therefore they repelled one another, but the moment the electricity was taken away, they fell into their natural 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 glasslegged 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 cobwebs over my face.

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

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 conductor, 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 pithballs will not move, because glass being a nonconducting 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 connected with the cushion, and two insulated pith-balls be electrified by it, they will repel each other. (3.) If one insulated ball be electrified by the prime conductor, and another by the conductor connected with the cushion, they will attract each other.

(4.) If one ball be electrified by glass, and another by wax, they will attract each other.

(5.) If one ball be electrified by a smooth, and another by a rough excited glass tube, they will attract one another.

CONVERSATION XXXH.

Of Electrical Attraction and Repulsion.

Tutor. I will show you another instance or two of the effects of electrical attraction and repulsion.

This apparatus (Plate vII. Fig. 4.) consists of three bells suspended from a brass-wire, the two outer ones by small brass chains; the middle bell, and the two clappers x x, are suspended on silk. From the middle bell there is a chain N, which goes to the table, or any other conducting substance. The bells are now to be hung by c on the conductor, and the electrical ma chine to be put in motion.

James. The clappers go from bell to bell, and make very pretty music: how do you explain this?

Tutor. The electric fluid runs down the chains a and b to the bells A B, these having more than their natural quantity, attract the clappers xx, which take a portion from A and B, and carry it to the centre bell N, and this, by means of the chain, conveys it to the earth.

Charles. Would not the same effect be produced if the clappers were not suspended on silk?

Tutor. Certainly not: nor will it be produced if the chain be taken away from the bell N, because then there is no way left to carry off the electric fluid to the earth.

Another amusing experiment is thus shown: Let there be two wires placed exactly one above another, and parallel; the upper one must be suspended from the conductor, the other is to communicate with the table. A light image