Mr. Grove on Voltaic Reaction. 445 



a certain interval the wires clipping into the mercury cups gg', 

 so as to reverse the plates a c, with regard to the direction of 

 the current, making what was the anode the cathode, and vice 

 versa, as shown by the dotted lines ; and at the expiration of 

 a similar interval to restore them to their original positions, 

 and to continue thus alternating the position of these plates 

 with reference to the current during six hours. 



The interval was to be dependent upon the following ob- 

 servation : — When first the circuit was completed, a marked 

 evolution of gas was perceptible in the voltameter, this gradu- 

 ally subsided, and when it had become nearly imperceptible 

 the change was to be made, when a fresh burst of gas took 

 place, as this again subsided the wires were to be again 

 changed, and so on. At the expiration of six hours the water- 

 level was marked, as in the previous experiments. 



The following is the quantity of gas evolved in the volta- 

 meter, deduced from a mean of several experiments : — 



cubic inch. 

 Experiment 1. = 0*15 

 Experiment 2. = 0*10 

 Experiment 3. = 0*23. 



In neither of the last two experiments was a bubble of gas 

 perceptible on the large plates a c. 



It appears from these experiments, that the nitric acid bat- 

 tery will decompose water across two pairs of interposed in- 

 oxidable electrodes, provided one be of considerable size with 

 reference to the other parts of the circuit, so as to lessen re- 

 sistance. 



Whether this diminished resistance be occasioned by the 

 mere increase of the sectional area of the electrolyte; whether 

 by the increased facility for solution of the oxygen and hydro- 

 gen ; whether the oxygen and hydrogen be not eliminated, but 

 merely thrown into a state of polar tension, or made to adhere 

 in a liquid or gaseous form to the plates; or whether any of 

 these effects take place conjointly, I will not stop to inquire, 

 but proceed to the more remarkable fact, viz. that the quan- 

 tity of gas evolved in Experiment 3. is greater for a given 

 time, not only than that evolved in Experiment 2, but even 

 than that evolved in Experiment I ; thus we get the seeming 

 paradox, that a battery performs more work with an inter- 

 posed resistance than without it. 



While the battery is decomposing water in the voltameter 

 v, it is polarizing the plates a c, or accumulating by its own 

 force an antagonist force ; when the wires are changed this 

 reacting force is united in direction with the initial force, in 

 fact two voltaic pairs are constituted. The reaction being ex- 



