193 
Dr. Joule said in noticing Mr. Highton’s remarks, — I 
would refer him to my paper on the caloi'ific effects of mag- 
neto-electricity and the mechanical value of heat, published 
in the Phil. Mag. for 1843, vol. 23. He will there find it 
stated, pp. 274, 351, as the result of my experiments, that the 
heat evolved by the wire of my revolving electro-magnet 
varied with the square of the current passing through it, 
and was not affected by the resistance presented by magneto- 
electric induction in consequence of the working of the 
electro-magnetic engine. This fact is the basis of my 
reasoning in that paper, and the neglect of it has involved 
Mr. Highton in error, as may be seen in his reply to Mr. 
Apjohn’s most lucid exposition of the true theory in the 
Chemical News, vol. 23, p. 105. 
The correctness of Jacobi’s formula for the proper arrange- 
ment of the wires of a battery to produce the maximum 
magnetic effect is not necessarily connected with the subject 
of economy of work. Nevertheless 1 may refer Mr. Highton 
to my experiments on this subject in Sturgeon’s Annals for 
1839, by which I showed that the attraction of electro- 
magnets for one another is proportional to the square of the 
current between very wide limits. 
Mr. Highton seems to forget, when commenting upon the 
large amount of duty obtained in the first two experiments 
of my paper with Scoresby, that in them the theoretical 
duty was also greater than in the others, owing to the current 
being worked down to a lower intensity. Another reason, 
explained in the paper was, that in those two experiments, 
recently mixed, and therefore hot solutions were used in 
the battery, the potential of which was thereby increased. 
Mr. Highton is in error if he supposes that my paper in 
the Proceedings for March 21 contains a new theory, or that 
I have abandoned any of my original views. My object in 
that paper was simply to place the true theory in a form in 
which it might be easily understood by those who have not 
worked on the subject. 
