s successors have always assumed that it was impossible for the
principle of gravity to be true, and a Cartesian plenum also;
consequently, the question has not been fairly treated. It is true that
Descartes sought to explain the motions of the planets, by the
mechanical action of a fluid vortex _solely_; and to Newton belongs the
glorious honor of determining, the existence of a centripetal force,
competent to explain these motions mathematically, (but not physically,)
and rashly rejected an intelligible principle for a miraculous virtue.
If our theory be true, the visible creation depends on the existence of
both working together in harmony, and that a physical medium is
absolutely necessary to the existence of gravitation.

If space be filled with a fluid medium, analogy would teach us that it
is in motion, and that there must be inequalities in the direction and
velocity of that motion, and consequently there must be vortices. And if
we ascend into the history of the past, we shall find ample testimony
that the planetary matter now composing the members of the solar system,
was once one vast nebulous cloud of atoms, partaking of the vorticose
motion of the fluid involving them. Whether the gradual accumulation of
these atoms round a central nucleus from the surrounding space, and thus
having their tangential motion of translation converted into vorticose
motion, first produced the vortex in the ether; or whether the vortex
had previously existed, in consequence of conflicting currents in the
ether, and the scattered atoms of space were drawn into the vortex by
the polar current, thus forming a nucleus at the centre, as a necessary
result of the eddy which would obtain there, is of little consequence.
The ultimate result would be the same. A nucleus, once formed, would
give rise to a central force, tending more and more to counteract the
centripulsive power of the radial stream; and in consequence of this
continually increasing central power, the heaviest atoms would be best
enabled to withstand the radial stream, while the lighter atoms might be
carried away to the outer boundaries of the vortex, to congregate at
leisure, and, after the lapse of a thousand years, to again face the
radial stream in a more condensed mass, and to force a passage to the
very centre of the vortex, in an almost parabolic curve. That space is
filled with isolated atoms or planetary dust, is rendered very probable
by a fact discovered by Str