obtained
there to the queen of Spain. Since that time the fisheries have been
carried on with a varying degree of persistence from time to time, the
beds having occasionally become practically exhausted through too
reckless dredging. The right to work the beds is held by the Mexican
government, and the fisheries are leased by it to different companies.
Both the shells and the pearls are of value, the sales of the one
reaching as high a figure as of the other. Black pearls are the
specialty of these fisheries, and some of the finest known have been
found here. The total annual product from the fisheries reaches at the
present time a value of half a million dollars a year. American pearls
are known in trade as "Panama" pearls, and bring a somewhat lower price
than those of the Orient.
Besides
the pearl oyster of the sea, a number of mussels which make their home
in the beds of fresh-water streams or lakes produce fine pearls. These
mollusks belong chiefly to the family Unionidae, and include
many species. They are bivalves, and live both in the beds of running
streams and in still bodies of water on muddy bottoms. They are usually
to be found at a depth below the surface of the water of from two to
twenty feet. They lie either on the surface of the mud, or partly
imbedded in it, and with their valves slightly open, to allow access of
water containing oxygen and food. At the slightest touch the valves
close, and remain so until danger is past. The lumbermen of Canada
take advantage of this peculiarity to collect the mollusks for food by
tying bushes on the rear of their rafts as they float down stream, to
which the clams attach themselves in considerable numbers. A somewhat
similar method is pursued by the fishermen of the Mississippi Valley,
who collect the clams in great numbers for the manufacture of pearl
buttons. They row about with long iron rods fastened across their
boats, from which at intervals series of hooks and chains dangle in the
water, and to these the mollusks attach themselves. The mollusks are
removed from their shells by boiling, hence any pearls which they might
contain are rendered worthless. The same method of fishing might,
however, be used to gather shells for pearls. Other methods used to
gather the mollusks to search for pearls are: raking the bottom with an
iron rake; wading with naked feet, and picking up any projecting shell
as it is felt; or systematic dredging. The use of a water telescope is
said to facilitate the work of individual search for mollusks likely to
contain pearls. It consists simply of a long, light, wooden box, one
end of which is strapped to the face, while the other, covered with
glass, is immersed in the water. Provided with this appliance the
bottom of a river or lake can
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