294 POPULAR SCIENCE MONTHLY. 



capable of losing an electron, of having at least one chipped ofE it. 

 The election has been shown to possess in kind, though not in degree, 

 the fundamental properties of the original atom of which it had 

 formed a part; and it becomes a reasonable hypothesis to surmise that 

 the whole of the atom may be built up of positive and negative elec- 

 trons interleaved together, and of nothing else; an active or charged 

 ion having one electron in excess or defect, but the neutral atom 

 having an exact number of pairs. The oppositely charged electrons 

 are to be thought of on this hypothesis as flying about inside the atom, 

 as a few thousand specks like full stops might fly about inside this 

 hall; forming a kind of cosmic system under their strong mutual 

 forces, and occupying the otherwise empty region of space which we 

 call the atom — occupying it in the same sense that a few scattered but 

 armed soldiers can occupy a territory — occupying it by forceful ac- 

 tivity, not by bodily bulk. 



6. The hypothetical part of the statement about the size of an elec- 

 tron is the following. Whereas both the mass and the charge of an 

 electron is known, it is not yet quite certain that the mass is wholly 

 due to the charge. It is possible, but to me very unlikely, that the 

 electron, as we know it, contains a material nucleus in addition to its 

 charge, so in that case it need not be so concentrated, because a portion 

 of its mass would be otherwise accounted for. 



I say 'accounted for,' but it would be equally true to say unac- 

 counted for. The mass which is explicable electrically is to a con- 

 siderable extent understood, but the mass which is merely material 

 (whatever that may mean) is not understood at all. We know more 

 about electricity than about matter; and the way in which electrical 

 inertia is accounted for electromagnetically and localized in the ether 

 immediately surrounding the nucleus of charge, is comparatively clear 

 and distinct. 



There may possibly be two different kinds of inertia, which exactly 

 simulate each other, one electrical and the other material; and those 

 who hold this as a reasonable possibility are careful to speak of elec- 

 trons as 'corpuscles,' meaning charged particles of matter of extremely 

 small size, much smaller than an atom, consisting of a definite electric 

 charge and an unknown material nucleus; which nucleus, as they 

 recognize, but have not yet finally proved, may quite possibly be zero. 



The chief defect in the electrical theory of matter at present is 

 that the positive electron, if it exists, has never yet been isolated from 

 the rest of an atom of matter. It has never been found detached 

 from a mass less than the hydrogen atom; whereas the negative elec- 

 tron is constantly and freely encountered flying about alone, its mass 

 being little more than the thousandth part of an atom of hydrogen. 



