string of jewels. Finally, at the Paris Exhibition
of 1855, Queen Victoria displayed some
magnificent pearls. On the same occasion, the
Emperor of the French exhibited a collection
of four hundred and eight pearls, each weighing
over nine pennyweights, and all of perfect form
and the finest water.

Pearls from mussels are less generally known
—produced, however, not by marine, but by
fresh-water species. For the best of these, we
must go to Scotland. Linnæus, who was
acquainted with the origin of pearls in general,
was aware of the possibility of producing them
artificially from various mollusks. He
suggested the collection of a number of mussels,
piercing holes in their shells with an augur to
produce a wound, and afterwards "parking"
them for five or six years to give the pearls time
to form. The Swedish Government consented
to try the experiment, and long did so secretly.
Pearls were produced, but they were of no
value, and the enterprise was abandoned as
unsuccessful.

Scotch pearls were much celebrated in the
middle ages. Between the years 1761 and 1784
pearls to the value of ten thousand pounds were
sent to London from the rivers Tay and Isla;
"and the trade hitherto carried on in the
corresponding years of the present century," says
Mr. Bertram, "is more than double that
amount. The pearl fisheries of Scotland," he
adds, "may become a source of wealth to the
people living on the large rivers, if prudently
conducted." Mr. Unger, a dealer in gems in
Edinburgh, having discerned the capabilities of
the Scotch pearl, has established a scale of
prices, which he gives according to their size
and quality; and it is now a fact that the
beautiful pink-hued pearls of our Scottish streams
are admired beyond the orient pearl.
Empresses, queens, and royal and noble ladies,
have made large purchases of these gems; and
Mr. Unger estimates the sum paid to pearl-
finders in the summer of 1864 at ten thousand
pounds. The localities successfully fished
have been the Forth, the Tay, the Spey, the
Isla, and most of the Highland rivers of note.

Passing from the mussels to the pholades, we
have a family who not merely bury themselves
in sand, like cockles and razor-fish, but who
are able in some mysterious way to excavate for
themselves a dwelling in argillaceous rocks and
even in harder stone. Our wonder is increased
on finding their shell not stouter than paper.
One species, indeed, is called Pholas papyracea.
Besides this faculty of boring and burrowing,
they possess another curious property—
phosphorescence. The bodies of many mollusks
shine in the dark, but none emit a more brilliant
light than the pholades. Those who should
eat them in the dark in an uncooked state—and
they are well-flavoured and delicate—would
seem to be swallowing phosphorus.

Most Italian tourists have beheld the
evidence, furnished by pholades, of geological
disturbance. On the shore of Pozzuolo, is a
ruin called the Temple of Serapis, but probably
a thermal establishment for the use of its
mineral waters. All that is now left, are three
marble columns, each about forty feet high.
These three columns, at about ten feet from
their base, are riddled with holes, and full of
cavities bored deep into the marble. The
borings occupy a space of three feet on each
column. There is no doubt about the cause of
the perforations. In some of the cavities, the
shell of the operator is still found, and
naturalists seem agreed that it is a species of
pholas.

To enable the stone-boring mollusks, which
live only in the sea, to excavate this marble,
the temple and its columns must have been
sunk in sea water. Only under these conditions
could the borers have worked upon the
marble. But since the traces of perforation
are now visible ten feet above the surface, it
follows that, after being long immersed in water,
the columns have been elevated to their present
position. The temple has been raised again,
carrying with it, engraved in marble, ineffaceable
proofs of its immersion.

After the pholades, come the teredos or
shipworms—marine creatures with an irresistible
propensity for perforating submerged wood.
The galleries bored by these unsuspected
miners, riddle the whole interior of a piece of
wood; destroying it entirely, without any
external indication of their ravages. By a strange
kind of instinct, however multiplied may be
their furrows or tubes in the same log of wood,
they never mingle—there is never any
communication between them. The wood is thus
attacked at a thousand different points, until
its entire substance is destroyed. Ships thus
silently and secretly mined, have suddenly gone
down with their crews, solely through the
ravages of these relentless enemies.

At the beginning of the eighteenth century,
half the coast of Holland was threatened with
destruction, because the piles which support
its dikes and sea-walls were attacked by the
teredo. Hundreds of thousands of pounds
were expended in order to avert the danger.
Fortunately a closer attention to the habits of
the mollusk has brought a remedy against a
formidable evil. The teredo has an invincible
antipathy to rust, and timber impregnated with
oxide of iron is safe from its ravages. The
creature's aversion being known, all that is
necessary, is, to sink the timber to be submerged,
in a tank of prepared oxide of iron—to clothe
it, in short, in a thick coating of iron rust.
Ships' timber may be so protected; but the
copper with which ships' bottoms are usually
sheathed serves the same purpose even better.

Respecting the cephalopods (cuttle-fish,
sepias, and other creatures with eight or ten
arms round their heads), it is hard to say
whether the facts concerning them, or the fictions,
are the stranger. There exists a fearful fragment,
a beak nearly two feet in length, which belonged
to a great sucker or cuttle-fish. This monster,
if the other parts of its body were large in
proportion, must have been enormous, with arms