The Returning Comet of 1812 [pp. 278-283]

280 TirE RETURArING COMET OF 1812. [Nov.,
the comet itself would apparently occupy among the stars at
those times? To this it must be answered that such a thing
would be highly desirable; it is often done when our knowledge
is precise enough, and the result is what we call an ephemens
simply, without any "sweeping" about it. But the difficulty of
doing it in this case was this: that though, as has been said, we
knew the position and shape of the orbit very accurately, at least
in its nearer portions, we did not know with sufficient accuracy
the position of the comet in that orbit. It had, indeed, been predicted that it would arrive at perihelion in September, i88~ but
this result was confessedly liable to great error one way or the
other, so that no one could say with certainty at any time wh&
ther the comet would be one hundred millions or three hundred
millions of miles from the sun. It was like an expected train,
with the telegraph broken down: we know it is somewhere on
the track, but where it is no one can tell till he sees it.
Such was the state of things at the beginning of September
just past. At that time Mr. W. R. Brooks, of Phelps, N. Y., announced the detection by himself of an object suspected to be a
comet. He telegraphed its position among the stars to other astronomers, that they might observe it and help to determine its
orbit, should it be a comet, as soon as possible. After a few
days, observations were obtained sufficient for the computation
of an orbit, which was,assumed, as it is always with new comets,
to be parabolic in form.
Well, now, it may be asked, was this comet of Mr. Brooks
anywhere on the line corresponding to that date in the sweeping
ephemeris for the comet of 1812? If so, surely it would have
been suspected at once as being that object. The answer is that
it was not on that line, or rather that the line was not on it;
though it ought to have been, as will be seen subsequently. The
new comet was, therefore, not suspected of identity with the
expected visitor, and vaflou~s calculations of its path from the
present observations alone were made, which did not agree very
well with each other. This discordance was probably partly
owing to the considerable error of the assumption which had
been made as to the parabolic form of the orbit; but it was
ascribed rather to the shortness of time as yet elapsed since
discovery and the Slowness of the comet's apparent motion.
Further calculation was, therefore, postponed till more observations should have been made.
It is principally by the discordance of these orbits, and the
want of confidence in them, that the failure of astronomers to