414 On the magnetic Phenomena produced by Electricity. 
which it passes, or in which it is generated, contains a greater 
number of alternations of bad conductors ? 
Mr. Children, in his account of the experiments made with 
his battery of large plates, has ingeniously referred the heat pro- 
duced by the passage of electricity through conductors, to the 
resistance it meets with, and has supposed, what proves to be 
the fact, that the heat is in some inverse ratio to the conducting 
power. The greatest heat however is produced in air, where 
there is reason to suppose the least resistance; and as the pre- 
sence of heat renders bodies worse conductors, another view may 
be taken, namely, that the excitation of heat occasions the im- 
perfection of the conducting power. But till the causes of heat 
and of electricity are known, and of that peculiar constitution of 
matter which excites the one, and transmits or propagates the 
other, our reasoning on this subject must be inconclusive. 
I found that when equal portions of wires cf the same diame- 
ter, but of different metals, were connected together in the cir- 
cuit of a powerful Voltaic battery, acting as two surfaces, the 
metals were heated in the following order: iron most, then pal- 
ladium, then platinum, then tin, then zinc, then gold, then lead, 
then copper, and silver least of all. And from one experiment, 
in which similar wires of platinum and silver joined in the same 
circuit were placed in equal portions of oil, it appeared that the 
generation of heat was nearly inversely as their conducting power. 
Thus, the silver raised the temperature of the oil only four de- 
grees, whilst the platinum raised it twenty-two. The same re- 
lations to heat seem to exist, whatever is the intensity of the 
electricity; thus, circuits of wires placed under water, and acted 
on by the common electrical discharge, were heated jn the same 
order as by the Voltaic battery, as was shown by their relative 
fusion; thus, iron fusing before platinum, platinum before gold, 
and so on. 
If a chain be made of wire of platinum and silver, in alter- 
nate links soldered together, the silver wire being four or five 
times the diameter of the platinum, and placed in a powerful 
Voltaic circuit, the silver links are not sensibly heated, whilst all 
those of the platinum become intensely and equally ignited. 
This is an important experiment for investigating the nature of 
heat. If heat be supposed a substance, it cannot be imagined 
to be expelled from the platinum; because an unlimited quan- 
tity may be generated from the same platinum, 7.e. as long as 
the electricity is excited, or as often as it is renewed. Or if it 
be supposed to be identical with, or an element of, electricity, it 
ought to bear some relation to its quantity, and might be ex- 
peeted to be the same in every part of the chain, or greatest in 
those parts nearest the battery. IX. The 
SP Se. 
