This was the first determination of the dynamical equivalent of heat.
Other naturalists and experimenters about the same time were attempting
to compare the quantity of heat produced under certain circumstances
with the quantity of work expended in producing it; and results and
deductions (some of them very remarkable) were given by Seguin (1839),
Mayer (1842), Colding (1843), founded partly on experiment, and partly
on a kind of metaphysical reasoning. It was Joule, however, who first
definitely proposed the problem of determining the relation between heat
produced and work done in any mechanical action, and solved the problem
directly.

It is not to be supposed that Joule's discovery and the results of his
investigation met with immediate attention or with ready acquiescence.
The problem occupied him almost continuously for many years; and in 1878
he gives in the _Philosophical Transactions_ the results of a fresh
determination, according to which the quantity of work required to be
expended in order to raise the temperature of one pound of water weighed
in vacuum from 60 deg. to 61 deg. Fahr., is 772.55 foot pounds of work at the
sea level and in the latitude of Greenwich. His results of 1849 and 1878
agree in a striking manner with those obtained by Hirn and with those
derived from an elaborate series of experiments carried out by Prof.
Rowland, at the expense of the Government of the United States.

His experiments subsequent to 1843 on the dynamical equivalent of
heat must be mentioned briefly. In that year his father removed from
Pendlebury to Oak Field, Whalley Range, on the south side of Manchester,
and built for his son a convenient laboratory near to the house. It was
at this time that he felt the pressing need of accurate thermometers;
and while Regnault was doing the same thing in France, Mr. Joule