320 Prof. J. J. Thomson on the Discharge 



tendency to rearrangement among the atoms some of them 

 will become comparatively free, when, as before, the electric 

 field in the region around them will become stronger, and 

 consequently the tendency of the steam in that region to con- 

 dense will increase. Thus this incipient chemical combina- 

 tion may produce throughout the region occupied by the gas 

 minute drops of water. When,, however, these are formed, it 

 is not difficult to see that we have the possibilities for very 

 great increase in the chemical action. These drops offer sur- 

 faces on which the molecules of A and B may condense ; thus 

 a portion of A and B, instead of being in the gaseous state, 

 exists as layers condensed on the drops. Experience shows 

 that combination usually goes on more freely between gases 

 condensed on a surface than between the same gases when 

 free. If, however, the drop acted in this way, it would not 

 seem necessary that the substances condensing into drops 

 should be w r ater, or any other solvent; we might expect this 

 kind of effect to be produced by mercury-vapour, for example. 

 The drop might, however, promote chemical combination in 

 another way, in which the combination, instead of being 

 merely a surface -effect, proceeded through the volume of the 

 drop, — the drop and the gases condensed on its surface be- 

 having like a Grove's gas-battery, the drop itself acting as 

 the electrolyte, and the combination taking place by means 

 of electrolytic process in the drop ; the drop itself thus 

 playing an active part in assisting the combination. The 

 view that chemical action is electrolytic in character has been 

 repeatedly urged by Prof. Armstrong. The ability of water 

 to further this kind of action w r ould be much greater if, while 

 the chemical action was going on, the water existed in the 

 liquid than it would if the water were in the gaseous state. 



If we take the view that the forces which hold the atoms 

 in the molecule together are electrical in their origin, it is 

 evident that these forces will be very much diminished w T hen 

 the molecule is close to the surface of, or surrounded by, a 

 conductor or a substance like water possessing a very large 

 specific inductive capacity. 



Thus let AB represent two atoms in a molecule placed near 

 a conducting sphere, then the effect of the 

 electricity induced on the sphere by A will 

 be represented by an opposite charge 

 placed at A' the image of A in the sphere. 

 If A is very near the surface of the sphere, 

 then the negative charge at A' will be 

 very nearly equal to that at A. Thus 

 the effect of . the sphere will be practically to neutralize the 



