302 Sir J. J. Thomson on a Theory of 



carried by a corpuscle, or a particle in the Canalstrahlen, 

 which as far as we know is incapable of further sub-division, 

 the corresponding tube of force will be incapable of further 

 subdivision and will form a natural unit. Now the ques- 

 tion at once arises does the tube of force attached to a 

 corpuscle spread out uniformly in all directions, like the 

 lines of force round a charged sphere, or is the tube confined 

 within a cone of small vertical angle. We usually regard 

 the electric field round an electric charge as spreading out 

 ■uniformly in all directions, so that the force remains unaltered 

 an magnitude as long as we keep at the same distance from 

 the electric charge. We must remember, however, that the 

 charges used in the experiments by which this result has 

 been established are many million times the charge on a 

 corpuscle, and it is evident that when we superpose the fields 

 ■due to millions of corpuscles the result will be the same 

 whether each individual field is uniformly distributed in all 

 directions or is confined within a small solid angle. Each 

 would give a field uniform in all directions : on the first 

 supposition the field would be continuous, while on the second 

 it would have a structure. We are now, however, able, in 

 cathode rays, to observe the behaviour of particles carrying 

 the indivisible unit, so that the nature of the field round the 

 unit charge is an important subject, and one which we might 

 hope to be able to settle by experiment. The properties of a 

 corpuscle, on the supposition that the electric field around it 

 is uniformly distributed, have been known for some time. In 

 "this paper I shall consider what the properties would be if 

 the electric force due to a corpuscle was practically exerted 

 in only one direction. Let us suppose then that the tube of 

 force attached to a corpuscle is a double cone of small semi- 

 vertical angle, so that it is only within this cone that the 

 corpuscle exerts any electric force. There is discontinuity 

 between the electric force inside and outside this cone : to 

 reconcile this with the principle of the Conservation of Energy 

 we may suppose that a finite amount of work is spent or 

 gained when one corpuscle crosses the boundary of a tube of 

 force due to another. 



On this view the electric field due to a number of corpuscles 

 is a mosaic, as it were, made up of a number of detached 

 fields. The electric field itself, as well as the electric charges 

 in it, being molecular in constitution. 



In this paper I shall consider the properties of the field 

 due to a single corpuscle : in another paper I propose to 

 consider the action of two or more such fields upon each other. 



We assume that the properties of the isolated tubes are 



