THE STRUCTURE OF THE WORLD-STUFF 277 



atom is not small enough for the difference between its charged and 

 uncharged states to be appreciable. 4 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 elec- 

 trons. 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 neutral- 

 izing 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, there- 

 fore, unnecessary to attribute to such an atom any additional sub- 

 stance, "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 sepa- 

 rate hypotheses to account for the same thing. Some of the mass of 

 atoms must be electrical. Why not all? 5 



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 



4 The electrical mass of a hydrogen atom due to its atomic charge is cal- 

 culated to be about one hundred-millionth of its whole mass. 



5 It may be said that the dualism still remains. But it is now a dualism 

 of form rather than of fact. Positive and negative electricity, like action and 

 reaction, are but two sides of the same phenomenon. We can not have one 

 without the other. But this would lead us too far into speculations as to the 

 nature of electricity. 



