ARTILLERY IN COAST DEFENCE. 
407 
while therefore replying to it sufficiently to keep the vessels at a dis¬ 
tance, and to prevent such an attack from becoming dangerous in 
itself, the main power of the defence would be directed to defeating 
the ulterior object of the enemy. Should this object be the landing of 
a force, arrangements should be made to keep up as heavy a shell fire 
as possible on the landing places and their approaches; for this pur¬ 
pose a large part of the secondary armament (and possibly a portion of 
the primary armament) should be held in reserve, as also batteries of 
movable armament. These guns should not open fire until the boats 
carrying the landing parties are within effective shrapnel range, so that 
they may not prematurely show their position and draw on themselves 
the fire of the fleet. As the boats near the landing the fire from the 
ships must necessarily slacken and then the heaviest possible fire 
should be opened from all available guns on the boats. 
Ranges from forts and from the positions of the movable armament 
to landing places would be ascertained beforehand, and Group officers 
would be provided with charts showing the fire-area of their guns and 
these ranges, so that if they have to act independently they may still 
be able to keep up effective fire. Infantry and machine guns would be 
used to assist in the defence. 
The conditions necessary for a successful attack by landing parties 
are that the garrison should be taken by surprise, or that the attacking 
force should be superior in numbers and the defenders shaken by a 
preliminary fire from the ships (these were the conditions which resulted 
in the fall of Fort Fisher) ; the best way to obviate this is that the 
defenders should not unnecessarily show their positions and that the 
enemy's ships should be kept at such a distance as will ensure their fire 
being ineffective. 
The destruction of mines, or other obstructions in the channel, would 
usually be attempted by boats under cover of darkness, fog, or the 
smoke of the ship's guns (as was successfully done at Milford Haven). 
In the first instance this attack would be resisted by boats of the defence, 
but if these were unsuccessful they would draw off behind the obstructed 
channel, leaving the further defence to the Artillery. Quick-firing and 
machine guns are the best weapons for this purpose, but they would 
be assisted in most cases by other guns of the secondary or movable 
armament. If the attack takes place by daylight, or if the electric-light 
can be used, the enemy's boats would be attacked by the ordinary 
methods of fire-control; but if, by reason of fogs, &c., the boats cannot 
be seen, other means have to be adopted. For this purpose the mine¬ 
field (or obstructed channel) is divided into portions, and to each 
portion certain guns are allotted; the range and training to the centre 
of its portion and length of fuze are ascertained and painted on the 
range-board or side of the gun-carriage. Elevation is given by index- 
plate or other means of giving quadrant elevation; or, if the guns are 
not so fitted, by clinometer, in which case the elevation in degrees and 
minutes, taking into account the height above the water, must be 
calculated ; (all converted 64-prs. and 80-prs. now have planes cut on 
them for using the clinometer). The training must be arranged for 
when there are no arcs, by marking the racers, or by nailing battens 
