produced by electricity. 431 
in researches of this nature, it is impossible to gain more than 
approximations to true results ; for the gas disengaged upon 
the plates, the different distances of the connecting plates, and 
the slight difference of time in making the connections, all 
interfere with their perfect accuracy. 
The most remarkable general result that I obtained by 
these researches, and which I shall mention first* as it influ- 
ences all the others, was, that the conducting power of metallic 
bodies varied with the temperature , and was lower in some inverse 
ratio as the temperature was higher. 
Thus a wire of platinum of and three inches in length, 
when kept cool by oil, discharged the electricity of two bat- 
teries, or of twenty double plates ; but when suffered to be 
heated by exposure in the air, it barely discharged one 
battery. 
Whether the heat was occasioned by the electricity, or ap- 
plied to it from some other source, the effect was the same. 
Thus a wire of platinum, of such length and diameter as to 
discharge a combination without being considerably heated ; 
when the flame of a spirit lamp was applied to it so as to make 
a part of it red hot, lost its power of discharging the whole 
electricity of the battery, as was shown by the disengagement 
of abundance of gas in the secondary circuit ; which disen- 
gagement ceased as soon as the source of heat was with- 
drawn. 
There are several modes of exhibiting this fact, so as to 
produce effects which, till they are witnessed, must almost 
appear impossible. Thus, let a fine wire of platinum of four 
or five inches in length be placed in a voltaic circuit, so that 
the electricity passing through it may heat the whole of it to 
