Intelligence and Miscellaneous Articles. 77 



varies — that is, the time during which the condenser is in connexion 

 with the electrical source. I suppose the tension of this source to 

 be invariable, as is the duration of the discharge. This was always 

 a fraction of a second, the same in all the experiments. The ob- 

 servations were made in the following manner. 



The lower armature of the fulminating pane on which I worked 

 being in connexion with the ground, I connect for a definite time 

 the upper armature with a source of constant tension ; the con- 

 denser once charged, I detach the upper armature, and measure its 

 total charge by the method which I have called gauging. 



Secondly, after this first operation, and when the dielectric has 

 reverted to the neutral state, I charge the condenser again for the 

 same time as at first, then I discharge it immediately by connecting 

 for an instant the armatures ; that done, I remove the higher arma- 

 ture, and gauge the quantity of electricity which it retains ; this 

 quantity represents the residual charge according to the definition 

 given above. 



When this double series of operations is performed on the same 

 condenser, giving successively different values to the duration of the 

 discharge, this very simple result is attained — that the difference be- 

 tween the total and the residual charge is constant. This difference, 

 which represents the quantity of electricity which has disappeared 

 in an instantaneous discharge, is precisely equal to the total instan- 

 taneous charge. I denote in this manner the quantity of electricity 

 which the influencing armature would receive if the condenser, com- 

 pletely discharged, were put in connexion with the source of elec- 

 tricity during a small interval of time equal to that taken for the 

 discharge. This law was verified by a great number of experiments, 

 and on very different dielectrics. I worked successively on disks of 

 shellac, of stearic acid, and of gutta percha, and on a cake made of 

 flour of sulphur moistened by salad oil. I give the results obtained 

 by a series of experiments made with the latter substance : — 



Duration of Total Residual Differ- 



the charge. charge. charge. ence. 



Fraction of a second 26 . . 26 



2 minutes 44 18 26 



4 minutes 49 23 26 



8 minutes 55 28 27 



16 minutes 59 33 26 



The difference between the total and the residual discharge was 

 sensibly the same for all durations of the charge, and equal to 26, 

 a number which exactly represents the total instantaneous charge. 



Although observation alone would have enabled me to ascertain 

 this relation, it is easy to see d, priori that it must exist if the bodies 

 called insulating are generally formed, as I have been led to admit, 

 of many elements of very different conductibilities. 



In the experiments I have just cited, the condenser was charged 

 for a more or less long time, but always discharged immediately 

 after being separated from the electric source. In another series of 



