Four such arms, each with a dop, are used with the polishing lap (Plate VII), and each stands on two square legs on the bench. Pins, _p_, in pairs are fixed to the bench to prevent the arms being carried round by the friction; one near the lap holds the arm not far from the dop, and the other engages in a strong metal tongue, which is best seen at the end of the arm _b_ on Plate VI. Though the arm, which is made of iron, is heavy, yet for polishing purposes it is insufficient, and additional lead weights are laid on the top of it, as in the case of the arm at the back on Plate VII. The copper stalk is strong, yet flexible, and can be bent to suit the position of the facet to be polished; on Plate VII the dops _a_ and _b_ are upright, but the other two are inclined. In addition to the powder resulting from bruting, boart, _i.e._ diamonds useless for cutting, are crushed up to supply polishing material, and a little olive oil is used as a lubricant. Owing to the friction so much heat is developed that even the solder would soften after a time, and therefore, as a precaution, the dop is from time to time cooled by immersion in water. The stone has constantly to be re-set, about six being the maximum even of the tiny facets near the girdle that can be dealt with by varying the inclination of the dop. As the work approaches completion the stone is frequently inspected, lest the polishing be carried too far for the development of the proper amount of ‘fire.’ When finished, the stones are boiled in sulphuric acid to remove all traces of oil and dirt. The whole operation is evidently rough and ready in the extreme; but such amazing skill do the lapidaries acquire, that even the most careful inspection by eye alone would scarce detect any want of proper symmetry in a well-cut stone.