Page:Harper's New Monthly Magazine - v109.djvu/417



LECTRICITY is of two kinds, positive and negative, each repels itself and attracts the other. So begins or might begin every text-book of Electricity since the era of Gilbert of Colchester in the days of Queen Elizabeth.

The most freely movable kind of electricity is the negative variety: a body containing an excess of negative is said to be negatively charged; a body with a defect of negative is what we are accustomed to call positively charged. Anything which possesses the two kinds in equal quantities is not charged at all, but is neutral. So virtually taught that eminent man Benjamin Franklin a century and a half ago.

Electricity is not a form of energy, any more than water is a form of energy. Water may be a vehicle of energy when at a high level or in motion: so may electricity. Electricity cannot be manufactured, as heat can, it can only be moved from place to place, like water; and its energy must be in the form of motion or of strain. Electricity under strain constitutes "charge"; electricity in locomotion constitutes a current and magnetism; electricity in vibration constitutes light. What electricity itself is we do not know, but it may perhaps be a form or aspect of matter. So have taught for thirty years the disciples of Clerk-Maxwell.

Now we can go one step further and say, Matter is composed of electricity, and of nothing else,—a thesis which I wish to explain and partially justify.

First we must ask what is positive electricity? and the answer is still we do not know. For myself I do not even guess,—beyond supposing it to be a mode of manifestation, or a differentiated portion, of the continuous and all-pervading Ether. It seems to exist in lumps the size of the atoms of matter; and no portion of it less in bulk than an atom has ever been isolated, nor appears likely to be isolated. But although it may have bulk, it appears as if it had no appreciable mass: the massiveness or inertia of the atom is probably due to something else, in fact to the possession of negative charges in equal amount. This part of the doctrine is not yet certain. More investigation is urgently needed into the meaning and properties of positive electricity. Meanwhile we shall only be following the lead of Professor J. J. Thomson if we assume that a unit of positive electricity has a massiveness (or what is often inaccurately called "weight") either zero or very small, most probably very small; perhaps about one per cent. of the mass of some atoms of matter may be due to the positive electricity which they contain. At the same time it appears probable that the space occupied by a unit of positive electricity is not small compared with the size of a material atom. Its range, or sphere of influence, may be said to determine that size.

But concerning negative electricity we know a great deal more. This exists in excessively minute particles, sometimes called electrons and sometimes called corpuscles: these are thrown off the negatively charged terminal in a vacuum tube, and they fly with tremendous speed till they strike something. When they strike they can propel as well as heat the target, and they can likewise make it emit a phosphorescent glow: especially if it be made of glass or precious stones. If the target is a very massive metal like platinum, the sudden stoppage of the flying electrons which encounter it causes the production of the ethereal pulses known as X-rays. Electrons are not very easy to stop however; and a fair proportion of them can penetrate not only wood and paper, but sheets of such metals as