Specific Inductive Capacity ofShelUlac. 415 



App. i. Lac. App. ii. Air. 



Charge divided. 



113° . . . . 



.... 121° 



. . . . after being discharged. 



. . . . 7 after being discharged. 



1258. Here 297°, minus 7°, or 290°, may be taken as the 

 divisible charge of app. ii. (the 7° being fixed stem action 

 (1203. 1232.)), of which 145° is the half. The lac app. i. 

 gave 113° as the power or tension it had acquired after divi- 

 sion ; and the air app. ii. gave 121°, minus 7°, or 114°, as the 

 force it possessed from what it retained of the divisible charge 

 of 290°. These two numbers should evidently be alike, and 

 they are very nearly so, far indeed within the errors of ex- 

 periment and observation. But these numbers differ very 

 much from 145°, or the force which the half charge would 

 have had if app. i. had contained air instead of shell-lac; and 

 it appears that whilst in the division the induction through 

 the air has lost 176° of force, that through the lac has only 

 gained 113°. 



1259. If this difference be assumed as depending entirely 

 on the greater facility possessed by shell-lac of allowing or 

 causing inductive action through its substance than that pos- 

 sessed by air, then this capacity for electric induction would 

 be inversely as the respective loss and gain indicated above ; 

 and assuming the capacity of the air apparatus as 1, that of 

 the shell-lac apparatus would be i|-f, or 1*55. 



1260. This extraordinary difference was so unexpected in 

 its amount, as to excite the greatest suspicion of the general 

 accuracy of the experiment, though the perfect discharge of 

 app. i. after the division showed that the 113° had been taken 

 and given up readily. It was evident that, if it really existed, 

 it ought to produce corresponding effects in the reverse order; 

 and that when induction through shell-lac was converted into 

 induction through air, the force or tension of the whole ought 

 to be increased. The app. i. was therefore charged in the 

 first place, and its force divided with app. ii. The following 

 were the results : 



App. i. Lac. App. ii. Air. 



. . » . 0° 



215° .... 

 204 .... 



