354 
Dr. Herschel/s observations of the satellites 
to the calculated situation of the satellite in its orbit, is to be 
found by the tabular quantity 104° 45', which is the distance 
of the ascending node from the zero of that circle ; and as 
the satellite is 5 0 18' from the same node, the quantity given 
by the Table must be deducted from the same ; that is from 
565° 18', and the remainder 260° 33' will be the place of the 
satellite on the moveable circle. 
Finally, to get the angle of position at which the satellite 
will be seen, the two ends of a proportional compass must be 
adjusted to each other, so that when one end of it is opened 
to six inches, the other may give the quantity in the last 
column of the Table, which in the present case is 4,76 inches. 
The distance from 260^-° to the transverse must then be mea- 
sured by the long end of the compass, in a direction parallel 
to the lines in the figure ; and the opening of the short end 
must be set back again in the same direction, from the trans- 
verse towards z6o±° ; a fine point must be marked with the 
end of it upon the pasteboard. A black silk thread fixed to 
the centre of the circle, may then be stretched over the im- 
pressed point to intersect the degrees of the outer circle, upon 
which the positions are reckoned in the order they are marked ; 
and this being done, it will be seen that the intersection of the 
thread falls upon 2$ degrees of the south following quadrant; 
which sufficiently identifies the satellite. 
*/ 
In observations that are made when we are in, or very 
near the node of the orbits of the satellites, their angular 
positions undergo hardly any change, and can therefore be of 
no use for identifying them ; but they may then be distin- 
guished by their proportional distances from the planet ; and 
these may be very conveniently had in six hundredth parts 
