172 



TABLES 159-162. 

 STANDARD WAVE-LENGTHS, 



TABLE 159. Absolute Wave-length of Red Cadmium Line In Air, 760 mm. Pressure, 15 C. 



6438.4722 Michelson, Travaux et Mem. du Bur. intern, des Poids et Mesures, n, 1895. 

 6438.4700 Michelson, corrected by Benoit, Fabry, Perot, C. R. 144, 1082, 1907. 

 6438.4696 (accepted primary standard) Benoit, Fabry, Perot, C. R. 144, 1082, 1907. 



TABLE 160. International Secondary Standards. Iron Arc Lines. 



Adopted as secondary standards at the International Union for Cooperation in Solar Research 

 (transactions, 1910). Means of measures of Fabry-Buisson (i), Pfund (2), and Eversheim (3). Re- 

 ferred to primary standard = Cd. line, A = 6438.4696 Angstroms (serving to define an Angstrom). 

 76o mm., 15 C. Iron rods, 7 mm. diam. length of arc, 6 mm.; 6 amp. for A. greater than 4000 

 Angstroms, 4 amp. for lesser wave-lengths; continuous current, + Ple above the , 220 volts; 

 source of light, 2 mm. at arc's center. Lines adopted in 1910. 



TABLE 161. International Secondary Standards. Iron Arc Lines. 



Adopted in 1913. (4) Means of measures of Fabry-Buisson, Pfund, Burns and Eversheim. 



(i) Astrophysical Journal, 28, p. 169, 1908; (2) Ditto, 28, p. 197, 1908; (3) Annalen der Physik, 30, 

 p. 815, 1909. See also Eversheim, ibid. 36, p. 1071, 1911 ; Buisson et Fabry, ibid. 38, p. 245, 1912 ; 

 (4) Astrophysical Journal, 39, p. 93, 1914. 



TABLE 162. Some of the Stronger Lines of Some of the Elements. 



SMITHSONIAN TABLES. 



