Fig. 448.—Rock crystal—second system.
Figs. 449 and 450.—Quadratic, or third system.
Fig. 451.—Prism of quadratic system.
The fifth is the oblique, or Monoclinic system, which displays three unequal axes, two of which are at right angles; the third, or principal axis, is at right angles to one and oblique to the other of the preceding. Ferrous sulphate, tartaric acid, and gypsum crystallize in this system.
Fig. 452.—Rhombic, or fifth system of crystals.
