O OBSERVATIONS OF A COMET. 



Comparing the nucleus also with the impressions, which 

 the view of the second and third had left in my memory, and 

 of which the real diameters were *0325 and '0290 of an inch : 

 and magnitudes at the station of the mirror 2""77 and 2"*47> 

 I found, that the comet was almost as large as the second, and 

 a little larger than the third. 



Oct. 18. The nucleus is less than the globule which sub- 

 teuds 2"-77. 



Oct. 19. The air being uncommonly clear, I saw the co- 

 met 40 minutes after five, and being now at a considerable 

 altitude, I examined it with 289, and having but very lately 

 reviewed my globules, I judged its diameter to be not only 

 less than my second globule, but also less than the third : 

 that is, less than 2"*47. 



Oct. 6. The 20-feet reflector, notwithstanding its great 

 light, does not show the nucleus of the comet larger than 

 the 10 feet, with an equal magnifier, makes it. 



Oct. 28. My large. 10 feet telescope, with the mirror of 

 24 inches in diameter, does not increase the size of the nu- 

 cleus. 

 Compared Oct. 6. Being fully aware of the objections, that may be 



wUh theSdsa- m ade against the method of comparing the magnitude of 



tellitfcof Juui- 7 . • ,. , , 



ter. the nucleus ot the comet with objects that cannot be seen 



together, I had recourse to the satellites of Jupiter for a more 



decisive result, and with ray 7 feet telescope, power 202, I 



- viewed the disk of the third satellite and of the nucleus of the 



comet alternately. They were both already too low to be 



seen very distinctly ; the diameter of the nucleus however 



appeared to be less than twice that of the satellite. 



Oct. 18. With the 10 feet reflector, and the power 221, a 



similar estimation was made; but the light of the moon 



would not permit a fair comparison. 



Examined with Oct. 19. I had prepared a new 10 feet mirror, the delicate 



a new mirror. p ij sn G f my former one having suffered a little from being 



exposed to damp air in nocturnal observations. This new 



one being uncommonly distinct, and the air also remarkably 



clear, I turned the telescope from the comet to Jupiter's 



third satellite, aud saw its diameter very distinctly larger 



than the nucleus of the comet. I turned the telescope again 



to the comet, and as soon as I saw it distinctly round and 



well 



