and the
action of marine currents are the chief agents in coast sculpture. A
coast of homogeneous rock exposed to similar action will present a
regular outline, but if exposed to differential action it will be
embayed where that action is greatest. A coast consisting of rocks of
unequal hardness or of unequal structure will present headlands,
"stacks" and "needles" of hard rocks, and bays of softer or more loosely
aggregated rocks, when the wave and current action is similar
throughout. The southern shore-line of the Isle of Wight and the western
coast of Wales are simple examples of this differential resistance. In
time the coast becomes "mature" and its outline undergoes little change
as it gradually recedes, for the hard rock being now more exposed is
worn away faster, but the softer rock more slowly because it is
protected in the bays and re-entrants.

COAST DEFENCE, a general term for the military and naval protection and
defence of a coast-line, harbours, dockyards, coaling-stations, &c.,
against serious attack by a strong naval force of the enemy,
bombardment, torpedo boat or destroyer raids, hostile landing parties,
or invasion by a large or small army. The principal means employed by
the defender to cope with these and other forms of attack which may be
expected in time of war or political crisis are described below. See
also for further details NAVY; ARMY; FORTIFICATION AND SIEGE-CRAFT;
AMMUNITION; ORDNANCE; SUBMARINE MINES; TORPEDO. The following is a
general description of modern coast defences as applied in the British
service.

No system of coast defence is of any value which does not take full
account of the general distribution of sea-power and the resultant
strength of the possible hostile forces. By resultant strength is meant
the balance of one side over the other, for it is now generally regarded
as an axiom that two opposing fleets must make their main effort in
seeking one another, and that the force available for attack on coast
defences will be either composed of such ships as can be spared from the
main engagement, or the remnant of the hostile fleet after it has been
victorious in a general action.

Coast defences are thus the complement and to some extent the measure of
naval strength. It is often assumed that this principle was neglected in
the large scheme of fortification associated in England with the name of
Lord Palmerston, but it is at least arguable that the engineers
respon