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



decomposed, while at the positive electrode it is only those mole- 

 cules which are moving away from it which are in this condition. 



The consequence of this will be that the molecules will be 

 more easily decomposed at the negative than at the positive 

 electrode. For consider first of all the case of a non-uniform 

 field, when the intensity of the field diminishes as we recede from 

 the electrodes. At the negative electrode those molecules which 

 are approaching the electrode are the ones which tend to get 

 decomposed, and these are going from weak to strong parts of the 

 field, so that the tendency to dissociate gets stronger and stronger, 

 while it keeps getting a better leverage, as it were, for the atoms 

 in the molecule get further and further apart as the molecule 

 moves, and thus the difference in the alteration in their radii 

 would increase even if the field were uniform, but when the field 

 increases in intensity, as the molecule moves on, the effect is still 

 more increased. On the other hand, those molecules at the positive 

 electrode which are likely to be decomposed are those which are 

 moving away from the electrode, and in this case when the inten- 

 sity of the field is greatest the atoms are nearest together, so that 

 the separating tendency which is the difference in the effects on 

 the atoms is minimized as much as possible ; while in the case of 

 the negative electrode, when the tendency to produce a difference 

 was greatest the distance between the molecules was greatest too, 

 so that we see in this case the molecules will dissociate more 

 easily at the negative than at the positive electrode. Again, we 

 must remember that those molecules which are near to the 

 positive electrode and moving away from it, must previously have 

 been approaching the electrode, and that during this time the 

 action of the electric field was to make the atoms come closer 

 together. When the direction of motion of the molecule is reversed 

 by reflection at the positive electrode, the action of the electric 

 field in separating the atoms in the molecule is reversed, so that 

 unless the course of the molecule is extraordinarily unsymmetrical 

 it will be in the same state when it gets away from the electrode 

 as it was before it approached it, and as it was not dissociated in 

 the one case it will not be in the other. 



Next let us suppose that the electric field is uniform, as in the 

 experiments described above ; then as there is no evidence for any 

 considerable condensation of gas about the electrodes, we shall 

 suppose that the density of the gas is approximately uniform. 

 Since everything is uniform the molecules will dissociate most easily 

 when they are moving for the longest time in the direction of the 

 lines of force. Now according to the vortex atom theory of gases 

 the vortex rings as they approach the planes which form the elec- 

 trode will expand, and as they expand they move more and more 

 slowly, so that the molecules will be moving for the longest time 



