ITS MODIFICATIONS. 



173 



Class b. Obtuse solid angles replaced by two 

 planes. 



This modification would produce a series of four- 

 sided pyramids, replacing- the terminal plane, and 

 the new figures would be octahedrons with rhombic 

 bases. 



Class c. Acute solid angles replaced by single 

 planes, which intersect the terminal plane parallel 

 to its short diagonal. 



An octahedron with a rectangular base, as shewn 

 in fig. 231, may result from this class of modifications 

 also, but reversed in its position when compared with 

 that produced by modification a. 



Fig. 231. 



Class d. Acute solid angles replaced by two planes. 



This class produces octahedrons with rhombic bases, 

 differing from those which might result from class . 

 only in the relative inclination of the secondary planes 

 to each other. 



