CONSTRUCTION OF COMETS, &C. 
193 ' 
distinctly through the rocks which cover it, at a place where 
it sounds like a stream falling into an extensive chamber. 
IX. 
Observations of a second Comet , with Remarks on its Construe - 
tion. By William Herschel, LL. D. F. R. S. 
A S w T e have lately had two comets to observe at the same The present 
time, I have called that of which the following observa- comet differed 
° from the for- 
tions are given, the second. Its appearance has been so totally mer 7 
different from that of the first, that every particular relating to 
its construction becomes valuable; and, notwithstanding the 
unfavourable state of the weather at this time of the year, I 
have been sufficiently successful to obtain a few good views .of 
the phenomena which this comet has afforded. 
A short detail of the observations, in the order of their rela- 
tion to the different cometic appearances, is as follows : 
The Body of the Comet. 
January 1, 1812. — I viewed the second comet with several having a large 
of my telescopes, and found it to have a considerable nucleus ^hevdure!* 1 
surrounded with very faint chevelure. 
Jan. 2. — The comet had a large round nucleus within its 
faint nebulosity. Not seeing it very well defined, and of so 
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 five or six seconds. 
By way of comparing the two comets together, I viewed them The former 
alternately. The first within a nebulosity which, in the forfn ^ e b iflouV head? 
of a brilliant head, was of great extent, had nothing resembling brightest in 
s nucleus : the light of this head was very gradually much tb€ mlddle ’ 
brighter up to the very middle ; its small planetary body being 
invisible. The second comet, on the contrary, although sur- 
:ounded by a faint chevelure, seemed to be all nucleus ; for 
he abrupt transition from the central light to that of the che- 
Vol, XXXV.— No, 163. O velure. 
