124 2 >. HeRSChel's Observations of a Comet, 
The 9th, it had a very conspicuous one, about 9 or 10 de- 
grees in length. 
On the 18th, the length was 11 or 12 degrees. 
The 6th of October it was 25 degrees. 
The 12th I estimated it to be only 17 degrees long. 
The 14th it appeared to extend to 17^ degrees. 
The 15th, by very careful attention, and in a very clear 
atmosphere, I found the tail to cover a space of 23 \ degrees 
in length. 
The greatest real Length of the Tail. 
Of the two observations which were made of the greatest 
length of the tail of the comet, I prefer that of the 15th of Oc- 
tober, on account of the clearness of the night. 
The apparent length being 23!- degrees, its real extent, 
taking into the calculation the oblique position in which we 
saw it, must have been upwards of 100 millions of miles. 
The Breadth of the Tail. 
The variations in the breadth of the tail will hardly admit 
of any description ; the scattered light of the sides being ge- 
nerally lost by its faintness in such a manner as to render its 
termination very doubtful. 
The 12th of October its breadth in the broadest part was 6| 
degrees, and about 5 or 6 degrees from the head it began to 
be a little contracted. 
The 15th, it was nearly of the same breadth about the middle 
of its length. 
By calculating from the observation of the 12th, we find 
that the real breadth of the tail on that day was nearly 15 mil- 
lions of miles. 
