Chap. 5.] Recapitulation of Principles. 343 



very curious phenomenon has been produced by in- 

 jecting the electric light in a vacuum. 



If a wire with a round end is included in an exhauft- 

 cd receiver, and prefented to a conductor of an elec- 

 trical machine, every fpark will pafs through the va- 

 cuum in a broad ftream of light, vifible the whole 

 length of the receiver, moving with regularity (unlefs 

 it is turned back by fome non-electric) and then di- 

 viding itfelf into a number of beautiful rivulets, which 

 are continually feparating and uniting in a pleafing 

 mariner. When the veflel is grafped by the hand, a 

 pulfation is perceived like that of an artery, and the fire 

 inclines towards the hand. A fmall quantity of air is, 

 however, neceflary to occafion the greateft luminous 

 effect. 



The following is a recapitulation of what M. Brif- 

 fon confiders as fundamental principles, confirmed, he 

 fays, by his own experiments/ feconded by thofe of 

 other philofophers *. 



The electric fluid is the fame in efience with that of 

 light and heat, but combined with a fubftance which 

 affects the organs of fcent. 



When bodies are electrified by glafs, they furnifh 

 tufts or pencils of light ; but if electrified by fulphur.or 

 refmous fubflances, they only produce points or fparks 

 of light ; bodies prefented to thofe electrified by glafs 

 produce only luminous points, while thofe which are 

 prefented to bodies which are electrified by fulphur, 

 produce beautiful pencils or tufts of light. 



To electrify bodies by communication, it is necef- 

 fary to infulate them j the fubftances the mod proper 

 for this purpofe are thofe which electrify the beft by 

 friction. 



Traitc Element, de Phylique, Tom. iii. p. 435 

 Z 4 



