ITS MODIFICATIONS. 179 



Class 6. Acute solid angles replaced by single 

 planes. 



The planes of both these modifications are scalene 

 triangles. 



Class c. Greater terminal edges replaced by single 

 planes. 



Class d. Lesser terminal edges replaced by single 

 planes. 



The relative dimensions of the terminal edges can 

 be ascertained only from some modification which is 

 supposed to indicate the direction of one of the diago- 

 nals of the terminal plane ; from this the angle which 

 the diagonal makes with an edge of the same plane 

 may be deduced, and thence the ratio of the terminal 

 edges may be known. 



Class e. Obtuse edges of the prism replaced by 

 single planes. 



