Some of those that have flashed into sight recently have been comparatively small, and their contact with
{p. 89}
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THE EARTH'S ORBIT
the earth might produce but trifling results. Others, again, are constructed on an extraordinary scale; but even the largest of these may be but children compared with the monsters that wander through space on orbits
{p. 90}
that penetrate the remotest regions of the solar system, and even beyond it.
When we consider the millions of comets around us, and when we remember how near some of these have come to us during the last few years, who will undertake to say that during the last thirty thousand, fifty thousand, or one hundred thousand years, one of these erratic luminaries, with blazing front and train of débris, may not have come in collision with the earth?
{p. 91}