190 Mr. G. J. Knox on the Direction and Propagation 



produced by heat depends, whether upon a pecuhar arrange- 

 ment of the crystalline parts of the metal, or of their compound 

 elementary particles, we are as yet perfectly ignorant. 



That the same general law of the contact of metals and of 

 fluids applies equally (although in an inferior degree, owing 

 to their want of conducting power) to the contact of the gases, 

 may be shown by the experiment of Dr. Faraday (Sixth Se- 

 ries) of the union of hydrogen and oxygen by a plate of pla- 

 tinum ; the electrical force, which circulates by the interposed 

 platinum plate, facilitating the union of the two gases*. 



To return to the source of the voltaic force in the battery. 

 Zinc, when placed in contact with a dry acid, has been found 

 to become positively electrified. "When the zinc plate has 

 been immersed in the acid solution, being positive, it attracts 

 oxygen, by union with which its electrical state is disguised, 

 while the hydrogen, set free in a highly positive electrical 

 state, reacts upon the oxide of zinc, rendering it negative by 

 induction. The platinum wire connecting the positive solu- 

 tion with the negative zinc plate, reduces all for the moment 

 to a state of equilibrium, so that the electricity becomes dis- 

 guised, not transferred bodily from the platinum to the zinc ; 

 which state of equilibrium is no sooner restored than it is de- 

 stroyed, the zinc regaining its positive state, and the oxide 

 being removed by the acid. 



If we consider then what takes place, we shall perceive ihat 

 the zinc plate undergoes alternate states of induction and equi- 

 librium, as do likewise the particles of the solution between 

 the zinc and platinum plates, and, in fine^, the platinum plate 

 itself, and that as the number of alternations of zinc and plati- 

 num increases, the electrical energy of the zinc plate increases, 

 as does also the rapidity of its oxidation and. deoxidation, and 

 as a consequence the rapidity of change of indnctio7i and equi- 

 librium upon "di'hich the intensity of the current depends. 



The decomposition of the electrolyte may be considered to 

 be the effect produced by two forces acting upon its particles; 

 the attraction of the polesf of the battery (whether they be 



* Aqueous solutions of different gases, when brought into contact, have 

 been found to produce electrical currents. 



t In place of poles, I should more properly have said electrodes, their 

 bounding surfaces. It follows, as a consequence of the theory, that the 

 panicles of oxygen in contact with the electrodes should be attracted by, 

 and set free from, those electrodes upon each alternation of the states of 

 induction and equilibrium ; and that, when the induced state has not suf- 

 ficient energy to overcome the afEinities already engaged, the current of 

 electricity passes without producing electrolyzation. For a different ex- 

 planation, vid.Dr. Faraday's Series of Researches, 493, 494, 495,534, 535, 

 636, 537, 807. 



