ON BODIES SMALLER THAN ATOMS. 327 



regions in which cathodic rays are found. I have" found that they are 

 given off by incandescent metals, by metals when illuminated by 

 ultra-violet light, while the researches of Bccquerel and Professor and 

 Madame Curie have shown that they are given off by that wonderful 

 substance the radio-active radium. 



In fact in every case in which the transport of negative electricity 

 through gas at a low pressure (i. e., when the corpuscles have nothing 

 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 elec- 

 tricity. 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 incan- 

 descent wire. The results of these experiments show a remark- 

 able difference between the property of positive and negative electri- 

 fication, for the positive electricit}^, instead of being associated with a 

 constant mass 1/1000 of that of the hydrogen atom, is found to be 

 always connected with a mass which is of the same order as that of an 

 ordinary molecule, and which, moreover, 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 un- 

 mistakably to a very definite conception as to the nature of electricity. 

 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' ; we know that 

 it is molecular or rather corpuscular in character; we know the mass 

 of each of these corpuscles and the charge of electricity carried by 

 it; we have seen too that the velocity with which the corpuscles 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 {%. c, the electric fluid) has mass; a body 

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



-o^ 



