alf of the earth
which chanced to be in sunlight at the time; and if (as could scarcely
fail to happen) the duration of that abnormal splendour were more than
half a day, then the whole earth would probably be depopulated by the
intense heat. The danger, as I have said, is slight--partly because
there is small chance of a collision between the sun and a comet, partly
because we have no certain reasons for assuming that a collision would
be followed by the heating of the sun for a while to a very high
temperature. Looking around at the suns which people space, and
considering their history, so far as it has been made known to us, for
the last two thousand years, we find small occasion for fear. Those suns
seem to have been for the most part safe from any sudden or rapid
accessions of heat; and if they travel thus safely in their mighty
journeys through space, we may well believe that our sun also is safe.
Nevertheless, there _have_ been catastrophes here and there. Now one sun
and now another has blazed out with a hundred times its usual lustre,
gradually losing its new fires and returning to its customary
brightness; but after what destruction among those peopling its system
of worlds who shall say? Spectroscopic analysis, that powerful help to
the modern astronomical inquirer, has shown in one of these cases that
just such changes had taken place as we might fairly expect would follow
if a mighty comet fell into the sun. If this interpretation be correct,
then we are not wholly safe. Any day might bring us news of a comet
sailing full upon our sun from out the depths of space. Then astronomers
would perhaps have the opportunity of ascertaining the harmlessness of a
collision between the ruler of our system and one of the long-tailed
visitors from the celestial spaces. Or possibly, astronomers and the
earth's inhabitants generally might find out the reverse, though the
knowledge would not avail them much, seeing that the messenger who would
bring it would be the King of Terrors himself.

It was well, perhaps, that Newton's discovery of the law of gravitation,
and the application of this law to the comets of 1680 and 1682 (the
latter our old friend Halley's comet, then properly so called as studied
by him), came in time to aid in removing to some slight degree the old
superstitions respecting comets. For in England many remembered the
comets of the Great Plague and of the Great Fire of London. These comets
came so closel