How Shells were Invented
There is a great difference between the old-fashioned solid iron cannon-balls and the shells which guns fling among the enemy to-day. The cannon-ball was a very harmless thing so long as it did not hit anyone, but a shell explodes among the enemy and may kill many who are at some distance from it. We wish to see how such shells were invented.
Shells were originally called bombs, and that word seems more expressive of an explosion than the word "shell" does. You can guess that the word "shell" is descriptive of the empty shell or casing which holds the explosive. Explosive shells were used in war some four hundred or five hundred years ago. At that time, and indeed until recent times, the shell was an empty ball of cast-iron; some were the size of a large rubber ball, and others as large as a football. The iron walls of the ball were sometimes one-half inch in thickness, and in others as much as two inches.
These early shells had a bung-hole such as a barrel has, and through this hole the shell was filled with gunpowder and small pieces of metal. The bung-hole was then closed by a plug of slow-burning powder, which when lighted would require a certain number of seconds to elapse before the flame could reach the gunpowder in the shell.
In some old books I have seen pictures of those bombs with a man standing with a lighted taper in each hand. With one taper he is setting a light to a slow-burning fuse in the bomb, and with the other he is setting a light to the gunpowder in the gun, which is to throw the bomb among the enemy. The old-time gunner who did this ran considerable risk, for after lighting the fuse which would explode the bomb in so many seconds he had to set the gun off, and if he failed to do so in time, through the powder in the gun misfiring, then the bomb would explode in the gun and probably kill the gunner.
During the Great European War, our enemy used hand bombs or grenades in which they had to pull a string, which started the fuse that exploded the bomb in a few seconds. Some of our officers informed me that the enemy soldier had such a fear of his bomb exploding, while still in his hand, that he took no time to judge the distance or direction to which he should throw it, so that most of the hand-thrown bombs never reached our trenches.
We used hand-bombs also, but there was no fear of these going off while in the soldier's hand. In our bombs there was a little lever which when allowed to spring up would start a fuse, and in so many seconds after that the bomb would explode. Until the soldier was ready to throw the bomb the little lever was held down by a metal pin. When the soldier withdrew this pin, the lever was still held down by the hand with which he threw the bomb, and not until it left his hand did the fuse begin to burn.
The French provided their bomb-throwers with a special arrangement. The bomb-thrower had a leather bracelet which was fastened round his wrist, and to this bracelet there was attached a strong cord with a hook at the free end. When about to throw a bomb, the soldier slipped this hook into a small ring which was attached to the time-fuse of the bomb. He then threw the bomb, and not until it pulled the cord tight did the time-fuse begin to act. The fuse, being long enough, could burn some seconds before exploding the bomb. In this way the bomb did not explode until it had time to reach the enemy's trenches. Of course the ring to which the bomber attached his bracelet hook was pulled out of the bomb when the cord tightened; it was the sudden withdrawal of the small friction tube attached to the ring which set the fuse alight, just as one does in striking a match.
You will see that this arrangement which was used by the French was very much safer than that used by our enemy bombers, for when a man had to start the time-fuse before throwing the bomb there were grave risks if the bomber should be shot before he had succeeded in throwing the bomb. In that case he would fall in his own trench and probably kill some of his companions, but if the French bomber was unfortunate enough to be shot while in the act of throwing the bomb, he would cause no danger to his friends, as the bomb in falling into his own trench would reach the ground before the cord could pull out the friction tube, so that the time-fuse would not be set off.
Another form of small bomb was what was called a rifle bomb or grenade. From its descriptive name you will understand that it was a bomb thrown by a rifle. In these bombs or grenades there was no time-fuse, but merely a detonator with a percussion-cap which was set off when the bomb struck the ground or any other obstacle. It was just like a rocket, being a hand grenade with a long metal rod attached to it. The rod fitted the barrel of the rifle, and therefore took the place of an ordinary bullet. When the grenade was shot off by the rifle, the nose of the bomb would be sure to strike first, as the heavy head would fall before the rod which acted as a tail.
Some hand-thrown bombs acted in the same way as these rifle grenades. They had no time-fuse to be started in the act of throwing, but depended upon a percussion cap exploding the bomb on striking the obstacle. These hand bombs required to have bushy rope tails attached to them to ensure that they would fall nose first, otherwise the percussion cap would not be operated, and the bomb would not explode.
There were larger bombs, which were thrown out of our trenches by means of catapults or by very large-mouthed guns called "mortars." Why are they called mortars? I think you will have seen a mortar and pestle as used by chemists for grinding or pulverising their chemicals. The chemist's mortar is a shallow bowl, wide-mouthed and with heavy thick walls. It looks as though it ought to have been bigger for the weight and strength of its walls. Now a gun for firing bombs is not wanted to grind or pulverise the bomb, so there is no connection between the use of a chemist's mortar and one of these guns. However, if you have a look at one of these guns which shoot bombs to a short distance you will see that they do remind you somewhat of a chemist's mortar, because they are short, wide-mouthed, and have thick walls.
If a mortar has to throw a shell to some distance, then the mortar has to be made longer, as you will see in the photograph facing page 64. Of course, all our large guns now throw explosive shells, but these shells which have to travel to a long distance are more like great, long-shaped bullets having explosives within them. How then were such shells invented? You have all heard of shrapnel shells, and if you have thought of the matter at all, you have no doubt asked why these are called shrapnel shells. If there was no one about to tell you, you could guess that they have been called after the inventor. If you have looked up any encyclopedia or other book upon the subject, you will find that the inventor is described as Lieut. Shrapnel, or Major Shrapnel, or Colonel Shrapnel, from which you will see that he was an army officer who gained promotion.
The shrapnel shell looks exactly like a giant bullet in a giant cartridge, but in the accompanying drawing part of the outer case has been removed.
You know that the shell contains an explosive; it also contains bullets, so it is in reality a gun in itself. Not only does it explode like a bomb, but when it bursts it shoots out a shower of bullets in the direction in which it is travelling. The time-fuse is arranged so as to cause the shell to burst at about 100 yards from the point at which it would fall to the ground. It therefore explodes right in front of the enemy and acts like a gun firing at close quarters.
But how can the gunner be sure that the shrapnel shell will explode at the right moment? He has to arrange the length of the fuse so that the flame will reach the explosive just before the shell gets to the end of its journey. If the gun is going to throw the shell to a distance of two miles, the gunner knows that it will take the shell so many seconds (say five seconds) to travel that distance. The gunner therefore sets the time-fuse so that it will explode the shell at the right moment. This he does by setting the time-fuse to a certain mark, and in doing this the fuse is adjusted automatically to the required length. The flame therefore reaches the explosive at the right moment, bang goes the shell and off fly the bullets with their message of death.
It is possible that through some fault in the fuse it might go out before its flame reached the explosive, in which case the shell would fail to burst, and would be no more effective than the old solid cast-iron ball. But the modern shell is usually fitted with a percussion-cap in the nose of the shell, so that if the time-fuse should happen to fail, this shell will burst whenever it strikes the ground or other obstacle.
We have seen how the fuse of the old-time shell had to be set alight by the gunner immediately before he set alight the explosive in the gun. We appreciate the risks that the early gunner ran. The modern gun throws its shrapnel shell with great speed, and if the distance the shell has to travel is not great, it may be required to explode in two seconds. If the gunner sets the time-fuse for two seconds, how can he find time to place the shell in the gun, close the breech-block, and fire the gun before the shell explodes? It goes without saying that the shell does not explode in two seconds after the time-fuse is set. The setting of the fuse merely arranges the length of the fuse, but does not set the fuse alight. The sudden shock which the shell experiences when the gun flings it at the enemy causes the detonator to light the fuse; and two seconds later the shell explodes, having by that time reached the enemy.
If it is intended to destroy a great military fort the shell is arranged so that it will not burst until it has pierced the concrete wall. This is done by using a fuse which does not begin to burn until the shell strikes the fort, and the flame does not reach the explosive until the shell has had time to pass through the fortifications. Similar shells are used in naval warfare, and must pierce the great armour plate which protects the battleship; they are usually called armour-piercing shells.
I have seen a photograph of a large 12-inch shell which had been shot through a steel target a foot in thickness. Of course this shell had not been loaded with the usual explosive, or it could not have been photographed after doing its work, as it would have burst into fragments. You remember that when we speak of a 12-inch shell we mean one that will fit into a gun or mortar with a 12-inch bore. The 12-inch shell of which I am telling you was standing on its end on the ground when photographed, and beside it stood a man. The nose of the shell reached up to the man's waist. What interested me most were the huge scratches made upon the shell by ripping its way through the heavy steel target. The interesting point was that these great scratches were at an angle, which showed the heavy shell was still spinning round while it forced its way through the target.
The Great European War brought terrible evidence of the damage that can be done by modern shrapnel shells. It was difficult to realise what an enormous number of shells were used in that war. It was said that in one short engagement the enemy fired 700,000 shells.
One who has had experience of war has said that the sound of a large shrapnel shell flying through the air is like a moan, a groan, a shriek and a wail, all rolled into one; that it is not unlike a winter gale howling through the branches of a pine-tree.