204 W. D. HALLIBURTON. 



in different parts of the field. These are depicted in the 

 accompanying cuts. 



Mr. Fletcher kindly examined these for me, and expressed 

 it as his opinion that the triangular and rhombic forms were 

 merely variations of the hexagons. In the case of b faces 1, 

 3, and 5, and in the case of d faces 3 and 6 have virtually 

 disappeared. 



