advised Mr. Joule not to
submit the paper to the Royal Society. But its drift and results are
summed up in these memorable words by its author, written some time
subsequently: 'In that paper it was demonstrated experimentally, that
the mechanical power exerted in turning a magneto-electric machine is
converted into the heat evolved by the passage of the currents of
induction through its coils; and, on the other hand, that the motive
power of the electromagnetic engine is obtained at the expense of the
heat due to the chemical reaction of the battery by which it is
worked.' [Footnote: Phil. Mag. May, 1845.] It is needless to dwell
upon the weight and importance of this statement.

Considering the imperfections incidental to a first determination, it
is not surprising that the 'mechanical values of heat,' deduced from
the different series of experiments published in 1843, varied widely
from each other. The lowest limit was 587, and the highest 1,026
foot-pounds, for 1 degree Fahr. of temperature.

One noteworthy result of his enquiries, which was pointed out at the
time by Mr. Joule, had reference to the exceedingly small fraction of
the heat actually converted into useful effect in the steam-engine.
The thoughts of the celebrated Julius Robert Mayer, who was then
engaged in Germany upon the same question, had moved independently in
the same groove; but to his labours due reference will be made on a
future occasion. [Footnote: See the next Fragment.] In the memoir now
referred to, Mr. Joule also announced that he had proved heat to be
evolved during the passage of water through narrow tubes; and he
deduced from these experiments an equivalent of 770 foot-pounds, a
figure remarkably near the one now accepted. A detached statement
regarding the origin and convertibility of animal heat strikingly
illustrates the penetration of Mr. Joule, and his mastery of
principles, at the period now referred to. A friend had mentioned to
him Haller's hypothesis, that animal heat might arise from the
friction of the blood in the veins and arteries. 'It is
unquestionable,' writes Mr. Joule,' that heat is produced by such
friction; but it must be understood that the mechanical force expended
in the friction is a part of the force of affinity which causes the
venous blood to unite with oxygen, so that the whole heat of the
system must still be referred to the chemical changes. But if the
animal were engaged in turning a piece of