40-1 Royal Society : — 



together, and the iron core is absent, the vibrations are vcrv much 

 smaller and the sound is much higher. In each case the quantity 

 of the current, however, remains the same. If a voltameter is used 

 instead of the galvanometer, a greater number of elements (about 

 eight Smee's) must be employed, and the difference in the effects is 

 then less striking. If a battery of much greater intensity, say 

 twenty Smee's elements, is employed, no difference in the vibrations 

 or sounds is produced by the introduction of the soft iron core, nor 

 by closing the secondary coil. 



Bo not voltaic currents therefore of equal quantities* from 

 different sources, or under different external conditions, like heat 

 and light from different sources, possess different qualities ? 



4. From these results (as well as from additional ones that I have 

 obtained) it appears to me that voltaic electricity, like heat or light, 

 may be viewed as consisting of vibrations or successive impulses, 

 which under ordinary circumstances occupy so minute a period of 

 time as to be inappreciable, but when acting under suitable condi- 

 tions upon suitable substances, such as the metal and liquid referred 

 to (1), the vibrations of the current are taken up by the substances, 

 and the oscillations of the substances thereby produced are gradually 

 increased by the synchronous impulses of the current until they 

 become visible and attain their maximum (see paper " On the pro- 

 duction of Vibrations and Sounds by Electrolysis," paragraph 11), 

 like visible oscillations of a pendulum produced by minute syn- 

 chronous mechanical impulses. This I beg leave to state as an 

 hypothesis for the purpose of making the subject more clear and 

 aiding future inquiry. 



Note by Professor Stokes, Sec. R.S. 



[The results mentioned in this paper are well worthy of attentive 

 consideration, in relation to that curious and still mysterious pheno- 

 menon which the author is investigating with so much care. As 

 regards, however, the conjecture thrown out by the author, — while the 

 importance of such a conclusion as that of the existence of qualitative 

 differences in permanent electric currents, according as few or many 

 voltaic elements are concerned in their formation, or of periodicity 

 as a necessary condition of a voltaic current, if fully established, 

 cannot be overrated, the conclusion does not seem to be fairly deducible 

 from the experiments described. It would rather seem that, from 

 some cause yet to be investigated, the motion of the mercurial cathode, 

 or rather the change of figure resulting from the motion, alters the 

 total electromotive force or resistance (more probably the resistance) 

 in the circuit, and thus, by altering the current, reacts upon the forces 

 whereby the motion of the cathode is produced. In a circuit of 

 small resistance, it might be expected according to this view that a 

 smaller motion of the cathode would suffice to bring about a given 

 change in the current, and a corresponding change in the force pro- 



* I employ the word " quantity " in its ordinary sense, viz. as that indicated 

 by measurement of gases from decomposition of water in a voltameter. 





