ITS MODIFICATIONS, 



Primary form. The cube. 



Modifications. 



Class a. Solid angles replaced by tangent planes. 



The modifying planes are equilateral triangles. 



When the modifying planes are so extended as to 

 efface the primary planes, a regular octahedron will 

 be produced. 



Plane a on P, P' or P", 120 9 15' 52". 



Class b. Solid angles replaced by three planes 

 resting on the primary planes. 



Each of the series of new figures produced by this 

 class, would be contained within 24 equal trapezoidal 

 planes. But the trapezoidal planes belonging to each 

 figure of the series would differ in their angles from 

 those belonging to every other figure of the same 

 series. 



Obs. A trapezoid is a four-sided figure whose 

 opposite edges are unequal^ and in which, if lines be 

 drawn through the angles a, and 6, c, and rf, they 

 o2 



