414 



Dr. L. Vegard on 



In the same way we can show, by a comparison with the 

 faces (110), (100), and (001), that the arrangement (3) is 

 unable to explain the observed distribution o£ intensities. 



We are then to consider the arrangement (1) (fig. 6), 

 which also, on account of the peculiar grouping of the 

 C atoms, might seem the most probable. 



The position of the hydrogen planes for any face is easily 

 found from the assumption of similarity when we know the 

 position of the C planes. 



Let d, C 2 , C 3 , 4 (fig. 7) be the positions of four C planes 

 belonging to the same group of four atoms which are placed 



Fk-. 7. 







1 fl 



a r 



«- <•->£— 



i 



p 



Cj fi C 2 C$ Ljf. 



at the corners of the sphenoid, and passing through the four 

 C atoms O, P, Q, R, respectively ; then we easily see from 

 fig. 6 how the three H planes belonging to any of the 

 C atoms are going to be arranged. Let us, for example, find 

 the H planes belonging to the C 2 planes. Let the distance 

 between C and one of the other C planes be l c ; then a 

 corresponding H plane is found on the opposite side of C at 

 a distance 



where /is the ratio given in equation (17). 



The planes of the various atoms which form one period 

 are represented in fig. 8 for the five faces in question. The 

 arrangement of planes corresponds to the following values 

 of the parameters 



y = 70, «' = 33, /=0-64, 



which are values which were found to give a satisfactory 

 agreement between calculated and observed intensities. 



