532 
Proceedings of the Royal Society of Edinburgh. [Sess. 
Greenwich Observatory — 26-inch Photographic Refractor. 
Epoch. 
No. of 
Obsns. 
du. 
dN. 
dl. 
da. 
2e sin Q. 
2e cos Q. 
i 
1902*1 
51 
- 0°95 
- 0°42 
- 0°12 
+ 0-087 
+ -0005 
- -0004 
1903-1 
63 
- 0-67 
- 0-40 
- 0-30 
+ 0-092 
+ -0005 
+ •0016 
1904-1 
51 
- 0-83 
- 0-72 
- 0-20 
+ 0-033 
- -0017 
+ -0002 
1905-1 
57 
- 0-82 
- 0-95 
- 0-37 
+ 0-069 
+ -0038 
+ -0053 
1906-1 
59 
- 0-90 
- 1-17 
+ 0-12 
+ 0-085 
- -0043 
- -0027 
1907-2 
29 
- 1-02 
- 0*93 
- 0-20 
- 0-008 
+ -0024 
+ 0009 
1908-2 
25 
- 0-64 
- 0-44 
+ 0-11 
+ 0-244 
-•0110 
+ -0032 
8. The next table lias been formed by taking the means of these results,, 
giving to each set the weight represented by the number of observations.. 
The last line is the mean of the other five, the weights being given by the 
number of observations as before. 
Epoch. 
No. of 
Obsns. 
du. 
dN. 
dl. 
da. 
2<? sin Q. 
2e cos Q. 
Observations at 
1896 - 4 
1901-7 
1897 - 5 
1901*4 
1904-7 
100 
334 
47 
171 
335 
- 0*22 
- 0-17 
+ 0-19 
- 0-49 
- 0-83 
- 0-61 
- 0-34 
- 0-57 
- 0-50 
- 0-73 
+ 0°07 
- 0-16 
+ 0-24 
+ 0-22 
- 0-16 
- 0-016 
- 0-027 
+ 0-010 
- 0-090 
+ 0-080 
- -0104 
+ -0068 
- -0053 
- -0038 
- -0008 
-•0012 
+ -0039 
+ -0031 
+ -oooi 
+ -0010 
Lick 
Yerkes 
Lowell 
Washington 
Greenwich 
1901-9 
987 
- 0-44 
- 0°54 
- 0°05 
+ 0-0013 
- -oooi 
+ -0022 
9. The Eccentricity of the Orbit . — The values of 2e sin Q and 2e cos Q' 
just found show that the eccentricity of the orbit is extremely small. Dr 
Struve gave ‘01 as its maximum value ; the present observations give *001. 
10. The Mean Distance of the Satellite and the Mass of Neptune . — 
The value found for the mean distance is 16*270, which differs very little 
from that of Dr Struve, 16*271. The corresponding value of the mass of 
Neptune, i =19396, is the same as Dr Struve’s. It is interesting to notice 
that the photographic results give a smaller value for the distance of satellite.. 
11. The Movement of the Plane of the Satellites Orbit . — The values 
d~N — — 0°*54, dl = — 0°*05 give for the epoch 1901*9, N — 187°*45, I — 117°*44. 
The following table shows the changes in the node and the inclination since 
the discovery of the satellite : — 
Epoch . 
N . 
I . 
Epoch . 
N . 
I . 
1849*9 
179-12 
126-01 
1896*4 
186-71 
118-22 
1864-0 
181-49 
124-20 
1897-5 
186-83 
117-87 
1875-8 
183-10 
121-46 
1901*4 
187-34 
117-25 
1883-0 
184-36 
120-08 
1901-7 
187-22 
117-58 
1890-4 
185-27 
119-16 
1904-7 
188-06 
117 - 08 . 
