system, is the chief ``comet-catcher;'' but he catches them not for
himself, but for the sun. Yet if comets do come originally from
without the borders of the planetary system, it does not, by any
means, follow that they were wanderers at large in space before they
yielded to the overmastering attraction of the sun. Investigation of
the known cometary orbits, combined with theoretical considerations,
has led some astronomers to the conclusion that as the sun travels
onward through space he ``picks up en route'' cometary masses which,
without belonging strictly to his empire, are borne along in the same
vast ``cosmical current'' that carries the solar system.

But while no intelligent person any longer thinks that the appearance
of a great comet is a token from the heavenly powers of the
approaching death of a mighty ruler, or the outbreak of a devastating
war, or the infliction of a terrible plague upon wicked mankind,
science itself has discovered mysteries about comets which are not
less fascinating because they are more intellectual than the
irrational fancies that they have displaced. To bring the subject
properly before the mind, let us see what the principal phenomena
connected with a comet are.

At the present day comets are ordinarily ``picked up'' with the
telescope or the photographic plate before any one except their
discoverer is aware of their existence, and usually they remain so
insignificant in appearance that only astronomers ever see them. Yet
so great is the prestige of the word ``comet'' that the discovery of
one of these inconspicuous wanderers, and its subsequent movements,
become items of the day's news which everybody reads with the feeling,
perhaps, that at least he knows what is going on in the universe even
if he doesn't understand it. But a truly great comet presents quite a