364 HALLEY'S COMET. SECT. XXXV. 



might have been mistaken for a solid nucleus. M. Strove, how- 

 ever, saw a central occultation of a star of the ninth magnitude 

 by the comet, at Dorpat, on the 29th of September. The star 

 remained constantly visible, without any considerable diminution 

 of light ; and, instead of being eclipsed, the nucleus of the comet 

 'disappeared at the moment of conjunction from the brilliancy of 

 the star. The tail increased as the comet approached its peri- 

 helion, and shortly before it was lost in the sun's rays it was 

 between thirty and forty degrees in length. 



According to the observations of M. Valz, the nebulosity 

 increased in magnitude as it approached the sun; but no 

 other comet on record has exhibited such sudden and unac- 

 countable changes of aspect. It was invisible for two months 

 when near its perihelion passage, and when it reappeared on 

 the 24th of January, 1836, its aspect was completely changed ; 

 it had no tail, and to the naked eye was like a hazy star ; but 

 with a powerful telescope it presented a small, round, planetary- 

 looking nucleus 2" in diameter, surrounded by an extensive 

 coma, and in the centre it had a small, bright, solid part. The 

 nucleus, clear and well defined, like the disc of a planet, was 

 observed on one occasion to become obscure and enlarged in the 

 course of a few hours. But by far the most remarkable circum- 

 stance was the sudden appearance of certain luminous brushes 

 or sectors;, diverging from the centre of the nucleus through the 

 nebulosity. M. Struve describes the nucleus of the comet, in the 

 beginning of October, as elliptical, and like a burning coal, out of 

 which there issued, in a direction nearly opposite to the tail, a 

 divergent flame, varying in intensity, form, and direction, appear- 

 ing occasionally even double, and suggesting the idea of luminous 

 gas bursting from the nucleus. On one occasion M. Arago saw 

 three of these divergent flames on the side opposite the tail, rising 

 through the nebulosity, which they greatly exceeded in brilliancy : 

 after the comet had passed its perihelion, it acquired another of 

 these luminous fans, which was observed by Sir John Herschel 

 at the Cape of Good Hope. Hevelius describes an appearance 

 precisely similar, which he had witnessed in this comet at its 

 approach to the sun in the year 1682, and something of the kind 

 seems to have been noticed in the comet of 1744. Possibly the 

 second tail of the comet of 1724, which was directed towards the 

 sun, may have been of this nature. 



