34 2 Mr. Smeaton’s Qbfervauon of Mercury 
Take 41 ow Lb, fig. i. = L c, : g. 2. = 24', and draw the line 
fig. 1. parallel to the line /zy, and then fay, as Ls = 
3 8'. 2 : Lb (or Lij= 2 f :: /% — 20A3 : ht— 13", which d-4^.4 
=: i7 7/ .4 for the whole error in right afcenfion, with a declina- 
tion or diftance from the center of 24' ; but as the errors both of 
light afcenfion and declination are in proportion todiftance from 
the center, as the difference of the planet and ffar is only 23', 
fay, as 24' : 23' :: : i&'.y — \".i time; and for the de- 
clination, fay again, as z\ : zf :: 6 ". 2 : 6 /7 declination*. 
Reduction of Mercury’s comparlfon with a .Orionis, to right 
afcenfion and declination . 
We have laid it down, that the 23d Sept. 1786, A.M. at 
5 h. 22' 34A9 mean time, Mercury preceded « Orionis 18 h. 
43' 43". 5, and had then a more northern declination by 
* 3 ' 8// « 
According to Dr. Maskelyne’s Catalogue of 34 flars, the 
right afcenfion of a Orionis reduced to the time when he was 
obferved is 85° 54' 12A 
Now as the whole circle of the fphere makes a revolution 
in the time that u Orionis makes one turn, which is 
< // 
23 56 4.1 then from this deduft 
18 43 43-5 
5 12 20.6 remains for the time that a Orionis preceded 
* If the companion had been with o Tauri, then we mull have faid, 
/ / // // // 
As 24 : 3 1 § :: 17.5 : 23=1.5 of time, 
and 24 : gif :: 6.2 : 8.1 corredtion for declination. 
N. B. All thefe and the above proportions will be commodiouHy wrought with. 
tjje Hide -rule. 
Mercury 
