340 
NATURE 
[Aug. 25, 1870 
force. It strained racers and pivots almost beyond 
the endurance of iron, and shook the granite foundations 
on which they rested ; and artillerists sought to coax it to 
waste itself as harmlessly as they could in friction. The 
Protected Barbette Gun-Carriage utilised this force by 
causing it to raise a counter-weight, while the gun de- 
scended below the parapet into safety and concealment 
fromthe enemy. This was effected by interposing between 
the gun and counter-weight a »oving fulcrum. Any fixed 
fulcrum, such as a pivot, was found, no matter how strong, 
incapable of resisting the almost inconceivably rapid 
action of exploding gunpowder; it was torn from its 
position before it had time to move. But in the moving 
fulcrum there is nothing to be broken. The recoil of the 
gun rolls back the elevators, which raise the counter- 
weight, and this is retained inits position when the recoil is 
exhausted, and when released and allowed to fall restores 
the gun to the firing position again. It should be further 
observed that the gun commences to move in the direction 
of the recoil, gradually descending on a cycloidal curve, 
and thus the force of the recoil is not suddenly checked, 
but guided. This is one of the conditions essential to its 
success.* 
The invention, which it is the design of this paper to 
discuss, effects a similar object for naval gun-carriages to 
that accomplished on land by the Protected Barbette 
Gun-Carriage. By it the gun is gradually lowered in its 
recoil below the surface of the deck of the vessel, and 
the force of the recoil is stored up to raise the gun at 
pleasure to its firing position above the deck. But the 
means by which it is accomplished are wholly different. 
There is no counter-weight and there is no moving fulcrum. 
It is manifest that at sea the fall and rise of a counter- 
weight could not be used. The direction of the force of 
gravitation is fixed and invariable, but the platform of a 
ship’s deck is not always horizontal, and is often rapidly 
changing its inclination. In the Hydro-pneumatic Car- 
tiage, advantage is taken of the elasticity of air to store 
up and utilise the force of the recoil. A volume of air is 
compressed by the recoil of the gun, and being retained 
at pleasure in its compressed state, it is able to lift the 
gun to the position it occupied before the discharge ; 
and as the moving fulcrum transferred the force of the 
recoil to the counter-weight without any check or jar, so in 
this naval carriage a like office is performed by water, which 
smoothly and effectually conveys the force of the recoil to 
compress the air in its reservoir. This is accomplished in 
a very simple manner, which can be easily understood by 
the accompanying diagram. The lines represent the gun 
and carriage in the firing position, the dotted lines in the 
loading position, showing the effect of the recoil. The gun 
is carried in asmall triangular carriage (A, B, C), and this 
moves down through a quarter circle by the parallel 
motion of four strong bars, jointed on the carriage and 
on a platform on the lower deck of the vessel. In the 
firing position this part of the apparatus is supported by 
a plunger (D, E) or piston, and by the descent of the 
carriage this plunger is forced into a cylinder filled with 
water. This cylinder communicates with an air vessel or 
reservoir ; consequently by the recoil a volume of water 
equal in bulk to the cubic content of the plunger is forced 
into the air reservoir ; the volume of air is diminished by 
that amount and the pressure increased. The valve at 
F is self-acting in one direction only; it allows the 
water to flow into the air reservoir, but not to return. 
Consequently, when the recoil has exhausted its force in 
compressing the air, the gun remains in the loading posi- 
tion. When the valve G is turned, the water is driven 
* While this article was going through the press, an attempt to make a 
gun descend an inclined plane by recoil and raise a weight, and so to form a 
protected Barbette carriage, was tried in the Royal Arsenal, and failed for this 
reason: The horizontal force of the recoil was not met in its own direction, 
but at an angle. The gun would not descend the inclined plane beyond a 
foot or two, and the violent concussion destroyed the elevating gear at the 
second shot. 
from the reservoir by the compressed air, rushes into 
the cylinder, raises the plunger, and with it the gun and 
its carriage into the firing position. It should be observed 
that there is a circular portion of the upper deck, which, 
with the platform on the lower deck, to which the parallel 
bars are attached, traverses round on the plunger as a 
pivot, and so enables the gun to be pointed in any direc- 
tion. In this rotating circular portion of the upper deck 
there is a rectangular opening which opens and closes by 
a pair of self-acting shutters with the rise and fall of the 
gun. A minute description of these minor arrangements 
is not here necessary. 
One of the most remarkable features of this invention 
is the extraordinary power of adjusting the force employed 
to meet the recoil of the gun. By the descent of the 
plunger the air space is reduced by the cubic content of 
the plunger ; and as the air space can be varied by ad- 
mitting more or less water into the reservoir, so can the 
elastic force be varied to meet the recoil. For instance, 
did the air space in the reservoir equal the volume of the 
plunger, then the plunger could not possibly descend en- 
tirely into the cylinder, as that would compress the air to 
nothing. On the other hand, were the air space three or 
four times the volume of the plunger, then a small force 
of recoil would be sufficient to bring it completely down. 
The resisting force may thus be adjusted within almost 
any limits to meet the force of the recoil. It will be 
further observed that as in the Protected Barbette Carriage 
with counterweight, the recoil is met by a very slight 
resistance at the commencement, and is allowed to start 
in motion in its own direction. The first backward 
motion of the gun depresses the plunger very slightly, but 
as the recoil goes on it causes an increasingly rapid de- 
scent. For instance, the rollers must travel over two- 
thirds of the quadrant A H, to send the plunger half 
way down into the cylinder; the remaining one-third 
would send it down to the bottom. Thus the resistance 
to the recoil goes on increasing in a double progression, 
both from the increased pressure of the air as its volume 
is diminished, and also from the fact that the motion of 
the gun produces an increasing diminution of that volume. 
Let us go through the process of adjusting the machine 
into working order. The reservoir and cylinder are both 
empty, the plunger is at its lowest descent, the gun lies 
down in the loading position. By a pump communicating 
with the reservoir, water is driven into the reservoir until 
the air space is reduced to one-half or one-third, as the 
case may be, of the volume of the plunger. This will 
raise but very slightly the plunger and its load. Now 
air must be pumped in till its pressure in the air space is 
sufficient to raise the plunger with the gun and its carriage 
into the firing position. The gun may then be brought 
down to the loading position. 
This entire process need not be literally gone through 
in every case to adjust the machine. When once (if the 
expression may be borrowed) the “ constants” of the car- 
riage have been determined, z.e., the amounts of air and 
water required in the reservoir, those quantities can be 
pumped in, keeping the valve G closed, and the gun 
remaining quiescent in the loading position. Water 
should be pumped in so as to leave a fixed air space, and 
then an amount of air, such that, with the added volume 
of the plunger, the pressure would still be sufficient to 
sustain the gun in the firing position. For a twenty-five 
ton gun the weight to be raised, including that of the 
plunger and the moveable part of the carriage, would be 
about thirty tons. Supposing the sectional area of the 
plunger to be two square feet, this would require a pres- 
sure of air of a little over 230lbs. on the square inch, or a 
little under sixteen atmospheres. When once adjusted, 
the carriage would remain in complete working order for 
days or weeks, in fact, until the water was allowed to 
run off. 
While the main object and purpose to be accomplished 
