ELECTRICITY. 325 



other, because the same kind of electricity is com- 

 municated to both. 



If both balls be electrified by touching them 

 with sealing-wax, they will repel each other ; and 

 if they be both touched by excited glass they will 

 repel each other : but if one ball be electrified by 

 glass and the other with sealing-wax, they will at- 

 tract each other. Hence there seems some differ- 

 ence between the electricity excited by the sealing- 

 wax and the glass. Formerly it was supposed that 

 this was owing to two sorts of electricity, and they 

 were accordingly called vitreous and resinous elec- 

 tricity. But the explanation of Dr. Franklin is 

 now generally adopted ; viz. that these phenomena 

 are owing to the electricity of sealing-wax being 

 negative, and that of glass being positive. 



When glass is rubbed with silk, the natural elec- 

 tricity of the silk leaves it and is accumulated on 

 the glass : but when sealing-wax is rubbed with 

 flannel, the electricity is accumulated on the flan- 

 nel at the expense of the sealing-wax. The elec- 

 tricity, therefore, in these cases, of the silk and the 

 sealing-wax, and that of the flannel and the glass, 

 are the same. 



If a bundle of hairs or feathers be hung upon 

 the prime conductor, the moment they are electri- 

 fied by turning the wheel of the machine, they 

 begin to fly from one another ; so that some of 

 of them will stand quite erect. 



A large plumy feather grows beautifully turgid 

 when it is electrified, expanding its fibres in all di- 

 rections. 



When the conductor is discharged by the approach 

 of a conducting substance, as the finger, or a piece 

 of metal, the fibres collapse, because then they are 



y 3 



