276 THE POPULAR SCIENCE MONTHLY 



molecules, of dimensions similar to those almost simultaneously dis- 

 covered by Thomson. Later developments of optical theory stimulated 

 by this discovery indicated the presence in molecules of positively 

 charged particles as well, but that these were atomic in size. 



Thus three independent lines of investigation have almost simul- 

 taneously converged to furnish a basis for a new theory of electricity, 

 which we need follow only so far as it affects the theory of matter. 

 Of the two kinds of electricity we find but one — the negative — that 

 can be detached from atoms. We find the negative electron too as a 

 constituent of the atom. The electron, whatever its source, is always 

 the same, while the positive charge partakes of the varying nature of 

 the matter with which it is associated. Emphasis is thus laid upon the 

 electrons as forming the true electrical fluid, the positive electricity 

 playing a subordinate part. According to this theory a neutral 

 atom, which we know contains some electrons, contains also enough 

 positive charge to exactly neutralize them. If one or more additional 

 electrons become attached to it, it becomes negatively charged with 

 the atomic quantity or its multiple. If, on the other hand, it loses 

 some of its electrons, it becomes positively charged. The terms 

 positive and negative have here exchanged their usual roles. It is 

 the positive electricity that is 



der Geist der stets verneint, 



" the spirit of negation." Except for this exchange (due to the un- 

 fortunate original allotment of the terms) the theory bears a remark- 

 able resemblance to the single fluid theory of Franklin. 



Some atoms normally contain too many electrons, others too few. 

 These will attract each other, forming neutral molecules. Thus an 

 oxygen atom, which normally holds two extra electrons, will attract 

 to itself two hydrogen atoms which each lack one, and thus will form 

 a molecule of water. By the number of electrons in excess or deficiency 

 the combining power of an atom with others is determined. Such 

 considerations have proved efficient in disentangling many puzzling 

 questions connected with chemical combination. 



The most salient point of this theory is that we seem to be con- 

 fronted with a dualism, matter and electricity, atoms and electrons. 

 A closer study of the electron has suggested a possible way of escaping 

 this, or rather of turning it, in what is called the electrical theory of 

 matter. 



Long before electrons were observed J. J. Thomson had shown 

 theoretically that a body when charged with electricity would by mechan- 

 ical tests appear to have a slightly greater mass than when uncharged, 

 and the smaller the body the greater the effect. Thus it would require 

 more work to stop a moving charged body than if it were uncharged ; a 

 greater force would be needed to deflect it from its path. But even an 



