Some 6,000,000,000
billion tons of the nebulous matter were attracted to a common
centre. As the particles pressed centreward, the temperature
rose, and for a time the generation of heat was greater than its
dissipation. Whether the earth ever shone as a small white star
we cannot say. We must not hastily conclude that such a
relatively small mass would behave like the far greater mass of a
star, but we may, without attempting to determine its
temperature, assume that it runs an analogous course.
One of the many features which I have indicated as pointing to a
former fluidity of the earth may be explained here. We shall see
in the course of this work that the mountain chains and other
great irregularities of the earth's surface appear at a late
stage in its development. Even as we find them to-day, they are
seen to be merely slight ridges and furrows on the face of the
globe, when we reflect on its enormous diameter, but there is
good reason to think that in the beginning the earth was much
nearer to a perfectly globular form. This points to a liquid or
gaseous condition at one time, and the flattening of the sphere
at the poles confirms the impression.
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