[ 542 ] 
the Sun and planet. In like m.inner, If the g'adcs 
of the mjcrotneter be opened to a greater or lefs 
diltance (according as the planet is nearer the North 
or South limb of the Sun) every thing elfe remaining 
unmoved, the difference of declination of the South- 
ern limbs of the Sun and planet may be obferved, by 
bringing the Southernmoll limb of the Southern- 
mod: image of the planet to run along the wire EW, 
at the fame time that the Southernmoff limb of the 
Noi thernrnc^l: image of the Sun runs along the fame. 
Half the dilterence of thele tv/o meafures (if taken 
immediately after one another) is equal to the differ- 
ence of the declination of the centers of the Sun and 
planet at the intermediate time, without any regard to 
the quantities of liie diametei’s of the Sun or planet, 
or the error of adjudment of the micrometer. 
T he difference of the trandts of the Eadern or 
\\edein limbs of the Sun and planet will give the 
difeience of right alcendon, as in the common 
micrometer. 
Indead of diderences of right arcenfion, diflances of 
the planet from the Sun’s limb in lines parallel to the 
equator may be more accurately obferved as follows. 
Xhe glalics being leparated to a convenient didance, 
turn both the wires and micrometer about, lb that 
the two images of the planet may both run along the ' 
wire E W (lee Fig. JIl ) and leparate the glad'es, fo 
that V one of the images of the planet may touch the 
limb of the Sun to the Ead or Wefi, or rather both 
alternately. Or perhaps the following method may be 
preferable ; feparatc the two images of the Sun to any 
convenient didance, fo as to produce a conliderahle 
angle of interfedtion of the circumferences at I and T; 
5 Turn 
