A text-book on chemistry : for the use of schools and colleges . In the figure (Fig. 139), 1 is the regular six-sided prism ;2, the dodecahedron ; 3. Rhombohedron ; 4. another dode-cahedron. It often happens, owing to a change in the deposit ofnew matter on a crystal while forming, that other figuresthan the proper one are produced ; thus, the cube maypass into the octahedron, as shown in Fig. 140. How many axes arc in the rhornbohedral system, and what is their re-lation ? In what manner may crystals of one fomi pass into those ofanother, as the cube into the octahedron ? 140
A text-book on chemistry : for the use of schools and colleges . In the figure (Fig. 139), 1 is the regular six-sided prism ;2, the dodecahedron ; 3. Rhombohedron ; 4. another dode-cahedron. It often happens, owing to a change in the deposit ofnew matter on a crystal while forming, that other figuresthan the proper one are produced ; thus, the cube maypass into the octahedron, as shown in Fig. 140. How many axes arc in the rhornbohedral system, and what is their re-lation ? In what manner may crystals of one fomi pass into those ofanother, as the cube into the octahedron ? 140. 159. The effect may, perhaps, be better conceived by imagin-ing the solid angle of the cube 1 to be cut off by planesequally inclined to the constituent faces. 2 represents anincreased removal of the same kind; 3 one still fartheradvanced. Sometimes it happens that each alternate plane of acrystal grows at the expense of the adjacent one, givingrise to hemihedral, or half-sided crystals, as is shown inFig. 141, which represents the tetrahedron, arising in thismanner from the octahedron by the growth of each alter-nate face. 1. The octahedron partially modified; 2. Thechange farther advanced; 3. The tetrahedron completed. Fig. 141.
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