Tutor. When I turned the wheel they all had more than their share of the elec tric 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.

James. 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.

Charles. Now your hairs stand all an

end.

James. And I feel something like cob. webs over my face.

Tutor. There are, however, no cobwebs, but that is the sensation which a person al-.

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 conduc 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 flannel, 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

ductor, and at the distance of three or four inches below I will place some small feathers, or bits of paper cut into the figures of men and women. They lie very quiet at present; observe their motions as soon as I turn the wheel.

James. They exhibit a pretty country dance: they jump up to the top plate, and then down again.

Tutor. The same principle is evident in all these experiments. The upper plate has more than its own share of the electric fluid, which attracts the little figures: as soon as they have received a portion of it, they go down to give it to the lower plate; and so it will continue till the upper plate is discharged of its superabundant quantity.

I will take away the plates, and hang a chain on the conductor, the end of which shall lie in several folds in a glass tumbler; if I turn the machine, the electric fluid will run through the chain, and will electrify the inside of the glass. This done,

I turn it quickly over eight or ten small pith-balls, which lie on the table.

Charles. That is a very amusing sight: how they jump about! They serve also to fetch the electricity from the glass, and carry it to the table.

Tutor.

If, instead of the lower metal plate, I hold in my hand a pane of dry and very clean glass, by the corner, the paper figures or pith-balls will not move, because glass being a non-conducting substance, it has no power of carrying away the superabundant electricity from the plate suspended from the conductor. But if I hold the glass flat in my hand, the figures will be attracted and repelled, which shows that the electric fluid will pass through thin glass.

Take now the following results, and commit them to your memory.

(1.) If two insulated pith-balls be brought near the conductor, they will repel each

other.

(2.) If an insulated conductor be con