128 Dr. Faraday's Expei'imetiial Researches in Electricity, 



I 922. It might at first be supposed that a conducting body, 

 not electrolytic, might answer as the third substance between 

 the zinc and the platina; and it is true that we have some such 

 capable of exerting chemical action upon the metals. They 

 must, however, be chosen from the metals themselves, for there 

 are no bodies of this kind except those substances and charcoal. 

 To decide the matter by experiment, I made the following 

 arrangement. Melted tin was put into a glass tube bent into 

 the form of the letter V, fig. 6, (Plate I.) so as to fill the half 

 of each limb, and two pieces of thick platina wire, /?, w, in- 

 serted, so as to have their ends immersed some depth in the 

 tin ; the whole was then allowed to cool, and the ends jp and 

 *iso connected with a delicate galvanometer. The part of the 

 tube at X was now reheated, whilst the portion y was retained 

 cool. The galvanometer was immediately influenced by the 

 thermo-electric current produced. The heat was steadily in- 

 creased at jr, until at last the tin and platina combined there ; 

 an effect which is known to take place with strong chemical 

 action and high ignition ; but not the slightest additional effect 

 occurred at the galvanometer. No other deflection than that 

 due to the thermo-electric current was observable the whole 

 time. Hence, though a conductor, and one capable of ex- 

 erting chemical action on the tin, was used, yet, not being an 

 electrolyte^ not the slightest effect of an electrical current 

 could be observed (947.). 



923. From this it seems apparent that the peculiar charac- 

 ter and condition of an electrolyte is essential in one part of the 

 voltaic circuit ; and its nature being considered, good reasons 

 appear why it and it alone should b6 effectual. An electrolyte 

 is always a compound body ; it can conduct, but pnly whilst 

 decomposing. Its conduction depends upon its decomposition 

 and the transmission of its "particles in directions parallel to 

 the current ; and so intimate is this connexion, that if their 

 transition be stopped, the current is stopped also; if their 

 course be changed, its course and direction changes with them ; 

 if they proceed in one direction, it has no power to proceed 

 in any other than a direction invariably dependent on them. 

 The particles of an electrolytic body are all so mutually con- 

 nected, are in such relation with each other through their 

 whole extent in the direction of the current, that if the last is 

 not disposed of, the first is not at liberty to take up its place 

 in the new combination which the powerful affinity of the 

 most active metal tends to produce ; and then the current it- 

 self is stopped ; for the dependencies of the current and the 

 decomposition are so mutual, that whichever be originally de- 

 termined, 7. e, the motion of the particles or the motion of the 



