In old Greek mythology there is a story of a man named Dædalus who was said to be very clever in making inventions. According to the myths he escaped from imprisonment by means of wings fastened to his body with wax. I can remember when at school reading of his son Icarus trying to fly and falling into the sea.
The poet tells us how Dædalus warned his son Icarus that he must fly in the middle air, that he must not go too low lest the waves might wet his wings, that he must not go too high lest the sun should melt the wax with which his wings were fastened on.
The poet then proceeds:
"Thus teaching, with a fond concern, his son
He took the wings and fix'd them on:
He fix'd with trembling hands; and, as he speaks,
The tears rolled gently down his aged cheeks."
And it happened that Icarus, flying too high, had the wax melted by the sun, and losing his wings, he fell into the Ægean Sea, a part of which the Greeks called after Icarus. But the flying, like that of Peter Pan, only took place in the story. However, you see how the idea of flying through the air is a very, very old one, for those who wrote the Greek story lived before the time of Christ.
Probably you all know something of that clever English monk, Roger Bacon, who lived about seven hundred years ago. Here is one sentence from his writings: "There may be made some flying instrument, so that a man sitting in the middle of the instrument and turning some mechanism may put in motion some artificial wings which may beat the air like a bird flying." That is a remarkable prophecy, and although the wings of an aeroplane do not flap like the wings of a bird, yet many such experimental machines were made when your father was still a boy.
You know that a bird is heavier than air, else it could not alight. To keep up in the air the bird must beat the air with its wings; it may glide along as it comes downwards. You know that an aeroplane is heavier than air, and that it must keep the propeller going in order to keep up in the air; it may also glide downwards like a bird.
Before we ever had an aeroplane, people saw that it would be very much easier and safer to fly with a machine which was lighter than air, for it would be able to float in the air.
But what could be lighter than a globe filled with air? One boy suggests that a globe with no air in it would be lighter. He is quite right, and this same idea occurred to an inventor more than two hundred years ago. This man made four huge brass globes, meaning to withdraw all the air from them, thinking they would then float in air. Why did it not succeed? One boy suggests that it was because he could not withdraw the air, but that was not the reason, for the air pump had been invented at that time. Of course the inventor knew that there was no use in using heavy copper globes, as the withdrawal of the air would make very little difference in the actual weight of the globes. And so he made the globes of extremely thin copper, but he had not considered the matter carefully enough, for as soon as he withdrew the air from the inside of these copper globes, the pressure of the surrounding atmosphere crushed inwards the thin walls of the globes, just as it crushed the thin walls of your toy balloons when there was no air inside.
Knowing that when air becomes heated it expands, so that the same quantity will occupy a much larger space, some inventors got the idea of filling a large bag with heated air. At first they tried paper bags, then linen and silk, and by burning a fire beneath the open mouth of a large bag or balloon, it was possible to expand the air so much that the balloon soared right up into the air. A basket containing some living animals, a sheep, a cock, and a duck, was attached to one of these balloons, and even then the balloon could fly up into the air. Then a young Frenchman was bold enough to venture up in the basket of one of those hot-air balloons. Of course he could not travel very far, as the air soon cooled.
Even before the success of these hot-air balloons, some people had tried to fill a balloon with hydrogen gas, which, you know, is very much lighter than air. The difficulty was to get any material which would prevent the hydrogen escaping through it. A bag made of linen allowed the gas to escape, and so the inventors abandoned hydrogen and tried hot air. However, they very soon found how to make bags which would imprison the hydrogen gas.
Although the first balloons were not war inventions, it soon became apparent that they would be most useful in time of war. After Paris was surrounded by the Germans in 1870, two balloons rose from the French capital and soared away over the heads of the enemy. It was by this means that Gambetta, the most popular of French statesmen, was able to escape from the besieged city, and thus render great assistance from without. Having brought carrier pigeons with them out of Paris, it was easy to send word back to the imprisoned city.
It also became apparent that balloons would be of great use in war as a means of observing the enemy. But so long as a balloon was merely a gas bag with a basket-car attached, it must be at the mercy of the winds, and could not be made to go anywhere its master desired.
Then came the idea of having an air-ship with an engine and propellers, but in order to carry so much weight the balloon would require to be very large. This large balloon would make its way through the air much more easily if shaped like an egg. The first attempt at such an air-ship was made in France. It was called a "dirigible balloon," to signify that its direction could be controlled. The earliest inventions were French, Russian and British. As the size of the balloon was increased in order to carry the heavy engines, the shape of the balloon became more like a great fish, or a giant sausage. and less egg-like, and so we came to have that kind of air-ship which is usually described as a Zeppelin, after Count Zeppelin, of Germany, who built many such ships.
We are proud of our huge battleships; they are our protectors. There is something grand and noble about a dreadnought, but the Zeppelin does not stand out as a noble craft, because the Germans have put it to a very ignoble use. Had we built our warships for the purpose of murdering men, women and children in defenceless coast towns, we should no longer be proud of our battleships. The British Navy would not be our pride, but our shame; this state of affairs is unthinkable. And so those great air-ships which were used largely by the enemy in the European War are inventions to be abhorred because of the use to which they were put. Many air-ships were built in Great Britain during the Great War, but the purpose of these was to act as scouts for our Navy.
One boy asks how big the enemy's Zeppelins were. We know that one of these monsters, which was wrecked in Sweden, measured 650 feet long and 80 feet in diameter. The measurement round its waist would be about 250 feet. The earliest air-ships measured only about 50 feet in length, so they have grown to thirteen times their original size.
This enemy air-ship which was wrecked in Sweden had six motors of 800 h.p., whereas the earliest air-ships had only propellers to be driven by hand, and the first with an engine was only 3 h.p.
In the illustration facing page 232 you see part of a great Zeppelin, with one of its gondolas or cabins. The air-ship is so large that the artist would have had to draw it on a very small scale, as though it were very distant, in order to get it into the picture. But he wished to show us what the inside of a Zeppelin is like, and so he could only get a part of the ship into the picture.
Mending a Zeppelin Puncture
This Zeppelin looks as though a great part of the cover had been torn away, but it is the artist who has done this, in order to show us what is beneath, and how a man may leave the car and climb up the metal structure beneath the outer cover, and thus repair ally damage done to the separate gas balloons.
The damage to the air-ship is not that it has a great part of the outer cover torn off, for as the legend below the illustration states, it is the artist who has done this in his imagination, to let us see how one of the crew can climb up under the outer cover to mend a puncture in any of the balloons. Of course you know that instead of one giant balloon there are a great many sections all built alongside of one another under the outer envelope.
But why must air-ships be made in such giant sizes? Why make the balloon part any bigger than the cabin? For the same reason as you would not think of going to sea on a broomstick: it could not support the weight of your body. Why? Because all the water which presses against it is not sufficient to support your weight. The more weight we wish to float on the sea the larger must we make the boat. You know that air cannot lift or support things as water can. Water has a thousand times more lifting power. That is why we have to spread the weight of the air-ship over such a large space.
You will agree that the idea of sailing about in the air on a lighter-than-air machine seems a much simpler thing than flying through the air on a heavier-than-air machine. We are not surprised that balloons were invented long before aeroplanes. Balloons seem quite ancient things; grown-up people will be able to remember the beginning of aeroplanes. It was just a few days before Christmas of 1903 when the first aeroplane made its first flight. It was not a long journey. Nowadays we can reckon an aeroplane flight in hours, but this first flight could not be reckoned even in minutes, as it did not occupy one minute. The flying machine remained in the air for fifty-nine seconds.
I think you are sure to have heard of the brothers Wright of America: Wilbur and Orville Wright. They were the first men to fly. For three years before this they had been busy making experiments with what are termed "gliders"; you would call them aeroplanes without engines. Of course these never went high up in the air, but they gave people the sensation of flying just like large birds gliding down with outstretched wings to alight on the ground. Many other inventors as well as the Wrights were busy making and trying gliders, but the Wrights were of a mechanical bent, and they added guiding planes, by which they could cause the glider to rise or fall a little during the short glide. They also had means by which they balanced the machine in the air. When the Wrights made their experiments with a real flying machine having an engine and air propeller, they did not tell the world what they were doing. They made their experiments very quietly in a country district, and when the country people carried the news to town telling about the doings of the Wrights, no one believed them; the idea of men flying was too absurd. But these brothers did not care whether the people believed them or not; they were bent on conquering the air.
In 1904 Orville Wright wrote to a friend in London, telling him that he had succeeded in flying a distance of 24 miles without coming down; some people believed this, and others did not. The Wrights still kept their flying machines a secret, as they were trying to get the French Government to buy the patent rights. There was a long delay, and in the meantime other inventors were making progress. One inventor in France had already succeeded in making long hops with his aeroplane, just like a bird. Then others increased the length of the hops, until someone actually flew a distance of one mile, returning to the same point at which he set out, and gaining a prize of £2000 for doing this. Another experimenter remained up in the air for nine minutes; France was making real headway.
At last the Wrights came before the world. Wilbur came to France, and he certainly astonished the world. The aviators did not think much of the look of his machine, but he soared up into the air and flew about for more than two hours without alighting. He even took up a number of passengers with him to a height of 400 feet. The air was really conquered, and so one improvement after another was made, until in 1916 an aeroplane could carry four passengers to a height of over two miles, and by this time it was possible for a man to fly about for twelve hours without alighting.
Now that we have seen how flying machines were invented, we shall have a talk about their uses in actual warfare.
We have had hymns asking protection for our soldiers and sailors, and during the Great European War A Hymn for Aviators was written which was set to music by Sir Hubert Parry. Here are two verses of it:
"Lord, guard and guide the men who fly,
Through the great spaces of the sky,
Be with them traversing the air
In darkening storm or sunshine fair.
Thou who dost keep with tender might,
The balanced birds in all their flight,
Thou of the tempered winds be near,
That, having Thee they know no fear."