[ re* ] 
limbs of the San and Moon do not come to touch 
one another at the wire fartheft from the plane of the 
quadrant, the objed end of the telefcope is inclined 
towards the plane of the quadrant, and mufl be 
altered by the adjufttnent accordingly. JLet thefe 
• operations he repeated until the obiervation is the 
fame at both the parallel wires, and the axis of the 
telefcope will be adjufted parallel to the plane of the 
< quadrant. In like manner, the axis of the telefcope 
may be alfo adjufted parallel tp the plane of the 
.quadrant for the fore-obfervatipn. 
Second method. Set the index to (o) and hold the 
plane of the quadrant parallel to the horizon of the 
tea, with the divided arch upwards, the two wires 
being parallel to, and including both the dired fore- 
la orizon, and the refleded back-horizoji, between 
them. Raife or lower the plane of the quadrant 
until the dired and refleded horizons coincide to- 
gether : if the coincidence happens in the middle 
between the two wires, or rather, to be more ekad, 
above the middle by fuch a part of the field of view 
as anfwers to the number of minutes in the deprefiion 
of the horizon (which may be eafily eflimated if the 
angular interval of the wires be firft found by experi- 
ment, in manner hereafter mentioned) the axis of the 
telefcope is parallel to the plane of the quadrant; 
but if it does not, the line of fight is inclined to the 
plane of the quadrant, and muft be correded as follows. 
If the dired and refleded horizons, when they coin- 
cide, appear higher above the middle between the 
wires, than what the quantity of the deprefiion of the 
horizon amounts to, the objed end of the telefcope is 
inclined from the plane of the quadrant, and muft: 
.be altered by the adjuftment made for that purpofe; 
