net as the
various planets recede from the sun--

MEAN PERIOD OF VELOCITY IN
DISTANCE. REVOLUTION. ORBIT PER HOUR.

Mercury 35,900,000 87.9 days

Venus 67,000,000 224.7 77.000

Earth 92,700,000 365.2 66.500

Mars 141,000,000 686.9 53.000

Jupiter 482,000,000 4,332.6 28.744

Saturn 884,000,000 10,759. 21.221

Uranus 1,780,000,000 30,687. 14.963

Neptune 2,780,000,000 60,127. 11.958

ART. 100. _Aether and Third Law of Motion._--We have seen (Art. 16) that
action and reaction are equal and opposite, and that it is true of the
centripetal force in its application to all matter throughout the
universe. If, therefore, the centrifugal force is the exact opposite of
the centripetal force, then the Third Law of Motion should equally hold
good in relation to that force also.

We have, therefore, to form a physical conception of the application of
the third law of motion, as it relates to the centrifugal force. As we
have already learned, this force is due to the universal
electro-magnetic Aether, which being gravitative, surrounds all atoms
and molecules that may exist throughout the whole universe. It can
readily be seen, therefore, that if the Aether surrounds every atom and
molecule, then each atom repels another atom or molecule when the two
forces are in equilibrium with exactly the same intensity with which the
atom and molecule attract each other.

But the centrifugal force in each case is due to the pressure of the
Aether, which presses always proportionately to the density of the
Aether surrounding the atom or molecules, as suggested by Professor
Challis.

The mean density, however, of each atomic or molecular atmosphere is
regulated solely by the mass of the atom or planet, therefore the
pressure exerted by one atom on another is proportionate to the mass of
each atom, and to that extent is strictly in accordance with the law
which governs the proportion of the forces between the two atoms or
molecules. If, therefore, we have two atoms, A and B, of different
masses, then it is true that while A exerts a pressure on B, which
pressure takes the form of a repulsion, at the same time B exerts a
pressure on A which is equal and opposite in its cha