424 Mr. J. Larmor on the Molecular 



i. e. is equal to the electrical surface-energy per unit area of 

 the surface, with negative sign. 



The effect of the galvanic polarization will therefore be to 



E 

 diminish the capillary surface-tension by this amount -«• 



In the actual case in which the polarization is maintained 

 by a battery, the difference of potential V between the faces 

 of the condenser is what remains constant ; and the system is 

 no longer conservative, because the battery can be drawn 

 upon ; we have then 



E = iCSV 2 , 

 and 



_E 



therefore dE=-YdS; 



L e. this force T' now acts so as to increase the total energy 

 of electrification E,and is measured by its rate of increase per 

 unit extension of area; for the work done by the contractile 

 force T 7 in an extension of surface d$ is equal to — T^S, 

 which is now the increment of the energy, but under the 

 previous conditions was its decrement. 



It follows that under these circumstances the battery is 

 drawn upon for an amount of energy equal to twice that 

 required to do the electrical work of extension, viz. the energy 

 required to do this work together with the equal amount used 

 up in increasing E, as has just been found. This is a particular 

 case of a general theorem of Sir W. Thomson's. We have gone 

 into the matter here to show the consistency of the propositions 

 which make the capillary surface-tension equal to the rate of 

 increase of the ordinary surface-energy per unit extension, 

 while the electric surface-tension is equal to the rate of decrease 

 of the electrical surface-energy per unit extension. 



Once the surface-tension becomes negative, a free surface 

 becomes unstable, and therefore practically impossible. We 

 notice therefore that, as the polarization is made stronger 

 and stronger, this state of affairs would finally supervene were 

 not the polarization previously relieved by electrolytic separa- 

 tion of the charged layer. 



3. We have proved that the surface-tension is diminished 

 by galvanic polarization by an amount equal to ^CV 2 , where 

 C is the electric capacity of the surface per unit area. 



The polarization-charge is therefore zero when T is a maxi- 

 mum, and the surface is then most curved. 



The method that we have employed to determine the capil- 



