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THE BOOK OF THE PEARL
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struction
of this drill a piece of round steel wire of suitable size is chosen;
this is hammered flat at one end and then filed away at each side,
leaving a small spike standing in the center, which projects a little
beyond the cutting edges and acts as a pivot on which the drill
revolves. The steel on both sides of this spike is filed down to a fine
edge, care being taken to preserve the horizontal line, so that when
the spike is embedded in the metal both cutting edges come into play
simultaneously. If the drill is in good condition, it does its work
very rapidly, since it is used in an upright drill-stock, whose weight
gives a uniform and constant pressure. A good range of sizes of this
drill should be kept ready for use, so that one may be found to suit
the dimensions of any given pearl. This is essential in order to make
an opening just large enough to hold the gem, so that it may fit
tightly, without the necesssity of reaming out the hole.
Half-pearls
were frequently used with the most pleasing effect in the decoration of
antique watches. A number of remarkable examples of this type are among
the collection of antique watches of Henry Walters of Baltimore. This
collection had been acquired by Tiffany & Co. after the sale of the
San Donato Palace, the watches having been withdrawn from the prince's
collection by his sister sometime before the sale.
In mounting pearls on gold, a white paste is sometimes employed in half-pearl mounting, which is called by the French jewelers gouache. This
substance contains white lead, and its use is liable to be injurious to
the workmen, cases of lead colic having been recently recognized as
thus produced. This subject has lately (1907) been brought forward at
the Société Médicale des Hôpitaux in Paris. The cases were at first
mistaken for appendicitis, but proved to be well-marked cases of lead
poisoning. They had not been reported previously, and are evidently not
frequent, those noted being confined to instances in which the
employees had carelessly been in the habit of removing an excess of the
paste with the tongue.
Pearls
that are constantly worn with judicious care do not seem to deteriorate
in any way. By judicious care we mean that pearls should not be dropped
or thrown down violently or placed on any substance which is likely to
act injuriously on the surface of the pearl itself.
Strings
of pearls should never be dipped into water or solutions of any kind,
because the string which passes through them is likely to absorb and
to draw the liquid into the pearl, and as the pearl is made up of many
concentric layers, it is quite possible that, through capillary action,
some liquid, either pure, or stained with a foreign substance, might be
brought into the pearl, which would in this way eventually become
discolored. Rings and brooches containing half-pearls fre-
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