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runs not exa&ly along the wire A B, the pofition of 
that wire muft be altered a little, till the ftar runs 
exactly along it from the centre C, to the extremity 
of the field of the telefcope at B. Then turn the 
fcrew to carry back the ftar from B a little to the 
eaft of the firft or eaftern wire M N, and obferve 
the exadt minute, fecond, and quarter of a fecond, 
of the ftars palling the three horary wires M N, D E, 
O P j the telefcope remaining unmoved and undi- 
fturbed, obferve, in like manner, the tranfit of the 
moon’s enlightened limb acrofs the fame wires, whe- 
ther Ihe pafs fouth of the liar, as along the line S T, 
or north of the fame, as along to the line U V ; and 
the obfervation is completed. The like obfervation 
being repeated, after an interval of feveral hours, we 
fhall have the apparent motion of the moon in right 
afcenfion in this time ; whence the moon’s horary, 
and thence her horizontal parallax may be com- 
puted. 
If the moon precedes the flar, and the wire AB is 
adjufted by making fome bright point in the moon 
run along it, and W X is fuppofed to be the true par- 
allel of declination, it is manifeft that the ftar will 
pafs the horary wire at a , to the fouth of the centre 
of the telefcope fooner, and to the north of the 
centre of the telefcope later, than it pafles the true 
horary circle Y Z at e, by the time it takes to defcribe 
a e parallel to W X. Let C L be the apparent motion 
of the bright point of the moon, in four minutes of 
time; draw K L perpendicular to W X produced, 
and C K is the apparent motion reduced to a parallel 
of the equator in four minutes, and K L the appa- 
rent motion in declination in the fame time ; and, 
4 the 
