Page:A treatise on diamonds and precious stones including their history Natural and commercial.djvu/21

Nos. I. to VI. represent the sizes of brilliants of from one to six carats, cut in exact proportion.

A. An instrument called by diamond cutters "The Compass." It is formed of a piece of plain brass for the base, with a moveable arm in the centre, which in the fig. is set at 45 deg. measuring the inclination of the collet side to the girdle; and of the bizel to the table, at the supplement of the same angle. See p.73.

PLATE II.

FIGURES OF ROUGH DIAMONDS.

No.	1.	The dotted line shews the direction in which it will split.
	2.	The octahedron split in half.
	3.	Shews No. 2. split, forming a quadrant or sharp.
	4.	The octahedron passing into the tetrahedron.
	5.	Cubic octahedron, or the octahedron passing into the cube.
	6.	Octahedron truncated on the edges.
	7.	Dodecahedron complete.