l82 



Table 1 67. 

 INDEX OF REFRACTION. 



Index of Retraction of Metals and Metallic Oxides. 



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

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



Smithsonian Tables. 



t Nearly pure oxide. 

 § " Wied. Ann." vol. 39. 



