Observations of a* Comet. 5# 



dually lose the impression of the bright coma which sur- 

 rounds it. This impression will diminish gradually ; and 

 when the eye has got the better of it, the nucleus will then 

 be seen most distinctly, and of a determined magnitude. 



Oct. 4. With a ia ven-i'eet reflector I estimated the dia- 

 meter of the nucleus of the Comet at first to be about five 

 Seconds ; but earni after I called it four, and by looking at it 

 Ion c-r, t supposed it could uot exceed, three seconds. 



Oct. 6. W I •.; -ctor, power 221. The apparent disk 

 of the comet is much less than that of the Georgian planet, 

 which being an object I have seen so often with the same in- 

 strument, and magnifying power, this estimation from me- 

 mory cannot be very erroneous. 



Oct. 5. Micrometers for measuring very small diameters, 

 when high magnifying powers cannot be used, being very 

 little to be depended upon, I erected a s?t of sealing-wax 

 globules upon a post at 2422 inches from the object mirror 

 of my ten-feet reflector, and viewed them with an eye glass, 

 which gives the instrument a power of 221, this being the 

 same which I had found last night to show the nucleus of 

 the comet well. I kept them in their place all the day, and 

 reviewed them from time to time, that their magnitudes 

 might be more precisely remembered in the evening, when 

 I intended to compare the appearance of the nucleus with 

 them. 



On examining the comet, I found the diameter of its nu- 

 cleus to be certainly less than the largest of my globules, 

 which, being '0166 of an inch, subtended an angle of 3"*97 

 at the distance of the telescope in the day time. 



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"*4 7, 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- 

 tends 2-7 7. 



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

 met 40 mmutes after five ; and being now at a considerable 



altitude^ 



