According to some calculations, the comet of 1843 seemed to have a
period of about thirty-five years, which accorded well with the idea
that it was the comet of 1668, returned after five circuits. Nor was it
deemed at all surprising that the comet, conspicuous though it is, had
not been detected in 1713, 1748, 1783, and 1818, for its path would
carry it where it would be very apt to escape notice except in the
southern hemisphere, and even there it might quite readily be missed.
The appearance of the comet of 1668 corresponded well with that of the
comet of 1843. Each was remarkable for its extremely long tail and for
the comparative insignificance of its head. In the northern skies,
indeed, the comet of 1843 showed a very straight tail, and it is usually
depicted in that way, whereas the comet of 1668 had a tail showing
curvature. But pictures of the comet of 1843, as seen in the southern
hemisphere, show it with a curved tail, and also the tail appeared
forked toward the end during that part of the comet's career.
However, the best observations, and the calculations based on them,
seemed to show that the period of the comet of 1843 could not be less
than 500 years.
Astronomers were rather startled, therefore, when, in 1880, a comet
appeared in the southern skies which traversed appreciably the same
course as the comets of 1668 and 1843.
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