Royal Astronomical Society. 151 



Hope, by Piazzi Smyth, Esq. Communicated by Sir John F. W. 

 Herschel, Bart. 



The nucleus of the comet was first seen on the 3rd of March, but 

 it set about ten minutes after its discovery. It was looked at with 

 the 46-inch achromatic telescope, and an approximate observation 

 was attempted, by leaving the telescope fixed, and measuring, the 

 next morning, the azimuth and altitude of the point where it set. 



The nucleus seemed to consist of a planetary disc from which rays 

 emerged in the direction of the tail. To the naked eye there ap- 

 peared a double tail about 25° in length, the two streamers making 

 with each other an angle of about 15', and proceeding from the head 

 in perfectly straight lines. From the end of the forked tail, and on 

 the north side of it, a streamer diverged at an angle of 6° or 7° towards 

 the north, and reached a distance of upwards of 65° from the comet's 

 head ; a star (probably r Ceti) was near the end of this appendage ; 

 a similar, though much fainter, streamer was thought to turn off 

 south of the line of direction of the tail. 



On the 4th of March, Mr. Smyth, accompanied by some friends, 

 went to the Lion's Rump signal station, where the comet would set 

 in a sea horizon, and several distances were taken with sextants and 

 a reflecting circle. These not being reduced sufficiently are not in- 

 serted here. 



On the 5th the comet was seen, and several sextant observations 

 were made. The appearance of the comet on this evening appeared 

 considerably changed ; the angle of the north streamer with the di- 

 rection of the tail had been diminishing and was now south ; it had 

 also diminished in brightness. The total length was about 35°. All 

 the rays proceeding from the head were now of uniform brightness, 

 excepting one bright streak, which could be traced along the 

 tail. 



Though the observatory is very deficient in extra- meridional ap- 

 paratus, Mr. Smyth succeeded, on March 6, by various expedients, 

 in obtaining several comparative measures of the nucleus and neigh- 

 bouring stars, of which the unreduced observations only are given. 

 On this evening he makes the following remarks respecting the ap- 

 pearance of the comet : — " The nucleus is now the broadest part of 

 that end of the comet ; all the rays come from the posterior side, and 

 are pretty equal in brightness, with the exception of a narrow bright 

 streak in the middle, which runs for 3° or 4° along the middle of the 

 tail, and then verges to the north side." The tail this evening was 

 about 27° long. Several sextant observations of distance were made 

 this day. 



On the 8th several differential observations were made. 



On the 9th some good differential observations and some sextant 

 observations were made. The angle of the two sides of the tail at 

 the head appeared to have undergone a gradual diminution, and 

 the middle part was becoming more and more equal in brightness 

 to the sides. 



The paper contains also some observations of Laugier's Comet, 

 and some observations of occupations of stars by the moon. 



