of the Equatorial Instrument. n*r 
that supports one end of the axis of the level, and the other 
half by the declination handle ; invert the telescope, and re- 
peat the operation till the same object is covered in both po- 
sitions, and the level is found true ; then will the level and its 
axis be parallel to the line of collimation, and the object co- 
vered by the wire may be concluded to be in the horizon, 
(27.) Fourth. The index wires of the microscopes. The line: 
of collimation, with respect to east and west, has been already 
adjusted as above (sect. 24,) Let then the declination axis, by 
its level, be restored to an horizontal position; at this time adjust 
the index wires in the two equatorial microscopes W X, to bi- 
sect the two opposite divisions 360 and 180°, then will these- 
wires be rectified to their proper place. That being done, 
bring 90°, or the division that represents the equator on the^ 
declination circle, under its respective microscope, and turn 
the whole instrument one quarter round on the polar axis, 
viz. till 90° on the equatorial circle be bisected by the micro- 
meter ; and if, at this time, the bubble of the hanging level 
appear true, the index wire of the declination microscope is 
correct ; if not, correct half the error by the declination 
handle u, and half by the little screws b, (Tab. XI Y. fig. 2) at 
the side of the hanging level ; then reverse the telescope, viz. 
turn it till 270° on the equatorial circle come under the mi- 
crometer wire, and if the level then rest true, the adjustment 
is complete ; if not, repeat the operation, as before, till it 
does ; then, by its proper screw, bring the index wire of the 
declination micrometers to bisect the points 90 and 90°. The 
indexes of both circles will be then adjusted, and the axis of 
the hanging level brought parallel to the line of collimation, 
with respect to east and west, as ^well as with respect to 
