212 Biela' s Comet. 



in both perpendicular to the line connecting the two nuclei. 

 The first conjecture was that we had a second comet or a 

 nebula. But they move together with equal velocity, and in 

 the same direction." Challis appears to have been the first 

 European observer of this extraordinary appearance, on the 

 15th of January. Sir John Herschel observed it on the 28th, 

 and remarks, "What surprised me was the roundness of the v 

 almost detached nebula, and its distance." Bessel, at Konigs- 

 berg, remarked the change the same day as Professor Challis. 

 The day before (January 14th), he states that he saw nothing 

 unusual in its appearance, but on the 15th, the air being clear, 

 and the moon not yet risen, he saw quite distinctly two sepa- 

 rated nuclei, the one from three to four times as bright as the 

 other. News afterwards arrived from America that this ex- 

 traordinary phenomena had been seen at Washington as early 

 as January loth, by Lieutenant Maury, who then thought, 

 like Encke, that the smaller nucleus was a nebula, or fainter 

 comet near Biela ; but on January 14th, observing before 

 moonrise, he wrote in his note-book, ' ' Biela has a companion 

 close aboard ! The acolyte is about as faint as Biela was in 

 the moonlight of the 12th. Looking through the corner of my 

 eye, I can catch glimpses of a tail to each. Biela's tail reaches 

 off N.E., and his companion's is nearly parallel with, but slightly 

 inclined towards, it."* The first suspicion of anything unusual 

 was expressed by Mr. Hind, who, on the 19th of December, 

 1845, described the comet as being " somewhat elongated, or 

 pear-shaped," but that circumstance, he tells us himself, w^as 

 merely mentioned as a passing notice, such distortion being 

 not unfrequently noticed in telescopic comets. f 



Both divisions continued to travel together at very nearly 

 the same real mutual distance, although from their respective 

 visual positions, the apparent distance considerably increased. 

 The actual distance, however, from the beginning of February 

 until the middle of March, continued to be about 150,000 

 miles. Meanwhile, some very ' extraordinary changes of ap- 

 pearance manifested themselves. Whereas, at the time of 

 separation, the new, or companion comet, was extremely small 

 and faint in comparison with the other ; this difference 

 gradually diminished until, on the 10th of February, the two 

 were nearly equal. Afterwards, the new comet gained a 

 decided superiority of light over the old, presenting • also a 

 sharp and star-like nucleus. This, however, lasted but a few 

 days, the original comet re-asserting its superiority, and 

 becoming, by February 18th, nearly twice as bright as its 

 companion, which now began to, fade away, and ceased to be 

 visible after the 15th of March, although its originator was 

 * Ast. Notch., No. 561. f Hind's Comets, p. 77. 



