MODIFICATIONS. 255 



If p ^> 1, class b is represented, and as the value 

 of p increases, the planes b 

 incline more and more on the 

 primary planes. 

 p 1, mod. a is represented. 

 p <^ 1, class c is represented, and as the value 

 of p diminishes, the planes c 

 incline more and more on the 

 primary edges. 



Intermediary decrements produce the planes be- 

 longing to class d. 



The general symbol representing these, is 

 (Bp B'q B'"r : Bq B'p B"'r). 



Decrements on the edges, produce the planes be- 

 longing to the classes e and /. 



The general symbol representing these is 



fi 



p 

 If p = I, class e is represented. 



p ^> 1, class fis represented. 



2. Modifications not strictly conformable with the law 

 of symmetry ; or, such as have been termed defective 

 modifications. 



The following are the symbols representing these 

 classes. 



o 



04/0 



A' 'A 1 'a" a represents class g. 



A' P A P V a . . . . class h. 



(B' q B P B // r)(B" q B'p Br)(B'r B" P Bq) represents 



the planes at A' belonging to class i. 

 (B q B'" P B'r)(B'"q B'p Br)(B ; q B P B //7 r) represents 



the planes at A belonging to the same class. 



