PHYSICAL AND LITERARY. 97 



II. By art. 6. the part to be fubtraded 

 from the apparent femid. 0, muft bear the 

 fame proportion to the whole, as the di- 

 ftance of the vertex on the furface of the 

 earth-from its point on the difk^ to the di^ 

 fiance of the points V, v ; which is nearly 

 the fame with the femidiameter of the 

 moon's orbit, and may always be exprefled 

 by a conftant number, viz. that of the 2ds 

 of a degree equal to the radius of a circle. 

 The diftance of the vertex from its point on 

 the dilk may be conceived to be made up of 

 two parts, poftive^ or negative : the firft of 

 which is the perpendicular diftance of the 

 centre of the given parallel circle from the 

 plane of the difkj the fecond part is the per- 

 pendicular diftance of the given vertex from 

 a plane paffing thro' the forefaid centre, and 

 parallel to the difk. 



R ^ Neg. 3 and decl. Q are 



, C the fame 7 c 

 °fl different rP"'"' 



J ri _ Cof. Jat. pi. X cof.decl. Q X cof. dee. « noon 

 2ClfART ^^ ■ ^ 



Pofitiye 7 jj-^jj^ J ^^^^ f^^^ j^^^ jjg S j^s 7 j^^jj ^ 

 Negative 3 L ^O'^ j 



Vol. XL N 12. It 



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