424 HYPOTHESIS OF TWO FLUIDS. 



ready offered in regard to the relations of caloric 

 and electricity, it would be useless to multiply 

 arguments against so bald an hypothesis. It 

 was afterwards shown by Sir Humphry Davy 

 himself, that both heat and light are produced 

 by either positive or negative electricity alone, 

 though he adopted the doctrine of two fluids. 



The following experiments of De Saussure 

 clearly illustrate the identity of positive and ne- 

 gative, with plus and minus conditions of the 

 electric fluid. On pouring water into heated 

 iron or copper vessels when insulated, and con- 

 nected with an electrometer, rapid oxidation was 

 produced, and positive electricity evolved ; but 

 after the metal became covered over with a coat- 

 ing of oxide, less electricity was disengaged, 

 which was negative. (Voyages dans les Alpes, 

 torn. ii. p. 244.) 



It is also worthy of special notice, that he pro- 

 cured electricity from the vapour of water with- 

 out any chemical decomposition (a fact which 

 has been recently controverted by Pouillet, as 

 before stated, p. 316,) that the evaporation of 

 water from heated silver and white porcelain 

 vessels was attended with a disengagement of 

 electricity, that was generally positive, but some- 

 times negative. The same thing was observed 

 on placing incandescent pure white quartz in 

 water. 



The advocates of two fluids explain the phe- 



