454 RECTIFICATIONS AND ADDITIONS. 



Alkhayyami, writes to me from Paris, in 1851, as 

 follows : " The wish expressed by you in the astro- 

 nomical volume of Kosmos, has led me to examine four 

 manuscripts of the Uranography of Abdurrahman Al- 

 Ssufi, which are here; and I have found that a Bootis, 

 a Tauri, a Scorpii, and a Orionis, are ail expressly termed 

 ' red :' Sirius, on the contrary, has no such epithet applied 

 to it. The passage relating to Sirius is in all the four 

 manuscripts to the same effect, viz. that ' the first of these 

 stars' (in Cauis Major) 'is the large bright star in the 

 mouth, which is marked on the Astrolabe, and is called 

 Al-je-maanijah/ " Does it not appear probable from this 

 examination, and from what I cited from Alfragani (Note 2l6 ) 

 that the change of colour of Sirius took place intermediately 

 between the epoch of Ptolemy and that of the Arabian 

 astronomers ? 



Pages 191192. 



In the brief exposition of the method of finding the 

 parallax of double stars by the velocity of light, it should 

 have been said, that the interval of time which elapses be- 

 tween the moments when the planetary or secondary star is 

 nearest to, and farthest from, the Earth, is always longer 

 when the change is from the greatest proximity to the 

 greatest distance, than in the inverse case, when the change 

 is from the greatest distance to the greatest proximity. 



Page 214. 



In the French translation of the astronomical volume of 

 Kosmos (Part I.), which I have rejoiced to see undertaken by 

 Monsieur Faye, that highly-informed astronomer has greatly 



