Brightness of the Satellites of Uranus. 195 
Taste IV. 
Pressures are given in pounds on a square inch of longitudinal 
journal section. 
Fr; Coef’ts at 59” per min. Coef’ts at 2°17’ per min. 
"154 "159 136 0 
23°5 15 
36°8 157 "156 138 130 
50°1 149 147 119 124 
63°4 149 153 117 127 
76°7 153 “152 108 126 
90°0 151 "150 109 123 
103°3 155 "150 111 127 
116°6 149 "145 113 124 
129°9 147 "146 112 "123 
143°2 145 "146 113 121 
156°5 147 "147 113 124 
169°8 146 "146 112 121 
183°1 145 "148 109 124 
196°4 144 "145 111 125 
The larger part of the experiments referred to were made by 
esper, a student of the Institute, whose patience and care 
deserve especial mention. 
ArT. XXVI.— Observations of the Brightness of the Satellites of 
-_  Oranus. 
[Communicated by Rear-Admiral John Rodgers, U.S.N., Superintendent U. 8. 
Naval Observatory.] 
It was surmised by Professor Newcomb that the brightness 
of Ariel varied in different parts of its orbit (Wash. Ast. O 
1874, Appendix I, p. 48,) and that it was least bright in 
p=180°+ duri 74. koe 
There have been observed in 1874-5-6-7 nineteen position 
angles of Ariel: of these, seven were 180°, and twelve 
were 0°+. : : 
A better test is the following: on fifteen nights this satellite 
was bright enough to allow of measures of distance. On six 0 
these ee e nine the 
