338 
ARMOURED DEFENCES. 
The general arrangement is shown in Diagram No. VIII, from 
which it will be seen that there are two gun ports in each, and the gun- 
being mounted on the ordinary casemate carriage and platform, fires 
through 60° out of each port, the turntable being used merely for 
transferring the gun from one port to the other. 
The front protection is on much the same principle as that of the 
shields already described, only it is of necessity circular in plan. 
The armour is usually in two thicknesses of 9-in. plate, or in three 
of 6-in. (at St. Helen's, and Sliema Point, batteries it is in three thick¬ 
nesses of 5-in.) The roof structure is of strong girders, with arch 
plating between them, and carries some 6 ft. of concrete, and is 
thoroughly bomb-proof. 
The turntable consists of a very stiff circular platform, varying from 
20 ft. to 23 ft. in diameter, and strong enough to bear the weight and 
shock of the gun in any position of training. 
It revolves on a set of conical rollers running in a live ring, and is held 
in position by a central spindle which passes into a massive casting. The 
table is turned by hand-gear, working into cogs on its outer rim. It is 
locked by a set of tumbler stops when the gun is in position for firing. 
The larger-sized turntable weighs about 37tons. It can be lifted bodily, 
without dismounting the gun, for purposes of inspection and cleaning. 
It is proposed that the guns on these turntables should be turned to the 
the rear for loading, where there will be every facility for the operation. 
Sea forts. I now come to the sea forts, the batteries of which as I have said 
early in this paper, are protected by walls composed wholly of iron. 
These are the following :— 
Plymouth Plymouth Breakwater Fort. This iron battery is oval in form, 
Fo? water 144 ft. long and 114 ft. broad, and stands about 100 yds. behind the 
central part of the Breakwater (the floor being about 16 ft. above high 
water mark), on a mass of masonry resting on a rocky bed about six 
fathoms below low water mark. It will mount fourteen 38-ton guns, and 
four 18-ton guns, firing through small ports, (21 ft. 9 ins. from centre to 
centre). The iron-work was commenced in 1867, and finished in 1870. 
I shall not stop to describe this work further than to say that there are 
four thicknesses of 5-in. armour about the port, and three thicknesses 
supported by massive armour bars on edge elsewhere. The piers sup¬ 
porting the roof structure are separate from the armoured wall. The 
roof is of the usual girder construction, and bomb-proof throughout. 
There is to this, and to all the other sea forts, an entrance port into 
which, in preparing for action, a massive armoured shield on wheels is 
run, and over the entrance is a very strong cantilever beam for hoisting 
the guns and other heavy weights from vessels into the battery, and 
vice versa , by means of heavy hoisting gear placed on the roof. 
I do not give a diagram of this fort, because the general principles of 
our armoured structures are better illustrated in some of the other forts. 
Fort Cun- It may be mentioned here that there is another iron battery of this 
Bermuda, type at Fort Cunningham, Bermuda, constructed about the same time 
as the Plymouth Fort, only it has straight instead of curved faces ; it 
has also small ports for two 38-ton and five 18-ton guns. 
Portland The next kind of iron battery is that represented by Portland Break- 
Fo?t. kwaler water Fort. (See Diagrams IX, and X.) 
