fiew Syjlem of JVtres in a Tele/cope, 351 



thofe ftars pafs it. N. B, This be- 

 ing in tune muft be converted into 

 degrees^ and multiplied by cofine of 

 declination as ufual, to give the true 

 dIfFerencc in declination between the 

 ftars. 

 And the fame expreffion, viz, 

 ^ . w^yx iru tf — q_ ^ ^^^^ _ ^j_^^ difference in J^ between thofe two 



•JR. X lin. a 2 



points ; to be applied as a correction 

 to the obferved times. 

 The fame may be done by the larger intervals tn and ^, only 



by fubftituting ^ ~ ^ in the place of ^ 4-^, thus : 



1 . TTi '^ U.X fin. a— a r t/t* 'ii** i 



~-^ X col. q — ditterence ui dechnation as above ; 



R X fill, a 2 



or . . . . . X fin. ^ = afcenfional difference. 



If the ftars differ too much in declination to come within 



the expreflion above (as N° 2. and 3.) then the differences of 



the angles D and E in declination and right afcenfion may be 



fmind thus: 



— ^" ' ^ = difference in declination between D and E j, 



— ^"' ^ — their afcenfional difference ; 



K. 



and the difference of each ftar from its refpeflively neareft 

 angle of the rhombus, may be deduced by the former expref- 

 fion, leaving out the confideration of the other ftar, thus : 



2 . »x in.g + y ^ ^^|- _ difference of the ftar in declinatioa 



R X fin. a -* 



from its neareft angle, 

 and . . . X fin. ^=s its difference in right afcenfion. 



The application of thefe formulie is very eafy: for having 

 ound qy if you fet down its cofine in one column for declina- 



VoL. LXXV. A a a tion, 



