding a few observations on M. Muschenbroek's wonderful bottle.
1. The non-electric contained in the bottle differs, when electrized, from a non-electric electrized out of the bottle, in this; that the electrical fire of the latter is accumulated on its surface, and forms an electrical atmosphere round it of considerable extent; but the electrical fire is crowded into the substance of the former, the glass confining it.*
2. At the same time that the wire and the top of the bottle, &c. is electrized positively or plus, the bottom of the bottle is electrized negatively or minus, in exact proportion; that is, whatever quantity of electrical fire is thrown in at the top, an equal quantity goes out of the bottom. To understand this, suppose the common quantity of electricity in each part of the bottle, before
* See this opinion rectified in § 16 and 17 of the next letter. The fire in the bottle was found by subsequent experiments not to be contained in the non-electric, but in the glass. 1748.
† What is said here, and after, of the top and bottom of the bottle, is true of the inside and outside surfaces, and should have been so expressed.
the operation begins, is equal to twenty; and at every stroke of the tube, suppose a quantity equal to one is thrown in; then, after the first stroke, the quantity contained in the wire and upper part of the bottle will be twenty-one, in the bottom nineteen; after the second, the upper part will have twenty-two, the lower eighteen, and so on, till, after twenty strokes, the upper part will have a quantity of electrical fire equal to forty, the lower part none; and then the operation ends; for no more can be thrown into the upper part, when no more can be driven out of the lower part. If you attempt to throw more in, it is spewed back through the wire, or flies out in loud cracks through the sides of the bottle.
3. The equilibrium cannot be restored in the bottle by inward communication or contact of the parts; but it must be done by a communication formed without the bottle, between the top and bottom, by some nonelectric, touching or approaching both at the same time; in which case it is restored with a violence and quickness inexpressible; or touching each alternately, in which case the equilibrium is restored by degrees.
4. As no more electrical fire can be thrown into the top of the bottle, when all is driven out of the bottom, so, in a bottle not yet electrized, none can be thrown into the top, when none can get out at the bottom; which happens either when the bottom is too thick, or when the bottle is placed on an electric per se. Again, when the bottle is electrized, but little of the electrical fire can be drawn out from the top, by touching the wire, unless an equal quantity can at the same time get in at the bottom.* Thus, place an electrized bottle on clean glass or dry wax, and you will not, by touching the wire, get out the fire from the top.
* See the preceding note, relating to top and bottom.