In fact, two entirely different orbits would satisfy the
observations fairly, though one only could be regarded as satisfying
them well.
This orbit, however, was so remarkable that astronomers were led to
prefer the other, less satisfactory though it was, in explaining the
observed motions of the comet. For the orbit which best explained the
comet's movements carried the comet so close to the sun as actually to
graze his visible surface.
Moreover, there was this remarkable, and, indeed, absolutely unique
peculiarity about the orbit thus assigned: the comet (whose period of
revolution was to be measured by hundreds of years) actually passed
through the whole of that part of its course during which it was north
of our earth's orbit plane in less than two hours and a half! though
this part of its course is a half circuit around the sun, so far as
direction (not distance of travel) is concerned. That comet, when at its
nearest to the sun, was traveling at the rate of about 330 miles per
second. It passed through regions near the sun's surface commonly
supposed to be occupied by atmospheric matter.
Now, had the comet been so far checked in its swift rush through those
regions as to lose one thousandth part of its velocity, it would have
returned in less than a year. But the way in which the comet retreated
showed that nothing of this sort was to be expected.
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