(13.) Denning's First Periodical Comet (1881, v.).
On Oct. 4, 1881, Denning at Bristol discovered a bright telescopic comet in the constellation Leo. It was circular in form, about 1' in diameter with a slight central condensation. It soon became known that its orbit was elliptical, and its period about 834 years. It was expected to return in 1890 but was not found; the explanation perhaps being that the expected date of its perihelion passage indicated a path unfavourable for observation. As it could not be found in 1899 nor in 1907, in both of which years it was due to return to perihelion, and as its orbit could not be determined very accurately in 1881 for the lack of sufficient observations, this comet must for the present at least be set down as "lost".
The elements bear some resemblance to those of the Comet of 1819, discovered by Blainpain. Winnecke suggested that the comet seen by Goldschmidt at Paris in May 1855, and then regarded as perhaps Di Vice's, and Hind's Comet of 1846 (ix.), may both have been apparitions of Denning's Comet; but it can only be said of this suggestion that it is at best a plausible one.
(14.) Giacobini's First Periodical Comet (1896, v.).
Giacobini at Nice on Sept. 4, 1896, whilst searching for a faint comet discovered by Sperra on Aug. 31, detected a faint comet in Ophiuchus. It soon became evident that it was one of short period, but the early observations yielded very discordant results. In fact the first period obtained was only 17 months. The comet was not seen in 1903, when it was expected on the supposition that its period was 6⋅6 years, according to Ebell's calculation, but the Lick observations imply a period of 9 years.
