The comets which might be included under the above head are so numerous as to make it impossible for all to receive proper attention; we must therefore limit ourselves to some of the most interesting, commencing with—

The Comet of 1858 (vi). On June 2 in that year Dr. G. B. Donati, at Florence, descried a faint nebulosity slowly advancing towards the north, and near the star λ Leonis. Owing to its immense distance from the Earth (240,000,000 miles), great difficulty was experienced in laying down its orbit. By the middle of August, however, its future course, and great increase of brightness in September and October, had been ascertained with entire certainty. Up to this time (middle of August) it had remained a faint object, not discernible by the unaided eye. It was distinguished from ordinary telescopic comets only by the extreme slowness of its motion (in singular contrast to its subsequent career), and by the vivid light of its nucleus: “ the latter peculiarity was of itself prophetic of a splendid destiny.” Traces of a tail were noticed on August zo, and on August 29 it was faintly perceptible to the naked eye; for a few weeks it occupied a northern position in the heavens, and was thus seen both in the morning and evening sky.