28fl Professor Tho-MSOX on Transient Electric Currenis. 



oscillations in the discharger consequent on the successive sparks.* Thus, 

 if the general law of electro-chemical decomposition be applicable to cur- 

 rents of such very short duration as that of each alternation in such an 

 oscillatory discharge as may take place in these circumstances, there will 

 be decomposed altogether as much water as is electro-chemically equiva- 

 lent to the sum of the quantities of electricity that pass in all the succes- 

 sive currents in the two directions, while the quantities of oxygen and hy- 

 drogen which appear at the two electrodes will differ by the quantities 

 arising from the decomposition of a quantity of water electro-chemically 

 equivalent to only the quantity of electricity initially contained by the 

 principal conductor. The mathematical results of the present communi- 

 cation lead to an expression for the quantity of water decomposed by an 

 oscillatory discharge in any case to which they are applicable, and show that 

 the greater the electro-dynamic capacity of the charger, the less its re- 

 sistance, and the less electro-statical capacity of the principal conduc- 

 tor, the greater will be the quantity of water decomposed. Probably the 

 best arrangement in practice would be one in which merely a small ball 

 or knob is substituted for a principal conductor fulfilling the conditions 

 prescribed above ; but those conditions not being fulfilled, the circum- 

 stances would not be exactly expressed by the formulae of the present 

 communication ; the resistance would be much diminished, and conse- 

 quently the whole quantity of water decomposed much increased, by sub- 

 stituting large platinum electrodes for the mere points used by Wollaston; 

 but then the oxygen and hydrogen separated during the first direct cur- 

 rent would adhere to the platinum plates and would be in part neutralized 

 by combinatiou with the hydrogen and oxygen brought to the same plates 

 respectively by the succeeding reverse current ; and so on through all the 

 alternations of the discharge. In fact, if the electrodes be too large, all 

 the equivalent quantities of the two gases brought successively to the same 

 electrode will recombine, and at the end of the discharge there will be only 

 oxygen at the one electrode and only hydrogen at the other, in quantities 

 electro-chemically equivalent to the initial charge of the principal conduc- 

 tor. Hence we see the necessity of using very minute electrodes, and of 

 making a considerable quantity of electricity pass in each discharge, so 

 that each successive alternation of the current may actually liberate from 

 the electrodes some of the gases which it draws from the water. Pro- 

 bably the most effective arrangement would be one in which a Leyden 

 phial or other body of considerable capacity is put in connection with the 

 machine and discharged in sparks through a powerful discharger, not only 

 of great electro-dynamic capacity, and of as little resistance as possible 

 except where the metallic communication is broken in the electrolytic 

 vessel, but of considerable electro-statical capacity, so that all, or as great a 



* This conjecture was first, so far as I am aware, given by Helmliolz, the exist- 

 ence of electrical oscillations in many cases of discharge having been indicated by 

 him as a probable conclusion from the experiments of Riess, alluded to in the text. 



