Results 0] Crystal Analysis. 409 



elements ; the other two to the second molecular elementary 

 lattice. The sphenoid, drawn on a larger scale, is repre- 

 sented in fig. 5, which also shows the dimensions expressed 

 in terms of the two parameters ex,' and y' and the sides a' 

 and c' o£ the elementary lattice. 



Fig. 4. 



® / atoms 

 %N „ 



• c ,, 



The side OP = — a', and the distance between the lines OP 



7' j 



and QR is equal to 



iml It 



As shown in fig. 5, we can imagine the sphenoid placed 

 inside a prism with a square base and with the carbon atoms 

 placed at the middle points of four o£ the sides. The sides 

 of the prism are parallel to corresponding sides of the 

 lattice. 



The side of the square base of the prism a" is equal to OP 

 / / 



or— a'; and the height c" of the prism is equal to ¥-c'. 



