TABLES 375, 376. 



TRANSMISSIBILITY OF RADIATION. 



TABLE 375. -Color Screens. Jena Glasses. 



307 



See " Uber Farbglaser fur wissenschaftliche und technische Zwecke," by Zsigmondy, Z. fur In- 

 strumentenkunde, 21, 1901 (from which the above table is taken), and " Cber Jenenser Licht- 

 filter," by Grebe, same volume. 

 (The following notes are quoted from Everett's translation of the above in the English edition of 



Hovestadt's " Jena Glass.") 

 Division of the spectrum into complementary colors : 



1st by 2728 (deep red) and 2742 (blue, like copper sulphate). 

 2nd by 454"' (bright yellow) and 447'" (blue, like cobalt glass). 

 3rd by 433'" (greenish-yellow) and 424'" (blue). 

 Thicknesses necessary in above: 2728, 1.6-1.7 mm.; 2742, 5; 454, 16; 447 IU , 1.5-2.0; 433"', 



2.5-3.5; 424 1 ", 3 mm. 



Three-fold division into red, green and blue (with violet) : 

 2728, 1.7 mm. ; 414'", 10 mm.; 447"', 1.5 mm., or by 

 2728, 1.7 mm. ; 436'", 2.6mm. ; 447'", 1.8 mm. 



Grebe found the three following glasses specially suited for the additive methods of three-color 

 projection : 



2745, red ; 438"', green; 447"', blue violet ; 



corresponding closely to Young's three elementary color sensations. 

 Most of the Jena glasses can be supplied to order, but the absorption bands vary somewhat in 



different meltings. 

 See also "Atlas of Absorption Spectra," Uhler and Wood, Carnegie Institution Publications, 1907. 



TABLE 376. Water. 

 Values of a in I = I e ftd , d in c. m. I ; I, intensity before and after transmission. 



First 9; Kreusler, Drud. Ann. 6, 190.1; next Ewan, Proc. R. Soc. 57, 1894, Aschkinass, Wied Ann. 



55, 1895; last 3, Nichols. Phys. Rev. i, i. 

 See Rubens, Ladenburg, Verb. D. Phys. Ges.,p. 19, 1909, for extinction coefs., reflective power and 



index of refraction, i /* to 18 /*. 



SMITHSONIAN TABLES. 



