322 Mr. Smeatqn’s Obfervation of Mercury 
of the ftar to the fame place two evenings afterwards, both in- 
right afcenfion and declination, was fo near, that I concluded I 
might very well exped a good obfervation of Mercury, in cafe 
I could get a fight of him, though the bars wherewith he was 
to be compared lay at the didance of the following evening at 
the fooned. 
The micrometer is furnifhed with five horary wires, deno- 
minated in their order a. A, B, C, D ,(B being the mid- 
dle horary wire), and the two declination wires are deno- 
minated A and B , each moveable by a feparate and independent 
micrometer-fcrew, from the outfide of the field to the center, 
and a little beyond it ; fo that each wire can be moved into the 
place of the other when at or near the center *. 
The morning of the 23d of September, about a quarter pad; 
five o’clock, the air being clear and perfedly ferene, it being 
then about an hour, after Mercury’s riling, and 1 near three- 
quarters of an. hour before the riling of the fun, I very readily 
found Mercury with the telefcope., and when found could, 
eafily fee him with an opera glafs and Mercury, being then 
in a date of very little alteration of declination, I adjuded one 
of the declination wires to his apparent run, by making him 
traverfe the whole field. The obfervations were then taken as 
* In Dr. Bradley’s Paper it is faid; that before the late alterations, both the 
declination wires were made moveable; and that it was an improvement to make 
one of them fixed, and one only moveable. But however they might be imme- 
diately preceding the Do&or’s time, I believe, the original micrometers by Mr. 
Townl.ey were with one fixed and one moveable declination wire, as I have 
feen one in this form among the remaining apparatus of Mr. Abraham Sharpe. 
In an inftrument, however, fitted up for the purpofes of the equatorial ?nicro- 
metcr , I believe, it will be found moil convenient to have both thofe wires 
moveable ; as by this means they not only are enabled to Hide into each other's place , 
but every part of the frame of the inftrument remains fixed during the whole of 
the obfervation, the two Aides carrying thefe two wires excepted, 
