332 
M. Struve's Observations on Double Stars. 
Struve has fixed the difference of B. Asc. at -f 0".337 in 1810, 
The angle of position Jby the wire micrometer is 25° 9' S.Foll, and 
by the micrometer of projection, 26° 35', the mean of which is 
26° 6', a result which does not err 1°. Hence it is very re- 
markable to find, that Sir W. Herschel had observed an in- 
crease of that angle as follov/s. 
Angle of position in 1783.3, 25° 29' Herschel 
1802.2, 31 38 Ditto. 
1804.0, 31 54 Ditto. 
1804.5, 32 50 Ditto. 
According to these results, the angle should have increased 
11 1° in twenty-three years, and in 1819 it should have been 
nearly 40°, whereas it is only 26°, almost the same as in 1783. If 
Sir W. HerschePs observations are correct, and we see no reason 
to doubt their accuracy, one of the two stars must have moved 
backwards. M. Struve found their distance to be 5".61, and 
their difference of declination — 2".47. 
54. g Hercules. B. Asc. 17^ 17'. N. Deck 37° 19'. 
4th-5th and 5th-6th Mag. 
In 1819) the difference of B. Asc. was — 0".323, and^the angle 
of position 36° 9' N. Free. Hence, the distance will be 4''''.78, 
and the difference of declination -f- 2".82. In 1799, Sir W, 
Herschel found the distance 2". 967, and the angle of position 30® 
N. Free. 
55. 61 Serpentarius. B. Asc. 17^ 35'. N. Deck 2° 41'. 
5th-6th and 6th Mag. 
Angle of position in 1781, 
1819, 
Diff. of R. Asc. 1819, 
DifF. of Decl. 1819, 
Distance, - 1819, 
Ditto, - 1781, 
0° 0' Herschel. 
4 5 S. Fol. Struve. 
+ 1".361 Ditto. 
— 1.43 Ditto. 
20.44 Ditto. 
19.07 Herschel. 
56. 95 Hercules. B.. Asc. 17'^ 53'. N. Deck 21° 36'. 
5th and 5th Mag. 
One of these stars is white, and the other yellow. The dif- 
ference of B. Asc. in 1819 was — 0".4785 and the angle of po- 
sition 9° 55' S. Free. The calculated distance is 7".04, and the 
