Part 9 (1/2)
Each of these great guns is mounted upon a slide so that when it is fired it can slide back, thereby exhausting the effect of the recoil, yet can be returned instantly to its original position. Indeed, this return is brought about quite automatically by the agency of springs, compressed air and hydraulic power. Thus the gun fires, slides back, returns and is at once ready for the next shot.
It is trained, or pointed in a horizontal plane, by turning the turret in which it stands but the correct elevation is gained by the use of telescopic sights.
The principle of these sights is very simple. Imagine a graduated circle fixed to the side of the gun. Pivoted at the centre of the circle is a small telescope. The telescope can be turned round to any angle upon the circle and it can then be clamped at that particular angle.
The range having been given to the officer in command of the gun from the range-finding station on another part of the s.h.i.+p, the telescope is set to the correct angle. Then the gun is elevated or depressed until the s.h.i.+p being aimed at is precisely in the centre of the field of view of the telescope, in other words, until the telescope is pointing exactly at the s.h.i.+p. Then the gun is fired.
The effect, therefore, is this. The telescope always points (while the gun is being fired) at the object aimed at, but the gun is pointed upwards at a certain angle, which angle depends upon how the telescope is set upon the divided circle. Thus the setting of the telescope for a given range produces the correct upward tilt of the gun for that range.
The breech-block carries a trigger and hammer arrangement whereby the firing can be done and also an electrical arrangement so that an electric spark can be employed. Both these firing contrivances are so made that they cannot be operated until the breech-block has been inserted and _made secure_. Thus a premature explosion is guarded against.
CHAPTER X
Sh.e.l.lS AND HOW THEY ARE MADE
Modern warfare seems to resolve itself very largely into a question of which side can procure the most sh.e.l.ls. During the great war there was a time when the British and their allies were hard pressed because they had not sufficient sh.e.l.ls. The enemy had in that matter stolen a march upon them and had during the winter, when military activity is at its minimum, rapidly produced large supplies of high-explosive sh.e.l.ls.
Discovering their lack the British set about remedying it in true British fas.h.i.+on. It is quite characteristic of this strange people to let the enemy get ahead at the commencement, after which they pull themselves together and put on a spurt, so to speak, and after that the enemy had better prepare for the worst, for defeat is only a question of time. So, finding themselves short of sh.e.l.ls, they set to and dotted the whole country in an incredibly short time with huge factories entirely devoted to making sh.e.l.ls. Older factories also were adapted to the same purpose. Places intended and normally used for the manufacture of the most peaceable things--ploughs, gramophones and piano parts for example--were soon turning out sh.e.l.ls or parts thereof by the thousand.
Electric-light works, waterworks, cotton mills, technical schools, all sorts of places where, for doing their own repairs or for some similar reason, there happened to be a lathe or two, all these were organized and in a few weeks they too were working night and day ”something to do with sh.e.l.ls.”
Meanwhile other factories were springing up for the purpose of making explosives while others again were erected for producing the acids and other chemicals necessary for the explosive works; and yet another kind of works, the filling factories, came into being as if by magic and thousands of girls flocked from far and near to these places, there to fill the sh.e.l.ls with the explosives.
Even the soldiers did not realize a few years ago how important the supply of sh.e.l.ls was going to be. The rifle has fallen from its old place of importance while the gun and the sh.e.l.l have risen to the first place.
What, then, is a sh.e.l.l? It is what its name implies, a case covering something else, just as the sh.e.l.l of a fish covers its owner. It is a hollow cylinder of steel with certain things inside it. Its chief function is to hold these other things and to be shot out of a gun carrying them with it to their destination. You want to cause an explosion in an enemy's s.h.i.+p. You cannot get near enough to put the explosives there by hand, for he will not let you, so you put them into a steel sh.e.l.l and then hurl the whole thing at him out of a gun.
[Ill.u.s.tration: BOMB THROWING.
One of the most striking things about the war was the re-invention of the bomb thrown by hand. This officer hurled bombs at the enemy for twenty-four hours continuously.]
In the attempt to prevent your doing him any harm by thus throwing boxes of explosives at him, the enemy clothes the sides of his most valuable and important s.h.i.+ps with thick steel plates, wherefore you have to make your sh.e.l.l strong and tough so that it shall not splinter against the armour but shall on the contrary bore its way through, finally exploding in the interior of the s.h.i.+p.
If it is not a s.h.i.+p that you are attacking but, say, an earthwork or an arrangement of trenches, then you do not need to penetrate steel armour and your sh.e.l.l can be thinner and of lighter construction. It still needs to be strong, however, for it has another function besides simply carrying the explosive. It must hold the force of the explosion in for a moment while it gathers force so that when the hour comes the pent-up energy may strike all round with the utmost violence. Even the most powerful explosives are comparatively feeble if they go off in the open.
By holding them in check for a moment and then letting their force loose suddenly you get a much more forceful blow.
Sh.e.l.ls which contain only an explosive are called common sh.e.l.ls or high-explosive sh.e.l.ls. Shrapnel sh.e.l.ls const.i.tute another type in which the force of the explosion is simply employed to release a number of round bullets, which strike mainly because of the velocity which they derive from the original motion of the sh.e.l.l. These are above all things man-killing sh.e.l.ls, for their result is akin to a volley of bullets at close range.
We can thus sum up the chief types of sh.e.l.l as follows: the naval sh.e.l.l which has to be capable of penetrating armour: the high-explosive sh.e.l.l which must be able to break up earthworks and blow down the walls of trenches: and the shrapnel sh.e.l.l which scatters a shower of bullets and is most useful in attacks upon bodies of men rather than upon material structures.
Some sh.e.l.ls have their propellent explosive combined with them just as the familiar rifle cartridge contains the propellant combined with the bullet. In the larger sizes, however, it is much more convenient to have the propellant in a separate cartridge, which can be handled separately and loaded into the gun separately.
As has been already explained, the propellant is a ”powder” which gives a steady push rather than a destructive blow: moreover, it is practically smokeless, so as not to ”give away” the position of the gun to the enemy. The ”high explosive,” however, shatters and usually makes a dense smoke, so that the observers can see where it fell and report to the gunners whether or not they have got the range. Soldiers' letters have told us of the ”black Marias” and ”coal boxes” used by the Germans, those terms being simply soldiers' nick-names arising no doubt from the fact that certain particular sh.e.l.ls are filled with ”tri-nitro-toluene”
which gives a black smoke. Clearly, smoke, which is most objectionable in the propellant, is a positive advantage in the bursting charge.
And now let us take a glimpse at the manufacture of one of these terrible missiles. An ingot of sh.e.l.l-steel is first cast as described in an earlier chapter. Since impurities are apt to rise, while the metal is liquid, the top of the ingot is always cut off and discarded. This waste material is used for many other purposes, in which a chance flaw would not be a serious matter, under the t.i.tle of ”sh.e.l.l-discard” steel.
The lower part is then heated and pa.s.sed through a rolling mill, a machine very similar in principle to the domestic mangle, the rollers being of iron with suitable grooves cut in them. A few pa.s.sages through this machine transforms the ingot into a thick round bar. This is then sawn into short pieces called billets, each of which is the right size to form a sh.e.l.l. Again heated, a powerful press drives a pointed bar through the softened steel, thereby converting the short billet into a rough tube. Another press then slightly closes in one end, making it resemble a bottle without a bottom and with the neck broken off.
The rough forging is then ready to be machined, an operation which is performed in a lathe. The outside is made perfectly round and smooth and of precisely the right size. The inside is also bored out to the correct diameter and finished off to an exceeding smoothness so as to avoid the possibility of any rough places irritating the explosive which in due time will be filled into it. For the same reason, the inside, when finished, is varnished in a certain way and with a certain varnish. The formation of this varnish is one of those little thought of but highly important services which alcohol renders to us, as mentioned elsewhere.