distances and positions of 380 double and triple stars , &c. 291 
70 p Ophiuchi continued. 
motion continued nearly uniform from 1821, at its former 
rate of about 6° per annum, the position, at the time of the 
observations of 1822, should have been 6 o° sf, and on the 
9th of April, 1823, about 54 0 . The notes annexed to the 
last set of observations contain the result of two trials made 
to ascertain the quantity of error the eye would bear in a 
single measure of this star. When purposely set, either way, 
2°~ from the mean, the micrometer wire was found to be 
intolerably out of place. The corrections were cautiously 
made so as barely to give satisfaction, and from their read- 
ings off we are fairly entitled to conclude that no satisfactory 
measure can deviate above a degree, or a degree and a half 
from the truth, at most. On the 9th April the micrometer 
wire was purposely set to 9 o° — 33 = 57 0 sf, but its position 
was so offensive as to be marked “ shocking and when set 
to 51 0 it had no appearance of ever being intended for a mea- 
sure, the wire actually passing between the stars. Admitting 
the correctness of our measures and those of M. Struve in 
1819, 1820, the mean angular velocities, during the several 
different intervals of the observations, will stand as follows : 
Observation of 1779 to that of 1802— 
•mean annual motion . . 5°.o46. 
1802 . . 
. 1804 
1 804 . . 
. 1819 
9 .868. 
1819 . . 
. 1820 
. . . . . , .11 .000. 
1820 . . 
. 1821 
1821 . . 
1822 
« - 037 - 
1 822 * . . 
. 1823 
1 779 • • 
. 1823- 
-mean of the whole interval 6 .811. 
To account for so enormous a variation of angular velocity. 
