distances and positions of 380 double and triple stars , 31 
the following statement of the measures taken at different 
periods. 
Date. 
Position. 
Distance. 
Observer, &c. 
1779- 8 
ll". 1 
Sir W. Herschel (MSS. 
1780.5 
11 .5 
Ditto. 
1782.4 
2 9°- 9»/ 
— 
H. Catalogue of 1782. 
1803.I 
19 .22 nf 
— 
H. “ On the changes, &c/’ 
*l8l4. 
16. 7 nf 
9 -7 
Struve, by Bessei/s Obs. 
I819.8 
9. 8 nf 
10 .8 
Do. Additamenta, p. 174. 
1821.9 
7- 9 n f 
8 .8 
H & S., as above. 
The position of 1814 cannot be relied on, being deduced 
only from two estimations of the ratio of the differences of 
right ascensions and of declinations to the distance, which 
differ in their results as much as 8°. If we leave out this 
doubtful observation, and compute the most probable annual 
motion from this table by the formula ( 1 ) we obtain o°.5i33, 
which is the angle described per annum in the direction 
nfsp. If we compute back from the last observation as an 
epoch, with this mean motion, the comparison between the 
observed and calculated angles will stand as follows : 
Date. 
Calculated 
Angles. 
Observed 
Angles. 
Difference. 
1821. 9 
7 ° • 9' n f 
7 ° 9' n f 
o 0 .q' 
1819. 8 
9 -o 
9 -8 
+ 0 .8 
1814.08 
11 -7 
11 .5 
— O .2 
1814.13 
11 7 
1 9 -3 
+ 7.6 
1803. 1 
17 .6 
19 .2 
+ 1 .6 
1782. 4 
28 .2 
27 .9 
— 0 .3 
The observations marked with an asterisk are the two 
