38 



TERMINOLOGY. 



Fig. 69, represents the Octahedron with a square base, having 

 its pyramidal edges replaced by tangent planes. 



Fig. 70, the same, having the edges of the ba^e replaced by tan- 

 gent planes. 



Fig. 71, the same, with the solid angles of the base replaced by 

 tangent planes. 



Fig. 69. 



Fig. 70. 



Fig. 71. 



Fig. 72, the same, having its pyramidal edges replaced by two 

 planes. 



Fig. 73, represents the Octahedron with a rectangular base, hav- 

 ing the edges of the pyramids replaced by single planes. 



Fig. 72. 



Fig. 73. 



Fig. 74, represents the Octahedron with a rhombic base, having 

 the edges of the base replaced by tangent planes. 



Fig. 75, the same, with its terminal solid angles replaced by tan- 

 gent planes. 



