We have hitherto
considered the primary planets, their satellites, and the concentric rings
which belong to one, at least, of the outermost planets, as products of
tangential force, and as closely connected together by mutual attraction; it
therefore now only remains for us to speak of the unnumbered host of
'comets' which constitute a portion of the cosmical bodies revolving in
independent orbits round the Sun. If we assume an equable distribution of
their orbits, and the limits of their perihelia, or greatest proximities to
the Sun, and the possibility of their remaining invisible to the inhabitants
of the Earth, and base our estimates on the rules of the calculus of
probabilities, we shall obtain as the result an amount of myriads perfectly
astonishing. Kepler, with his usual animation of expression, said that
there were more comets in the regions of space than fishes in the depths of
the ocean. As yet, however, there are scarcely one hundred and fifty whose
paths have been calculated, if we may assume at six or seven hundred the
number of comets whose appearance and passage through known constellations
have been ascertained by more or less precise observations. While the
so-called classical nations of the West, the Greeks and Romans, although
they may occasionally have indicated the position in which a comet first
appeared, never afford any information regarding its apparent path, the
copious literature of the Chinese (who observed nature carefully, and
recorded with accuracy what they saw) contains circumstantial notices of the
constellations through which each comet was observed to pass.
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