Pearl.—A
peculiar product of certain marine and fresh water molluscs or shell
fish. Most of the molluscous animals which are aquatic and reside in
shells are provided with a fluid secretion with which they line their
shells, and give to the otherwise harsh granular material, of which
the shell is formed, a beautifully smooth surface, which prevents any
unpleasant friction upon the extremely tender body of the animal. This
secretion is evidently laid in extremely thin semi-transparent films,
which, in consequence of such an arrangement, have generally a
beautiful irridescenee, and form in some species a sufficient thickness
to be cut into useful and ornamental articles. The material itself in
its hardened condition is called nacre by zoologists, and by dealers
Mother-of-1'earl. Besides the pearly lining of the shells, detached and
generally spherical or rounded portions of the nacre are often found on
opening the shells, and there is great reason to suppose these are the
result of accidental causes, such as the intrusion of a grain of sauct
or other substance, which, by irritating the tender body of the animal,
obliges it in self-defence to cover the cause of offence, which it has
is no power to remove ; and as the secretion goes on regularly to
supply the growth and wear of the shell, the included body constantly
gets its share, and thereby continues to increase in size until it
becomes a pearl. The Chinese avail themselves of the knowledge of this
fact to compel one species of freshwater mussel, Unio Hyria, to produce
pearls. In order to do this, they keep the Unios in tanks, and insert
between the shell and the mantle of the animal either small leaden shot
or little spherical pieces of mother-of-pearl. These are sure to
receive regular eoatings of the nacreous secretion; and after a time
look like pearls formed under ordinary circumstances. These curious
people also practice another trick upon these animals; they insert
small images of the Buddha stamped out of metal, which soon become
coated with the pearl secretion, and are cemented by it to the shells;
to those ignorant of its origin, the phenomenon is a supernatural
testimony to the truth of Buddhism. Examples of these curiosities are
to be found in many of our museums.
A
plan of making pearls was suggested to the Swedish Government by
Linmeus. It consisted in boring a small hole through the shell of the
river mussel, and inserting a grain of sand, so as to afford a nucleus
for a pearl. The plan at first succeeded sufficiently well to prove its
practicability, and he was rewarded by a sum of money (£450) but it
failed as a profitable speculation, and was abandoned.
The
exact nature ot the secretion has never been satisfactorily determined;
it is, however, ascertained that it is deposited in thin films; which
overlie each other irregularly, and to this peculiar disposition of the
plates, the beautiful irridescenee of common pearls is attributed. This
formation was ft great puzzle to the ancients, amongst whom they were
highly prized. Dioscorides and Pliny mention the belief that they were
drops'of dew, or rain which fell into the shells when opened by the
animals, and were then altered by some power of the auimal into pearls.
This opinion which, obtained all over the east, is thus charmingly
alluded to by Moore:— " And precious the tear as that rain from the
sky, which turns into pearls as it falls in the sea."
The
most famous pearls are those from the east; the coast of Ceylon, or
Taprobane as it was called by the (Greeks, having from the earliest
.times been the chief locality for pearl fishing. They are, however,
obtained no.v of nearly the same quality in other parts of the world,
as Panama in South America, St. Magarita in the West Indies, the
Coromandel Coast, the shores of the Snlu Islands, the Bahrim Islands,
aud the islands of Karak and Corgs in the Persian Gulf. The pearls of
the Bahrim fishery are said to be even finer than those of Ceylon, and
they form an important part of the trade of Bassora. These, and indeed
all the foreign pearls used in jewellery, are produced by the pearl
oyster. The shells of the molluscs which yield the Ceylon, Indian and
Persian ones, are sometimes as much as a foot in diameter, and are
usually about nine inches. Those of the New World, although the shells
are smaller and thicker, are believed to be the same species. The chief
locality of the Oeylon pearl fishery is a bank about 20 miles long, 10
or 12 miles from shore, opposite to the villages of Oondatchy and
Arippo on the northern coast. The season of the fishery lasts about
three months, commencing at the beginning of February, and is carried
on uuder Government regulations. The boats employed »re open, and vary
in size from 10 to 15 tons burden ; they put out at night,
