Electric Residue in the Leyden Jar. 421 



iu the usual manner, it is nevertheless evident that some such 

 distribution causing equilibrium is possible. 



If we now insulate one of the coatings, and impart to it a fresh 

 quantity of the same kind of electricity as it already possesses, so 

 that on the other side a corresponding quantity of the opposite 

 kind of electricity will be rendered latent, then these new elec- 

 tricities will distribute themselves as if the plate had not been 

 charged. The principle of statics is here applicable, according 

 to which, if a system of forces are in equilibrium, they will still 

 remain so when another system, itself in equilibrium, is added 

 to the former. Hence the tension, at any point of the insulated 

 coating, will be proportional to the quantity of electricity newly 

 imparted, and the latter only will constitute the disposable 

 charge. 



It is only necessaiy to invert the process of reasoning here 

 given, in order to see that the phenomena of the electric residue 

 are contained in what has been said. 



At the commencement, let everything about the Pranklin^s 

 plate be non-electric. Next, let a quantity Q of positive elec- 

 tricity be imparted to the insulated coating, whereby a certain 

 distribution on both coatings will ensue. An electric moment 

 will now gradually establish itself in the glass, which, by its 

 reaction, will produce a new distribution in such a manner that 

 Q will be divided into two parts, belonging to two different sy- 

 stems of equilibrium, and consequently superposed upon one 

 another. The quantity r which must be present underneath the 

 insulated coating, in order that the newly created action of the 

 electric moment in the glass may be held in equilibrium, is so 

 withdrawn from Q that only the quantity Q— ?' = L can distri- 

 bute itself over the coating in the form of disposable charge as 

 at the commencement, and only this quantity can be discharged. 



Before long we shall assume a cause for the slow production 

 of the electric moment, and why it can but reach a certain maxi- 

 mum, r=pQ, dependent upon the quantity of electricity Q. At 

 present thus much is clear : in our representation of the phseno- 

 menon we must be prepared to admit, not only that the dis- 

 ])0sable part L of the charge, but also that the electromotive 

 force of the whole quantity Q or L + ?- of electricity on the sur- 

 faces of the glass has an influence on the formation of the elec- 

 tric moment, for there is no reason why in this respect one 

 part should be inactive. We attribute the same cause to the 

 slow disappearance of the electric moment as to its slow forma- 

 tion. 



In this manner we may easily explain why, after discharging 

 the plate, the concealed residue r continues to convert itself again 

 into disposable charge until the part r' of it which still remains 



