er will undoubtedly tend to move with increasing velocity
to the very centre of motion, obeying the great dynamical principle when
unresisted. If resisted, the law will perhaps be modified; but in this
case, its motion of translation will be converted into atomic motion or
heat, according to the motion lost by the resistance of atomic matter.
This question has a bearing on many geological phenomena. As regards the
general effect, however, the present velocity of the ether circulating
round the planets, may be considered much greater than the velocities of
the planets themselves.

PERTURBATIONS DUE TO THE ETHER.

In these investigations it is necessary to bear in mind that the whole
resisting power of the ether, in disturbing the planetary movements, is
but small, in comparison with gravitation. We will, however, show that,
in the case of the planets, there is a compensation continually made by
this resistance, which leaves but a very small outstanding balance as a
disturbing power. If we suppose all the planets to move in the central
plane of the vortex in circular orbits, and the force of the radial
stream, (or that portion which is not in accordance with the law of
gravitation,) to be inversely as the square roots of the distances from
the sun, it is evident, from what has been advanced, that an equilibrium
could still obtain, by variations in the densities, distances and
diameter of the planets. Supposing, again, that the planets still move
in the same plane, but in elliptical orbits, and that they are in
equilibrium at their mean distances, under the influence or action of
the tangential current, the radial stream, and the density of the ether;
we see that the force of the radial stream is too great at the
perihelion, and too small at the aphelion. At the perihelion the planet
is urged from the sun and at the aphelion towards the sun. The density
and consequent momentum is also relatively too great at the perihelion,
which also urges the planet from the sun, and at the aphelion,
relatively too small, which urges the planet towards sun; and the law is
the same in both cases, being null at the mean distance of the planet,
at a maximum at the apsides; it is, consequently, as the cosine of the
planet's eccentric anomaly at other distances, and is positive or
negative, according as the planet's distance is above or below the mean.

At the planet's mean distance, the circular velocity of the vortex is
equal to the cir