Propagation of the Electric Force. 261 



the galvanic battery) no development of electricity should take place from 

 their union ; but the hydrogen, whose positive pole had been previously united 

 with the negative pole of the oxygen, should induce negative electricity upon 

 the oxide, while the negative pole should induce positive electricity upon the 

 next particle, and so on to the platinum plate. 



The greater the number of particles of hydrogen inducing electricity upon 

 the platinum plate, the greater, of course, the quantity of electricity induced upon 

 that plate ; the number of particles of hydrogen being the measure of the quan- 

 tity, whether it was oxygen, chlorine, iodine, or bromine, with which the 

 hydrogen may have been previously in combination ; and that such is the case is 

 proved by experiment. That alternate recombinations and decompositions take 

 place has been shown by Grothhus and Faraday. 



How beautiful is the analogy which subsists between statical and voltaic 

 electricity when the contact theory is adopted ! By friction (lateral contact) 

 between silk and glass opposite electrical states are induced upon each. By the 

 contact of zinc with a dry acid, or alkali, opposite states are induced upon each. 

 When the plate of the electrical machine is put in motion, the prime conductor 

 receives a charge whose intensity is directly as the non-conducting or insulating 

 nature of the glass, and as the distance between the collecting forks and the 

 rubber when the axis is made of glass. When the zinc is placed in contact with 

 the acid, or alkali in solution, the charge is allowed to pass from the zinc to the 

 platinum, being in this case a charge by induction, as in the former case it was 

 one by convection ; and the intensity varies as the insulating state of the solution, 

 and as the distance between the platinum and zinc, as is proved by the experi- 

 ments of Delarive,* which show that the water battery charges to a higher 

 intensity than the acid battery, although it takes a longer time than the latter to 

 charge to a given amount. Again, when a small electrical machine is rotated 

 rapidly, while a larger one is rotated slowly, the former will charge to a given 

 intensity in a shorter time than the latter, although it never can rise to an equal 

 intensity. So in the acid and water batteries, the former, owing to the rapidity 

 of alternations of induction and equilibrium, charges to a given intensity In a 

 shorter time than the latter, yet still it never can rise to an equal intensity. 

 Similarly may be explained why, when two metals in a solution form a closed 



* Bib. Univer. torn. iv. p. 360. 



