Observations on the Tails of Halley^s Comet. 15i 



at the place where it joins the head. At the latter place, its width 

 appears to be about two thirds that of the head. The head appears 

 rather larger, though fainter, than a star of the first magnitude. 

 That part of the tail seen by indirect vision, the faint, narrow and 

 apparently straight tail of equable width, extends into the constel- 

 lation Lyra : the length of the whole tail is about thirty Jive de- 

 grees, which is 10° less than last evening. The sky is much less 

 clear than on last night, and the envelope condensed on one side to 

 form the short tail is indistinct, yet its direction and form seem not 

 to have been sensibly changed since last evening. 



Oct. 18, 7 P. M. — Tail as seen with the naked eye fixed stead- 

 ily on it, 9° in length ; by indirect vision, about 18°. Seen directly 

 it is longer, and indirectly, shorter than it was on the I6th. The 

 atmosphere appears to be less clear. In consequence of this, and 

 of the wind, the nucleus is not discernible. 



Oct. 19, 7A. 30m. P. M. — Length by direct vision, about 6°; 

 by indirect vision, about 18°: sky clear near it at the time. It 

 being windy and cloudy, the large telescope was not taken out. 



Oct. 22, 7 P. M. — Tail directed to /3 Serpentarii; length by 

 indirect vision about 9°, by direct vision about 2° 30'. Nucleus 

 not discernible. 



Oct. 23. — Tail fainter than on the preceding evening. 



Oct. 24, 7 P. M. — Length as seen by indirect vision, about 12° ; 

 by direct vision, about 3°. The sky is quite clear; but there is 

 considerable wind. It is probably owing to this circumstance, and 

 to the comet's distance, and to its small altitude after the disappear- 

 ance of the moon and twilight, that the nucleus could not, this eve- 

 ning, be seen with sufficient distinctness to enable me to determine 

 on which side of it the nebulous matter was most dense and elonga- 

 ted. If the nucleus was seen, it must have been somewhere near 

 the upper part. 



Oct. 25, Evening. — Tail directed about towards a Aquilse ; length 

 by indirect vision, about 3° ; by direct vision about 30'. The sky 

 is clear and the air still, but there is a new moon. The head ap- 

 pears to the naked eye about as large as a star of the second mag- 

 nitude. A kind of nucleus is visible with the telescope, with which 

 the tail and envelope are also distinctly seen. 



I am inclined to think that there have been seen at difierent times, 

 two apparent nuclei of different orders ; and that the smallest one, 

 seen when the comet was nearer, had a situation at one extremity 



