64 DR. FARADAY’S EXPERIMENTAL RESEARCHES IN ELECTRICITY. (SERIES XVI.) 
respectively behind them (2067.) : that the force which, at the point of contact, in- 
duces the particles to assume a new state, cannot enable them to keep that state 
(2069.) : that all this happens without any permanent alteration of the parts that 
are in contact, and has no reference to their chemical forces (2065. 2069.). 
1803. The chemical theory assumes, that at the place of action, the particles which 
are in contact act chemically upon each other and are able, under the circumstances, 
to throw more or less of the acting force into a dynamic form (947- 996. 1120.): 
that in the most favourable circumstances, the whole is converted into dynamic force 
(1000.): that then the amount of current force produced is an exact equivalent of 
the original chemical force employed ; and that in no case (in the voltaic pile) can 
any electric current be produced, without the active exertion and consumption of an 
equal amount of chemical force, ending in a given amount of chemical change. 
1804. Marianini’s paper* was to me a great motive for re-examining the subject; 
but the course I have taken was not so much for the purpose of answering particular 
objections, as for the procuring evidence, whether relating to controverted points or 
not, which should be satisfactory to my owri mind, open to receive either one theory 
or the other. This paper, therefore, is not controversial, but contains further facts 
and proofs of the truth of De la Rive’s views. The cases Marianini puts are of ex- 
treme interest, and all his objections must, one day, be answered, when numerical 
results, both as to intensity and quantity of force, are obtained ; but they are all de- 
bateable, and, to my mind, depend upon variations of quantity which do not affect 
seriously the general question. Thus, when that philosopher quotes the numerical 
results obtained by considering two metals with fluids at their opposite extremities 
which tend to form counter currents, the difference which he puts down to the effect 
of metallic contact, either made or interrupted, I think accountable for, on the facts 
partly known respecting opposed currents ; and with me differences quite as great, 
and greater, have arisen, and are given in former papers (1046.), when metallic 
contacts were in the circuit. So at page 213 of his memoir, I cannot admit that e 
should give an effect equal to the difference of b and d ; for in b and d the opposition 
presented to the excited currents is merely that of a bad conductor, but in the case 
of e the opposition arises from the power of an opposed acting source of a current. 
1805. As to the part of his memoir respecting the action of sulphuretted solutions^, 
I hope to be allowed to refer to the investigations made further on. I do not find, 
as the Italian philosopher, that iron with gold or platina, in solution of the sulphuret 
of potassa, is positive to them;};, but, on the contrary, powerfully negative, and for 
reasons given in the sequel (2049.). 
1806. With respect to the discussion of the cause of the spark before contact^, 
* Memorie della Societa Italiana in Modena, 1827, xxi. p. 205. 
+ Ibid. p. 217. 
f Ibid. p. 217. 
§ Ibid. p. 225. 
