in the relative Situation of double Stars, &c. 349 
following; 2d measure, 26° 49'. Mean of the two, 27° 34'. De- 
viation from the mean, 45'. 
February 9, 1803. a. Geminorum. 1st measure, 6° 11' north 
preceding; 2d measure, 4°48 / . Mean of the two, 5 29'. Devia- 
tion from the mean, 41'. 
September 6, 1802. vj Coronas. 1st measure, 89° 42' north 
following; 2d measure, 89° 38'. Mean of the two, 89° 40'. De- 
viation from the mean, 2'. 
When these observations are considered, we shall not err 
much if we admit that, in favourable circumstances, and with 
proper care, the micrometer, by a mean of two measures, will 
give the position of a double star true to nearly one degree ; but, 
as the opportunities of taking very accurate measures are scarce, 
it will be necessary to have recourse to some more discordant 
observations. 
February 18, 1803. (2 Orionis. 1st measure, 72 0 38' south 
preceding; 2d measure, 67° 24k Mean of the two, 70° n'. De- 
viation from the mean, 2 0 47'. 
But a memorandum to the observation says, that the evening 
was not favourable. We may therefore admit, that in the worst 
circumstances which can be judged proper for measuring at all, 
an error in the angle of position by two measures will not 
amount to three degrees. 
It will be remarked, when we come to compare single mea- 
sures which have been taken on different nights, that they 
are somewhat more discordant ; but I have not ventured to 
reject them on that account, except in cases where it was pretty 
evident that some mistake in reading off, or other accident to 
which all astronomical observations are liable, was to be appre- 
hended. Nor can such disagreements materially affect the 
MDCCCIII, Z Z 
