( 709 ) 



the investigation, described on p. (>'.' of "Die Lichl nnd Warme- 

 strahlung verbrannter Gase" thai many (tains were laken to reduce 

 this source of error. There the CO s -maximum of the Bunsen flame 

 was found at minimum deviation 38°54'20", the refracting angle ot 



the prism being 59°53'20" and the temperature 10°. From this 

 follows ra = 1,52103. Had the temperature been 20°, then the devia- 

 tion would have been found smaller by L'50", giving for the index 

 of refraction: n = 1.52069. 



If we suppose this value to be exact, then the angles of minimum 

 deviation given in my first paper in Arch, néerl. 22, and on pages 

 47 — 68 of "Die Licht- und Warmestrahlung" are too small by 

 nearly 3', owing to an instrumental error. In "Bolometrisch onder- 

 zoek van absorptiespectra" the deviation of the CO s -maximum has 

 been found 38°52'40" instead of 38°54'20" ; V of this difference 

 results from the fact that the refracting angle of the prism, then in 

 use, was smaller than that of the other one by 1'; only the 

 remaining 40" were owing to an instrumental error. 



I have now applied the corrections resulting from this re-exami- 

 nation, and calculated the indices of refraction for 20°, the tempe- 

 rature to which the dispersion curves as compared by Mr. Moll 

 also refer. In finding the wave-lengths corresponding to the indices, 

 advantage has been taken of elaborate tables, prepared by Dr. Moll 

 for a research of his own, and which he was kind enough to put 

 at my disposal. 



