COMETS OF SHORT PERIOD. 191 



until its re-discovery in 1826 that its orbit and period 

 were computed. An ellipse of moderate eccentricity, 

 extending beyond the orbit of Jupiter, was assigned 

 as the comet's orbit the period of revolution being 

 about six and a half years. The orbit was found to pass 

 within about twenty thousand miles of the earth's 

 orbit; and at the first return of the comet (in 1832), 

 some alarm was experienced lest the near approach of 

 the two bodies should lead to mischief of some sort. 

 The comet returned again in 1839 and 1845. It was 

 at the last-mentioned return that a singular pheno- 

 menon occurred, which is nearly unique in the 

 history of comets. On the 19th of December 1845, 

 Hind noticed a certain protuberance on the comet's 

 northern edge. Ten days later, observers in North 

 America noticed that the comet had separated into 

 two distinct comets, similar in form, and each having 

 a nucleus, a coma, and a tail. European observers did 

 not recognise the bi-partition of the comet until the 

 middle of January 1846. The new and smaller comet 

 appears to have sprung into existence from the pro- 

 tuberance observed by Hind, since this object moved 

 towards the north of the other. After a while, the new 

 comet became the brighter, but, shortly after, it re- 

 sumed its original relative brilliancy. Lieutenant 

 Maury noticed, on one occasion, a faint 'bridge-like 

 connection' between the two comets. The distance 

 between them gradually increased, until first the new 

 comet, and then the old one, had passed out of view. 

 In 1852, Biela's comet was again seen, and the 



