412 



Dr. L. Vegard on 



of the H atoms are determined by one parameter /, repre- 

 senting the ratio between corresponding sides of the 

 sphenoids at the corners to those of the central one, e. g., 



(y_<v_ 



f ~ UP " OR ~ etc * 



(17) 



Fig. 6. 



/?'*r 





& C atoms 

 # H // 





(2) Another arrangement which would naturally suggest 

 itself is shown in fig, 5. Eight of the twelve H atoms 

 associated with the four C atoms are placed at the corners 

 of the prism which can be constructed round the sphenoid 

 OPQR, the other four H atoms are placed at those middle 

 points of the sides of the base planes which are not occupied 

 by the G atom. In this case the position of the H atoms 

 would be determined without the introduction of any new 

 parameter. 



(3) We might also construct a prism round the sphenoid 



