philosophers, notably
Hooke and Huygens and Boyle, had held more correct views; but the
materialistic conception accorded so well with the eighteenth-century
tendencies of thought that only here and there a philosopher like Euler
called it in question, until well on towards the close of the century.
Current speech referred to the materiality of the "imponderables"
unquestioningly. Students of meteorology--a science that was just
dawning--explained atmospheric phenomena on the supposition that heat,
the heaviest imponderable, predominated in the lower atmosphere, and
that light, electricity, and magnetism prevailed in successively higher
strata. And Lavoisier, the most philosophical chemist of the century,
retained heat and light on a par with oxygen, hydrogen, iron, and the
rest, in his list of elementary substances.

COUNT RUMFORD AND THE VIBRATORY THEORY OF HEAT

But just at the close of the century the confidence in the status of
the imponderables was rudely shaken in the minds of philosophers by the
revival of the old idea of Fra Paolo and Bacon and Boyle, that heat,
at any rate, is not a material fluid, but merely a mode of motion or
vibration among the particles of "ponderable" matter. The new champion
of the old doctrine as to the nature of heat was a very distinguished
philosopher and diplomatist of the time, who, it may be worth recalling,
was an American. He was a sadly expatriated American, it is true, as his
name, given all the official appendages, will amply testify; but he had
been born and reared in a Massachusetts village none the less, and
he seems always to have retained a kindly interest in the land of his
nativity, even though he lived abroad in the service of other powers
during all the later years of his life, and was knighted by England,
ennobled by Bavaria, and honored by the most distinguished scientific
bodies of Europe. The American, then, who championed the vibratory
theory of heat, in opposition to all current opinion, in this closing
era of the eighteenth century, was Lieutenant-General Sir Benjamin
Thompson, Count Rumford, F.R.S.

Rumford showed that heat may be produced in indefinite quantities by
friction of bodies that do not themselves lose any appreciable matter
in the process, and claimed that this proves the immateriality of heat.
Later on he added force to the argument by proving, in refutation of the
experiments of Bowditch, that no body either gains or loses weight in
virtue