Chap. 4.]" [ 329 3 



CHAP. IV, 



THE LEYDEN PHIAL.ELECTRICAL BATTERY, 

 AND OTHER PARTS OF THE APPARATUS. 



Theory of the Leyden Phial. Its Ufe in Ekaridty.Defcription of 

 the beft Apparatus of this Kind. 'The Charge rejides in the Glafs. 

 -Curious Experiments -with the Leyden Phial. Elecirical Battery. 

 Injlruftions relative to it. Experiments <with the eledrical Bat- 

 tery '. -Electrical Bells.-r<'Ekftrapborus.-~Eletfrometer, 



IN order to underftand properly the nature of what 

 is called the Leyden phial, or electrical jar, it will 

 be neceflfary to revert o what has been faid both in 

 the introduction and in the preceding chapter on pofi- 

 tive and negative electricity. If a piece of glafs is 

 coated with any conducting fubftance, it may be made 

 to accumulate the electrical matter to a furprifing de- 

 gree. In this cafe one fide of the glafs, if it does not 

 exceed a given thicknefs, will be pofitively electrified, 

 and the other negatively. The form of the glafs is of 

 no confequence in this experiment j it may be either 

 flat, cylindrical, or otherwife. 



The object of the philofopher being, therefore, on 

 many occafions, to collect a large quantity of electri- 

 city, by means of the furfaces, of electrics, and, as flat 

 plates are neither neceflary nor convenient for this pur- 

 pofe, he accommodates himfelf with a fufficient num- 

 ber of prepared jars. Thefe are made of various (hapes 

 and magnitudesj but the moft ufeful are thin cylindri- 

 cal glafs veflels, about four inches in diameter, and 

 fourteen in height, coated within and without (except 



about 



