INACTIVE CONDUCTING VOLTAIC CIRCLES, — ALKALIES. 
77 
moistened in dilute nitric acid (1831.), a current was the result. So here, as in the 
many former cases, the arrangement with a little chemical action and no metallic con- 
tact produces a current, but that without the chemical action and with the metallic 
contact produces none. 
1855. Iron or nickel associated with platinum in this strong solution of potassa was 
positive. The force of the produced current soon fell, and after an hour or so was 
very small. Then annulling the metallic contact at x, fig. 2, and substituting a feeble 
chemical action there, as of dilute nitric acid, the current established by the latter 
would pass and show itself. Thus the cases are parallel to those before mentioned 
(1849, &c.), and show how little contact alone could do, since the effect of the conjoint 
contact of iron and platinum and chemical action of potash and iron were very small 
as compared with the contrasted chemical action of the dilute nitric acid. 
1856. Instead of a strong solution of potassa, a much weaker one consisting of one 
volume of strong solution and six volumes of water was used, but the results with 
the silver and platinum were the same : no current was produced by the metallic 
contact as long as that only was left for exciting cause, but on substituting a little 
chemical action in its place (1831.), the current was immediately produced. 
1857. Iron and nickel with platinum in the weak solution also produced similar 
results, except that the positive state of these metals was rather more permanent than 
with the strong solution. Still it was so small as to be out of all proportion to 
what was to be expected according to the contact theory. 
1858. Thus these different contacts of metals and other well-conducting solid 
bodies prove utterly inefficient in producing a current, as well when solution of pot- 
assa is the third or fluid body in the circuit, as when that thirdbody is either solution 
of sulphuret of potassium, or hydrated nitrous acid, or nitric acid, or mixed nitric and 
nitrous acids. Further, all the arguments respecting the inefficacy of the contacts 
of bodies interposed at the junction of the two principal solid substances, which were 
advanced in the case of the sulphuret of potassium solution (1833.), apply here with 
potassa ; as they do indeed in every case of a conducting circuit where the inter- 
posed fluid is without chemical action and no current is produced. If a case could 
be brought forward in which the interposed fluid is without action, is yet a sufficiently 
good conductor, and a current is produced ; then, indeed, the theory of contact would 
find evidence in its favour, which, as far as I can perceive, could not be overcome. 
I have most anxiously sought for such a case, but cannot find one (1798.). 
1859. The argument is now in a fit state for the resumption of that important point 
before adverted to (1835. 1844.), which, if truly advanced by an advocate for the 
