Table: 1 87. 



INDEX OF REFRACTION. 



Index ol Retraction ol Metals and Metallic Oxides. 



• " Wied. Ann." vol. 34, and " Phil. Mag." (5) vol. 26. 

 t Wave-lengths A are in millionths of a centimetre. 



t Nearly pure oxide. 

 § " Wied. Ann." vol. 39- 



Smithsonian Tables. 



181 



