Page:Popular Science Monthly Volume 76.djvu/281

Rh atom is not small enough for the difference between its charged and uncharged states to be appreciable. With an electron, however, it is different. Application of the theory has shown convincingly that the entire observed mass of the electron may be accounted for by its electrical charge and that there is no evidence of any other mass apart from its charge. An electron is thus literally a disembodied spirit—a concentrated charge, and nothing more.

But what of the atom? We have seen that its mass can not be accounted for by its positive charge. We may, however, meet the difficulty in another way. Let us imagine a structure of the following nature. Scattered through the volume of a sphere of the size of our microcosmic tennis ball let its suppose a congeries of some 1,800 electrons. To get the scale of our image correct we shall have to magnify it still more and we shall then see this number of fine shot scattered through a space the size of a large hall. Let the equivalent neutralizing positive charge be uniformly diffused throughout the sphere. The electrical mass of such a system would be that of its electrons, in other words would be equal to that of a hydrogen atom. It is, therefore, unnecessary to attribute to such an atom any additional substance, "matter," distinct from the positive and negative charges.

This is the electrical theory of matter. I do not say that it has been established. It is at present only a fruitful speculation. But it strongly appeals to those who seek for unity in science and who prefer to have a single interpretation of a phenomenon rather than two separate hypotheses to account for the same thing. Some of the mass of atoms must be electrical. Why not all?

Let us call upon the scientific imagination and attempt to picture the atom of the twentieth century for comparison with the atoms of the earlier theories. We see a large number of electrons immersed in what may be called a positive jelly. In some cases, if not in all, the atom is partly at least compounded of sub-atoms of the size of the hydrogen or helium atom. Of the electrons some may be vibrating about neutral positions, or circling in closed orbits, and in doing so sending forth waves of light; others may be more firmly fixed. We may even have systems of electrons revolving in concentric rings like the rings of Saturn. A few, especially if the atom is that of a metal, are so loosely attached that they readily escape, leaving the atom positively charged. Sometimes under the action of light-waves a vibrating electron is so violently shaken that it breaks its bonds and