Experiments on Positive Rays. 225 



they are in other gases. On one or two plates I have 

 observed a negative line tor which mje was about 22. 



On the way tlie Positive Mays are produced. — One very 

 remarkable feature of the photographs is the length of some 

 of the arcs of the parabolas, the horizontal deflexion of the 

 end of the arc being often a large multiple of that of the 

 beginning. Since the kinetic energy possessed by the 

 particle is inversely proportional to its horizontal deflexion, 

 this result shows that the kinetic energies of particles having 

 the same value of ejm vary within wide limits. Assuming 

 that the kinetic energy of the particle is due to the action 

 upon it when in the dark space of the electric field, we might 

 get this variation in the kinetic energy : — 



1. If the charged particles all started from the same region, 



the end of the dark space, but before reaching the 

 cathode got neutralized and so were only under the 

 action of the electric field for a fraction of the journey 

 through the dark space. 



2. If the ionization which produced the positive rays 



occurred not merely at the end of the dark space, 

 but to some extent throughout the whole of this 

 space. 



3. That the small amount of kinetic energy possessed by 



some of the particles is due to their colliding with 

 the molecules of the gas whilst passing through 

 this space, and in this way losing some of their 

 kinetic energy. 



Let us begin with the first of these suggestions. We know 

 by direct experiment that unless the pressure is very low 

 the rays after they pass through the cathode get neutralized 

 and lose their charge for a time, sometimes acquiring it 

 again by being ionized by the collisions they make. If this 

 process went on in front of the cathode as well as as behind 

 it, we should get variation in the kinetic energy of the 

 positive rays, as some of them would have passed a larger 

 fraction of their time than others in the uncharged state, 

 when in the electric field. I do not think that this explana- 

 tion is the true one, for the reason that the conditions in the 

 dark space differ essentially from those which prevail after 

 the particles have passed the cathode ; there is no electrical 

 field after passing the cathode, so that the relative velocity 

 of the positive rays and the corpuscles with which they are 



Phil Mag. S. 6. Yol. 24. No. 140. Aug 1912. Q 



