with Remarks on its Construction. 231 
looking away from the telescope, I mentally reviewed the im- 
pression its appearance had made on the imagination, in order 
to see whether it was a faithful picture of the object ; and by 
looking again into the telescope I was satisfied of the simi- 
litude. 
In the next place I used a deeper magnifier, and alternately 
viewed and remembered the appearance of the nucleus. It 
was fainter with this power. 
The third observation Was made in the same manner with 
a magnifier of 170. This showed the nucleus of a larger dia- 
meter, but much less bright, and not so well defined. 
The next morning, having recourse to my usual experiment 
with a set of globules, by viewing them at a given distance 
with the same telescope and eye-glasses, I found that one of 
them, on which I fixed, gave me, as nearly as could be esti- 
mated, the same magnitude with the first eye-glass, and was 
proportionally magnified by the second and third, with only 
this difference, that the highest power showed the globule with 
more distinctness than it did the nucleus ; and by trigonome- 
try the angle under which I saw the globule was found to be 
5", 2744.* 
It will be necessary to mention that in the calculations be- 
longing to this comet, I have used the elements of Mr. Gaus, 
with a small correction of the longitude of the perihelion, 
which I found would answer the end of giving the observed 
place with sufficient accuracy from the 1st of January to the 
• I prefer this method of ascertaining the small diameter of a faint object to mea- 
suring it with a micrometer, which requires light to show the wires, and a high 
magnifying power to give an image sufficiently large for mensuration ; neither of 
Which conditions the present comet would admit. 
Hhs 
