ELASTICITY AND CRYSTALLINE FORMS. 
281 
The following is a synoptical table of the various possible systems of euthytatic 
axes, arranged according to their degrees and kinds of symmetry, and of the crystal- 
line forms to the faces and edges of which such systems of axes are respectively 
normal. 
Systems op Euthytatic Axes. 
Crystalline Forms. 
c 
I. Asymmetry. 
Faces. Edges. 
Tetarto-prismatic System. 
1. Three unequal Oblique Axes 
. Oblique Hexahedron. 
II. Symmetry about one plane. 
Hemipeismatic System. 
2. Two unequal oblique axes, and one rectangular axis.. Right Rhomboidal Prism Oblique Rhombic Prism. 
3. Two equal and one unequal oblique axis 
.. Oblique Rhombic Prism Right Rhomboidal Prism. 
III. Rhombic and Hexagonal Symmetry. 
Rhombohedral System. 
4. Three equi-oblique principal axes round one axis] 
of symmetry J 
5. Three equi-oblique principal axes in one plane,] 
normal to axis of symmetry J 
|- Rhombohedron Rhombohedron. 
)■ Hexagonal Prism Hexagonal Prism. 
6. Three pairs of secondary axes in planes of symmetry. Pyramidal Dodecahedron Pyramidal Dodecahedron. 
IV. Orthorhombic Symmetry. 
Prismatic and Pyramidal Systems. 
7. Two equal oblique transverse axes normal to one ] 
longitudinal axis J 
8. Two pairs of secondary axes in longitudinal planes . 
Right Rhombic Prism Rectangular Prism. 
.. Octahedron with Rhombic Base ... Octahedron with Rectangular Base. 
V. Okthogonal Symmetky. 
9. Three orthogonal axes, not all equal 
1 . Rectangular and Square Prisms Right Rhombic and square prisms. 
10. Three pairs of secondary axes in principal planes 
. -TV , , , r Octahedron with Rhombic Base and 
.. Irregular Rhombic Dodecahedron •< 
L Rectangular Pnsm. 
11. Two pairs of secondary axes -j 
C Octahedron with square or rectan- ] Octahedron with square or Rhombic 
L gular base J Base. 
Same with 7. One pair of secondary axes 
Right Rhombic Prism Rectangular Prism. 
VI. Cyboid Symmetry. 
Tessular System. 
12. Three equal Orthogonal Axes 
13. Six Diagonal Axes 
14. Four symmetrical intermediate axes 
. Cube. 
Regular Rhombic Dodecahedron ... Cube and regular Octahedron- 
.. Regular Octahedron Rhombic Dodecahedron. 
VII. Monaxal Isoteopy. 
15. One Axis of Isotropy 
16. Innumerable Transverse Axes 
17. Innumerable Equi-Oblique Axes 
. Isotropic Laminae. 
. Isotropic Fibres. 
. Conical Cleavage. 
VIII. Complete Isotropy. 
18. Innumerable Axes of Isotropy 
Amorphism. 
