Experimental Philosophy. [Lecture 9. 



That the electrical matter is possessed of force, 

 even while it proceeds in a stream imperceptible 

 to our senses, is evident from an easy experi- 

 ment. To the under part of the Leyden phial 

 an apparatus is often adapted, as in fig. 38. It 

 consists of the wire b c, and a brass fly at the 

 top. While the bottle is charging the fly will 

 turn round, and when it is charged it will stop. 

 If the top of the bottle is touched with the 

 finger, or any conducting surface, the fly will 

 turn again till the bottle is discharged. The fly 

 will electrify cork balls positively while the bottle 

 is charging, and negatively while it is discharging. 

 A similar effect is observable in what is called 

 the electrical bells (fig. 37.). In this apparatus 

 three small bells a b c are suspended from a nar- 

 row plate of metal, the two outermost a c by 

 chains, and that in the middle b (from which a 

 chain passes to the floor) by a silken thread. 

 Two small knobs of metal d e are also hung by 

 silken threads on each side of the bell, in the 

 middle, which serve for clappers. When this 

 apparatus is connected with an electrified con- 

 ductor, the outermost bells, suspended by chains, 

 will be charged, will attract the clappers, and be 



remains, that electric action follows the inverse ratio of 

 the square of the distance ; as has been decisivelyproved by 

 Coulomb and others. It is also an established fact, that the 

 whole fluid of a conducting body is diffused about its sur- 

 face. Electrical facts are well confirmed; but the theory, 

 like that of magnetism is, as yet, uncertain. 



