ivliich acts the part of a Valve. 209 



electricities, developed by the induction apparatus, accumulate on 

 the two surfaces of the condenser during the time the electro- 

 motive force is active, and that they recombine as soon as this 

 force ceases to act. According to this latter hypothesis, the 

 current ought to pass in opposite directions alternately; the 

 rigorous discussion of the facts M. Gaugain believes sufficient 

 to decide which of those hypotheses is the true one ; but the 

 question may be resolved in a decisive manner by means of the 

 electric valve. 



To render our language definite, let us suppose the condenser 

 employed to be a Franklin^s plate, placed horizontally, and that 

 its inferior surface is in communication with the negative pole of 

 the induced circuit of the induction apparatus ; let two different 

 communications A and B be established between the positive 

 pole of the apparatus and the superior armature of the con- 

 denser : in each of these portions of the circuit let a galvano- 

 meter and valve be introduced, and let the two valves be disposed 

 in such a manner that the currents can pass in the circuit A from 

 the pole to the condenser, and that, on the contrarjr, they can 

 only pass in the circuit B when they are directed from the con- 

 denser towards the pole : it is easy to see what must take place 

 acording to each of the hypotheses between which it is our wish 

 to decide. If the direction of the currents be constant, they 

 will pass exclusively in the circuit A, or exclusively in the cir- 

 cuit B ; if, on the contrary, the motion of the electricity consists 

 of a siiccession of two currents alternately opposed to each other, 

 the two circuits A and B will be traversed simultaneously by the 

 opposed currents; ^and the direction of these currents, deter- 

 mined only by the disposition of the valve, will be independent 

 of the direction of the inducing current. Now it is in this latter 

 way that the facts exhibit themselves ; the existence of currents 

 which traverse at the same time the circuits A and B may be 

 proved, cither by the siuiultaneous appearance of light in the 

 electric eggs, or by the deviation of the galvanometers. The in- 

 tensities of the two currents differ very little from each other; 

 this may be inferred from the following numbers : in one of the 

 experiments the deviation corresponding to tlie current which 

 jharged the condenser was 63 degrees ; the deviation due to the 

 current which discharged the condenser was 61 degrees. It 

 evidently results from this experiment, that the motion of the 

 electricity in a circuit interrupted by the interposition of an 

 insulating film is formed by the succession of two alternate 

 currents. 



In a recent number of the (Jontptcs Rrndus, j\l. Gaugain has 

 dLscribed furtlicr experiments of this nature ; we shall take occa- 

 sion to refer to them in an early Number of this Journal. 



