BASE, AND ITS MODIFICATIONS. 159 



Class r. Acute lateral solid angles replaced by 

 four oblique planes, inclining on the edges of the 

 pyramids. 



Class s. Acute lateral solid angles replaced by 

 four oblique planes, inclining on the edges of the base. 



The planes r, and s, intersect the primary planes 

 in lines which are not parallel to the edges of the 

 pyramids. 



The new figures resulting from class q, r, and s, 

 would be octahedrons, more acute than the primary, 

 with rhombic bases. 



Class t. Obtuse edges of the pyramids replaced 

 by tangent planes. 



