HUMBOLDT'S CORRECTIONS AND ADDITIONS 

 TO VOL. III. 



Page 40, line 20. 



Since the printing of that part of the Cosmos, where a doubt is expressed 

 as to whether it has been " shown with certainty that the positions of the 

 Sun influence the terrestrial magnetism," the new and excellent inves- 

 tigations of Faraday have proved the reality of such an influence. Long 

 series of magnetic observations in opposite hemispheres (e. g., Toronto 

 in Canada, and Hobart Town in Van Diemen's Land), show that the 

 terrestrial magnetism is subject to an annual variation, which depends 

 upon the relative position of the Sun and Earth. 



Page 75, line 29. 



The remarkable phenomenon of the undulation of stars has very 

 recently been observed at Trier by very trustworthy witnessses, in Sirius, 

 between 7 and 8 o'clock, while near the horizon. See the letter of Herrn 

 Flesch, in John's Unterhaltungenfiir Freunde der Astronomic. 



Page 178, line 17, note 50. 



The wish which I strongly expressed that the historical epoch in which 

 the disappearance of the red colour of Sirius falls should be more 

 positively determined, has been partially fulfilled by the laudable industry 

 of Dr. Wopcke, a young scholar, who combines an excellent acquaintance 

 with Oriental languages with distinguished mathematical knowledge. 

 The translator and commentator of the important Algebra of Omar 

 Alkhayyami, writing to me from Paris, in August, 185 1, says, " I have 

 examined the four manuscripts in this place of the Uranography of 

 Abdurrahman Al-Sufi, in reference to your suggestion contained in the 

 astronomical volume of the Cosmos, and found that a Bootis, a Tauri, 

 a Scorpii, and a Orionis, are all expressly called red; Sirius, on the 

 contrary, is not. Moreover, the passages referring to it are uniformly as 

 follows in ail the four manuscripts : " The first among its (Great Dog) 

 stars is the large, brilliant one in his mouth, which is represented on the 

 Astrolabium, and is called Al-jemaanijah." Is it not probable from this 

 investigation, and from what I quoted from Alfragani, that the epoch of 

 the change of colour falls between the time of Ptolemaus and the Arabg. 



