On Electricity excited in Paper. 331 



be taken hold of, and the paper raised in such a way that it 

 shall still be parallel to the surface on which it had been 

 placed, a crackling noise will be heard between the paper and 

 the table. Being entirely removed, if the knuckle be ap- 

 proached, it will receive sparks fi-om different parts of the ex- 

 cited surface, though perhaps too small to be visible in the 

 day-light. A piece of board large enough to rub the paper 

 on, and which could also be held to the fire, answers better 

 than the table alone ; for to succeed in the experiment it is ne- 

 cessary to make the paper so warm that the part of the gum 

 elastic which comes in contact, should be decomposed in pass- 

 ing over its surface: therefore, without the addition of such 

 a piece of board, the paper must be warmed and laid down 

 several times before this effect can be produced. It is worth 

 observing, tiiat some gum elastic sold in London, which seems 

 to be made up of a number of small pieces joined together, 

 and which appears to have lost some of the original properties 

 during the process to which it has been subjected, is not fit 

 for the experiment. 



Two half sheets of letter paper pasted together, with a piece 

 of gold leaf about 2\ inches square between them, placed so 

 as to be nearly at an equal distance all round from the edges, 

 look when dry like half a sheet of thick paper. This, treated 

 as above directed for the single piece of paper, gives, when the 

 knuckle is brought near it, a bright spark half an inch or an inch 

 long, for the leaf acts as a conductor. A line drawn so l/W 

 with a black-lead pencil about two inches long from over the 

 edge of the metal towards that of the paper, which is held in 

 the hand while raising it up, conducts the spark fiom the leaf 

 to the hand; and is at the same time illuminated throuo-hout 

 its turnings, thereby giving a lively representation of the 

 lightning as it is seen to pass between the clouds and the 

 eaxik. 



Two £qual pieces of thick paper laid one on the other, imd 

 excited, will not adhere to the board, or at least but slightly ; 

 they will however adhere closely to each other. Taken' jis un- 

 der, the uppermost, or that which has been directly subjected 

 to the rubbing, shows the same state of electricity as excited 

 glass; the other piece shows the contrary state. 



Whether the pajier be excited over wood, glass, or metal, 

 it exhibits when raised up the same state of electricity as ex- 

 cited glass, but while yet adhering die contrary state. 



In order to pursue the experiment a little further, two cy- 

 linders of tin-phite were procuretl, e;icii about eight inches 

 long and from three and a half to foiu- in diameter : through 

 the centres and ends were iron axles ; and to one of theui a 

 I t 2 winch 



