Comets lost or strayed: the comet of 1743; the comet of Lexell, or 1770; perturbations caused by Jupiter; in 1767 the action of Jupiter shortens the period, and in 1779 produces an opposite effect–Comet of De Vico; short period comets of 1783, 1846, and 1873.

During the month of February 1743 a comet was observed at Paris, Bologna, Vienna, and Berlin whose parabolic elements were calculated by Struyct and Lacaille. A mathematician of our time, M. Clausen, identified it as a comet of short period, performing its revolution in five years and five months. Is this, as has been supposed, the same comet that was seen in November 1819? If so, its period must have greatly changed, since the calculations of Encke assign to the latter a period of about four years and ten months.

The comet of which we are now about to speak is celebrated in the history of astronomy. The following extract from a memoir by M. Le Verrier gives an account of the circumstances of its first apparition:–

‘ Messier perceived, during the night of the 14–15th of June, 1770, a nebulosity situated amongst the stars of Sagittarius, but not discernible by the naked eye ; it was a comet first coming into view. On the 17th of June it appeared surrounded by an atmosphere the diameter of which was about 5′ 23″. In the centre appeared a nucleus; its light was bright, like that of the stars. Messier estimated its diameter at 22 seconds.