VOL. I. PLATE I. 



FIG. 1. H. The hexahedron, with a pyramidal 

 section, and a pyramidal axis. 



FIG. 2. O. The octahedron. 



FIG. 3. H. O. Combination of the hexahedron 

 and the octahedron. 



FIG. 4. The same, the faces of the octahedron 

 larger. 



FIG. 5. The hexahedron, with two rhombohedral 

 sections, and a rhombohedral axis. 



Fit;. 6. The hexahedron, with two prismatic sec- 

 tions, and a prismatic axis. 



