produced by the Electric Current, 471 



the work of transport of the iodine is greater than that of the 

 transport of the metal. 



It is important to observe that, our reasoning being based 

 on the possibility of applying to these phenomena the principle 

 of the conservation of energy, i. e. the theorem of vires vivce, 

 the value of the work accomplished is determined solely by 

 the initial and final states of the system of bodies under con- 

 sideration, and is consequently independent of any possible 

 hypothesis on the nature of electrolysis. As the liquid be- 

 yond the immediate vicinity of the electrodes undergoes no 

 alteration, the total work is equal to the algebraic sum of the 

 weights of material transported from one electrode to the 

 other, multiplied by the height of the liquid column. As the 

 phenomenon takes place in the interior of a liquid, the appli- 

 cation of the Archimedean principle necessitates the introduc- 

 tion of a correction. 



We have seen that all work produced by the current, or 

 supplied by external forces and serving to reinforce the cur- 

 rent, is accompanied by the appearance of a new electromotive 

 force in the circuit. In the first case this electromotive force, 

 which I will designate by e, will have the opposite sign, in the 

 second the same sign as that of the pile, E. From this it 

 follows that in a column of nitrate of silver an ascending cur- 

 rent will be feebler than a descending one ; for, in a circuit of 

 the same resistance, we shall have in the first case the electro- 

 motive force E— e, and, in the second, E+<?. The inverse 

 phenomenon will take place with iodide of cadmium. The 

 experiments described below were undertaken for the purpose 

 of verifying this result*. 



The details of the numerical calculations will be found in 

 the articles mentioned above. The following are the final 

 values of the electromotive force for a column of 1 metre : — 



Nitrate of silver e= 0*000005195 Daniell. 



Iodide of cadmium, -e= -0O00015670 „ 



* The experiments were commenced in 1872 (with sulphate of copper). 

 They did not at first promise any success ; for this reason I did not pub- 

 lish any thing about them, though I communicated the results to my 

 scientific friends in Moscow. At that period I was obliged, for personal 

 reasons, to suspend for nearly two years all experimental work. In 1873 

 appeared Prof. Maxwell's book, 'A Treatise on Electricity and Magnetism.' 

 I saw with pleasure that the eminent English physicist had conceived the 

 same idea (I willingly acknowledge that to him belongs the merit of 

 having been the first to enunciate it through the press) ; to me the co- 

 incidence was an additional assurance of the correctness of my theoretic 

 previsions. As far as one can judge from the ten lines devoted by Mr. 

 Maxwell to the subject (vol. i. p. 317), he has calculated the electro- 

 motive force e by taking into consideration only the transport of the 

 metal. He does not indicate any experimental means of verification. 



