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648 THE SECRET DOCTRINE.
What has he given so wonderfully new and original, that its groundwork,
at any rate, should have served as a basis for the modern Nebular
Theory The following is what one gathers from various astronomical
works.
I^aplace thought that, in consequence of the condensation of the
atoms of the primeval nebula, according to the "law" of gravity, the
now gaseous, or perhaps, partially liquid mass, acquired a rotatory
motion. As the velocity of this rotation increased, it assumed the form
of a thin disc; finally, the centrifugal force overpowering that of
cohesion, huge rings were detached from the edge of the whirling
incandescent masses, and these rings contracted necessarily by gravitation
(as accepted) into spheroidal bodies, which would necessarily still
continue to preserve the orbit previously occupied by the outer zone
from which they were separated.* The velocity of the outer edge of
each nascent planet, he said, exceeding that of the inner, there results
a rotation on its axis. The more dense bodies would be thrown off
last; and finally, during the preliminary state of their formation, the
newly-segregated orbs in their turn throw off one or more satellites.
In formulating the history of the rupture and planetation of rings
Laplace says
Almost always each ring of vapours must have broken up into numerous masses,
which, moving with a nearly uniform velocity, must have continued to circulate at
the same distance around the sun. These masses must have taken a spheroidal
form with a motion of rotation in the same direction as their revolution, since the
inner molecules (those nearest the sun) would have less actual velocity than the
exterior ones. They must then have formed as many planets in a state of vapour.
But, if one of them was sufficiently powerful to unite successively, by its attraction,
all the others around its centre, the ring of vapours must have been thus transformed
into a single spheroidal mass of vapours circulating around the sun with a
rotation in the same direction as its revolution. The latter case has been the more
common, but the solar system presents us the first case, in the four small planets
which move between Jupiter and Mars.
While few will be found to deny the "magnificent audacity of this
hypothesis," it is impossible not to recognize the insurmountable difficulties
with which it is attended. Why, for instance, do we find that
the satellites of Neptune and Uranus display a retrograde motion
* I^aplace conceived that the external and internal zones of the ring would rotate with the same
angular velocity, which would be the case with a solid ring; but the principle of equal areas requires
the inner zones to rotate more rapidly than the outer. ( World-Life, p. 121.) Prof Winchell points
out a good many mistakes of I^aplace ; but as a geologist he is not infalUble himself in his
"astronomical speculations."