HUMBQLDT'S CORRECTIONS AND ADDITIONS 



TO VOL. III. 



Page 34, line 22. 



Since the printing of that part of the Cosmos where a doubt is ex- 

 pressed as to whether it has been " shown with certainty that the posi- 

 tions of the Sun influence the terrestrial magnetism," the new and ex- 

 cellent investigations of Faraday have proved the reality of such an in- 

 fluence. Long series of magnetic observations in opposite hemispheres 

 (e. g.j 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 59, line 2. 



The remarkable phenomenon of the undulation of stars has very re 

 cently been observed at Trier by very trustworthy witnesses, in Sirius, 

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

 Herru Flesch, in John's Unterhaltungtn fur Freunde der Astronomic. 



Page 132, line 21, note *. 



The wish which I strongly expressed that the historical epoch in 

 which the disappearance of the red color of Sirius falls should be more 

 positively determined, has been partially fulfilled by the laudable in- 

 dustry of Dr. Wopcke, a young scholar, who combines an excellent ac- 

 quaintance 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, 1851, 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, aud.a Orionis, are all expressly called red; Sirius, on the 

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

 as follows in all the four manuscripts: "The first among its (Great 

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

 on the Astrolabiurn, and is called Al-jemaanijak." Is it not probable 

 from this investigation, and from what I quoted from Alfragani, that the 

 epoch of the change of color falls between the time of Ptolemseus and 

 the Arabs. 



Page 194, line 21. 



In the condensed statement of the method by which the parallax of 

 the double stars is found by means of the velocity of light, it should be 



