106 GALVANIC ELECTRICITY. 



for the sake of definiteness, we will conceive of as ar- 

 ranged in straight lines, between the two electrodes. 

 The circles iiUhe figure, inscribed H and O, represent 

 one of these lines of molecules. The difficulty now 

 arises, to account for the fact, that when the hydrogen is 

 liberated at the negative pole, the oxygen, combined 

 with it a moment before, is not also liberated at the same 

 point. The view to be taken of it is as follows : that as 

 soon as the atom of oxygen loses its hydrogen, it combines 

 with the hydrogen of the next molecule of water. 

 The oxygen of this second one being thereby liberated, 

 combines with the hydrogen of the next ; and this 

 decomposition and recomposition continues throughout 

 the series. The end of the series being reached, the 

 last oxygen atom escapes in the form of gas. The action 

 being simultaneous throughout the series, this evolution 

 occurs at the instant that the hydrogen is set at 

 liberty at the negative electrode. It is, therefore, 

 quite as proper to give the explanation of the diffi- 

 culty first stated, by beginning with the liberation of 

 oxygen at the positive electrode, and supposing the 

 hydrogen to combine with the oxygen of the next 

 molecule of water in the series, and so on to the nega- 

 tive electrode, where hydrogen is evolved. The ac- 

 tion is, in fact, as before stated, simultaneous. 



256. DEPOSITION OF METALS. The me- 



Explain the . . . 



deposition of tals are electro-positive. Oxygen, chlorine, 



niL bygal ' &c '' on the other hand > are negative. If, 



therefore, oxides, chlorides, or cyanides 



of the metals are subjected to the action of the 



electrodes, they are decomposed, while the metal 



