in a dustlike or vaporous condition, and that the weight of these
bodies is relatively very small.

[Illustration: Fig. 2.--The Great Comet of 1811, one of the many
varied forms of these bodies.]

Owing to their strange appearance, comets were to the ancients omens
of calamity. Sometimes they were conceived as flaming swords; their
forms, indeed, lend themselves to this imagining. They were thought to
presage war, famine, and the death of kings. Again, in more modern
times, when they were not regarded as portents of calamity, it was
feared that these wanderers moving vagariously through our solar
system might by chance come in contact with the earth with disastrous
results. Such collisions are not impossible, for the reason that the
planets would tend to draw these errant bodies toward them if they
came near their spheres; yet the chance of such collisions happening
to the earth is so small that they may be disregarded.


MOTIONS OF THE SPHERES.

Although little is known of the motions which occur among the
celestial bodies beyond the sphere of our solar family, that which has
been ascertained is of great importance, and serves to make it likely
that all the suns in space are upon swift journeys which in their
speed equal, if they do not exceed, the rate of motion among the
planetary spheres, which may, in general, be reckoned at about twenty
miles a second. Our whole solar system is journeying away from certain
stars, and in the direction of others which are situated in the
opposite part of the heavens. The proof of this fact is found in the