C 47 3 
III. the Discovery of four additional Satellites of the 
Georgium Sidus. The retrograde Motion of its old Satel- 
lites announced ; and the Cause of their Disappearance at 
certain Distances from the Planet explained . By William 
Herschel, LL.D . F. R. S. 
Read December 14, 1797. 
Having been lately much engaged in improving my tables 
for calculating the places of the Georgian satellites, I found it 
necessary to recompute all my observations of them. In look- 
ing over the whole series, from the year of the first discovery 
of the satellites in 1787 to the present time, I found these ob- 
servations so extensive, especially with regard to a miscella- 
neous branch of them, that I resolved to make this latter part 
the subject of a strict examination. 
The observations I allude to relate to the discovery of four 
additional satellites : to surmises of a large and a small ring, at 
rectangles to each other : to the light and size of the satellites : 
and to their disappearance at certain distances from the planet. 
In this undertaking, I was much assisted by a set of short 
and easy theorems I had laid down for calculating all the par- 
ticulars respecting the motions of satellites; such as, finding 
the longitude of the satellite from the angle of position, or the 
position from the longitude : the inclination of the orbit from 
the angle of position and longitude : the apogee : the greatest 
\ 
