osphere capture a hundred million meteors a day, what would the
millions or billions of times larger net of a nebula catch, even if the
gas is so much thinner? In other words, it is not wise to draw too fine
a line between a gaseous nebula and one consisting of solid particles
with gas.

The more important question is: How do astronomers conceive the
condensation of this mixed mass of cosmic dust? It is easy to reply that
gravitation, or the pressure of the surrounding ether, slowly drives the
particles centre-ward, and compresses the dust into globes, as the boy
squeezes the flocculent snow into balls; and it is not difficult for the
mathematician to show that this condensation would account for the
shape and temperature of the stars. But we must go a little beyond this
superficial statement, and see, to some extent, how the deeper students
work out the process. [*]

* See, especially, Dr. P. Lowell, "The Evolution of Worlds"
(1909). Professor S. Arrhenius, "Worlds in the Making"
(1908), Sir N. Lockyer, "The Meteorite Hypothesis" (1890),
Sir R. Ball, "The Earth's Beginning" (1909), Professor
Moulton, "The Astrophysical Journal (October, 1905), and
Chamberlin and Salisbury, "Geology," Vol. II. (1903).

Taking a broad view of the whole field, one may say that the two chief
difficulties are as follows: First, how to get the whole chaotic mass
whirling round in one common direction; secondly, how to account for the
fact that in our solar system the outermost planets and satellites do
not rotate in the same direction as the rest. There is a widespread idea
that these difficulties have proved fatal to the old nebular hypothesis,
and there are distinguished astronomers who think so. But Sir R. Ball
(see note), Professor Lowell (see note), Professor Pickering (Annals of
Harvard College Observatory, 53, III), and other high authorities deny
this, and work out the newly discovered movements on the lines of the
old theory. They hold that all the bodies in the solar system once
turned in the same direction as Uranus and Neptune, and the tidal
influence of the sun has changed the rotation of most of them. The
planets farthest from the sun would naturally not be so much affected
by it. The same principle would explain the retrograde movement of the
outer satellites of Saturn and Jupiter. Sir R. Ball further works out
the principles on which the particles of the condensing nebula would
tend to form