20 



CRYSTALLOGRAPHY. 



Again, fig. 20 represents a cube with three planes on each 

 angle, which, if enlarged to the obliteration of the faces of tha 

 cube, become the trigonal trisoctahedron, fig. 21. So again, fig. 



22 represents a cube with six faces on each angle, which, if en* 

 larged to the same extent as in the last, would become the hex* 

 octahedron, fig. 23. 



Again, fig. 25 is a form between the octahedron (fig. 24) and 



dodecahedron (fig. 26) ; and figs. 27 and 28 are forms between 

 the dodecahedron, fig. 26, and trapezohedron, fig. 29. 



