fet 
XXV. Some Remarks on Heat, and the Constitution of Elastic 
Fluids. By J.P. Journ, F.R.S. &e.* 
To the Editors of the Philosophical Magazine and Journal. 
Oakfield, Moss Side, Manchester, 
GENTLEMEN, August 22, 1857. 
UAE you deem it to be of sufficient interest, I shall feel 
much obliged by your republishing the enclosed paper, re- 
ferred to by Professor Clausius in his paper “On the Nature of 
the Motion which we call Heat,” inserted in your last Number. 
I may observe in reference to the note at the foot of p. 109, that 
the Memoirs of the Literary and Philosophical Society of Man- 
chester are at present regularly forwarded to the principal scien- 
tific societies of Europe and America. 
I have the honour to remain, 
Yours very respectfully, 
James P, Jouxe. 
In a paper “On the Heat evolved during the Electrolysis of 
Water,” published in the seventh volume of the Memoirs of this 
Society, I stated that the magneto-electrical machine enabled us 
to convert mechanical power into heat; and that I had little 
doubt that, by interposing an electro-magnetic engine in the 
circuit of a voltaic battery, a diminution of the quantity of heat 
evolved, per equivalent of chemical reaction, would be observed, 
and that this diminution would be proportional to the mechanical 
power obtained. 
The results of experiments in proof of the above proposition 
were communicated to the British Association for the Advance- 
ment of Science, in 1843+. They showed that whenever a cur- 
rent of electricity was generated by a magneto-electrical machine, 
the quantity of heat evolved by that current had a constant rela- 
tion to the power required to turn the machine; and, on the 
other hand, that whenever an engine was worked by a voltaic 
battery, the power developed was at the expense of the calorific 
power of the battery for a given consumption of zinc, the mecha- 
nical effect produced having a fixed relation to the heat lost in 
the voltaic circuit. 
The obvious conclusion from these experiments was, that heat 
and mechanical power were convertible into one another ; and it 
became therefore evident that heat is either the vis viva of pon- 
* Read at a Meeting of the Manchester Literary and Philosophical 
Society, October 3, 1848, and published in the Society’s Memoirs, No- 
vember 1851. 
+ Phil. Mag. vol. xxiii. pp. 263, 347, 435. 
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