ITS MODIFICATIONS. 213 



conceive the edges to represent wires, united at the 

 solid angles by universal hinges or joints, and capable 

 of being moved in every direction ; and, together 

 with the axes, capable also of being lengthened or 

 shortened. 



If we conceive one of the axes of the cube to be 

 lengthened, the resulting figure would be an acute 

 rhomboid. If we suppose the axis shortened by 

 pressing at the same time upon the two opposite 

 solid angles through which the axis to be shortened 

 passes, an obtuse rhomboid would be produced. 



If two opposite lateral edges of the square prism 

 be supposed to be gradually pressed together, so as 

 to shorten one of the diagonals of the terminal plane, 

 and to lengthen the other, the resulting figure would 

 be a right rhombic prism. 



If we now suppose pressure applied to an acute or 

 an obtuse solid angle of this rhombic prism^ and the 

 prism to be forced from its perpendicular in the 

 direction of one or other of the diagonals of its ter- 

 minal plane, an oblique rhombic prism would be pro- 

 duced. 



If two opposite lateral edges of the right rectangular 

 prism be pressed more or less towards each other, a 

 right oblique-angled prism would be produced. 



And if this right oblique-angled prism were slightly 

 forced from its perpendicular position, in the direc- 

 tion of either of its diagonals, a doubly oblique prism 

 would result. 



So if the vertical axis of the regular octahedron 

 were to be lengthened or shortened, an octahedron 

 with a square base would be produced. And if two 

 opposite angles of that square base were pressed 

 together so as to shorten one of its diagonals, and, to 

 lengthen the other, the resulting figure would be the 

 octahedron with a rhombic base. 



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