OBSERVATIONS OF A COMET. 



Nucleus. 



Nucleus has a 

 Visible dirk, 



"which is real. 



Apparently 



observation, however, will be added, that any person who 

 may hereafter be in possession of more accurate elements of 

 the comet's orbit, than those which 1 have at present, may 

 repeat the calculations in order to obtain a more accurate rer 

 suit. 



Of the Nucleus. 



From what has already been said, it will easily be tinder? 

 stood, that, by the nucleus of the comet, I mean that part 

 of the head which appears to be a condense3 or solid body, 

 and in which none of the very bright coma is included. It 

 should be remarked, that from this definition it follows, that 

 when the nucleus is very small, no telescope, but what has 

 light and power in an eminent degree, will show it distinctly. 



Observations. 



Oct. 4, 1807. 10-feet reflector. The comet has a nu- 

 cleus, the disk of which is plainly to be seen. 



Oct. 6. I examined the disk of the comet with a proper 

 set of diaphragms, such as described in a former paper*, 

 in order to see whether any part of it were spurious ; but 

 when the exterior light was excluded, so far from appearing 

 larger, as would have been the case with a spurious disk, it 

 appeared rather diminished for want of light; nor was its 

 diameter lessened when I used only the outside rays of tiie 

 mirror. The visible disk of the comet therefore is a real 

 one. 



Oct. 4. I viewed the comet with different magnifying 

 powers, but found that its light was not sufficiently intense 

 to bear very high ones. As far as 200 and 300, my ]0 feet 

 reflector acted very well, but with 400 and 500 there was no? 

 thing gained, because the exertion of a power depending 

 on the quantity of light was obstruetedf, which I found was 

 here of greater consequence than the increase of magnitude. 



Illumination of the Nucleus. 

 Oct. 4, Ch. 15/ The nucleus is apparently round, an4 



* See Phil. Trans, for 1805, page 53. Use of the Criterion 

 + See Phil. Trans, for 1800, p. j8. 



equally 



