A Journey in Other Worlds
Much of the material was like slag from a furnace, having evidently been partly fused.
Whether this heat was the result of collision or of its near approach to the sun at
perihelion, they could not tell, though the latter explanation seemed most simple and
probable. When at about the centre of the nucleus they were in semi-darkness--not
twilight, for any ray that succeeded in penetrating was dazzlingly brilliant, and the
shadows, their own included, were inky black. As they approached the farther side and
the sunlight decreased, they found that a diffused luminosity pervaded everything. It was
sufficiently bright to enable them to see the dark side of the meteoric masses, and, on
emerging from the nucleus in total darkness, they found the shadow stretching thousands
of miles before them into space.
"I now understand," said Bearwarden, "why stars of the sixth and seventh magnitude can
be seen through thousands of miles of a comet's tail. It is simply because there is nothing
in it. The reason ANY stars are obscured is because the light in the tail, however faint, is
brighter than they, and that light is all that the caudal appendage consists of, though what
produces it I confess I am unable to explain. I also see why the tail always stretches away
from the sun, because near by it is overwhelmed by the more powerful light; in fact, I
suspect it is principally in the comet's shadow that the tail is visible. It is strange that no
one ever thought of that before, or that any one feared the earth's passing through the tail
of a comet. It is obvious to me now that if there were any material substance, any gas,
however rarefied, in this hairlike accompaniment, it would immediately fall to the
comparatively heavy head, and surround that as a centre."
 Comet means literally a hair.
"How, then," asked Cortlandt, "do you account for the spaces between those stones?
However slight gravitation might be between some of the grains, if it existed at all, or
was unopposed by some other force, with sufficient time--and they have eternity--every
comet would come together like a planet into one solid mass. Perhaps some similar force
maintains gases in the distended tail, though I know of no such, or even any analogous
manifestation on earth. If the law on which we have been brought up, that 'every atom in
the universe attracts every other atom,' were without exceptions or modifications, that
comet could not continue to exist in its present form. Until we get some additional
illustration, however, we shall be short of data with which to formulate any iconoclastic
hypothesis. The source of the light, I must admit, also puzzles me greatly. There is
certainly no heat to which we can attribute it."
Having gone beyond the fragments, they applied a strong repulsion charge to the comet,
creating thereby a perfect whirlpool among its particles, and quickly left it. Half an hour
later they again shut off the current, as the Callisto's speed was sufficient.
For some time they had been in the belt of asteroids, but as yet they had seen none near.
The morning following their experience with the comet, however, they went to their
observatory after breakfast as usual, and, on pointing their glasses forward, espied a
comparatively large body before them, a little to their right.