Ball — On the Binary Star S Ursae Majoris. 327 
TAELE YL 
Comparison of the Angles of Position, computed from the New Approxi- 
mate Elements of ^ Ursae Majoris, with Olservation. 
No. 
01b server. 
Epoch.. 
Observed 
Position. 
Compute 
Position. 
Difference. 
1 
Herschel L, . . . . 
1781-97 
1430-78 
147°-37 
-t- 
3° 
-59 
2 
Herschel I., . . . . 
Herschel I., .... 
1802-09 
97 
•52 
98 -53 
+ 
1 
A 1 
3 
1804 08 
92 
-63 
92 -55 
A 
Uo 
4 
Struve, 
1819-10 
284 
•55 
287 -93 
+ 
3 
6o 
5 
Herschel II. and South, . 
1823-29 
258 
•45 
259 -20 
0 
75 
6 
South, 
1825-22 
244 
•53 
246 -20 
1 
67 
7 
Struve, 
1827-27 
228 
•27 
231 -63 
+ 
3 
36 
8 
Dawes, 
1832-27 
196 
•72 
195 ^13 
1 
59 
9 
Dawes, 
1840-29 
150 
•85 
152 ^95 
1 
10 
1 n 
iU 
Dawes, 
1842"27 
144 
•76 
i.'±o vo 
+ 
1 
22 
11 
Dawes, ..... 
1843-28 
142 
•17 
142 -85 
+ 
0 
68 
12 
Dawes, 
1849-30 
126 
•68 
127 -10 
0 
52 
13 
Miller, 
1852-13 
122 
•28 
120 -87 
1 
41 
14 
Jacob, 
1853-20 
119 
•47 
118 -58 
0 
•89 
15 
Dawes, 
1854-36 
115 
•87 
116 ^12 
0 
•25 
16 
Dembowski, .... 
1858-20 
108 
•09 
107 -80 
0 
•29 
17 
Dembowski, .... 
1863-23 
96 
•66 
94 •S? 
1 
•79 
18 
Engelmann, .... 
1865-12 
91 
•42 
88 -43 
2 
•99 
19 
Dembowsl^i, .... 
Dembowski, .... 
1866-30 
86 
•76 
83 -52 
3 
•24 
20 
1867-31 
82 
•22 
78 ^55 
3 
-67 
21 
Dembowski, .... 
1868-30 
77 
•50 
72 •SB 
4 
-92 ! 
22 
Dembowski, .... 
1870-24 
57 
•74 
66 •lO 
1 
•64 
23 
Dembowski, .... 
1871-22 
47 
•70 
43 -80 
3 
•90 
24 
Briinnow, .... 
1872-28 
24 
•19 
26 ^47 
+ 
2 
•28 
"We must probably look for tlie final correction of the elements to 
observations which will be made during the next ten years. 
To facilitate the comparison of the approximate elements now 
presented with observation, an ephemeris of the position angle has 
been computed. The ephemeris gives the position angle, at intervals 
of three months, from 1872"50 to 1878'75. The greatest velocity of 
change in the angular position occurs about 1873*25. At this date 
the rate will be fully 20" per annum. The periastron passage takes 
place about 1876-28, thus the period included in the ephemeris con- 
tains the most critical part of the entire orbit. 
