TABLE 189. 

 TRANSMISSIBILITY FOR RADIATION. 



Transmissibility of the Various Substance! of Tables 166 to 175. 



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



Metallic reflection at 9.05/4 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 0.110/4, 0.156, 51.2, and 87/1. 

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



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



Iceland Spar : Merritt (Wied. Ann. 55, 1895) S ives 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 0.222/4, 94.2%; 0.214, 92 ; 0.203, 83-6; 0.186, 67.2%. 

 Merritt {Wied. Ann. 55, 1895) gives the following values for k (see formula under Iceland Spar) : 

 For the ordinary ray : 



For the extraordinary ray : 



For \>7 f^ becomes opaque, metallic reflection at 8.50/4, 9.02, 20.75-24.4/4, then trans- 

 parent again. 



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

 SMITHSONIAN TABLES. 



