Page 138

138                THE LAIOWIATORY.
   Salt, well dried and ground, is as effectual as any of the
former things, for cleansing of pearls, by rubbing them
therewith; and if afterwards you lay them up in some
ground millet, it will contribute to their natural brightnes
                    OF DOUBLETS.
  A DOUBLET, among lapidaries, implies a counterit
stone composed of tw pieces of crystal, with proper o.
fours between them; so that they may make the same
appearance to the eye as if the whole substance of the
crystalhad been tinged with these colours.
   The impracticability of imparting tinges to the bodyo
genuine natural crystals, without depriving them of thei
brilliancy, gave inducements to the introduction of colour
ing the surface of them, so as to give them, when finished,
the appearance of a gem. They have not the property
which artificial stones have of being'set transparent, as s
required for drops of earings, &c. but they suit very well
for rings, and other ornaments which allow of an opaqv
back-ground. They are made after the following manner:
   A crystal, or glass in imitation of crystal, is to be ct
by a lapidary into the shape of, the precious stone it is to
resemble; a brilliant, for instance, must be composed of
two separate stones, or two parts of one stone, forming
the upper and under parts of the brilliant, dividing the
whole stone in a horizontal plane, a little lower than die
middle. No division appearing between the two iices
when duly polished and placed on one another, the colou
of the intended stone is put betwepn them, after the fo1
lowing method:
  Take of Venice or Cyprus turpentine two scruples, and
add to it one scruple of the grains of mastich, chosen per-
                                                   fecty