SYMMETRY OF SECONDARY PLANES. 



43 



From the foregoing, it necessarily results that the modifications of 

 the terminations, in order to be symmetrical, must always take place 

 in a different manner upon two halves of this solid, supposing the 

 division to be made by a vertical plane passing through the edge G 

 and its opposite. The following examples, drawn also from actual 

 crystals, are in exact coincidence with these relations. 



Fig. 93 represents the oblique rhombic Prism, with the oblique 

 edges of the prism replaced by tangent planes. 



Fig. 94, the same, with the lateral edges of the prism replaced by 

 tangent planes. 



Fig. 93. 



Fig. 94. 



Fig. 95, the same, with the obtuse terminal edges replaced by 

 single planes. 



Fig. 96, the same, with the acute terminal edges replaced by sin- 

 gle planes. 



Fig, 95. 



Fig. 96. 



