90 DR. FARADAY'S EXPERIMENTAL RESEARCHES IN ELECTRICITY. 



since the actions at all the surfaces might have increased or diminished together. The 

 deficiency in the evidence is, however, completely supplied by the former experiments 

 on different- sized electrodes ; for with variation in the size of these, a variation in the 

 intensity must have occurred. The intensity of an electric current traversing con- 

 ductors alike in their nature, quality, and length, is probably as the quantity of elec- 

 tricity passing through a given sectional area perpendicular to the current, divided 

 by the time (360. note) ; and therefore when large plates were contrasted with wires 

 separated by an equal length of the same decomposing conductor {714.), whilst one 

 current of electricity passed through both arrangements, that electricity must have 

 been in a very different state, as to tension, between the plates and between the wires; 

 yet the chemical results were the same. 



725. The difference in intensity, under the circumstances described, may be easily 

 shown practically, by arranging two decomposing apparatus as in fig. 12, where the 

 same fluid is subjected to the decomposing power of the same current of electricity, 

 passing in the vessel A. between large platina plates, and in the vessel B. between 

 small wires. If a third decomposing apparatus, such as that delineated fig. 11. (71 1.)> 

 be connected with the wires at a h, fig. 12, it will serve sufficiently well, by the degree 

 of decomposition occurring in it, to indicate the relative state of the two plates as to 

 intensity ; and if it then be applied in the same way, as a test of the state of the wires 

 at a' V, it will, by the increase of decomposition within, show how much greater the 

 intensity is there than at the former points. The connexions of P and N with the 

 voltaic battery are of course to be continued during the whole time. 



726. A third form of experiment in which difference of intensity was obtained, for 

 the purpose of testing the principle of equal chemical action, was to arrange three 

 volta-electrometers, so that after the electric current had passed through one, it 

 should divide into two parts, which, after traversing each one of the remaining in- 

 struments, should reunite. The sum of the decomposition in the two latter vessels was 

 always equal to the decomposition in the former vessel. But the intensitij of the di- 

 vided current could not be the same as that it had in its original state ; and therefore 

 variation of intensity has no influence on the results if the quantity of electricity remain 

 the same. The experiment, in fact, resolves itself simply into an increase in the size 

 of the electrodes (725.). 



727. The third point, in respect to which the principle of equal electro-chemical 

 action on water was tested, was variation of the strength of the solution used. In order 

 to render the water a conductor, sulphuric acid had been added to it (707.) ; and it 

 did not seem unlikely that this substance, with many others, might render the water 

 more subject to decomposition, the electricity remaining the same in quantity. But 

 such did not prove to be the case. Diluted sulphuric acid, of different strengths, was 

 introduced into different decomposing apparatus, and submitted simultaneously to 

 the action of the same electric current (714.). Slight differences occurred, as before, 

 sometimes in one direction, sometimes in another ; but the final result was, that 



