1157.  But when the twenty pairs of four-inch plates (1129.) were tried in a similar manner, the results were in the opposite direction.  With one volta-electrometer 52 cubic inches of gas were obtained; with two, only 14.6 cubic inches from each.  The quantity of charge was not the same in both cases, though it was of the same strength; but on rendering the results comparative by reducing them to equivalents (1126.), it was found that the consumption of metal in the first case was 74, and in the second case 97, equivalents for the whole of the water decomposed.  These results of course depend upon the same circumstances of retardation, &c., which have been referred to in speaking of the proper number of plates (1151.).

1158.  That the transferring, or, as it is usually called, conducting, power of an electrolyte which is to be decomposed, or other interposed body, should be rendered as good as possible[A], is very evident (1020. 1120.).  With a perfectly good conductor and a good battery, nearly all the electricity is passed, i.e. nearly all the chemical power becomes transferable, even with a single pair of plates (807.).  With an interposed nonconductor none of the chemical power becomes transferable.  With an imperfect conductor more or less of the chemical power becomes transferable as the circumstances favouring the transfer of forces across the imperfect conductor are exalted or diminished:  these circumstances are, actual increase or improvement of the conducting power, enlargement of the electrodes, approximation of the electrodes, and increased intensity of the passing current.

  [A] Gay-Lussac and Thenard, Recherches Physico-Chimiques, tom. i. pp.
  13, 15, 22.

1159.  The introduction of common spring water in place of one of the volta-electrometers used with twenty pairs of four-inch plates (1156.) caused such obstruction as not to allow one-fifteenth of the transferable force to pass which would have circulated without it.  Thus fourteen-fifteenths of the available force of the battery were destroyed, local force, (which was rendered evident by the evolution of gas from the being converted into zincs,) and yet the platina electrodes in the water were three inches long, nearly an inch wide, and not a quarter of an inch apart.

1160.  These points, i.e. the increase of conducting power, the enlargement of the electrodes, and their approximation, should be especially attended to in volta-electrometers.  The principles upon which their utility depend are so evident that there can be no occasion for further development of them here.

Royal Institution, October 11, 1834.

ELEVENTH SERIES.

S 18. On Induction. P i. Induction an action of contiguous particles. P ii. Absolute charge of matter. P iii. Electrometer and inductive apparatus employed. P iv. Induction in curved lines. P v. Specific inductive capacity. P vi. General results as to induction.