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rations, that there should be one fluid rather than two, provided that known facts can be equally well accounted for, by one as by two.
Charles. Can you account for all the leading facts by either theory?
Tutor. Yes, we can.
You saw when the pith-balls were electrified, they repelled one another. It is a general principle in electricity that two bodies having more than their natural share of the electric fuid, will repel one another. But if one have more, and the other less, than its share, they will attract one another.
James. How is this shown?
Tutor. I will hold this ball, which is insulated, by a silk thread, to the conductor, and do you, Charles, do the same with the other. Let us now bring them together.
Charles. No, we cannot: they fly from
Tutor. I will hold mine to the insulated cushion, and you shall hold yours to the conductor while the machine is turn. ed ; now I suspect they will attract one another.
James. They do indeed.
Charles. The reason is this ; that the cushion, and whatever is in contact with it, parts with a portion of its electricity; but the conductor, and the adjoining bodies have more than their share ; therefore, the ball applied to the cushion, being negatively electrified, will attract the one connected with the conductor, which is positively electrified.
Tutor. Here is a tuft of feathers, which I stick in a small hole in the conductor : now see what happens when I turn the cy, linder,
James. They all endeavour to avoid each other, and stand erect, in a beautiful manner.
Let me take a spark from the conductor: now they fall down in a moment.
Tutor. When I turned the wheel they all had more than their share of the electric fluid, and therefore they repelled one another, but the moment the electricity was taken away, they fell into their natu. ral position. A large plume of feathers, when electrified, grows beautifully turgid, expanding its fibres in all directions, and they collapse when the electricity is taken off.
Yames. Could you make the hairs on my head repel one another?
Tutor. Yes, that I can. Stand on the glass-legged stool, and hold the chain that hangs on the conductor, in your hand, while I turn the machine.
Chdrles. Now your hairs stand all an end.
James. And I feel something like cob. webs
face. Tutor. There are, however, no cobwebs, but that is the sensation which ways experiences if he be highly electrified.
Hold the pith-ball, Charles, near your brother's face.
James. It is attracted in the same manner as it was before with the conduce tor.
Tutor. Hence you may lay it down as a general rule, that all light substances coming within the influence of an electrified body, are attracted by it whether it is electrified positively or negatively.
Charles. Because they are attracted by the positive electricity to receive some of the superabundant quantity ; and by the negative, to give away some that they possess.
Tutor. Just so: and when they have received as much as they can contain, they are repelled by the electrified body. The same thing may be shown in various ways. Having excited this glass tube, either by drawing it several times through my hand, or by means of a piece of Aannel, I will bring it near this small feather. See how quickly it jumps to the glass.
James. It does, and sticks to it.
Tutor. You will observe, that after a minute or two, it will have taken as much electricity from the tube as it can hold, when it will suddenly be repelled, and jump to the nearest conductor ; upon
which it will discharge the superabundant electricity that it has acquired.
James. I see it is now going to the ground, that being the nearest conductor.
Tutor. I will prevent it by holding the electrified tube between it and the floor. You see how unwilling it is to come again in contact with the tube : by pursuing, I can drive it where I please without touching it.
Charles. That is, because the glass and the feather are both loaded with the same electricity
Tutor. Let the feather touch the ground, or any other conductor, and you will see that it will jump to the tube as fast as it did before.
I will suspend this brass plate, which is about five inches in diameter, to the con