50 



PROCEEDINGS OF THE AMERICAN ACADEMY 



Crystalline Form — Triclinic. 



From these were calculated : — 



Brachydiagonal a = 1 

 Macrodiagonal b = 1.00362 

 Vertical axis c = 1.00185 



Fig. 2 shows the distribution of planes upon a second set of crystals 

 which were taken from the same specimen of Cryolite as those repre- 



