Bring the poles together and heat, light, motion, etc., will be produced as witnessed in the dazzling electric light.
Or, to produce chemical change only, plunge the wires constituting “the poles” of the battery into water, and wonderful to say the molecules of water will have such motion imparted to them that they will be broken up into their constituent gases; and what is most marvelous, the oxygen will always be given off at one pole and the hydrogen at the other.
This is electrolysis or electro-chemical decomposition. Numbers of compounds in solution may have the molecular states of their atoms broken up thus, by the voltaic current, and curious to say of the atoms so dissevered, as above noted, those composing a given element will always be evolved by the same pole—the positive pole or the negative pole as the case may be. Some elements, that is to say, always appearing at the positive pole and others always at the negative.
Lastly I will say a few words specially as to motion.
We saw how the motion of striking the lucifer match produced chemical change, and light, and heat. We have seen also that chemical change—that is, the movement and change of place of the infinitely small atoms of matter—could be produced by heat, and light, and electricity; and that chemical change could also itself interchangeably produce all these.
We have seen, too, that motion can be produced by heat—as by the production of steam which drives the engine; also that light can cause motion, as in the growth and nutrition of plants; and it remains only in this brief summary of an immense subject, to remind the reader that electricity and magnetism can also both of them produce motion, not merely amongst atoms, but even in large masses, by means of their attractions and repulsions. Rub a piece of sealing-wax or glass with cloth or silk, and the friction will cause such a change of state in the glass or wax as to set free electricity, and this force, thus made evident by motion (rubbing), can itself produce motion by attracting pieces of paper, etc.; indeed, by using well-known methods you may lift hundreds of pounds’ weight.
So likewise as to magnetism; it can produce motion, as we see in the oscillation of the needle of the mariner’s compass—the attraction by a magnet of iron filings, etc.