184 
NATURE 
| Fune 24, 1886 
change of volume produces, but also the work which has to be 
expended in producing the change of volume. The work is ca!- 
culated by multiplying the decrease of volume by the mean 
pressure per unit of area which producedit. The ordinates of the 
dotted curve on the diagram with the corresponding scale of foot- 
pounds on the right-hand side are drawn equal to the work done 
in compressing a cubic foot of cork to the several volumes marked 
on the base-line. I have not been able to find an equation to 
the pressure curve ; it seems to be quite irregular, and hence the 
only way of calculating the effects of any given change of volume 
is to measure the ordinates of the curve constructed by actual 
experiment. As may be supposed the pressures indicated by ex- 
periment are not nearly so regular and steady as corresponding 
experiments on a gas would be, and the actual form of the curves 
will depend on the quality of the cork experimented on. 
The last point of importance in this inquiry relates to the 
permanence of elasticity in cork. 
So far as preservation of elasticity during years of compression 
is concerned, we have the evidence of wine corks to show that a 
considerable range of elasticity is retained for a very long time. 
With respect to cork subjected to repeated compression and ex- 
tension, I have very little evidence to offer beyond this, that 
cork which had been compressed and released in water many 
thousand times had not changed its molecular structure in the 
least, and had continued perfectly serviceable. Cork which has 
been kept under a pressure of three atmospheres for many weeks 
appears to have shrunk to from 80 to 85 per cent. of its original 
volume. 
I will conclude this lecture by bringing under your notice two 
novel applications of cork to the arts. 
Before the lecture-table stands a water-raising apparatus called 
a hydraulic ram. The structure of the machine is shown by a 
diagram on the wall. The ram consists of an inclined pipe, which 
leads the water from a reservoir into a chamber which terminates 
in a valve opening inwards. Branching up from the chamber is 
a passage leading toa valve, opening outwards and communicating 
with a regulating vessel, which is usually filled with air, but which 
I prefer to fill with cork and water. Immediately beyond the 
inner valve is inserted a delivery pipe, which is laid to the spot 
to which the water has to be pumped, in this case to the fountain 
jet in the middle of this pan. 
The action of the ram is as follows :—The outer valve, which 
opens inwards, is, in the first instance, held open, and a flow of 
water is allowed to take place through it down the pipe and 
chamber. The valve is then released, and is instantly shut by 
the current of water which is thus suddenly stopped, and, in 
consequence, delivers a blow similar to that produced by the fall 
of a hammer on an anvil, and just as the hammer jumps back 
from the anvil, so does the water recoil back to a small extent 
along the pipe. 
During this action, first, a certain portion of water is forced 
by virtue of the blow through the inner valve, opening outwards, 
into the cork vessel, and so to the delivery pipe, and instantly 
afterwards the recoil causes a partial vacuum to form in the body 
of the ram, and permits the atmospheric pressure to open the 
outer valve and re-establish a rush of water as soon as the recoil 
has expended itself. In the little ram before you, this action, 
which it has taken so long to describe, is repeated 140 times in 
a minute. 
The ram is now working. You hear the regular pulses of the 
valve, and you see a jet of water rising some I0 feet into the air. 
I throw the electric light on the water, and I ask you to notice 
the regularity of the flow. You can, indeed, detect the pulses 
of the ram in the fountain, but that is because I am only using a 
regulating vessel of the same capacity as that generally used for 
air, and you will recollect that 44 per cent. of the substance of 
cork is solid and inelastic. By closing a cock I can cut off the 
cork vessel from the ram; you see the regularity of the jet has 
disappeared, it now goes in leaps and bounds. This demon- 
strates that the elasticity of cork is competent to regulate the 
flow of water. When air is used for this purpose the air-vessel 
has to be filled, and, with most kinds of water, the supply has to 
be kept up while the ram is working, because water under 
pressure absorbs air. For this purpose a “‘sniff-valve” is a 
necessary part of all rams. It is a minute valve opening inwards, 
placed just below the inner valve ; at each recoil a small bubble 
of air is drawn in and passed into the air-vessel. This “ sniff- 
valve” is a fruitful source of trouble. Its minuteness renders it 
liable to get stopped up by dirt ; it must not, of course, be sub- 
merged, and, if too large, it seriously affects the duty performed 
by the ram. The use of cork gets rid of all these difficulties, no 
sniff-valve is needed, the ram will work deeply submerged, 
and there is no fear of the cork vessel ever getting empty. The 
duty which even the little ram before you has done is 65 per 
cent., and larger ones have reached 8o per cent. 
The second novel application of cork is for the purpose of 
storing a portion of the energy of the recoil of cannon, for the 
purpose of expending it afterwards in running them out. 
The result of the explosion of gunpowder in a gun is to drive 
the shot out in one direction, and to cause the gun to recoil with 
equal energy the opposite way. To restrain the motion of the 
gun ‘‘compressors” of various kinds are used, and in this 
country, for modern guns, they are generally hydraulic, that is 
to say, the force of recoil is expended in causing the gun to 
mount an inclined plane, and, at the same time, in driving a 
piston into a cylinder full of water, the latter being allowed to 
squeeze past the piston through apertures, the areas of which are 
either fixed or capable of being automatically varied as the gun 
recedes ; or else the water is driven out of the cylinder through 
loaded valves. As a rule, the gun is moved out again into its 
firing position by its weight causing it to run down the inclined 
plane, up which it had previously recoiled. For naval purposes, 
however, this plan is inconvenient, because the gun will not run 
out to windward if the vessel is heeling over, on account of the 
inclined plane becoming more horizontal, or even inclined in the 
reverse direction, and should the ship take a permanent list, from 
a compartment getting full of water, the inconvenience might be 
very considerable. 
In land service guns, when mounted in barbette, the rising of 
the gun exposes it and the loading detachment more to the 
enemy’s fire, and in both cases, when placed in ports or embra- 
sures, the ports must be higher than if the gun recoiled horizon- 
tally, and will therefore offer a better mark to the enemy’s fire, 
especially that of machine guns, while the sudden rise of the gun 
in recoiling imposes a severe downward pressure on the deck or 
on the platform. 
To obviate these disadvantages I have contrived the gun- 
carriage a model of which is before you on the table, and a 
diagram of which on the wall illustrates the internal construction. 
The gun is mounted on a carriage composed of two hydraulic 
cylinders, united so as to form one piece. The carriage slides 
on a pair of hollow ways, and also on to a pair of fixed rams, the 
rear ends of which are attached to the piece forming the rear of 
the mounting. There are water passages down the axes of the 
rams, and these communicate through an automatic recoil-valve, 
opening from the cylinders, with the two hollow slides. There 
is a second communication between the cylinders and slideseby 
means of a cock, which canbe opened or shut at pleasure. The 
hollow slides are packed full of cork and water, the latter also 
completely filling the cylinders, rams, and various connecting 
passages. re 
By means of a small force-pump enough water can be injected 
to give the cork so much initial compression as will suffice to 
run the gun out when the slides are inclined under any angle 
which may be found convenient. 
When the gunis fired, the cylinders are driven on to the rams, 
and the water in the cylinders is forced through the hollow rams 
into the cork and water vessels formed by the slides, and the 
cork is compressed still farther. When the recoil is over, the 
automatic recoil-valve closes, and the gun remains in its rearward 
position ready for loading. 
As soon as loaded, the running-out cock is opened, the ex- 
pansion of the cork drives the water from around it into the 
cylinders, and so forces the gun out. ‘ : 
If it be desired to let the gun run out automatically imme- 
diately after recoil, itis only necessary to leave the running-out 
cock open, and then the water forced among the cork by recoil 
returns instantly to the cylinders, and runs the gun out quicker 
than the eye can follow the motion. 
I will now load the model and fire a shot into this strong steel 
cylinder, at the bottom of which is a thick layer of soft wood. 
I will close the running-out valve, so that the gun shall remain 
in the recoiled position. 
some of his electric fuses specially to fit this minute ordnance, 
and I can fire the gun by means of a small electro-magnetic 
battery. The gun has now recoiled, and remains in its rear 
position. I load again, open the running-out cock, the gun runs 
out, and I fire without closing the cock. You see the gun has 
recoiled and run out instantly again. 4 é 
The arrangement I have adopted may be made by using air 
Sir Frederick Abel has kindly arranged 
eet 
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aie te & Sake on Oren ~ 
