BATTERIES.
A battery, in respect to its profile, may be either elevated, half sunken, or sunken; and it is usually reveted with gabions, fascines, sand-bags, &c.
An elevated battery has its whole parapet raised above the natural surface of the ground, and, to procure the mass of earth required, a ditch is usually dug directly in front of the parapet.
A half-sunken battery has its interior space, or terreplein, sunk some inches below the natural surface, and its parapet is composed of the earth thus obtained, and of that taken from a narrow ditch in front.
A sunken battery has the whole of the earth taken from the interior space to form the parapet; and it must therefore be lowered from 2 feet to 3 feet 6 inches, according to the height of the gun carriages to be used.
The half-sunken battery is constructed the quickest, as the diggers can work both in front and rear, at the same time. In a sunken battery, the diggers are as much crowded as in an elevated one, but, since the mass of parapet to be raised is smaller, it may be completed in much less time.
Casemates, or vaulted batteries, are made bomb-proof, and the embrazures are cut through the revetment.
Barbet batteries have no embrazures, the guns being placed on traversing platforms to enable them to fire over the parapet.
A direct fire from a battery is when the line of fire is perpendicular to the parapet, and an oblique fire when it is oblique. The direct fire being preferable, the battery should be placed parallel to the object against which the fire is to be directed.
The line of fire is an imaginary line drawn through the centre of an embrazure, in the direction of the object against which a battery is constructed.