every separate creek and cove a diversity will
be perceptible in the colour of the sand, and
microscopic examination will in general discover
that each distinct variety partakes of the nature
of the substance composing the adjacent cliff,
from which in the lapse of ages it has been
washed, and mixed with the minute particles
which have been fretted by its action from the
strata beneath the sea, combined with numberless
fragments of coral and shells. In the
successive and constant flow of the ocean the
remains of shells are drifted on shore, and by the
action of the water are ground and triturated
with portions of the honeycombed rock, so as to
assume forms as varied as they are innumerable;
but the value of sand as a fertiliser of the soil
depends upon the quantity of shells or
compounds of lime which it contains. The varied
changes of light and shade upon the surface
awaken our senses:

       See the broad bosom of the ocean keeps
       An equal motion, swelling as it sleeps;
       Then slowly sinking, curling to the strand,
       Faint lazy waves o'ercast the ridgy sand.

Observe the little sandpipers, in what flocks
they congregate, and how incessantly they are
upon the move, shifting their ground perpetually,
now running nimbly, now taking short flights,
now wading to follow aquatic insects, while the
bill, like a probe, enables them to search every
spot for food. Our approach has disturbed
them; the flock has taken wing; they wheel
in half circles near the edge and surface of
the water, where they will soon settle again.
The rapid and graceful flight skimming the
surface is that of the tern or sea-swallow, with
its elegant and boat-like form. It is not a
diving-bird, but it swims with great buoyancy,
and notwithstanding the length of its wings,
flapping them until it finds a wave sufficiently
high to start from, see how readily it mounts
again in air. That large and stately bird at a
distance is the great northern diver: how
gracefully he floats and seems to walk the waters,
happy amidst myriads of minute fish; the skin
of the neck, which is black with greenish tints,
and two ring-like collars of mottled feathers, has
great softness and beauty; several of them united
frequently form a handsome tippet.

We are now upon the wet sand over which
the tide ebbs and flows; the shell-coated
families of living beings which inhabit it are
termed Conchifera, the shell consisting of two
principal pieces, somewhat saucer-shaped,
covering the body, and united together by a
complex hinge, bound by a highly elastic ligament,
which enables the shells to open. As the
cockle is the most common of the Mollusca,
and presents very perfect organisation, let us
search for one; and if we can discover on the
sand a slight depression and small white speck,
from which a little jet of air and water
apparently bubbling up may appear to issue, we
may expect to find what we desire. On digging
quickly down we reach the fish lying beneath
at his ease, but so rapidly can he burrow in the
sand that it requires dexterity and promptness
to surprise him, before he can have buried
himself beyond our reach. The shells are equivalve,
furnished with radiate ribs, invariably regular,
and the interior appears enamelled by nature.
On inspecting the fish, we perceive a protrusion,
which it uses as a strong muscular foot for its
mining operations, and which also acts as a kind
of ploughshare in making a furrow. But the
cockle does not confine its use merely to that
of a digging implement, it extends its use to
actual locomotion on the surface of the sand,
on which it enables the animal to advance with a
crawling movement, and even—strange though
it may seem—actually to make jumps. Such
power does this limb possess, that it is said a
conchifer has been known to clear in its leaps a
boat's gunwale, when laid on the bottom board.
Its motive-power on the sand is effected by the
protrusion of this foot to its utmost extent
beyond the shell, and by fixing and bending it
against the surface, on which the shell rests,
then, by a sudden muscular spring, it is
enabled literally to throw itself into the air, and
by constantly repeating this process it hops
along at a comparatively rapid pace. The mode
in which the cockle subsists—and it thrives best
in mixed sand and mud—is equally curious, for
it feeds like a vegetable, without the trouble
of seeking its food, which nature brings to the
door of its shells for the inmate merely to gape
and swallow. The water which enters at the
opening retains within it numerous, although to
us invisible, nourishing particles, which float
about in the shell, and when thus presented to his
lips, the cockle possesses the power of rejecting
what does not suit his taste: the lips standing as
sentinels to refuse or admit entrance. This is
effected by a kind of mantle or brancial fringe,
which is in constant vibratory motion, either to
receive or exclude: and this mantle is a part
of the exquisite structure by which the shells
are secreted. The vital organs, consist of an
extremely firm and strong muscle, which connects
the two valves of shell together, causing them to
open or close by its expansion or contraction. The
power which a similar muscle exercises must be
familiar to every oyster opener, for the resistance
to the knife only ceases when it is cut asunder.
The cockle burrowing in the sand would be
soon choked by the particles it displaces, but
for a tubular opening through which minute
currents of water enter, and while they effectually
protect the delicate breathing apparatus, lead to
its own discovery.

This empty shell, frequently found in
numbers, and resembling the article from which
the name is derived, is that of the razor-fish,
which are also endowed with the power of
burrowing in the wet sand to a great depth,
and the rapidity of whose movements below
the surface can only be understood by those
who have succeeded in effecting their capture.
They are enabled to ensconce themselves in
safety, the tubes by which they communicate
with the water protruding some distance, and
the lateral cohesion of the shell is very perfect
and prolonged.