in one view as many as a dozen of these
plant-borne stones, sometimes six inches in diameter, hanging in the
walls of water as it was about to topple over. As soon as they strike
the wave-beaten part of the shore these stones are apt to become
separated from the plants, though we can often notice the remains or
prints of the attachments adhering to the surface of the rock. Where
the pebbles off the shore are plenty, a rocky beach may be produced
by this process of importation through the agency of seaweeds without
any supply being brought by the waves along the coast line.

Returning to sand beaches, we enter the most interesting field of
contact between seas and lands. Probably nine tenths of all the coast
lines of the open ocean are formed of arenaceous material. In general,
sand consists of finely broken crystals of silica or quartz. These
bits are commonly distinctly faceted; they rarely have a spherical
form. Not only do accumulations of sand border most of the shore line,
but they protect the land against the assaults of the sea, and this in
the following curious manner: When shore waves beat pebbles against
each other, they rapidly wear to bits; we can hear the sound of the
wearing action as the wave goes to and fro. We can often see that the
water is discoloured by the mud or powdered rock. When, however, the
waves tumble on a sandy coast, they make but a muffled sound, and
produce no mud. In fact, the particles of sand do not touch each other
when they receive the blow. Between them there lies a thin film of
water, drawn in by the attraction known as capillarity, which sucks
the fluid into a sponge or between plates of glass placed near
together. The stroke of the waves slightly compresses this capillary
water, but the faces of the grains are kept apart as sheets of glass
may be observed to be restrained from contact when water is between
them. If the reader would convince himself as to the condition of the
sand grains and the water which is between them, he may do so by
pressing his foot on the wet beach which the wave has just left. He
will observe that it whitens and sinks a little under the pressure,
but returns in good part to its original form when the foot is lifted.
In the experiment he has pushed a part of the contained water aside,
but he has not brought the grains together; they do not make the sound
which he will often hear when the sand is dry. The result is that the
sand on the seashore may wear