What had happened? Had some catastrophe occurred in the outer realms of
Space in which some other world had been involved in fiery ruin, or had
the comet been dragged away from its orbit by the attraction of one of
those dead suns, those derelicts of Creation which, dark and silent,
drift for age after age through the trackless ocean of Immensity?

There was no cooler-headed man alive than Gilbert Lennard when it came
to a matter of his own profession and yet the world did not hold a more
frightened man than he was when he went to re-adjust the machinery which
regulated the movement of the great telescope, and so began his search
for the lost comet all over again. One thing only was certain--that the
slightest swerve from its course might make the comet harmless and send
it flying through Space millions of miles away from the earth, or bring
the threatening catastrophe nearer by an unknown number of days and
hours. And that was the problem, here, alone, and in the silence of the
night, he had to solve. The great gun at Bolton and the other at
Pittsburg might by this time be useless, or, worse still, they might not
be ready in time.

It was curious that, even face to face with such a terrific crisis, he
had enough human vanity left to shape a half regret that his
calculations would almost certainly be falsified.

That, however, was only the sensation of a moment. He ran rapidly over
his previous calculations, did about fifteen minutes very hard
thinking, and in thirty more he had found the comet. There it was: a few
degrees more to the northward, and more inclined to the plane of the
earth's orbit; brighter, and therefore nearer; and now the question was,
by how much?

Confronted with this problem, the man and the lover disappeared, and
only the mathematician and the calculating machine remained. He made his
notes and went to his desk. The next three hours passed without any
consciousness of existence save the slow ticking of the astronomical
clock which governed the mechanism of the telescope. The rest was merely
figures and formulae, which might amount to the death-sentence of the
human race or to an indefinite reprieve.

When he got up from his desk he had learnt that the time in which it
might be possible to save humanity from a still impending fate had been
shortened by twelve days, and that the contact of the comet with the
earth's atmosphere would take place precisely at twelve o'clock,
midnight, on the th