PHENOMENA OF BIELA*S COMET. 



ever witnessed in the heavens, which has been not only seen, 

 but observed with the most scrupulous accuracy in our own 

 times. 



A periodical comet, called Biela's from its discoverer, revolves 

 round the sun in an oval orbit of 6| years. On the occasion of its 

 appearance in 1846, it was seen to resolve itself into two distinct 

 comets, which, from the latter end of December, 1845, to the 

 epoch of its disappearance in April, 1846, moved in distinct and 

 independent orbits. The paths of these two bodies were in such 

 optical juxtaposition, that both were always seen together in the 

 field of view of the telescope, and the greatest visual angle between 

 their centres did not amount to more than a third of the apparent 

 breadth of the moon. 



M. Plantamour, director of the Observatory of Geneva, calculated 

 the orbits of these two comets, considered as independent bodies ; 

 and found that the real distance between their centres was, 

 subject to but little variation while visible, about thirty-nine 

 semi-diameters of the earth, or two-thirds of the moon's 

 distance. The comets moved on thus side by side, without 

 manifesting any reciprocal disturbing action ; a circumstance no 

 way surprising, considering the infinitely minute masses of such 

 bodies. 



The original comet was apparently a globular mass of nebulous 

 matter, semi-transparent at its very centre, no appearance of a 

 tail being discoverable. After the separation, both comets had 

 short tails, parallel in their direction, and at right angles to the 

 line joining their centres ; both had nuclei. From the day of 

 their separation the original comet decreased, and the companion 

 increased in brightness until (on the 10th February) they were 

 sensibly equal. After this the companion still increased in 

 brightness, and from the 14th to the 16th was not only greatly 

 superior in brightness to the original, but had a sharp and starlike 

 nucleus compared to a diamond spark. The change of brightness 

 was now reversed, the original comet recovering its superiority, 

 and acquiring on the 18th the same appearance as the companion 

 had from the 14th to the 16th. After this the companion gradually 

 faded away, and disappeared previously to the final disappearance 

 of the original comet on 22nd April. 



It was observed also that a thin luminous line or arc was 

 thrown across the space which separated the centres of the two 

 nuclei, especially when one or the other had attained its greatest 

 brightness, the arc appearing to emanate from that which for the 

 moment was the brighter. 



After the disappearance of the companion, the original comet 

 threw out three faint tails, forming angles of 120 with each 



