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other hardly showed any signs of its being in connexion with it.* Even a thoroughly wet packthread sometimes fails of conducting a shock, though it otherwise conducts electricity very well. A dry cake of ice, or an icicle held between two in a circle, likewise prevents the shock, which one would not expect, as water conducts it so perfectly well. Gilding on a new book, though at first it conducts the shock extremely well, yet fails after ten or a dozen experiments, though it appears otherwise in all respects the same, which we cannot account for.t
29. There is one experiment more which surprises us, and is not hitherto satisfactorily accounted for; it is this. Place an iron shot on a glass stand, and let a ball of damp cork, suspended by a silk thread, hang in contact with the shot. Take a bottle in each hand, one that is electrified through the hook, the other through the coating; apply the giving wire to the shot, which will electrify it positively, and the cork shall be repelled; then apply the requiring wire, which will take out the spark given by the other; when the cork will return to the shot; apply the same again, and take out another spark, so will the shot be electrified negatively, and the cork in that case shall be repelled equally as before. Then apply the giving wire to the shot, and give the spark it wanted, so will the cork return; give it another, which will be an addition to its natural
* Probably the ground is never so dry,
† We afterwards found, that it failed after one stroke with a large bottle; and the continuity of the gold appearing broken, and many of its parts dissipated, the electricity could not pass the remaining parts without leaping from part to part through the air, which always resists the motion of this fluid, and was probably the cause of the gold's not conducting so well as before; the number of interruptions in the line of gold, making, when added together, a space larger, perhaps, than the striking distance. VOL. y.
quantity, so will the cork be repelled again ; and so may the experiment be repeated as long as there is any charge in the bottles. Which shows, that bodies having less than the common quantity of electricity repel each other, as well as those that have more.
Chagrined a little that we have been hitherto able to produce nothing in this way of use to mankind; and the hot weather coming on, when electrical experiments are not so agreeable, it is proposed to put an end to them for this season, somewhat humorously, in a party of pleasure on the banks of the Skuylkill.* Spirits, at the same time, are to be fired by a spark sent from side to side through the river, without any other conductor than the water; an experiment which we some time since performed, to the amazement of many. A turkey is to be killed for our dinner by the electrical shock, and roasted by the electrical jack, before a fire kindled by the electrified bottle; when the healths of all the famous electricians in England, Holland, France, and Germany are to be drank in electrified bumpers,* under the discharge of guns from the electrical battery.
* The river that washes one side of Philadelphia, as the Delaware does the other; both are ornamented with the summer habitations of the citizens, and the agreeable mansions of the principal people of this colony.
+ As the possibility of this experiment has not been easily conceived, I shall here describe it. Two iron rods, about three feet long, were planted just within the margin of the river, on the opposite sides. A thick piece of wire, with a small round knob at its end, was fixed on the top of one of the rods, bending downwards, so as to deliver commodiously the spark upon the surface of the spirit. A small wire fastened by one end to the handle of the spoon, containing the spirit, was carried across the river, and supported in the air by the rope commonly used to hold by, in drawing the ferry-boats over. The other end of this wire was tied round the coating of the bottle; which being charged, the spark was delivered from the hook to the top of the rod standing in the water on that side. At the same instant the rod on the other side delivered a spark into the spoon, and fired the spirit; the electric fire returning to the coating of the bottle, through the handle of the spoon and the supported wire connected with them.
That the electric fire thus actually passes through the water, has since been satisfactorily demonstrated to many, by an experiment of Mr. Kinnersley's, performed in a trough of water about ten feet long. The hand, being placed under water in the direction of the spark (which always takes the straight or shortest course, if sufficient, and other circumstances are equal), is struck and penetrated by it as it passes.
TO PETER COLLINSON.
Observations and Suppositions towards forming a new
Hypothesis for explaining the several Phenomena of Thunder-gusts.t
SIR, Non-electric bodies, that have electric fire thrown into them, will retain it till other electrics, that have less, approach ; and then it is communicated by a snap, and becomes equally divided.
2. Electrical fire loves water, is strongly attracted by it, and they can subsist together.
3. Air is an electric per se, and, when dry, will not conduct the electrical fire; it will neither receive it, nor give it to other bodies; otherwise no body surrounded by air could be electrified positively and negatively; for, should it be attempted positively, the air would immediately take away the overplus; or negatively, the air would supply what was wanting.
4. Water being electrified, the vapors arising from it will be equally electrified; and floating in the air, in the form of clouds, or otherwise, will retain that quantity of electrical fire, till they meet with other clouds or bodies not so much electrified, and then will communicate as before mentioned.
* An electrified bumper is a small, thin, glass tumbler, nearly filled with wine, and electrified as the bottle. This when brought to the lips gives a shock, if the party be close shaved, and does not breathe on the liquor. - April 29th, 1749.
† Thunder-gusts are sudden storms of thunder and lightning, which are frequently of short duration, but sometimes produce mischievous effects.
5. Every particle of matter electrified is repelled by every other particle equally electrified. Thus the stream of a fountain, naturally dense and continual, when electrified, will separate and spread in the form of a brush, every drop endeavouring to recede from every other drop. But, on taking out the electrical fire, they close again.
6. Water being strongly electrified (as well as when heated by common fire) rises in vapors more copiously; the attraction of cohesion among its particles being greatly weakened, by the opposite power of repulsion introduced with the electrical fire; and, when any particle is by any means disengaged, it is immediately repelled, and so flies into the air.
7. Particles happening to be situated as A and B (Fig. 6, representing the profile of a vessel of water) are more easily disengaged than C and D, as each is held by contact with three only, whereas C and D are each in contact with nine. When the surface of the water has the least motion, particles are continually pushed into the situation represented by A and B.
8. Friction between a non-electric and an electric per se will produce electrical fire; not by creating, but collecting it; for it is equally diffused in our walls, floors, earth, and the whole mass of common matter. Thus the whirling glass globe, during its friction against the cushion, draws fire from the cushion, the cushion is supplied from the frame of the machine, that from the floor on which it stands. Cut off the communication by thick glass or wax, placed under the cushion, and no fire can be produced, because it cannot be collected.
9. The ocean is a compound of water, a non-electric, and salt, an electric per se.
10. When there is a friction among the parts near its surface, the electrical fire is collected from the parts below. It is then plainly visible in the night; it appears in the stern and in the wake of every sailing vessel ; every dash of an oar shows it, and every surf and spray; in storms the whole sea seems on fire. The detached particles of water, then repelled from the electrified surface, continually carry off the fire as it is collected; they rise and form clouds, and those clouds are highly electrified, and retain the fire till they have an opportunity of communicating it.
11. The particles of water, rising in vapors, attach themselves to particles of air.
12. The particles of air are said to be hard, round, separate, and distant from each other; every particle strongly repelling every other particle, whereby they recede from each other, as far as common gravity will permit.
13. The space between any three particles, equally repelling each other, will be an equilateral triangle.
14. In air compressed, these triangles are smaller ; in rarefied air they are larger.
15. Common fire, joined with air, increases the repulsion, enlarges the triangles, and thereby makes the · air specifically lighter. Such air, among denser air, will rise.
16. Common fire, as well as electrical fire, gives repulsion to the particles of water, and destroys their attraction of cohesion; hence common fire, as well as electrical fire, assists in raising vapors.
17. Particles of water, having no fire in them, mutually attract each other. Three particles of water then, being attached to the three particles of a triangle of