347 
Brightness of the Satellites of Jupiter. 
tude has been compared. To manage the space allotted to the 
figure advantageously, I have used the abbreviations formerly 
employed in my catalogue of Nebulas, v B, c B, B, p B, p F, 
F, c F, v F, for all the gradations of light that are necessary 
to express the brightness of the satellites at the time of ob- 
servation. It will be easily remembered that B and F mean 
bright and faint; and p , c, v, stand for pretty, considerably, 
and very. 
Now, when the observation mentions the brightness of the 
satellite, I place it in the figure as it is given. In that of the 
first, for instance, July 19, 1794, we find the satellite called very 
bright; I therefore put down in fig. 1. (Tab. VIII.) ati27degrees, 
v B. But where the brightness is not expressed, I have recourse 
to the comparative magnitude, if that can be had. By fig. 3. 
(Tab. IX.) it appears that the 2d satellite is less subject to a 
change of brightness than either the 1st or 4th : it becomes, for 
that reason, a pretty good standard for the light of these other 
satellites. Therefore, in the observation of October 2, 1795, for 
instance, where the 1st satellite is described as undoubtedly less 
than the 2d, I put down very faint, or v F, at 341 degrees of 
the circle in fig. 1.; for in the observation of July 19, before 
mentioned, when the satellite was called very bright, it was at 
the same time described as undoubtedly larger than the 2d. 
In this case, as regard must be had to the relative state of the 
satellite we refer to, the four figures I have given will assist .us 
in determining the condition of the light of the satellite we 
wish to admit as a standard. 
In reducing the 2d satellite to the circle, I have generally 
used a reference to the magnitude of the 1st, where marks of 
MDCCXCVII. Z Z 
