Rub two pieces of fine lump sugar together in the dark, and a bright electric light will be produced. The same effect, but in a more intense degree, may be produced with two pieces of silex or quartz, the white quartz being best for this purpose. The same effect may also be witnessed by rubbing the pieces of quartz together, under water.
SIMPLE MEANS OF PRODUCING ELECTRICITY.
To show the nature of electrical action, rub a piece of sealing-wax or amber upon the coat sleeve, and it will be found that while warm by the friction, it attracts light bodies, such as straws or small pieces of paper. In our experiments we have shown that if a clean glass tube be rubbed several times through a silken or leather cloth, and presented to any substance, it will immediately attract or repel them; and if a poker suspended by a dry silk string be presented to its upper end, then the lower end of the poker will exhibit the same phenomena as the tube itself, which shows that the electrical fluid passes through the metal. But if for a metallic body a stick of glass or sealing wax be substituted, these phenomena will not occur, which proves that the electrical fluid does not pass through these substances.
By this it will be perceived that besides the class of bodies called electrics, there is another which we call conductors. These bodies cannot be excited themselves, but have the power of transmitting the electric fluid through them. These bodies comprise all the metals, some metal and metallic ores; the fluids of animal bodies; water, and other fluids, except oil; ice, snow, earthy substances, smoke, steam, and even a vacuum.
When any electrified conductor is wholly surrounded by non-conductors, so that the electric fluid cannot pass from the conductor along conductors to the earth, it is said to be insulated. Thus the human body is a conductor of electricity; but if a person standing on a glass stool (as represented in the drawing) be charged with electricity, the electric fluid cannot pass from him to the earth, and he is said to be positively electrified, because he has more than his natural share; he is also insulated, and if he be touched by another person standing on the ground, sparks will be exhibited at the point of contact, where also the person touching will feel a pricking sensation.
ATTRACTION AND REPULSION EXHIBITED.
In order to illustrate certain remarkable facts in this science of an amusing character, attention must be directed to the figure A B, which is a metal stand; C is a small piece of cork or pith, which is suspended from the hook by a dry silken thread. Having rubbed an electron, as a dry rod of glass, and presented it to C, the ball will be instantaneously attracted to the glass, and will adhere to it. After they remain in contact for a few seconds, if the glass be withdrawn without being touched by the fingers, and again presented to the ball, the latter will be repelled instead of attracted, as in the first instance. By being touched with the finger, the ball can be deprived of its electricity, and if, after this has been done, we present a piece of sealing-wax in place of the glass formerly employed, the very same phenomena will take place. On the first application the ball will be attracted, and on the second repelled.