Page:The story of the comets.djvu/104

68 Tempel's Comet returned again to perihelion in August 1878. It was seen at Oxford with difficulty in the 12-inch refractor of the University Observatory and resembled a faint round nebula 1' in diameter with a very slight central condensation.

It was missed at its returns in 1883 and again in 1889, but it was seen in 1894 and 1899. In 1899 it was described as a fairly easy object in a 6-inch telescope; but it is thought to have become fainter at each return. A short diffused tail was noticed on a photographic plate. It was seen again during the winter of 1904-5.

On Oct. 10, 1880, Swift, at Rochester. New Jersey, U. S., found a small comet with a very diffused and ill-defined disc several minutes in diameter. It was soon ascertained that the orbit was elliptic with a period of about 6 years, and that the comet was identical with the Comet of 1869 (iii.) discovered by Tempel on Nov. 27, 1869. Hence astronomers designate this object by the very inconvenient title prefixed to this paragraph. The comet was very unfavourably circumstanced for observation at the return of 1874, and escaped detection, not only then but 12 years later, namely, in 1886. But at its next return in 1891 it was detected by Barnard on Sept. 27. Of no particular interest in itself, it may at least be said that its orbit is interesting in so far that when the comet returns to perihelion its position is such that it is alternately favourably and unfavourably placed for observation. Consequently its history thus far is as follows:—Seen in 1869 it was missed in 1875; seen in 1880 it was missed in 1886; seen in 1891 it was missed in 1897, when it passed through perihelion in June but was always at a great distance from the Earth. The above rule did not hold good in 1902 when the comet was due in January, and was not seen in that year; but it was seen again in 1908.