OBSERVATIONS OF A COMET. 5 



equally bright all over its disk. I attended particularly to round and uni- 

 its roundness. formly bright. 



Oct. 18* The nucleus is not only round, but also every- 

 where of equal brightness. 



Oct. 19. I see the nucleus again, perfectly round, well 

 defined, aud equally luminous. Its brilliant colour in my 

 10 feet telescope is a little tinged with red; but less so than 

 that of Arcturus to the naked eye* 



Magnitude of the Nucleus. 



Oct. 2G. In order to see the nucleus as small as it really i ts magnitude* 

 is, we should look at it a long while, that the eye may gra- 

 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 7 feet reflector I estimated the diameter Diameter less 

 of the nucleus of the comet at first to be about five seconds, than 3 seconds. 

 but soon after I called it four, and by looking at it longer, 

 I supposed it could not exceed three seconds. 



Oct. 6. 10 feet reflector, power 221. The apparent disk Apparent disk 

 of the comet is much less than that of the Georgian planet, Iess than tha * 

 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,Compared with 

 when high magnifying powers cannot be used, being very globules of 

 little to be depended upon, I erected a set of sealing wax sea U 'S wax ' 

 globules upon a post at 2422 inches from the object mirror 

 of my 10 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 -04G6 of an inch, subtended an angle of 3"*97 

 at the distance of the telescope in the day time. 



Comparing 



