[ 543 ] 
Tarn the wires about, fo that the planet’s centre* 
North, or South limb, may run along the wire EWi 
Then turn the micrometer about till the two inter- 
fei^iions I T pafs the horary wire N S at the fame 
inffant, and the micrometer will be in a proper po- 
fition for meakiring didanees in a line parallel to the 
equator ; and the dilLnce of the pl.met from the 
Sun’s limb in a line parallel to the equator will be- 
obtained by only bringing the glades nearer togetiier, 
or leparating them farther, till the planet’s limb is in 
contact with the Sun’s limb. If didances of tltc 
planet’s near limb Irom the Sun’s limb be thus taken 
to the Ead and Wed alternately, and reduced to a 
given time, by allowing- for the motion of the planet- 
by calculation, half the did'crence of the two reduced 
meafures will be the didance (d the planet’s centre 
from the middle of the chord ol the Sun’s di(c 
pafiing through the planet’s centre parallel to tire- 
^quator at the given time, without any regard to ilie 
c]uantities of the diameters of the Sun or planet, t.r 
the error of, the adjudment of the micrometer. It 
may be proper to remark, that when the planet is- 
brought to touch the Sun’s limb, the point ofcontadb 
will be North' or South of the planet’s centre accord- 
ing as the planet itfelf is North or boutk of the Sun’s 
centre. 
In like manner, didances of Venus or Mercury 
from the Sun’s limb may be meafured in lines per- 
pendicular to the equator, fee Fig. IV. (the micro- 
meter being brought into die proper pofition, in the 
very fame manner as for meafuring the difference of 
declination from the Sun’s north or fouth limb, before 
defcribed)j and if- the planet be brought inro contact 
with 
