396 Prof. Thomson, On some experiments on the [May 10, 



direction of displacement of the glow was reversed. When this 

 component was in one direction the striated discharge was not 

 only deflected but split up into several discharges, there being 

 in this case often 7 or 8 striated discharges proceeding from 

 the negative glow ; when the direction of the magnetic force was 

 reversed, the discharge was deflected in the opposite direction, 

 and instead of being split up seemed to be more concentrated 

 than before. This part of the effect seemed to be due to the 

 action of the magnet on the glow; the place where the striated 

 discharge starts is where the glow is furthest from the glass'; if 

 the magnetic force by its action on the glow reduces the in- 

 equalities in the distance of the edge of the glow from the glass 

 the discharge may start from several places at once, while if it 

 tends to increase the inequalities the glow will be more rigorously 

 confined to one place. 



Theoretical considerations about the electric discharges in gases. 



In a paper published in the Philosophical Magazine for June, 

 1883, page 427, I gave a theory of the electric discharge in gases, 

 in which the discharge was regarded as the splitting up of some 

 of the molecules of the gas through which the discharge takes 

 place ; the energy of the electric field being spent in decomposing 

 these molecules, and finally by the heat given out on the recom- 

 bination of the dissociated atoms appearing as heat, except in the 

 numerous cases where the gas is permanently decomposed by the 

 spark, when part of the energy of the field remains as potential 

 energy of dissociated gas. 



In that paper I did not discuss the difference between the 

 effects observed at the positive and negative electrodes. I think 

 however that the theory is capable of explaining these differences. 

 For we may imagine a molecule of such a kind that the atoms in 

 it would tend to separate when the molecule was moving in one 

 direction in an electric field, say that of the lines of force, but 

 would be pushed nearer together when the molecule was moving 

 in the opposite direction. A molecule of the following kind would 

 possess this property. 



Fig. 7. Fig. 8. 



B TiJ 



