Crystalline Structure of Antimony. 235 



arrangement of these lattices is, however, different, as may be 

 seen from a consideration of the intensities of the spectra 

 from the different faces. 



The following structure will be found to account com- 

 pletely for the observed angles and intensities of the spectra. 

 The antimony atoms lie in two interpenetrating face-centred 

 lattices. Suppose for one of the lattices, diagonals are drawn 

 parallel to the trigonal axis for each of the eight equal rhom- 

 bohedral cells into which the unit lattice may be divided. 



Fig. 2. 



^1 



kl 



From considerations of symmetry, it will be seen that the 

 atoms of the second lattice must lie in these diagonals. 

 If they lay at the unoccupied corners of the first lattice, the 

 structure would become a simple rhombohedral one. This 

 will not fit in with the observed facts, but if the atoms of the 



R 2 



