ELECTRICAL MEASUREMENT. 429 



and electrified body is exactly zero, then the law 

 of variation of the electric force must be according 

 to the inverse square of the distance. On the 

 other hand, if a certain attraction of a small 

 positively electrified body towards the sides of 

 the supposed hollow electrified conductor is 

 observed, then the force varies according to a 

 law of greater variation than according to the 

 inverse square of the distance ; and vice versa if a 

 small body electrified in the opposite way to the 

 electrification of the conductor seems to be repelled 

 from the sides, then the law of diminution of force 

 with the distance will be something less than would 

 be calculated according to the inverse square of 

 the distance. The case supposed is an insulated 

 electrified body an infinitely small body charged 

 with electricity opposite to that of the electrified 

 body. If this small body, then, put into the 

 interior as a test, exhibits attraction towards the 

 sides, the law of variation of the force will 

 show a greater increase than according to the 

 inverse square of the distance, and vice versa. 

 It was left for Faraday to make with accuracy 



