M. Arago on Double Stajs. 



The 38tli of Gemini. Greater star wlxite ; lesser blue. 



... J of Gemini. white; ... blue. 



... a of the Lion. white; ... bluish. 



... 2d of the Canes Venatici red; ... blue. 



... i of Cancer. a beautiful yellow ; ... indigo blue. 



... I of Bootes. yellow; ... greenish blue. 



... J of Bootes. white; ... deep blue. 



... J of the Serpent. both blue. 



... $ of the Crown. white; ... blue. 



... /3 of the Scorpion. white; ... blue. 



... X of Hercules. white; ... reddish. 



... 43d of Hercules. red; ... bluish. 



... a of Hercules. reddish; ... green. 



... a of Opiachus. red; ... blue. 



... 63d of Opiachus. Both blue ; very unequal in size. 



... V of the Dragon. ... bluish ; have the same intensity. 



... a of the Serpent. Greater star white ; lesser blue. 



... 12th of Berenice's Hair. white; ... red. 



... 24th of Berenice's Hair. reddish;... beautiful green. 



... I of the Great Bear. white; ... bluish. 



. N TT • 1 Both bluish ; and of the same intensity, 



mce s Hair. ) ■' 



... I of Lyra. Greater Star white ; lesser blue. 



... /3 of Lyra. '^ ''*^'^'^'^'''' i^^ '''"iAA^i^- ^vlv'-WiiO;- </- ' 



... a of the Dragon* :^')^0 ;U'>'Jif'i^'iin:;;=d^if<id}>-,,.5i, W^ 



,., ^ of Lyra. white; ... blue. 



... /S of the Swan. yellow; ... intense blue. 



... •(/' of the Swan. white; ... clear blue. 



*" H A ^ I Both bluish; very nearly equal. 



... y of the Dolphin. ... whiti; ... yellowish. 



Anonymous *. Both blue ; nearly of the same intensity. 



Anonymous f. ... blue ; have the same lustre. 



The 47th of Cassiopeia. Greater Star white ; lesser blue. 



... »} of Cassiopeia. red; ... green. 



... / of the Painter's Easel. white; ... blue. 



... K of the Ceutaur. white; ... blue. 



... £ of the Flying Fish. >;, ,.j<iw'- white; ... blue. 



... K of Argus. .:'olo3 -^Ajti^rRff. Blue ; ... dull red. 



... ^ of the Centaur. ;.U*,. yellow; ... blue. 



2. Whi/ is it tJiat these double Stars Jiave suddenly become an object of 

 such assiduous attention 9 



It has already been remarked, that the two distinct stars which 

 go to compose the double star, have generally intensities which 

 are exceedingly dissimilar. Each group in which these great 

 inequalities of intensity occur, along with a considerable differ- 

 ence in the distance of two stars, would furnish, as we shall pre- 

 sently see, a very simple means of observation by which to judge 

 pf t))Q distance of the more brilliant star from the earth. Even 



• Right ascension, 19 h. 19' ; declination 20* 40' north. 

 f Right ascension, 19 h. 21'; declination 36' 10' north. 



