Page:Popular Science Monthly Volume 66.djvu/67

Rh prevalence among electricians to the fact that by virtue of long familiarity we prefer to think in terms of matter, which is tangible, rather than of ether.

Charge is to be regarded as fundamental, and its substitute, quantity of electricity, as merely an artificial term of convenience; because of the former we have a definite mechanical conception, whereas we can intelligently define a quantity of electricity only in terms of charge.

In the science of heat the case differs in that the term heat is used, if not as precisely synonymous with energy, at least for a quantity having the same dimensions as energy and having as its unit the erg. It might easily have happened, as has happened in electrical theory, that the ancient notion of a heat substance should survive, in which case we should have had for the quantity of heat not something measured in terms of energy, but, as in the case of electricity, one of the terms which enter into our expression for energy. We should then have had to struggle continually, in thermo-dynamics, as we now do in electrical theory, against the tendency to revert to an antiquated and abandoned view.

It would, I can not but think, have been fortunate had the word electricity been used for what we now call electrical energy; using charge, or some other convenient designation, for the quantity Q. That aspect of the science in accordance with which we regard it as a branch of energetics in which movements of the ether are primarily involved would have been duly emphasized. We should have been quit forever of the bad notion of electricity as a medium, just as we are already freed from the incubus of heat as a medium. We should have had electricity—a mode of motion (or stress) of the ether as we have heat—a mode of motion (of matter). When our friends asked us: 'What is electricity?' we should have had a ready answer for them instead of a puzzled smile.

One real advance which has been attained by means of the theory of ionization, and it is of extreme significance and of far-reaching importance, consists in the discovery that electrification or the possession of charge, instead of being a casual or accidental property, temporarily imparted by friction or other process, is a fundamental property of matter. According to this newer conception of matter, the fruit of the ionic theory, the ultimate parts of matter, are electrically charged particles. In the language of Rutherford:

It must then be supposed that the process of ionization in gases consists in a removal of a negative corpuscle or electron from the molecule of gas. At atmospheric pressure this corpuscle immediately becomes the center of an aggregation of molecules which moves with it and is the negative ion. After removal of the negative ion the molecule retains a positive charge and probably also becomes the center of a cluster of new molecules.

The electron or corpuscle is the body of smallest mass yet known to science.