218 



TABLE OF SECONDARY FORMS. 



Secondary forms. 



The hexagonal prism .... 



How they may be derived. 



From the rhomboid, by a 

 combination of Modifica- 

 tions a and e, or a and m. 



hexagonal prism. 



Modification d. 



right rhombic prism 



of 120, Modification h. 



4. CONTAINED WITHIN 

 TWELVE PLANES. 



a. The planes being isosceles 

 triangles. 



Fig. 289. 



From the regular tetrahedron, 



Modification c. 

 cube, Modification 



Fig. 290. 



From the regular tetrahe- 

 dron, Modification/. 



