Grischau's Comet of 1743 (i.), discovered on Feb. 10, 1743, was very imperfectly observed for only a fortnight. Clausen assigned to it an elliptic orbit with a period of 5⋅43 years, and thought that the comet of 1819 (iv.) might be a return of it.
Helfenzrieda's Comet of 1766 (ii.) was discovered at Dillengen on April 1, and remained visible for 6 weeks. It had a tail 3° or 4° long. Burckhardt calculated for it an elliptic orbit, with a period of 5⋅0 years, but it has never been seen since. This is the more remarkable having regard to its size, and that the duration of its visibility was long enough one might suppose for the orbit obtained to be open to no doubt.
Pigott's Comet of 1783 (i.), was discovered at York on Nov. 19. Its orbit was undoubtedly elliptic, and Burckhardt assigned to it a period of 5⋅6 years : other computers obtained a longer period.
Blainpain's Comet of 1819 (iv.) was discovered at Marseilles on Nov. 28, 1819, and was observed at Milan until Jan. 25, 1820, a length of time fully sufficient to have yielded an accurate orbit. Encke investigated it and found it decidedly elliptical with a period of 4⋅8 years; but, strange to say, there have been no modern tidings of the comet.
Peters's Cornet of 1846 (v.) was discovered at Naples on June 26, and observed there till July 21. Peters and D' Arrest agree in ascribing to it an elliptic orbit of short period. Peters's result was 12⋅8 years with an uncertainty of about 1 year. It was badly placed for observation in 1859 and 1872: nor was it seen in 1885 or 1898.
Tuttle's Comet of 1858 (iii.) was discovered at Cambridge, U. S., on May 2. A parabola was supposed at first to satisfy the observations, but subsequently elliptic elements were obtained, and periods of 5⋅8 years and 7⋅5 years were assigned by Schulhof; but nothing further is known of the comet.
Coggia's Comet of 1873 (vii.) was the subject of an elaborate investigation by Weiss, who thought it might be a return of the comet of 1818 (i.), discovered by Pons on Feb. 23, 1818; but he could not satisfy himself whether its period was 55⋅8, 18⋅6, or 6⋅2 years, though he gave the preference to 6⋅2 years.
