'912.] THE LAW OF RATIONAL INDICES. 117 



complex, the complexity in general increasing with the rarity of the 

 face. The structure theory of Bravais offers a satisfactory ex- 

 planation of the abundance of faces with simple indices and the 

 rarity of faces with complex indices. There is a remarkable analogy 

 between the fundamental laws of chemistry and crystallography. 

 Stanford University, 

 California, 

 Feb., 1912. 



PROC. AMER. PHIL. SOC, LI. 204 E, PRINTED JUNE 5, I9I2. 



