chanical devices could not
transfer energy perfectly. There was always some friction in the
working parts. Friction was not only known to impede the transfer
of energy in the machine, but it was known to produce heat. In
order to simultaneously explain the work loss and the heat gain,
so that <b>conservation</b> could be satisfied, Helmholtz
postulated that heat was a form of energy consisting of a small,
random motion in the molecules of matter. He went on to speculate
that the loss of work in the 