This identity involved a conclusion before which more than one
astronomer shrunk. It was necessary to admit that the time of a complete
revolution of the comet was subject to a great variation, amounting to
as much as two years in seventy-six.

Were such great discordances due to the disturbing action of the
planets?

The answer to this question would introduce comets into the category of
ordinary planets or would exclude them for ever. The calculation was
difficult: Clairaut discovered the means of effecting it. While success
was still uncertain, the illustrious geometer gave proof of the greatest
boldness, for in the course of the year 1758 he undertook to determine
the time of the following year when the comet of 1682 would reappear. He
designated the constellations, nay the stars, which it would encounter
in its progress.

This was not one of those remote predictions which astrologers and
others formerly combined very skilfully with the tables of mortality, so
that they might not be falsified during their lifetime: the event was
close at hand. The question at issue was nothing less than the creation
of a new era in cometary astronomy, or the casting of a reproach upon
science, the consequences of which it would long continue to feel.

Clairaut found by a long process of calculation, conducted with great
skill, that the action of Jupiter and Saturn ought to have retarded the
movement of the comet; that the time of revolution compared with that
immediately preceding, would be increased 518 days by the disturbing
action of Jupiter, and 100 days by the action of Saturn, forming a
total of 618 days, or more than a year and eight months.

Never did a question of astronomy excite a more intense, a more
legitimate curiosity. All classes of society awaited with equal interest
the announced apparition. A Saxon peasant, Palitzch, first perceived the
comet. Henceforward, from one extremity of Europe to the other, a
thousand telescopes traced each night the path of the body through the
constellations. The route was always, within the limits of precision of
the calculations, that which Clairaut had indicated beforehand. The
prediction of the illustrious geometer was verified in regard both to
time and space: astronomy had just achieved a great and important
triumph, and, as usual, had destroyed at one blow a disgraceful and
inveterate prejudice. As soon as it was established that the returns of
comets might be calculated bef