1822.] produced by Electricili/. 9 



produced 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 conduct- 

 ing power. The greatest heat, however, is produced in air, 

 •where there is reason to suppose the least resistance ; and as 

 the presence of heat renders bodies worse conductors, another 

 view may be taken ; namely, that the excitation of heat occa- 

 sions the imperfection of the conducting power. But till the 

 causes of heat and of electricity are known, and of that pecuhar 

 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 of the same diame- 

 ter, but of different metals, were connected together in the 

 circuit 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 degrees, whilst the platinum raised it 22. The same rela- 

 tions to heat seem to exist, whatever is the intensity of the elec- 

 tricity ; thus circuits of wires placed under water, and acted on 

 by the common electrical discharge, were heated in 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 alternate 

 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 quantity may 

 be generated from the same platinum, i.e. as long as the electri- 

 city 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 expected to be 

 the same in everi/ part of the chain, or greatest in those parts 

 nearest the battery. 



IX. The magnetism produced by electricity, though with the 

 same conductors it increases with the heat, as I mentioned in 

 my last paper ; yet with different conductors I find it follows a 

 very diflerent law. Thus, when a chain is made of different 

 conducting wires, and they are placed in the same circuit, they 



