BASE, AND ITS MODIFICATIONS. 129 



t 



will apply to all those classes which produce only two, 

 or four ', parallel planes upon the primary form. In 

 these cases, as no entire secondary form can result 

 from the secondary planes alone, no new figure is 

 described. 



Class b. Terminal solid angles replaced by four 

 planes resting on the primary planes. 



The new figures would be more obtuse octa- 

 hedrons. 



Class c. Terminal solid angles replaced by four 

 planes resting on the primary edges. 



Another series of octahedrons more obtuse than 

 the primary would result from this class. 



Class /. Terminal solid angles replaced by eight 

 planes. 



The new figures would be double eight-sided pyra- 

 mids united at a common base, and measuring un- 

 equally over the two pyramidal edges of each of the 

 planes. The surfaces of the new planes would 

 generally be scalene triangles. 



