ical results, will enable
those who are disposed to institute a complete comparison between the
two rival theories of light, to derive from the _Mecanique Celeste_ the
materials of several interesting relations.

Is light an emanation from the sun? Does this body launch out
incessantly in every direction a part of its own substance? Is it
gradually diminishing in volume and mass? The attraction exercised by
the sun upon the earth will, in that case, gradually become less and
less considerable. The radius of the terrestrial orbit, on the other
hand, cannot fail to increase, and a corresponding effect will be
produced on the length of the year.

This is the conclusion which suggests itself to every person upon a
first glance at the subject. By applying analysis to the question, and
then proceeding to numerical computations, founded upon the most
trustworthy results of observation relative to the length of the year in
different ages, Laplace has proved that an incessant emission of light,
going on for a period of two thousand years, has not diminished the mass
of the sun by the two-millionth part of its original value.

Our illustrious countryman never proposed to himself any thing vague or
indefinite. His constant object was the explanation of the great
phenomena of nature, according to the inflexible principles of
mathematical analysis. No philosopher, no mathematician, could have
maintained himself more cautiously on his guard against a propensity to
hasty speculation. No person dreaded more the scientific errors which
the imagination gives birth to, when it ceases to remain within the
limits of facts, of calculation, and of analogy. Once, and once only,
did Laplace launch forward, like Kepler, like Descartes, like Leibnitz,
like Buffon, into the region of conjectures. His conception was not then
less than a cosmogony.

All the planets revolve around the sun, from west to east, and in planes
which include angles of inconsiderable magnitude.

The satellites revolve around their respective primaries in the same
direction as that in which the planets revolve around the sun, that is
to say, from west to east.

The planets and satellites which have been found to have a rotatory
motion, turn also upon their axes from west to east. Finally, the
rotation of the sun is directed from west to east. We have here then an
assemblage of forty-three movements, all operating in the same
direction. By the calculus of probabilities