406 Dr. L. Vegard on 



Let I, N, C, and'H denote the atomic numbers ; then we 

 get, after some reduction, 



For the face (100), 



A» = I + N + 2C(l + cos2?2«) ; 

 For the face (110), 



A n = I + N + 4Ccos??a; 

 For the face (001), 



A n = N cos nA + 4C cos nB + ( - 1)" I cos nQ ; 

 For the face (101), 



An= Ncosn^— A)4-2C(coswa + l)cosn^— B) 



+ Ico3w'i ^ — C J ; 

 For the face (111), 



A n = ( — l) n N cos nA + 4C cos no! cos ??B + 1 cos nO ; 

 where 



B=t- 8 + A 



For the atomic numbers, we introduce 



I = 53, N = 7, C = 6, H = 1. 



The fact that the atomic number of iodine is large as 

 compared with those of the other atoms is of great value 

 when we are going to determine the parameters. 



From the faces (100) and (110), we find that the value 

 of a must be near to 147°. 



Let us, then, introduce the atomic numbers and divide 

 by 7 ; then 



(001) A TC = cos/zA-f 3-43coswB + (-l)»7-57cosnC, 



^111) A n = ( - l) n cos n A + 3*43 cos n 33° cos nB + 7*57 cos wC, 



(101) A„=cos7i^-a]+1-72(1 + (-1) w cos7i33°)cos ? i^-B^ y ( 12 )' 



+ 7-57 cos (|-C), 



