COMMON LAPIDARY.
Such
common precious stones as are suitable to be cut fcr snuff-boxes,
rings, grinding mortars, seals, and earrings, are wrought by the
common lapidary, by means of copper or iron wheels revolving
vertically. The tools are generally of iron, and sometimes brass; some
are flat like chisels, gouges, ferrules, and some others have
coriicular heads. The polish is given with rotten-stone, on a tin
plate, or with crocus martis, on a wooden plate covered with felt. The
cuts applied by the workmen are either even, cup-shell form, excavated,
elevated, or quite simple; facets are not used by him.
Mr.
Jfawe describes a lapidary's apparatus, fit for polishing minerals,
shells, &c, and which may be placed in a parlor, where every
operation of polishing, on a scale suffi-' ciently large, may be
effected, and pebbles may be slit of three or four inches diameter. It
consists of the following mills:
1st. A lead mill, or wheel, to be used with emery and water, for grinding down substances preparatory to polishing.
2d. A pewter mill, to be used with rotten-stone a little wet, for polishing.
3d. Tin plate, properly prepared, the edge of which is to be used with diamond powder, to slit or cut hard stones asunder.
4th. Wood rriills, covered with leather, &c, for polishing marble, alabaster, shells, or other soft substances.
ENGRAVING.
The value of many precious stones is increased by engraving them. The common gems have, for several centu-
