different temperatures, according
to the second law of thermodynamics, there we have the power of doing
work by the transmission of heat, from the body of higher to the one of
lower temperature.

That Carnot ultimately came to believe in the dynamical theory of heat,
is proved by the following passage taken from his notes on the Motive
Power of Heat: "It would be ridiculous to suppose that it is an emission
of matter, while the light which accompanies it could only be a
movement. Could a motion produce matter? No! undoubtedly, it can only
produce a motion. Heat is then the result of motion. It is plain then
that it could be produced by the consumption of motive power, and that
it could produce this power. Heat is then simply motive power, or rather
motion which has changed its form. It is a movement among the particles
of bodies. Wherever there is a destruction of motive power, there is at
the same time production of heat in quantity exactly proportional to the
quantity of motive power destroyed. Reciprocally, whenever there is
destruction of heat there is production of motive power."

Let us apply this principle to the solar system, and endeavour to find
out whether in that system we have, in relation to the heat thereof,
either a cycle of operations or a reversible cycle. We have again to
consider the sun as the source of all light and heat in the solar
system, radiating forth on every side, year by year, the countless units
of heat which go to form the continuance of all planetary life and
existence. One of the problems that has confronted scientific men for
many years is this, Where does the sun get its supply of heat from? When
we remember the incessant loss of heat which the sun suffers through its
radiation of heat into space, we are compelled to ask, How is that
supply maintained, and how has it been kept up through the countless
ages of the past? Several suggestions have been made, and several
theories advanced to account for the fact. Mayer, of Germany, suggested
that the heat is partly maintained by the falling into the sun of
meteors, which, like comets, pursue a path through the heavens, and are
subject to the attractive influence of the sun. In the combustion of
these meteorites, or meteors, he contended there were the means by which
the light and heat of the sun might be maintained. Whatever theory,
however, may be suggested as to the maintenance and the source of the
continuity of the sun's heat, I do