ITS MODIFICATIONS. 177 



Class t. Acute lateral edges replaced by two planes. 



This modification would produce another series of 

 right rhombic prisms. 



A general analogy may be observed to prevail be- 

 tween these secondary forms, and those of the octa- 

 hedron and a rhombic base, and it is only from 

 cleavage that we are enabled to refer the secondary 

 forms to either of these primary ones. 



AND ITS MODIFICATIONS. 



Primary form. A right oblique-angled prism. 



The angles and edges of this class of prisms may 

 be designated as those of the right rhombic prism 

 have been, calling the solid angles at A the obtuse, 

 those at E the acute solid angles ; the lateral edges 

 at H the obtuse, those at G the acute lateral edges ; 

 the edges B may be called the greater, and C the 

 lesser terminal edges. 



The individuals belonging to this class of prisms 

 will differ from each other in the inclination of M on 

 T, and in the relative lengths of the edges C, B, 

 andH. 



Modifications. 



Class a. Obtuse solid angles replaced by single 

 planes. 



