bserved
by every one, _because of the great catastrophe which it produced as
soon as it appeared_, the submersion of Bura and Helice."

Comets are by no means rare visitors to our skies, and very few years
have elapsed in historical times without such objects making their
appearance. In the Dark and Middle Ages, when Europe was split up into
many small kingdoms and principalities, it was, of course, hardly
possible for a comet to appear without the death of some ruler occurring
near the time. Critical situations, too, were continually arising in
those disturbed days. The end of Louis le Debonnaire was hastened, as
the reader will, no doubt, recollect, by the great eclipse of 840; but
it was firmly believed that a comet which had appeared a year or two
previously presaged his death. The comet of 1556 is reported to have
_influenced_ the abdication of the Emperor Charles V.; but curiously
enough, this event had already taken place before the comet made its
appearance! Such beliefs, no doubt, had a very real effect upon rulers
of a superstitious nature, or in a weak state of health. For instance,
Gian Galeazzo Visconti, Duke of Milan, was sick when the comet of 1402
appeared. After seeing it, he is said to have exclaimed: "I render
thanks to God for having decreed that my death should be announced to
men by this celestial sign." His malady then became worse, and he died
shortly afterwards.

It is indeed not improbable that such superstitious fears in monarchs
were fanned by those who would profit by their deaths, and yet did not
wish to stain their own hands with blood.

Evil though its effects may have been, this morbid interest which past
ages took in comets has proved of the greatest service to our science.
Had it not been believed that the appearance of these objects was
attended with far-reaching effects, it is very doubtful whether the old
chroniclers would have given themselves the trouble of alluding to them
at all; and thus the modern investigators of cometary orbits would have
lacked a great deal of important material.

We will now mention a few of the most notable comets which historians
have recorded.

A comet which appeared in 344 B.C. was thought to betoken the success
of the expedition undertaken in that year by Timoleon of Corinth against
Sicily. "The gods by an extraordinary prodigy announced his success and
future greatness: a burning torch appeared in the heavens throughout the
night and preceded t