be considered as formed of two truncated pyramids united together by one common base, the upper pyramid being much more deeply truncated than the lower. The plane formed by the truncature of the upper pyramid is called the table (a); that formed by the truncature of the lower is called the collet (b); the common base is called the girdle (c); the space between the table and the girdle is the bizel (d), and that between the girdle and the collet is the collet-side (e). The inclination of the facets to the girdle ought to be 45°, and the bizel should be inclined to the table at the supplement of the same angle; it is absolutely necessary that the collet should be exactly parallel to the table.—If these measurements are accurately observed, the superlative splendor of the diamond will be displayed to the greatest advantage. The rule tobe adopted in regulating the height of the brilliant is, (supposing the stone to be a regular octahedron), to divide it into eigh-
