328 R. W. G. Wyckoff— Crystal Structures of 



another (fig. 2) ; in this way the indices of a plane are 

 expressed by their Bravais-Miller symbols. Then, if the 

 fundamental lattice is really rhomb ohedral so that it is 

 desirable to refer the planes to the rhombohedral, i. e. de- 

 formed cubic, axes, the necessary transformation to Mil- 

 ler indices may be made with the aid of the familiar trans- 

 formation: 12 



Fig. 6. — The gnoraonic projection of a simple Lane photograph (X-rays 

 parallel to the c-axis of rutile). The indices of the reflecting planes are 

 directly obtained from the coordinates of their projected positions. 



h = 2H + K + L 

 &=K— H + L 



I = — 2K — H + L. 



H K L, suppressing as unnecessary the third index, are 

 the Bravais-Miller indices, and h h I are the Miller indices. 



12 P. Groth, Physikalische Krystallographie, p. 434, 1895. 



