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brought near any conducting substance, it will fly to it in luminous streams.

Ex. 9. Place a drop of water on the conductor, and work the machine, the drop will afford a long spark, assume a conical figure, and carry some of the water with it.

Ex. 10. On this wire I have fixed a piece of sealing-wax, and having fixed the wire into the end of the conductor, I will light the wax, and the moment the machine is worked, the wax will fly off in the finest filaments imaginable.

Ex. 11. I will wrap some cotton-wool round one of the knobs of my dischargingrod, and fill the wool with finely bruised resin : I now discharge a Leyden jar, or a battery, in the common way, and the wool is instantly in a blaze. The covered knob must touch the knob of the jar, and the discharge should be effected as quickly as possible.

You will remember that the electric fluid always chooses the nearest road, and the

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best conductors to travel by ; in proof of which take the following experiment :

Ex. 12. With this chain I make a sort of w,(Plate vir. Fig. 15.) the wire w touches the outside of a charged jar, and the wire x, is brought to the knob of the jar, and in the dark a brilliant w is visible. But if the wire w is contined to m, the electric fluid takes a shorter road to x, and, of course, only half of the w is seen, viz. that part marked m zy: but if, instead of the wire w m, a dry stick be laid in its place, the electric matter will prefer a longer circuit, rather than go through a bad conductor, and the whole w will be illuminated.

Ex. 13. Here is a two ounce-phial, half full of sallad-oil, through the cork is passed a piece of slender wire, the end of which, within the phial, is so bent as to touch the glass just below the surface of the oil. I place my thumb opposite the point of the wire in the bottle, and in that position take a spark from the charged conductor. You observe that the spark, to get to my thumb, has actually perforated the glass,

James. At

In the same way I can make holes all round the phial.

Charles. Would the experiment succeed with water instead of oil ? Tutor. No, it would not.

any rate we see the course of the electric fluid in this experiment, for the spark comes from the conductor down the wire, and through the glass to the thumb.

Tutor. Its direction is, however, better shown in this way.

Ex. 14. At that end of the conductor which is farthest from the machine, I fix a brass wire, about six inches long, having a small brass ball on its extremity. To this ball, when the machine is at work, I hold the flame of a wax taper.

Charles. The fame is evidently blown from the ball, in the direction of the electric fluid: it has a similar effect to the blast of a pair of bellows.

Ex. 15. I will fix a pointed wire upon the prime conductor, with the point outward, and another like wire upon the insulated rubber. Shut the window-shutter,

and I will work the machine: now observe the points of the two wires.

James. They both are illuminated, but differently. The point on the conductor sends out a sort of brush of fire, but that on the rubber is illuminated with a star.

Tutor. You see then the difference between the positive and negative electricity.

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CONVERSATION XXXVIII.

Miscellaneous Experiments of the Electrophorus

Of the Electrometer, and the Thunder House.

TUTOR. I shall proceed this morning with some other experiments on the electrical machine.

Ex. 1. Here are two wires, one of whiclı is connected with the outside of this charged Leyden jar, the other is so bent as easily to touch the knob of the jar. The two straight ends I bring within the distance of the tenth of an inch of one another, and press them down with my thumb, and in this position, having darkened the room, I discharged the jar. Do you look upon my thumb.

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