‘ 
produced by Electricity. 413 
charged with a mixture of nitric acid and water, so-as to exhibit 
a considerable intensity of electrical action, and the relative con- 
ducting powers of silver and platinum in air and water ascer~ 
tained by means of it. In air, six inches of wire of platinum of 
zx discharged only four double plates, while six inches of silver 
wire of the same diameter discharged the whole combination : 
the platinum was strongly ignited in this experiment, whilst the 
silver was scarcely warm to the touch. On cooling the platinum 
wire by placing it in water, it was found to discharge 10 double 
plates. When the intensity of the electricity is very high, how- 
ever, even the cooling powers of fluid media are of little avail : 
thus, 1 found that fine wire of platinum was fused by the dis- 
charge of a common electrical battery under water; so that the 
conducting power must always be diminished by the heat gene- 
rated, in a greater proportion as the intensity of the electricity 
is higher. 
It might at first view be supposed, that when a conductor 
placed in the circuit left a residuum of electricity in any battery, 
increase of the power of the battery, or of its surface, would not 
enable it to carry through any additional quantity. This, how- 
ever, is far from being the case. 
When saline solutions were placed in the circuit of a battery 
of 20 plates, though they discharged a very smail quantity only 
of the electricity, when the troughs were only a quarter full, yet 
their chemical decomposition exhibited the fact of a much larger 
quantity passing through them, when the cells were filled with 
fluid. 
And a similar circumstance occurred with respect to a wire of 
platinum, of such a length as to leave a considerable residuum 
in a battery when only half its surface was used ; yet when the 
whole surface was employed, it became much hotter, and never- 
theless left a still more considerable residuum. 
VIII. I found long ago, that in increasing the number of al- 
ternations of similar plates, the quantity of electricity seemed to 
increase as the number, at least as far as it could be judged of 
by the effects of heat upon wires ; but only within certain limits, 
beyond which the number appeared to diminish rather than in- 
erease the quantity. Thus, the two thousand double plates of 
the London Institution, when arranged as one battery, would 
not ignite so much wire as a single battery of ten plates with 
double copper. 
It is not easy to explain this result. Does the intensity mark 
the rapidity of the motion of the electricity? or, merely its di- 
minished attraction for the matter on which it acts? and does 
this attraction Lecome less in proportion as the circuit, through 
which 
