to the Principia of Newton, which it supplements
and in a sense completes.

In the closing years of the eighteenth century Laplace
took up the nebular hypothesis of cosmogony, to
which we have just referred, and gave it definite
proportions; in fact, made it so thoroughly his own
that posterity will always link it with his name.
Discarding the crude notions of cometary impact
and volcanic eruption, Laplace filled up the gaps in
the hypothesis with the aid of well-known laws of
gravitation and motion. He assumed that the primitive
mass of cosmic matter which was destined to
form our solar system was revolving on its axis
even at a time when it was still nebular in character,
and filled all space to a distance far beyond the
present limits of the system. As this vaporous mass
contracted through loss of heat, it revolved more
and more swiftly, and from time to time, through balance
of forces at its periphery, rings of its substance
were whirled off and left revolving there, subsequently
to become condensed into planets, and in their turn
whirl off minor rings that became moons. The main
body of the original mass remains in the present as the
still contracting and rotating body which we call the
sun.

Let us allow Laplace to explain all this in detail:

"In order to explain the prime movements of the