BODIES SMALLER THAN ATOMS. 235 



to stick to) has been examined, it has been found that the carriers of 

 the negative electricity are these corpuscles of invariable mass. 



A very different state of things holds for the positive electricity. 

 The masses of the carriers of positive electricity have been determined 

 for the positive electrification in vacuum tubes by Wien and by Ewers, 

 while I have measured the same thing- for the positive electrification 

 produced in a gas by an incandescent wire. The results of these 

 experiments show a remarkable difference between the property of 

 positive and negative electrification, for the positive electricity, instead 

 of being associated with a constant mass one one-thousandth of that of 

 the hydrogen atom, is found to be always connected with amass which 

 is of the same order as that of an ordinaiy molecule, and which more- 

 over varies with the nature of the gas in which the electrification is 

 found. 



These two results — the invariability and smallness of the mass of the 

 carriers of negative electricity and the variability and comparatively 

 large mass of the carriers of positive electricity — seem to me to point 

 unmistakably to a very definite conception as to the nature of electric- 

 ity. Do they not obviously suggest that negative electricity consists 

 of these corpuscles, or, to put it the other way, that these corpuscles 

 are negative electricity, and that positive electrification consists in the 

 absence of these corpuscles from ordinary atoms? Thus, this point of 

 view approximates very closely to the old one-fluid theory of Franklin. 

 On that theory electricity was regarded as a fluid, and changes in the 

 state of electrification were regarded as due to the transport of this 

 fluid from one place to another. If we regard Franklin's electric fluid 

 as a collection of negatively electrified corpuscles, the old one-fluid 

 theory will, in many respects, express the results of the new. We 

 have seen that we know a good deal about the "electric fluid;' 1 we 

 know that it is molecular or rather corpuscular in character; Ave know 

 the mass of each of these corpuscles and the charge of electricity car- 

 ried by it. We have seen, too, that the velocity with which the cor- 

 puscles move can be determined without difficulty. In fact, the 

 electric fluid is much more amenable to experiment than an ordinary 

 gas, and the details of its structure are more easily determined. 



Negative electricity (i. e. , the electric fluid) has mass. A bod}' 

 negatively electrified has a greater mass than the same body in the 

 neutral state. Positive electrification, on the other hand, since it 

 involves the absence of corpuscles, is accompanied by a diminution in 

 mass. 



An interesting question arises as to the nature of the mass of these 

 corpuscles which we may illustrate in the following way. When a 

 charged corpuscle is moving, it produces in the region around it a 

 magnetic field whose strength is proportional to the velocity of the 

 corpuscle; now, in a magnetic field there is an amount of energy pro- 



