COMMON IRON-GLANCE. 235 taliedron *, fig. 209. This octahedron is some times truncated on the angles f, fig. 210. 6. When the truncating planes on the angles of the octahedron become of equal size with the planes of the octahedron, there is formed an equiangular six-sided table, in which the terminal planes are llatly bevelled j, fig- 211. 7. When the summits of the double three-sided py ramid are deeply truncated, there is formed a six-sided, table, in which the terminal planes are set alternately oblique and straight on the lateral planes ; and the lateral planes are sometimes straight and sometimes spherical-convex. 8. The lens, which is the double three-sided pyramid, having its summits and lateral edges rounded ||. 9. When the bevelling planes of N° 3. become so large as to obliterate the other planes, there is formed an acute double six-sided pyramid, in which the lateral planes of the one rest on the lateral planes of the other, and the pyramid is deeply truncated on the extremities §, fig. 212. Sometimes the alternate lateral edges are ti un- cated ^[, fig. 213.; and sometimes the angles on the common, base**, fig. 214. 10. Low * Per oligiste basis Hauy. + Fer oligiste imitatif, Hauy. 7 Fer oligiste imitatif, var. Ilauy. 1 Fer oligiste lenticulaire, Hauy. § Fer oligiste trapezien, Ilauy. Fer oligiste uniternaire, Hauy. ** Fer oligiste progressif, Hauy,