Page:Experimental researches in electricity.djvu/262

236 into dynamic force (736): 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.

792. 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 own 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 extreme 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 debatable, 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 (782), 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.

793. 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 (1037).

794. With respect to the discussion of the cause of the spark before contact, Marianini admits the spark, but I give it up