JAMES   PRESCOTT   JOULE     155
quantitative investigation of combustion arose out of the
philosophical study of heat measurement inspired by
the steam-engine and the demand of industrialism for the
measurement of commodities in order that their value could
easily be ascertained for the purposes of commerce.
Liebig's appreciation of Mayer's papers was characteristic
of his deep intelligence. His equal as a natural philosopher
has not been seen among his successors in chemical science.
Mayer's first paper received very little attention apart
from Liebig's acceptance for publication. He had become
a practising medical doctor in his native town, and his lack
of academic position prevented him from forcing his ideas
on to the academic world. His townsmen ridiculed his pre-
tensions to intellectual originality and confirmed their
opinion by pointing out that his claims had been ignored
by the professional scientists. The mental agony caused
by this experience drove him mad_3 and he was confined for
a period in a mental hospital. In 1862 Clausius privately
supplied J, Tyndall with information about him and copies
of his papers. On the basis of this material Tyndall engaged
in a controversy with W. Thomson and P. G. Tait, who
had not given sufficient recognition to Mayer. He wrote
with a personal candour that has rarely been equalled in
subsequent scientific controversies.
In 1843 the Danish scientist, Colding, also argued in
favour of the equivalence of heat and mechanical effect.
Reynolds comments that philosophical reasoning was not
sufficient to remove the prejudice and casuistry respecting
caloric. Mayer's brilliant reasoning convinced few.
Demonstrations with results of barn-door obviousness were
required. Joule produced such results with exquisite
experimental perfection and clarity of thought. But it is
possible that much of Joule's perfection was a concession
to human stupidity. A less prejudiced audience would
have required less belabouring with exactitude in order to
learn the truth. The demand for experimental proof can
be extravagant. It has been remarked as curious that Clerk
Maxwell did not search experimentally for the electro-
magnetic waves whose existence he had deduced theoretically.