286 



TABLE SiS. 



INDEX OF REFRACTION. 

 Selected Biaxial Minerals. 



The values are arranged in the order of increasing /3 index of refraction and are for the sodium D line, except where 

 noted. Selected by Dr. Edga; T. Wherry from private compilation of Dr. Esper S. Larsen of the U. S. Geological 

 Survey. 



SMITHSONIAN TABLES. 



