Electric Residue in the Leyden Jar. 417 



under examination ; an assumption which^ from the commence- 

 ment, appears requisite on account of the proportionality existing 

 between the disposable charge and the tension on the knob of 

 the jar. 



Further, the following facts ought to be considered : — 



1. If after discharging the Franklin's plate it be turned up- 

 side down, the sine-electrometer being connected with the coating 

 formerly in connexion with the earth, whilst the side which be- 

 fore was positive is now connected with the earth, a residue of 

 negative electricity will be obtained. 



2. If a Franklin's plate, with exactly equal sides, had equal 

 and opposite charges imparted to them, then the quantities 

 which penetrate the glass would certainly be exactly equal, in 

 reference to arrangement and magnitude. In such a case, how- 

 ever, the potential before referred to would certainly not be zero. 

 But how little this state must differ from that which ensues 

 when, with a thin plate, the one coating remains connected with 

 the earth ! And, bearing fact 1 in mind, is it not probable that 

 the residue would be obtained with exactly equal and oppositely 

 charged sides ? 



3. Why, with equal charge of coating, does the thicker Frank- 

 lin's plate give the greater residue ? 



4. Why does not the residue continually increase the longer 

 the jar remains charged, or why does it approach a definite 

 maximum dependent upon tlie magnitude of the charge ? 



These are points which after some consideration cause legiti- 

 mate doubts concerning the truth of the whole hypothesis which 

 regards the electricity as penetrating the glass ; and in any case 

 they authorize the attempt here made to substitute another hy- 

 pothesis which will solve all these problems. Departing, there- 

 fore, from the usual method of representation, let us seek some- 

 thing new. 



§10. 



In this investigation it will be best, for the present, entirely to 

 neglect the electricity lost in the air, which although unavoidable 

 is still accidental, and to deduce the phjenomena of the residue, 

 in their purity, from the facts already recorded, so as to arrive 

 at certain conclusions about them. The phaenomenon presents 

 itself in the following manner : — 



A quantity Q of electricity is imparted to the insulated coating 

 of the Franklin's plate, whereby a certain state of equilibrium is 

 established. This state of equilibrium next gradually changes, 

 80 that a part r of Q enters into a new state, in which it can no 

 longer act on the electroscopic tension ; and this part r increases, 

 at first quickly, but afterwards more and more slowly, towards a 



Phil. Mag. S. 4. Vol. 7. No. 47. June 1854. 2 F 



