SECT, xxxvi.] VELOCITY OF COMETS. 399 



February, 1846, came, on the 20th of April followiog, nearly 

 as close to Jupiter as his fourth satellite, when Jupiter's 

 attraction must have been ten times greater than that of 

 the sun : so there is every reason to believe that the comet's 

 orbit will be as much altered as that of Lexel's, and another 

 discovered by Padre de Vico at Rome, on the 22nd of 

 August, will, in all probability, be as much disturbed by 

 the same cause. One of the comets found by that astro- 

 nomer has a period which varies according to different 

 computations from 55 to 99 years, though it certainly has 

 an elliptical orbit. That discovered at Naples by Mr. Peter 

 revolves about the sun in 16 years ; but Mr. Giber's comet 

 of 1815 must go nearly the same distance into space with 

 Halley's, since its period is 74 years. Two discovered by 

 M. Brorsen have periods, one of 500 and the other of 28 

 years ; but of the latter there is some uncertainty. 



The comet which appeared in 1596 and 1845 has a period 

 of 249 years, and, should M. Argelander's computation be 

 accurate, the orbit which has hitherto been assigned to the 

 great comet of 1811 must be erroneous, since he has ascer- 

 tained its period to be 3066 years. 



The great comet of 1264, which had a tail that extended 

 over 100 of the celestial vault, was observed and recorded 

 by the Chinese, and was ascertained to be the same that 

 had appeared in 1556, and of whose motions observations 

 were taken at Vienna in the reign of the Emperor Charles 

 V. It was then less brilliant, and on its return in 1848, 

 predicted by Mr. Hind, it was shorn of its glory. Nearly 

 the whole of its orbit lies below the plane of the ecliptic, 

 and far from the paths of the larger planets, but it extends 

 into space more than twice the distance of Neptune, or 

 nearly six thousand millions of miles from the sun. 



Comets in or near their perihelion move with prodigious 

 velocity. That of 1680 appears to have gone half round the 

 sun in ten hours and a half, moving at the rate of 880,000 



