Biela's Comet. 213 



seen until nearly the end of April. Another curious phenome- 

 non was noticed in America in February. The companion 

 comet, besides its tail, extending in a direction parallel to that 

 of the other, threw out a faint streak of light, like a bridge, to- 

 wards the other, whilst the latter threw out additional rays, 

 presenting the appearance of a cometary nucleus with three 

 tails, one forming an archway of cometary matter extending to 

 the nucleus of the companion comet. 



The comet was also observed after its division by Otto 

 Struve, with the great refractor at the magnificent observatory 

 at Pulkowa, in Russia, of which place his distinguished father, 

 Wilhelm Struve, was then Director, and in which, since his 

 father's death, he has so worthily succeeded to his office. 

 From his observations on the 19th and 21st of February, the 

 drawings were made, representations of which are given in 

 Figs. 1 and 2 of our Plate. They show the change in the 

 appearances of the two nuclei during that short time. 



At this return the comet's perihelion passage took place 

 on the 11th of February. The last day it was observed was 

 on the 27th of April, by Professor Argelander, at Bonn, near 

 Cologne. 



Of course its next apparition was eagerly expected, though, 

 from its position on that occasion, it could only be visible for a 

 short time. Again was it first seen at Rome ; this time by 

 Father Secchi,* on the 26th of August, 1852, at about half- 

 past 3 o'clock in the morning. Shortly after that hour, it 

 centrally covered a small star of the 9-10th magnitude, pro- 

 ducing the appearance only of a slight nebulosity surrounding 

 the star. On the morning of the sixteenth of September, the 

 same astronomer saw also the separated companion comet : 

 it was very faint, without nucleus, and of elongated figure, the 

 elongation being on the opposite side to the sun. The obser- 

 vation was altogether very difficult, because, almost as soon as 

 the comet got out of the mists of the horizon, its light was 

 enfeebled by the increasing twilight. Two nights afterwards 

 it was observed at Berlin. Subsequently it was seen at Cam- 

 bridge : the shape was elongated, but the companion was not 

 perceived. There was, however, another witness of the con- 

 tinued duplicity, namely, Otto Struve, who again observed the 

 comet with the powerful refractor at Pulkowa, near St. Peters- 

 burg. He first saw it on the 18th of September, but could 

 then only perceive one of the nuclei, which proved to be the 

 northernmost of the two, and not the one first seen at Rome, 

 which was the only one observed at Cambridge, so much had 

 the relative brightness changed. Struve describes it as being 

 in amount of light about equal to a star of the 8-9th magni- 

 * AsL Nach., No. 822. 



