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Something about Pearls and Pearl-Dibing
HE majority of my young readers
have seen pearls. They are of a most beautiful white, called a pearly white, which nothing can surpass. Perhaps many of my little children may have seen the great pearl, nearly as large as Peter Parley's thumb,
which was exhibited among the “Hope jewels” at the Crystal Palace; if so, they will know how large pearls sometimes are. I saw one once, at the house of Sir John Philippart, belonging to a lady from Ceylon, who told me the whole history of pearl-diving, which I shall endeavour to relate.
In the island of Ceylon, numerous persons obtain their living by the pearl fishery, the pearl being found in an oyster, called the pearl oyster. The divers are many; and about half-past six in the morning, when the rays of the sun begin to emit some degree of warmth, the diving commences. A kind of open scaffolding, formed of oars and other pieces of wood, is projected from each side of the boat, and from it the
diving-basket is suspended, three stones on one side, and two on the other. The diving-stone hangs from an oar, hung by a light rope and slip-knot, and descends about five feet into the water : this is a stone of about fifty-six pounds in weight, of the shape of a sugar-loaf. The rope passes through a hole in the top of the stone, above which a strong loop is formed, resembling a stirrup-iron, to receive the foot of the diver. The diver wears no clothes, except a slip of calico about his loins. Swimming in the water, he takes hold of the rope and puts one foot into the loop or stirrup at the top of the stone. He remains in this perpendicular position for a little time, supporting himself by the motion of one arm. Then a basket, formed of a wooden hoop and net-work, suspended by a rope, is thrown into the water to him, and into it he places his other foot. Both the
of the stone and basket he holds for a little while in one hand. When he feels himself properly prepared and ready to go down, he grasps his nostrils with one hand, to prevent the water from rushing in, and with the other he gives a sudden pull to the running knot suspending the stone, and instantly descends. The remainder of the rope fixed to the basket is thrown into the water after him at the same moment; the
attached to the stone is in such a position as to follow him of itself. As soon as he touches the bottom, he disengages his foot from the stone, which is immediately drawn up, and suspended again to the projecting oar, in the same manner as before, to be in readiness for the next diver.
The diver at the bottom of the sea now throws himself as much as possible on his face, and collects everything he can get hold of into his basket. When he is ready to ascend he
gives a jerk to the rope, and the person who holds the other end of it hauls it up as speedily as possible. The diver, at the same time freed from every encumbrance, warps up by the rope, and always gets above water a considerable time before the basket. He presently comes up at a distance from the boat, and swims about, or takes hold of an oar or rope, until his time comes to descend again, but he seldom comes into the boat until the labour of the day is over. The basket is often extremely heavy, and requires more than one man to haul it up, containing, besides oysters, pieces of rock, trees of coral, and other marine productions.
Such are a few particulars regarding the pearl fishery. In another paper I may say something more about other kinds of marine productions.
The Industrial Arts and Manufactures of
MANUFACTURE OF PLATE GLASS.
LATE GLASS is so called from its
being cast in plates, or large sheets. It is used for mirrors, and for the windows of carriages and shops, when the panes are of very large size. It is composed of white sand, (the finest and best kind that can be obtained,) 300 parts ; dry purified soda, 100 parts ; carbonate of lime, 43 parts; manganese, l; callet, or broken plate plass, 300. The lime improves the quality of the glass, renders it dess brittle, and promotes the fusibility of the silex.
The sand, lime, soda, and mangautensils used in this process; the first and larger kinds are called pots; in these the glass is melted : the others
nese, being properly intermingled, are fritted in small furnaces. There are two kinds of
called cuvettes, and kept empty in the furnaces, exposed to the full degree of its heat. From the time of filling the pots it requires nearly forty hours' exposure to a strong heat ere the materials are properly vitrified, and in a state for casting. The process of filling the pots and removing the glar gall are precisely similar to what has been already described. But with regard to the filling of the cuvettes the operation is as follows:-A copper ladle, ten or twelve inches in diameter, is plunged into the pot and brought up filled with melted glass, which is immediately transferred to the cuvette, where it is suffered to remain during some hours in the furnace till it is properly purified. The materials are generally sixteen hours in the pots, and as many in the cuvettes, so that in about thirty-two hours the glass is ready to be cast.
The idea of casting glass into plates was suggested by an accident which happened to a man employed in a glass-house. The man was melting some glass, and overset the pot, and spilled part of its contents; the melted glass spread itself out upon the stone in the form of a flat cake. This suggestion was acted upon, and the invention of plate glass was the result.
The process is very simple. The melted glass is poured out on to a metallic table perfectly level; this table is of iron, fifteen feet long, nine wide, and weighs nearly fourteen tons. It is supported on castors, for the convenience of removing it to the mouths of the different annealing ovens.
The foundry wherein such a table as this is used is at Ravenhead, in Lancashire. The room in which it stands is