It is possible that a comet moving in a parabola or hyperbola, with the sun in the focus, may be thrown into an elliptic orbit by the disturbing influence of Jupiter or one of the other large planets. The celebrated Leverrier undertook to determine whether the comet of Faye had in this manner been recently fixed as a permanent member of the solar system. He found that it could not have been so introduced since 1747, and, consequently, that it must have completed at least thirteen revolutions before its discovery. This comet has been observed at each return from 1843 to the present time. V. De Vico's Comet. On the 22d of August, 1844, De Vico, of Rome, discovered a comet whose orbit is included between those of the earth and Jupiter. Its period is 1996 days, or about 5-1/2 years. This body, from some cause,--perhaps a gradual dissolution,--has not been observed at any subsequent return. VI. Brorsen's Comet. On the 26th of February, 1846, Mr. Brorsen, of Kiel, discovered a faint comet, the mean distance and period of which are almost identical with those of De Vico's. This comet was not observed during the perihelion passage of 1851, on account of its unfavorable position with respect to the sun. It has, however, been subsequently detected. VII. D'Arrest's Comet. Dr. D'Arrest discovered a comet on the 27th of June, 1851, which was soon found to move in an elliptic orbit, with a period of about 6-1/2 years. It entirely escaped observation, both in Europe and America, during its perihelion passage in 1857. It was observed, however, at the Cape of Good Hope. Its invisibility in 1864 was due to its unfavorable position. At its return in 1870, it was first seen on the 31st of August, by Dr. Winnecke, of Carlsruhe. VIII. Tuttle's Comet. A faint telescopic comet was discovered at the Observatory of Harvard College, on the evening of January 4, 1858, by Mr. H. P. Tuttle. The same body was independently found one week later by Dr. Bruhns, of Berlin. From observations made at Cambridge, Massachusetts, and Ann Arbor, Michigan, its elements were soon computed by different astronomers; the result in each case coinciding so closely with the elements of the second comet of 1790, as to place its identity wholly beyond doubt. Its period is nearly 13 years and 8 months. It had returned, therefore, without detection, in the years 1803, 1817, 1831, and 1844. On its approach to perihelion in 1871, it was first detected by M. Borelly, of Marseilles. IX. Winnecke's Comet.