648 
MOUNTING HYDRO-PNEUMATIC DISAPPEARING GUNS. 
heads of the gyn cheeks together by means of the pry-pole or uphirs, 
though a check-rope will be found advisable from one upper cross-bar 
to the other to prevent the cheeks springing over backwards were the 
main tackles to give way. As soon as the upper surface of the plat¬ 
form is flush with the concrete floor of the emplacement, steps can be 
taken to parbuckle on the gun. 
Now there are two methods of doing this. If the emplacement'pit 
is completely circular in form it will be found easiest to put up the 
shields first and skid them up underneath from the gun-floor. The 
elevator is then raised with jacks till the trunnion holes are above the 
shield and the gun parbuckled straight off the edge of the parapet to 
the trunnion holes. 
If the emplacement is semi-circular and open to the rear, the gun 
may be brought on skids from the ground before the shields are fitted, 
and considerable care exercised in building up under the baulks, which 
must be at least 15 inches in section for a 9*2-inch gun. 
Heavy and light drugs well lashed together, and supported under 
the transoms, will be found very useful in economising short skidding 
and in saving labour in piling up the four-foot and six-foot pieces. 
Two 80-ton jacks will be required at breech and muzzle respectively, 
and greased scotches on which to slide the gun forward into the trun¬ 
nion holes are easier to use than short rollers. 
The shields are swung on with a swinging derrick, and as each 
section has a ring (too small, as a rule, for a heavy gyn-tackle hook) 
rivetted on at its centre of gravity, there is little difficulty in getting 
on the shield after the derrick is once up. Care must be taken to 
place the foot of the upright spar (which is best against the wall of the 
parapet) clear of where the edge of the shield will come when fixed. 
Of course, if the pit is closed in, the main spar must be placed above 
on the top, and a shorter one will suffice. The platform can, if neces¬ 
sary, be traversed round for each quarter of the shield, which must be 
supported by a trench cart or other means, if that is done instead of 
heaving up the swinger (this latter would necessitate two capstans or 
a crab winch, and is a tiresome plan). 
Bolting the sections together takes a little time. 
Care must be taken before putting up the gun and the shields that 
all the clip plates work properly, as otherwise the gun may not traverse. 
New plates may have to be made, or the platform raised again, and the 
racer re-levelled and altered. 
Filling the buffer is easily done with reservoirs of compressed air. 
Note. —In the foregoing paper the term pit is held to mean the circular depression in the middle 
of the gun-floor of the emplacement. In this the platform traverses, and the bottom of the pit 
is shaped like an inverted truncated cone round which the lower end of the H.P. buffer revolves. 
Two gjn cheeks are used for lowering the platform containing the buffer and elevator, etc., and 
their feet are placed close up to the pit. 
If it is found necessary to raise the platform, etc., and gun, minus the shields, for any purpose, 
it can be done by placing a 30-ton jack under the muzzle and breech, fixing the gyn cheeks in 
position and raising gun and platform alternately a few inches at a time till clear of the centre 
pit. Two 15-inch baulks can then support it all, one being just in front of the centre and 
strutted up with a six-foot piece and the other further back towards the breech. 
