in the relative Situation of double Stars. 379 
quantity being too small for the precision of the micrometer, 
when only two measures are taken ; but the alteration in the 
distance of the two stars is well ascertained. Oct. 22, 1781, with 
278, it was 1^ diameter of L. April 28, 1783, with 460, it was 
2|- diameters; and. May 4, 1802, it was not less than 4 or 5 
diameters of L. If this change had arisen from a parallactic 
motion, there must have been a considerable alteration in the 
angle of position, which cannot be admitted ; it may, therefore, 
more properly be ascribed to a real motion of d Serpentis. 
North of 105 Herculis. I, 86. 
The alteration in the angle of position of this star is uncom- 
monly great. April 27, 1783, it was 79° 24' north-preceding ; 
and. Sept; 29, 1802, it measured only 22 0 27'; which denotes 
a change of 56° 57', in 19 years and 155 days. The distance 
has undergone very little alteration, but is rather less now than 
it was formerly. A real motion of the largest star, in a north- 
following direction, may explain this change, which cannot be 
ascribed to a parallactic motion of the stars. 
Rigel. II, 33. 
This bright star has undergone a change of situation with 
regard to its distance from the small one, which is near it ; but, 
in the angle of position, very little difference can be perceived. 
By eleven measures, taken between Jan. 1, 1802, and Feb. 18, 
1803, the mean position is, 69° 5' south -precedi ng ; which is but 
little more than 68 ° 12', the measure of Oct. 1, 1781, given in 
my Catalogue. 
The distance was estimated, Oct. 1, 1781, with 460, to be 
more than 3 diameters of Rigel ; and, as I supposed it to be 
