TABLE 372. 

 TRANSMISSIBILITY OF RADIATION. 



Transmissibility of the Various Substances of Tables 330 to 338. 



305 



Alum : Ordinary alum (crystal) absorbs the infra-red. 



Metallic reflection at 9.05/1 and 30 to 40/4. 



Rock-salt : Rubens and Trowbridge (Wied. Ann. 65, 1898) give the following transparencies for 

 a i cm. thick plate in % : 



Pfliiger (Phys. Zt. 5. 1904) gives the following for the ultra-violet, same thickness : 280/1/1, 95.5% 



231, 86%; 210, 77%; 186, 70%. 

 Metallic reflection at 0.110/1, 0.156, 51.2, and 87/1. 

 Sylvite : Transparency of a i cm. thick plate (Trowbridge, Wied. Ann. 60, 1897). 



Metallic reflection at 0.114,1*, 0.161, 61.1, 100. 

 Fluorite : Very transparent for the ultra-violet nearly to o.i/i. 



Rubens and Trowbridge give the following for a i cm. plate (Wied. Ann. 60, 1897) : 



Metallic reflection at 24/4, 31.6, 40/1. 



Iceland Spar: Merritt (Wied. Ann. 55, 1895) gi yes the following values of k in the formula 

 i = i e- kd (d in cm.) : 

 For the ordinary ray : 



For the extraordinary ray : 



Quartz : Very transparent to the ultra-violet ; Pfliiger gets the following transmission values for 



a plate i cm. thick : at 0.222/1, 94.2%; 0.214, 92 ; 0.203, 8 3-6; 0.186, 67.2%. 



Merritt (Wied. Ann. 55, 1895) gi ves tne following values for k (see formula under Iceland Spar) : 

 For the ordinary ray : 



For the extraordinary ray 



For X>7 /*, becomes opaque, metallic reflection at 8.50/1, 9.02, 20.75-24.4/1, then trans- 

 parent again. 



The above are taken from Kayser's " Handbuch der Spectroscopie," vol. iii. 



SMITHSONIAN TABLES. 



