[Illustration: FIG. 7.--CASEMATE OF CHILLED IRON AFTER RECEIVING
NINETY-SIX SHOTS.]

_Armor Plated Casemates_.--Fig. 7 shows the state of a chilled iron
casemate after a vigorous firing. The system that we are about to
describe is much better, and is due to Commandant Mougin.

[Illustration: FIG. 8.--MOUGIN'S ARMOR-PLATE CASEMATE.]

The gun is placed under a vault whose generatrices are at right angles
to the line of fire (Fig. 8), and which contains a niche that traverses
the parapet. This niche is of concrete, and its walls in the vicinity of
the embrasure are protected by thick iron plate. The rectangular armor
plate of rolled iron rests against an elastic cushion of sand compactly
rammed into an iron plate caisson. The conical embrasure traverses this
cushion by means of a cast-steel piece firmly bolted to the caisson, and
applied to the armor through the intermedium of a leaden ring.
Externally, the cheeks of the embrasure and the merlons consist of
blocks of concrete held in caissons of strong iron plate. The
surrounding earthwork is of sand. For closing the embrasure, Commandant
Mougin provides the armor with a disk, c, of heavy rolled iron, which
contains two symmetrical apertures. This disk is movable around a
horizontal axis, and its lower part and its trunnions are protected by
the sloping mass of concrete that covers the head of the casemate. A
windlass and chain give the disk the motion that brings one of its
apertures opposite the embrasure or that closes the latter. When this
portion of the disk has suffered too much from the enemy's fire, a
simple maneuver gives it a half revolution, and the second aperture is
then made use of.