40 Mr. Pi. Phillips on Frictional Electricity. 



removed from each other's vicinity, they will retain this state if 

 both bodies be insulators, and exhibit them upon their complete 

 separation*." 



It appears to me that this theory cannot be generally true ; 

 for by means of it I am unable to see how it comes to pass, that 

 gases being driven on solids produce no electricity. This excep- 

 tion is all the more worthy of attention, inasmuch as gases are 

 known to cohere with great force to some solids, as glass, char- 

 coal and platinum ; and probably all solids more or less condense 

 gaseous matter. Now the friction of gases on solids is charac- 

 terized by this remarkable circumstance, that no permanent 

 abrasion of the solid is produced ; and if a particle of the adhe- 

 rent gas becomes torn from the solid, it can be immediately 

 replaced by a similar particle. I conclude from this, that to 

 develope frictional electricity, there must be some permanent 

 mechanical division of one at least of the rubbing surfaces. I 

 will now take water as an example, and endeavour to account for 

 the electricity produced by its friction, by using the foregoing 

 electro-chemical theory. 



We know from Prof. Henry's experiments, that the cohesion 

 exerted between particles of water is very great ; perhaps at some 

 temperatures the cohesion of water may be even greater than 

 that of ice, for ice is lighter than water. It seems, therefore, 

 reasonable to regard the abrasion of water as quite comparable 

 with the abrasion of a solid. And since the abrasion of water 

 always causes the rubber to become negative, it is necessary to 

 suppose, when a mass of water is in its neutral condition, 

 that the external layer is negative with regard to the next layer. 

 Thus when a drop of water is in the air, the order of the alter- 

 nations of the molecular layers, reckoned from the surface, is 



f- . -] &c. ; but as each of these layers contains more 



particles than the next below, some at least of the inner particles 

 must be more highly charged than the more external. The pos- 

 sibility of a particle receiving more than one equivalent of elec- 

 tricity, seems proved by the existence of such compounds as 

 peroxides or perchlorides. 



Let then — • 



+•+ +•+ +•+ 



+•+ +•+ +■+ 



stand for a mass of water, the inner molecules containing an 

 excess of plus electricity corresponding to the negative condition 

 of the outer layers. Suppose that by means of a current of 

 steam or air the upper layer of particles becomes removed ; at 

 * Faraday's Researches in Electricity, vol. i. p. 555. 



