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logarithm of the number of feconds required, being 
the fecond correction of parallax ; and is always to 
be added to the diftance of the Moon from the 
ftar, firft corrected for refraCtion, and the principal 
effeCt of parallax found above, in order to obtain the 
true diftance ; unlefs the diftance exceeds 90 degrees, 
in which cafe it is to be fubftraCted. 
DEMONSTRATION. 
Let L Fig. 6. reprefent the Moon’s true place in 
the fphere, and r her apparent place as depreffed by 
parallax, S the place of the ftar, and L t a perpen- 
dicular let fall from the true place of the Moon L 
upon the great circle r S joining the ftar S and the 
apparent place of the Moon r; (all as in the four 
figures belonging to the preceding rule). Let L a 
be the arch of a parallel circle defcribed from the 
ftar S as a pole through the true place of the Moon L. 
S# terminated by the parallel circle L a, and not 
terminated by the perpendicular L f, as was fuppoled 
in the former demonstration, is equal to S L or the 
true diftance of the Moon from the ftar, which was 
therefore computed too fmall from the former rule 
by the little fpace a t. Let L T and a T be the 
equal tangents of the equal arches L S and a S in 
L and a, meeting in the radius C S, drawn from 
the centre of the fphere C and produced, in T. The 
fpace hat, on account of its fmallnefs, may be look- 
ed upon as lying all in one plane namely haT, and 
ha as the fmall arch of a circle defcribed from the 
point T as a centre with the line L T as a radius, 
V thro’ 
