7 6 Dr. Herschei/s Discovery of four additional 
First satellite invisible. 
First satellite visible. 
// 
1791. March 2 at 19,8 
1794. Feb. 2 6 at 14,1 
Second satellite invisible. 
17 91- 
Feb. 22 
at 
21,8 
1792. 
Feb. 21 
at 
23>3 
Dec. 19 
at 
i6*,9 
17 94>- 
March 17 
at 
2C,7 
1792. 
March 15 
at 
M 
00 
March 23 
at 
J 7>9 
1794- 
March 4 
at 
*0 
00 
rH 
1796. 
March 5 
at 
9>3 
March 7 
at 
12,5 
March 17 
at 
6,3 
March 17 
at 
17,0 
March 23 
at 
6 , 2 
March 21 
at 
15>5 
March 25 
at 
8,7 
April 4 
at 
8,5 
1797- 
March 17 
at 
4>8 
March 21 
at 
4,6 
March 25 
at 
4,8 
Second satellite visible. 
1794. March 22 at 17,5 
Thus, having the observations and calculated distances under 
our inspection, we find that both the satellites became always 
invisible when they were near the planet : that the 1st was ge- 
nerally lost when it came within 18" of the planet, and the 2d 
at the distance of about 20". In very uncommon and beautiful 
nights, the 1st has once been seen at 13",8, and the 2d at 17", 3; 
but at no time have they been visible when nearer the planet. 
I shall now endeavour to investigate the cause which can 
