Part 8 (1/2)

CHAPTER IX

THE GUNS THEY USE IN THE NAVY

Both the great English-speaking nations are immensely proud of their navies. They can, on occasion, produce soldiers by the million of the very highest and most efficient type, but they never feel quite that pride and patriotic fervour over their soldiers that they do over their s.h.i.+ps of war and their sailors.

The guns, therefore, with which the s.h.i.+ps are armed, always form a subject of great interest, especially those large ones which const.i.tute the armament of the Dreadnought battles.h.i.+ps and battle-cruisers.

Let us first consider what is required in a naval gun, for it must be remembered that the naval and military weapons are different in some respects. Experience at the Dardanelles showed that even the guns of the _Queen Elizabeth_, the largest and most powerful then known, fresh from the finest factories, were not particularly successful against the Turkish forts. The Germans, too, set up what was probably a naval gun and occasionally dropped sh.e.l.ls into Dunkirk with it at a range of twenty miles or so, but without causing much harm, and the fact that they only did it occasionally and then abandoned it altogether seems to indicate that in their opinion they were not doing much good with it.

It must not be a.s.sumed from this that naval guns are bad guns or poor guns, however, but simply that they are made for a special purpose for which they are highly efficient, from which it follows almost as a natural consequence that they are somewhat less efficient when used for some other purpose. Their purpose is to pierce the hard steel armour with which wars.h.i.+ps are protected and then to explode in the enemy's interior, whereas in modern warfare the greatest military guns are chiefly required to blow a big hole in the ground or to shatter a block of concrete. In both cases the ultimate object is to carry a quant.i.ty of explosive into the enemy's territory and there explode it, but whereas the land gun has simply to do that and no more, the naval gun has to pierce thick armour-plate as well.

And just think what that means. Many large s.h.i.+ps have their vital parts protected by armour-plates twelve inches thick. Moreover, the armour-plates are made of very special steel, the finest that can be invented for the purpose. Vast sums of money have been expended in experimenting to find out just the best sort of steel for resisting penetration by sh.e.l.ls. Some time ago I saw several pieces of armour-plate which had been used in one of these tests. They had been set up under conditions as nearly as possible the same as those obtaining on the side of a s.h.i.+p and then they had been fired at from varying distances, the effects of the various shots being carefully recorded. And that is only one experiment out of tens of thousands which have been tried again and again, while the steel manufacturers are always trying to improve and again improve the sh.e.l.l-resisting properties of their steel. Thus, we see, the presence of the steel armour which has to be perforated before the sh.e.l.l can do its work makes the task set before the naval gun somewhat different from that which confronts its military brother.

These considerations result in the naval gun needing to have as flat a trajectory as possible and its projectiles the highest possible speed.

Now trajectory, it may be useful to explain, is the technical term employed to denote the course of a projectile, which is always more or less curved.

Let us imagine that we see a gun, pointed in a perfectly horizontal direction, and let us also imagine that by some miracle we have got rid of the force of gravity and also that there is no air. Under those conditions the shot from the gun would go perfectly straight and with undiminished velocity for ever and ever. Then let us imagine that the air comes into being. The effect of that is to act as a brake which gradually slows the sh.e.l.l down until finally it stops it. Theoretically, perhaps, it would never quite stop it, but for all practical purposes it would.

Again, let us suppose that while the air is absent the force of gravity comes into play, what effect will that have? It will gradually pull the sh.e.l.l downwards out of its horizontal course, making it describe a beautiful curve.

But, someone may think, does not a rapidly-moving body remain to some extent unaffected by gravity? Not at all: it falls just the same and just as quickly as if it were falling straight down.

If our imaginary horizontal gun were set at a height of sixteen feet and a sh.e.l.l were just pushed out of it so that it fell straight down the sh.e.l.l would touch the ground in one second. If the ground were perfectly flat and the sh.e.l.l were fired so that it reached a point half a mile away _in one second_ it would strike the ground exactly half a mile away. You see, the horizontal motion due to the explosion in the gun and the downward motion due to gravity go on simultaneously and the two combined produce the curve.

To make this quite clear, let us imagine two guns precisely alike side by side and both pointed perfectly horizontally. From one the sh.e.l.l is just pushed out: from the other it is fired at the highest velocity attainable: both those sh.e.l.ls will fall sixteen feet or a shade more in one second, and if the ground were perfectly level both would strike the ground at the same moment although a great distance apart.

Clearly, then, the faster the sh.e.l.l is travelling the more nearly horizontally will it move, for it will have less time in which to fall, and the slower the more curved will be its path, from which we see that the air by reducing the velocity causes the curve to become steeper and steeper as the sh.e.l.l proceeds.

If, then, our gun is placed low down, as it must be on a s.h.i.+p, to get the longest range we must point it more or less upwards because otherwise the sh.e.l.l will fall into the water before it has reached its target. When we do that we complicate matters somewhat, for gravity tends to reduce the velocity while the sh.e.l.l is rising and to add to it again while it is falling. We need not go too deeply into that, however, so long as we realize that, whatever the conditions may be, the sh.e.l.l in actual use has to follow a curved course, first rising and then falling.

The really important part about a sh.e.l.l's journey is the end. So long as it hits it really does not matter what it does on the way, and if it misses it is equally immaterial. The reason why we need to bother about the first part of the trip is because upon it depends the final result.

Whatever the trajectory may be we see that the sh.e.l.l must necessarily arrive in a slanting direction. And the more steeply slanting that direction is _the less likely is the target to be hit_.

If the sh.e.l.l went straight it would only be necessary to point the gun in the right direction and the object would be hit no matter how far away it might be. The more curved the course is, the more likely the sh.e.l.l is to fall either too near or too far, in the one case dropping into the water, in the other pa.s.sing clear over the opposing s.h.i.+p.

Let us look at it another way. Suppose the vital parts of a s.h.i.+p rise 20 feet out of the water and the sh.e.l.l arrives at such an angle that it falls 20 feet in 100 yards: then, if the s.h.i.+p be within a certain zone 100 yards wide it will be hit in a vital spot. If it be nearer the sh.e.l.l will pa.s.s over, if it be further the sh.e.l.l will fall into the water.

That 100 yards is what is called the ”danger zone.” If the sh.e.l.l is falling less steeply, say, 20 feet in 200 yards, then the danger zone is increased to 200 yards and so on, which gives us the rule that the flatter the trajectory, or the more nearly straight the course of the sh.e.l.l the greater is the danger zone and the more likely is the enemy s.h.i.+p to be hit.

We have established two facts, therefore, first, that the trajectory must be as flat as possible and, second, that to make it flat the velocity must be high. We can also see another reason for high velocity, namely, to give penetrating power.

To obtain a high velocity the gun must be long, and consequently naval guns are always long, a fact which is very noticeable in the photographs of wars.h.i.+ps. The reason for this is quite obvious after a little thought. You could not throw a cricket ball very far if you could only move your hand through a distance of one foot. To get the best result you instinctively reach as far back as ever you can and then reach forward as far as you are able, so that the ball shall have as long a journey as possible in your hand. Perhaps you do not know it but all the time you are moving your hand with the ball in it you are putting energy into that ball, which energy carries it along after you have let go of it. And it is just the same with the sh.e.l.l in the gun. So long as it is in the gun energy is being added to it but as soon as it leaves the muzzle that ceases. After that it has to pursue its own way under the influence of the energy which has been imparted to it.

The powder which is employed as the propellant or driving power is of such a nature and so adjusted as to quant.i.ty that as far as possible it shall give a comparatively slow steady push rather than a sudden shock, so as to make full use of the gun's length, the expanding gases following up the sh.e.l.l as it goes forward and keeping a constant push upon it.

On the other hand, a gun can be too long, for no steel is infinitely strong and stiff, so that beyond a certain limit the muzzle of the gun would be likely to droop slightly of its own weight and so make the shooting inaccurate. The limit seems to be about 50 calibres or, in other words, fifty times the diameter of the bore.

For a considerable time the standard big gun of the British Navy was the 12-inch, that being the calibre or diameter of the bore. The famous _Dreadnought_ had guns of that calibre and so had her immediate successors.