e Ann, Mass., where the
seas are only moderately heavy, show that the storms of a single
winter reduce the fragments thrown into the sea from the granite
quarries to spheroidal shapes, more than half of their weight commonly
being removed in the form of sand and small pebbles which have been
worn from their surfaces.

We can best perceive the effect of battering action which the sea
applies to the cliffs by noting the points where, owing to some chance
features in the structure in the rock, it has proved most effective.
Where a joint or a dike, or perhaps a softer layer, if the rocks be
bedded, causes the wear to go on more rapidly, the waves soon excavate
a recess in which the pebbles are retained, except in stormy weather,
in an unmoved condition. When the surges are heavy, these stones are
kept in continuous motion, receding as the wave goes back, and rushing
forward with its impulse until they strike against the firm-set rock
at the end of the chasm. In this way they may drive in a cut having
the length of a hundred feet or more from the face of the precipice.
In most cases the roofs over these sea caves fall in, so that the
structure is known as a chasm. Occasionally these roofs remain, in
which case, for the reason that the floor of the cutting inclines
upward, an opening is made to the surface at their upper end, forming
what is called in New England a "spouting horn"; from the inland end
of the tunnel the spray may be thrown far into the air. As long as the
cave is closed at this inner end, and is not so high but that it may
be buried beneath a heavy wave, the inrushing water compresses the
air in the rear parts of the opening. When the wave begins to retreat
this air blows out, sending a gust of spray before it, the action
resembling the discharge of a great gun from the face of a
fortification. It often happens that two chasms converging separate a
rock from the cliff. Then a lowering of the coast may bring the mass
to the state of a columnar island, such as abound in the Hebrides and
along various other shores.

If a cliff shore retreats rapidly, it may be driven back into the
shore, and its face assumes the curve of a small bay. With every step
in this change the bottom is sure to become shallower, so that the
waves lose more and more of their energy in friction over the bottom.
Moreover, in entering a bay the friction which the waves encounter in
running along the sides is greater than that which they mee