294 Faraday's Researches

of character which contact force has been assumed to have; but
one that has all the variations which chemical force is known to
exhibit.

993. The changes occurring where any one of four or five
metals, differing from each other as far as silver and tin, can be
made positive or negative to the others (985, 986), appears to me
to shut out the probability that the contact of these metals with
each other can produce the smallest portion of the effect in these
voltaic arrangements; and then, if not there, neither can they
be effective in any other arrangements; so that what has been
deduced in that respect from former experiments (817, 821) is
confirmed by the present.

994. Or if the scene be shifted, and it be said that it is the
contact of the acids or solutions which, by dilution at one side,
produce these varied changes (862, 970, 979, 1002, 1048), then
how utterly unlike such contact must be to that of the numerous
class of conducting solid bodies (797, 855)! and where, to give
the assumption any show of support, is the case of such contact
(apart from chemical action) producing such currents?

995. That it cannot be an alteration of contact force by mere
dilution at one side (994) is also shown by making such a change,
but using metals that are chemically inactive in the electrolyte
employed. Thus when nitric or sulphuric acids were diluted at
one side, and then the strong and the weak parts connected by
platinum or gold (964), there was no sensible current, or only
one so small as to be unimportant.

996. A still stronger proof is afforded by the following
result. I arranged the tube, fig. 72 (960), with strong solution
of yellow sulphuret of potassium (800) from A to m, and a
solution consisting of one volume of the strong solution, with
six of water from m to B. The extremities were then con-
nected by platinum and iron in various ways; and when the
first effect of immersion was guarded against, including the first
brief negative state of the iron (1037), the effects were as follows.
Platinum being in A and in B, that in A, or the strong solution,
was very slightly positive, causing a permanent deflection of 2°.
Iron being in A and in B, the same result was obtained. Iron
being in A and platinum in B, the iron was positive about 2°
to the platinum. Platinum being in A and iron in B, the
platinum was now positive to the iron by about 2°. So that
not only the contact of the iron and platinum passes for nothing,
but the contact of strong and weak solution of this electrolyte
with either iron or platinum is ineffectual in producing ae Chimie, 1828, xxxvii. p. 240.ith nitric acid and iron or silver