274 RELATION OF DECREMENTS TO 



Decrements on the obtuse terminal edges. 



D represents the middle plane of clas'kf. 



P 



D is the general symbol of that class. 



i Decrements on the edges of the prism. 



1. On the lateral edges G. 



O 



1 G 1 represents mod. k. 

 r G p .... class I. 



2. On the oblique edges H. 



1 H 1 represents mod. h. 

 H P . . class ?'. 



The doubly Oblique Prism. 



Fig. SIS. 



Decrements on the solid angles. 



The planes comprehended under class a, may b^ 



represented by the following* symbols. 

 P 

 O, when the decrement proceeds along the plane P. 



P O . M. 



O p T. 



(Dp Ilq Fr) is intermediary. 



