254 



RELATION OF DECREMENTS TO 



This whole number or fraction may be either 

 greater than 1, which may be thus denoted p ^> 1 ; 



equal to J, . p 1 ; 



or less than 1, p <^ ]. 



The mark ^> signifying greater than, 

 = . . . equal to, 

 <^ . . . less than. 



The letter p will generally be used to denote the 

 greater edge of the defect, the letter q the next, and 

 r the least, when there are only three edges to be 

 denoted. But when the symbol represents a modifi- 

 cation on the solid angle of an octahedron, s is intro- 

 duced to denote the fourth and least edge of the 

 defect. Hence the relative values of p, q, r, and s, 

 may be thus expressed, p ^> q ^> r ^> s. 



The Cube. 

 Fig. 306. 



1. Symmetrical modifications. 



Simple and mixed decrements on the angles, produce 

 the planes belonging to modifications , b, and c. 

 The general symbol to represent these is 



P A P . 



