Place an ivory ball on the prime conductor of the machine, and take a strong spark, or send the charge of a Leyden phial through its centre, and the ball will appear perfectly luminous; but if the charge be not sent through the centre, it will pass over the surface of the ball and singe it. A spark made to pass through a ball of box-wood, not only illuminates the whole, but makes it appear of a beautiful crimson, or rather a fine scarlet colour.
Illuminated Phosphorus.
Put some of Canton's phosphorus into a clear glass phial, and stop it with a glass stopper, or a cork and sealing-wax. If this wire be kept in a darkened room (which for this experiment must be very dark) it will give no light; but let two or three strong sparks be drawn from the prime conductor, when the phial is kept about two inches distant from the sparks, so that it may be exposed to that light, and this phial will receive the light and afterwards will appear illuminated for a considerable time.
This powder may be stuck upon a board by means of the white of an egg, so as to represent figures of planets, letters, or any thing else, at the pleasure of the operator, and these figures may be illuminated in the dark, in the same manner as the above described phial.
A beautiful method of expressing geometrical figures with the above powder, is to bend small glass tubes, of about the tenth part of an inch diameter, in the shape of the figure desired, and then to fill them with the phosphoric powder. These may be illuminated in the manner described; and they are not so subject to be spoiled, as the figures represented upon the board frequently are.
The Luminous Writing.
Small pieces of tin-foil may be stuck on a flat piece of glass, so as to represent various fanciful figures. Upon the same principle is the word LIGHT produced, in luminous characters.
It is formed by the small separations of the tin-foil pasted on a piece of glass fixed in a frame of baked wood. To use this, the frame must be held in the hand, and the ball presented to the conductor. The spark will then be exhibited in the intervals composing the word, from whence it passes to the hook, and thence to the ground by a chain. The brilliancy of this is equal to that of the spiral tubes.
The Electric Explosion.
Take a card, a quire of paper, or the cover of a book; and keep it close to the outside coating of a charged jar: put one knob of the discharging-rod upon the card, quire of paper, &c., so that, between the knob and coating of the jar, the thickness of that card or quire of paper only is interposed; lastly, by bringing the other knob of the discharged rod near the knob of the jar, make the discharge, and the electric spark will pierce a hole (or perhaps several) quite through the card or quire of paper. This hole has a bur raised on each side, except the card, &c., be pressed hard between the discharging-rod and the jar. If this experiment be made with two cards instead of one, which, however, must be kept very little distant from one another, each of the cards, after the explosion, will be found pierced with one or more holes, and each hole will have burs on both surfaces of each card. The hole, or holes, are larger or smaller, according as the card, &c., is more damp or more dry. It is remarkable, that if the nostrils are presented to it, they will be affected with a sulphurous, or rather a phosphoric smell, just like that produced by an excited electric.