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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 superabun dant 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 clectrify 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 Auid 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
nected 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.
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 machine 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 quanticy, attract the clapper x x which take a portion from a
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 placed between these will, when the conductor is electrified, appear like a rope-dancer.