946 ‘ REPORT—1890. 
so long and so honourably associated, is more and more coming into favour, as the 
most effective mode of protection for the gun and its mounting, as well as for the 
gun detachment. During the last ten years much attention has been devoted to 
the designing of various mountings on this system for all weights of guns from 
3 up to 68 tons, 
In the earliest carriages of this type the gun was raised by the descent of a 
balance weight, but the most successful arrangement is that in which compressed 
air is employed for the purpose. The 9:2-inch and 10-inch hydro-pneumatie 
mountings are the largest sizes as yet adopted into the English service, and a 
description of them will serve for that of the type generally. 
The eun on this system is raised by compressed air stored in several chambers, 
and acting through the medinm of a fluid upon a recoil ram. 
On the recoil of the gun the liquid is driven from the cylinder by the incoming 
ram into the lower parts of the air chambers, so that as much as is required of the 
energy of recoil is stored up by the compression of the air, and is used to raise the 
gun for the next round. The gun is raised up and lowered on two heavy beams 
pivoted to the lower carriage. Two long light elevating rods, pivoted at one end 
to the breech of the gun, at the other to the lower carriage, hold the gun in correct 
position as it rises or falls; the elevation is changed by moving the position of the 
lower ends of the elevating rods. This can be done when the gun is down without 
disturbing it, and consequently with very little labour. The effect of the change is 
apparent after the gun rises, when any slight correction can be made if desired. 
Generally these mountings have been made with overhead shields placed a little 
below the level of the top of the gun pit, and entirely closing it. There is an 
aperture through which the gun rises, but which can be closed when the gun is 
out of action. 
In the case of the 10-inch gun the total weight of the revolving mass is 
80 tons. Only two men are required at the hand wheels to revolve it—in fact, it 
is within the power of one man to do the whole work. The ordinary speed of 
training is 90° in 14 minute, while the time required to raise the gun to the firing 
position is 20 seconds. The speed of rising might be considerably increased, but, 
taking the weight of the mass in motion into account, it does not appear to be 
desirable to accelerate it. 
At Maralunga, Spezia, in March of the present year, the first 68-ton dis- 
appearing mounting, manufactured for the Italian Government, was tried with most 
satisfactory results. Fifteen rounds were fired in all, some of them being made to give 
greatly increased energy of recoil, with the view of proving the gun and mounting. 
The gun was worked entirely by hand-power, and on land no difficulty is 
experienced in thus dealing with it, while the system possesses the advantage that 
it is always ready for use should it be required, but no great alteration is necessary 
to adapt the mounting for use with hydraulic power. 
In this case the water from the recoil press is driven through spring-loaded 
valves instead of into air chambers. There is, therefore, no storing up of the recoil 
energy, and to raise the gun to the firing position, water pressure from an 
accumulator kept charged by a steam-pumping engine in the usual way is em- 
ployed. These guns and mountings are too large to be easily covered by an over- 
head shield, but they are provided with shields at the front and rear to protect the 
gun detachments. 
Another very successful mounting for land service has been made for guns’ 
when the site is such that it is permissible to place them en barbette. The gun’ 
is entirely above the parapet, but the detachment is protected while loading and 
working the gun by a broad sloping shield carried on the gun carriage and 
recoiling with it. The shield is inclined so that any splinters, &c., striking it may: 
be deflected in an upward direction. 
The carriage runs back on a long slide inclined at 5°, and at the end of the’ 
recoil is caught by a spring catch, which retains it in the run in position until the 
loading is finished. To load, the gun is put at extreme elevation, so that the 
breech may be as much under protection as possible, the charge being rammed 
home with a hand rammer worked by rope tackle. The slide is mounted on front 
