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far we have been considering comets which are either known for a certainty to be revolving in elliptic orbits, and which have themselves verified the fact by returning one or more times to our view, or comets, the ellipticity of whose orbits seems open to no doubt, but which have not yet fulfilled the predictions which have been made in respect of them. It now becomes necessary to speak of some comets, to 3 of which in particular an extraordinary amount of unsolved mystery attaches.

This comet has already been mentioned, but something more needs to be said in regard to its claims to be considered a short-period comet.

Astronomers in the present day have to lament the "loss" of several comets which, at first, were regarded as assured members of the Solar System, because of the comparative smallness of their orbits, and the apparent certainty that their periods of revolution were under 10 years, but this loss is not unprecedented, and the comet which we have now to consider is not only the oldest, but in some senses the most notable instance which can be adduced of a "lost" comet.

On June 14, 1770, Messier at Paris discovered a fairly