[6] Grant's _Hist. Ph. Ast_., p. 267.

[7] _Nature_, November 12th, 1908.

[8] _Ast. Nach_., Nos. 791, 792, 814, translated by G. B. Airy.
_Naut. Alm_., Appendix, 1856.



14. COMETS AND METEORS.


Ever since Halley discovered that the comet of 1682 was a member of
the solar system, these wonderful objects have had a new interest for
astronomers; and a comparison of orbits has often identified the
return of a comet, and led to the detection of an elliptic orbit where
the difference from a parabola was imperceptible in the small portion
of the orbit visible to us. A remarkable case in point was the comet
of 1556, of whose identity with the comet of 1264 there could be
little doubt. Hind wanted to compute the orbit more exactly than
Halley had done. He knew that observations had been made, but they
were lost. Having expressed his desire for a search, all the
observations of Fabricius and of Heller, and also a map of the comet's
path among the stars, were eventually unearthed in the most unlikely
manner, after being lost nearly three hundred years. Hind and others
were certain that this comet would return between 1844 and 1848, but
it never appeared.

When the spectroscope was first applied to finding the composition of