I did not look for any help from the younger girl, as her explanation about wood floating was really no reason at all; "just because" is not an explanation. I found that my question puzzled the twelve-year old girl more than I had expected, but she was anxious to explain the matter. It happened, however, that she was very much in the same position as the Highlander who said that he did not understand it, but thought he could explain it. She said that the iron ship kept afloat because its engines kept driving it along so that it did not sink. I suggested that it would be rather hard lines for the passengers when the iron steamer came to rest alongside the pier. It may be that she thought that this was the reason why they fastened steamers by ropes to the pier to prevent their sinking, but I think that she would hardly have let her imagination go so far. When she saw that I thought her answer amusing about the steamer keeping on the move to prevent its sinking, she tried another line of reasoning. It was because the ship was made of a thin sheet of iron that it kept afloat. But when I told her that a thin sheet of iron as large as the floor of the room would not float, she jumped to the conclusion that it was because the iron ship was filled with air which caused it to float. But air has weight; a box full of air is heavier than a box with no air in it. Perhaps someone says air does really float things, for look at the "wings" which children use when bathing. The wings will not keep us afloat unless you fill them with air. The wings full of air are really heavier than the wings without air, but when filled with air they occupy a much larger space. The wings filled with air are certainly very much lighter than they would be if filled with water, therefore the air-filled wings are lighter than water, and will float on water.

Now I think you will understand why an iron ship floats on water. If you had a great box the size of a ship, and filled it with water, it would certainly sink, but the empty box occupies so much space for its weight that it is very much lighter than the same volume of water would be, and so it floats. Of course, if the ship were to fill with water it would sink; indeed that is the reason why ships do sink.

Some of you may wonder why I have brought the subject of iron ships into a book which deals with war inventions. Surely there are far more iron ships carrying on peaceful business than there are warships. That is quite true, but the iron ship was none the less an invention due to war. The steamship was not a war invention, as it was invented for peaceful operations. Therefore we are not going to talk about how steamers were invented, although it might interest you to hear of this in some future volume of this series.

You have heard warships spoken of as "ironclads," and originally they were merely wooden ships clad in iron: the old wooden ships with an iron jacket. When I think of the beginning of iron ships I think of Gibraltar. You all know of the great rocky fort which keeps guard at the entrance to the Mediterranean Sea. Even when only a few miles from Gibraltar, you would think it was an island rock, for the narrow peninsula which connects it to Spain lies very low. Gibraltar has been in the hands of the British for more than two hundred years, but not without other nations trying to steal it from us.

The most memorable of all the sieges of Gibraltar was when the Spaniards made a desperate effort to dislodge the British from it in 1782. In order to protect their ships from the cannon-balls shot by the British from the peninsula, Spain made iron roofs to protect her ships. The British then made the cannon-balls red-hot before firing them, and they also used shells which would burst into flame, and by this means they were able to set even those iron-protected ships on fire. So far as we know, this was the first occasion on which iron was used as a protection for ships.

Later on, guns were improved to such an extent that even the thick walls of wooden ships were burst by the shots, and so the French covered one of their wooden warships with an iron coat 41 inches thick. The British Navy followed the example of the French, and tried to go one better by building a warship with an iron framework, making the outside of the ship an iron shell 41 inches thick, then inside that they built a wooden wall made of 18-inch solid teak wood, on the inside of which they made another coat or skin of iron.

The people of old times thought that the wooden walls of the ship were necessary to keep her afloat, but as the gun-makers made guns capable of piercing those iron jackets the ship-builders increased the thickness of those iron plates, until the walls of the ship were made entirely of iron.

It is of interest to compare a modern sea fight with one of a hundred years ago. Imagine that you are a sailor on board a British frigate which is taking part in the American war of 1812. The name of your ship is the Guerriere, and it is quite apparent that the name has been borrowed from the French. Your battleship is, of course, a sailing ship, as steamers had not been invented at that time. You take a walk round and count the number of cannons, and you find that there are 49, while you have 282 men. Your ship has been with a British squadron lying off New York, but you are at present making your way to Halifax to have your ship overhauled and to get some improvements made.

It is the afternoon, and everything goes along quietly until the look-out reports a ship in the distance. It soon becomes apparent that this is an enemy ship bearing down upon us. We find out later that she is the American Constitution, and that some American brig had taken her word of our presence. Our orders are to prepare for a fight, and while we await the arrival of the enemy, we load every gun and remain ready to fire as soon as the signal is given. At five o'clock comes the order to fire, and every gun on the one side of the ship goes bang, but not a single cannon-ball manages to hit the enemy ship. Our ship then wheels round in the wind in order to bring our other side to face the enemy. We fire another broadside, and this time we land two cannon-balls on the Constitution. For three-quarters of an hour we are busy firing broadsides, first from one side of the ship, then wheeling and firing from the other side, but we do very little damage, although our men work very hard.

The American ship kept bow on and had not troubled to fire any broadsides as yet, contenting herself to fire only her bow guns. Then the American set full sail to bring her alongside of us. We could see that she was a good deal bigger, and that she carried more guns, and we find later that she had 456 men against our 282. Apart from these advantages, we have to admit that she fought better than we did. She saved her ammunition until she felt she could do real damage, and when she did start, it only took her ten minutes to do a great deal of damage, and over went our mizen-mast. This disabled our ship, and we could not get her to answer her helm. The American ship, as she crossed our bows, fouled with our rigging, and fired in a broadside at close quarters, and our two remaining masts went by the board, leaving us quite helpless. It was now 6:30 and our captain realised that our ship was lost, and fired a shot away from the enemy, and surrendered.

Then an American lieutenant came on board, and finding that our ship was gradually sinking, and could not be towed to port, he ordered our crew to be removed to the Constitution, and after this was done they set our ship on fire. We had lost 15 men, killed, while the American ship had 7 killed. There were 63 of our men more or less wounded, while there were only 7 of the Americans wounded. We all felt that our enemy had been brave, and there was no trace of bitter feeling. Indeed, the Americans could not have been more considerate. They gave the greatest possible attention to our wounded, and they even took care to see that none of our sailors lost a trifle of their belongings. Both sides fought like gentlemen, and kept to the laws of war.

Let us now picture one of the sea fights which took place in 1915, during the Great European War. The fighting ships are no longer dependent upon their sails, but can steam along at 30 miles per hour. They do not require to wait until they are at close quarters, as their guns can throw shells on to a ship 10 miles away.

Here is the story of a North Sea fight as told by some of the German survivors from the Blücher  whom we rescued and took prisoners. The British ships were away on the horizon when they started to fire. The hulls of the German vessels were not visible to those on deck the British battle cruisers. Only the officers on the look out upon the mast 100 feet above the deck could see the hulls of the enemy ships.

The shots came slowly at first. Some fell ahead and others fell short, but as each fell into the sea it sent a great water-spout up into the air. The British guns were finding their range. Those deadly water-spouts crept nearer and nearer. The men on deck watched them with a strange fascination. Soon one shell fell close to the ship, throwing a great volume of water right on to the decks; the range had been found. Then the shells came thick and fast, with a horrible droning hum. At once they did terrible execution. The electric machinery for giving light on the Blücher  was soon destroyed, so that the ship was all dark within.

At first the great deadly shells seemed to drop down from the sky; then as the British ships got nearer, the shells commenced tearing great holes in the side of the ship. Some shells bored their way into the coal bunkers and set the coals on fire. There was no hope of hiding from the shells; they searched out all parts of the ship. It was like one continuous explosion, until the great ship turned over and sank to the bottom of the sea.