oo Dr. Herschel’s observations of the satellites 
sufficient to keep the satellites in view, by way of ascertaining 
their identity ; for unless they were followed in their course 
and known to be satellites, it would have been endless to 
' measure either the distance or position of every small star 
that might have the appearance of one ; and as the opportu- 
nities for taking measures, which require a very clear and 
undisturbed atmosphere, were scarce, and often interrupted 
by cloudy or moonlight nights, the identity of the satellites 
would have been doubtful if their position had not been attended 
to, when seen in unfavourable circumstances. When no other 
stars interfered, it was often sufficient barely to mention the 
quadrant in which they were seen, by recording that such a 
satellite was np, nf, sf, or sp; or if necessary, some rather 
more determined account, such as 40 or 50 degrees np, sf, &c. 
As a check upon the description of the situations, a figure 
was always added to represent the planet, its satellites and 
the neighbouring stars as they appeared in the telescope. 
Very often indeed the configuration itself was deemed to be 
sufficient to point out the situation of the satellites, which by 
way of distinction were marked by numbered points ; 1 and 2 
being used to distinguish the known satellites ; 3, 4, 5, &c. 
those that might possibly be other suspected, but not ascer- 
tained ones. Stars instead of points, were marked by aste- 
risks. 
More careful estimations were made with a power not less 
than 300, and a wire in the focus of the eye glass, to ascer- 
tain the parallel ; they are capable of considerable accuracy 
in situations that are only a few degrees north or south pre- 
ceding or following, and also when the position of a satellite 
is nearly 90 degrees north or south of the planet. 
/ 
