270 RELATION OF DECREMENTS TO 



Intermediary decrements on the acute and obtuse solid 

 angles. 



General symbol (B' P G q Br : B'r G P BP) repre- 

 sents a further series of planes 

 belonging to class d. 



(B P H q B'r : Br Bq B'p) repre- 

 sents a further series of planes 

 belonging to class b. 



Decrements on the terminal edges. 



p 



General symbol B, represents class e, generally. 



i 



B 5 represents its middle plane. 



Decrements on the lateral edges. 



1. On the acute edges. 



*G* represents mod. h. 

 *G V .... class i. 



2. On the obtuse edges. 



1 H 1 represents mod. f. 

 P H P . . . class g. 



The exposition which has been given, in reference 

 to the preceding classes of primary forms, of the re- 

 lations of the laws of decrement to the several classes 

 of modifications, will, it is presumed, have been suf- 

 ficiently full, to render more than an outline of those 

 relations unnecessary, in reference to the classes of 

 primary forms which are to follow. 



