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Fig. 1. 
£ 
lli 
Let, therefore, in Fig. 1. the circle EDQB re- 
prefent the fun’s difk, in which let E Q^be parallel 
to the equator, and B D an hour-circle ; let the 
pricked line F G reprefent the fixed wire of the mi- 
crometer, H I the moveable wire, and K L the per- 
pendicular or horary wire. The difference of right 
afcenfion H v, and of declination C H, will be de- 
termined in the following manner : S C, or C D, the 
femidiameter of the fun is given, and CD — D H 
= C H, the difference of declination ; and S C and 
C H being given, S H may be found j and then the 
©bferved difference of right afcenfion S v being di- 
minifhed 
