MODIFICATIONS. 275 







The corresponding planes belonging to the other 

 classes, may be represented as follows. 



Class ^ A. Class c, E. Class d, I. 



P A. P E. p l. 



A p . E p , P. 



(Bp llq Cr). (Bp Gq Dr). (Fp G'q Cr). 



Decrements on the edges may be expressed as follows. 



P P Class i, P H. 



Class e, B. Class g, D. H p . 



p P 



Class f> C. Class //, F. Class k, P G. 



G p . 



Hexagonal Prism. 

 Fig. 319. 



Decrements on the angles. 

 i 



A represents the middle plane of the series be- 

 longing to class a. 

 P 

 A ... the other planes belonging to that 



class. 



P A P . . . those planes belonging to class b, 

 whose edges intersect the planes 

 M parallel to a diagonal. 



