Mr Dunlop's observations on the Comet of 1825. 89 



branch is increased in length, but is yet much fainter than any 

 of the others. 



At 10 h 40', the new branch on the preceding side is fully 2° 

 in length, and the nebulosity is extending to a greater distance 

 round the head. (Fig. 9.) 



Oct. 18th. — At ll h 13' mean time, the tail of the comet is 

 about 12° in length ; the following side is slightly concave near 

 the head ; there is a small branch about half a degree in length, 

 shooting out on the following side from the head. The comet 

 is pretty bright, although the moon is present. (Fig. 10.) 



Oct. 19th. — At 10 h 40' mean time, although the moonlight 

 is very considerable, I can trace the tail of the comet 8° or 9° 

 in length. It is composed of a principal or central branch, with 

 a smaller and fainter branch on each side, proceeding from the 

 head ; the branch on the preceding side is brighter and longer 

 than that on the following side, rather less than two degrees 

 from the head. The rays of the tail seem to cross each other, 

 and diverge much the same as the rays of light through a con- 

 vex lens. Fig. 11. will better explain it. A note to the obser- 

 vation says, — I have no doubt as to the apparent crossing of 

 the rays near the head. 



Oct. 20th. — At 10 h 36', the moonlight is too strong to per- 

 mit satisfactory observations ; the tail appears really to be short- 

 er than it was last night, and I am convinced it is. It appears 

 pretty bright for about 3° from the head ; and for about 2° it 

 is faint and difficult to trace its existence. Again, towards the 

 extremity it appears brighter, and I am sensible of its exist- 

 ence for about 7°> hut cannot trace it farther. There are also 

 branches, about 3° long, shooting out on each side from the 

 head, but cannot say which is the longest ; they are both very 

 faint. (See Fig. 12.) 



Oct. 21st. — At 10 h 32' the comet is pretty bright ; the head 

 and tail of a regular figure ; but the clouds prevent me from 

 making such observations as I could wish. See the figure. 



Oct. 24}th.—At 10 h 40' the comet has decreased considera- 

 bly. I cannot trace the tail above 3^° in length ; the head is 

 pretty bright, and the nucleus is in the centre of the head ; and 

 the tail is of a uniform figure, but cannot trace it more than 3° 

 in length. 



At ll h 15' the appearance much the same. 



