230 Dr. Herschel's Observations of a second Comet , 
large a diameter, I doubted whether it could be the body of 
the comet ; but although it might be called very large when 
supposed to be of a planetary construction, it was much too 
small for the condensed light of a head ; its diameter, by esti- 
mation not exceeding 5 or 6 seconds. 
Byway of comparing the two comets together I viewed them 
alternately. The first, within a nebulosity which in the form 
of a brilliant head was of great extent, had nothing resembling 
a nucleus : the light of this head was very gradually much 
brighter up to the very middle ; its small planetary body being 
invisible. The second comet, on the contrary, although sur- 
rounded by a faint chevelure, seemed to be all nucleus ; for 
the abrupt transition from the central light to that of the che- 
velure would not admit of the idea of a gradual condensation 
of nebulosity, such as I saw in the head of the first comet ; but 
plainly pointed out that the nucleus and its chevelure were 
two distinct objects. 
Jan. 8. The comet had a pretty well defined nucleus with 
very faint chevelure. When magnified 170 times the nucleus, 
though less bright, was rather better defined. 
Jan. 1 8. Within a very faint chevelure I saw the nucleus 
as before. 
Jan. 20. The air being uncommonly clear, I saw the body 
of the comet well defined ; and as the moon was already so 
far advanced in its orbit as to render future opportunities of 
viewing the comet very improbable, I ascertained the magni- 
tude of its body, with a very distinct 10 feet reflector, by the 
following three observations. 
First with a low power, which gave a bright image of the 
nucleus, I kept my attention fixed upon its apparent size ; then 
