wit/j an Equatorial Micrometer. 343 
Mercury in right afcenfion ; but if a ran the whole rotation 
— 360° in 23 h. 5b 7 4 7/ . 1, what portion of it will be run in 
5 h. i2 7 20 /7 .6= i8740 /7 .6 ? 
But 24 h. = 86,400 feconds, and 360 = 1,296,000 feconds: 
Time. Time. Of degrees. Of degrees 0 
Say then, as 86400" : 18740". 6 :: 1296000" : 281 109"— — 78 5 9 
But, according to Dr. Maskelyne’s feleft Catalogue, the right afcen- 
ficn of a Orionis for Sept. 30, 178b, was, (which add) - 85 54 12 
The right afcenfion of Mercury at the time of obfervation was therefore 163 59 21 
According to Dr. Maskelyne’s feleft Catalogue a Orionis had decli- 0 y 
nation north, corre&ed for precetfion — — 7 21 8.8 
The fum of aberration and nutation from ConnoiJJance des Temps — •+■ 8.4 
The correft declination north of a Orionis 
To which add that Mercury pafled more north 
7 21 17.2 
23 8 
Mercury’s declination therefore was 
7 44 25.2 
The refult. 
1786, Sept 23. A.M. 1 Mercury , s f right afcenfion 
at 5 h. 22' 35" M.T. J l declination north 
163 59 21 
7 44 25 
Vol. LXXVII. 
Ddd 
