now so easily destroyed that they are not worth the money spent on them. The trenches hastily dug by the troops are far more effective in defense than the costly forts against these monster long range guns.

More hideous than anything else are the gas shells that explode and suffocate the soldiers in the trenches. The Germans first used these deadly gases. They waited until the wind was blowing toward the enemy and then let loose great volumes of gases which are a little heavier than air. The wind carried them to the trenches and caves of the enemy and the Allied forces were overwhelmed. As soon as possible the British and French furnished their soldiers with masks to protect them from the deadly effect of the poisonous gases and adopted gas bombs in their own defense.

Machines are also used to shoot liquid fire and boiling oil at the enemy. Hand grenades are thrown very effectively in trench fighting by all the armies. Men of science are using all their knowledge and skill to make still more murderous machines-anything that will more speedily kill and cripple the enemy. It was said before the war opened that men would never go to war again, for all these new devices would destroy an army in one engagement, but we have learned to combat even these diabolical contrivances, the only difference being that men are killed by the hundred thousand instead of by the thousand, as in previous wars.

The two most important aids to modern warfare we have not yet discussed. They are the aircraft and the submarine. We shall treat of aircraft in the next chapter.

CHAPTER IX

WAR IN THE AIR

Ever since we have learned to fly it has been known that aircraft would play an important part in war. Aside from its use to drop bombs and explosives on the enemy's works, the airplane has been used as a superscout. And, more than this, it has become one of the fighting units. It not only combats other aircraft, but attacks troops on the ground with its deadly machine guns.

The element of surprise, which in all wars of the past has been a great factor in the winning of battles, has now been largely eliminated because of the airscouts. Today it is impossible to make an unexpected flanking movement unless the army attempting it can keep down all enemy flyers. It was news gleaned by the airscouts that saved the British army from annihilation in the early part of the war. Many times the troops on both sides have been saved by timely warnings from the sky. With the long range of modern artillery and the introduction of the indirect method of firing, big THE EYES OF guns are virtually blind without THE ARTILLERY the direction of the aerial observer. The armies have used a kite balloon for observation. These are huge sausage-shaped bags floating high in the air at a height from 1,000 to 5,000 feet. They are easily shot down by the enemy's infantry and are likely to be bombed by the enemy's airmen so that the main artillery must depend for

their direction upon the other types of aircraft. There are two other types of flyers used in war, the airplane and the airship, or Zeppelin. The fighting biplane or monoplane, in which the pilot ascends alone, bears only its own load and nothing more. Its motor is powerful and the body shaped to offer the least possible resistance to the air. With its engine roaring and a gale of wind blowing in the wake of its propeller, this machine will leap across the ground, spring into the air and climb at an amazing pace-a mile in seven minutes. It must be able to fly above an enemy plane so as to drive down upon him and thus fire a fatal shot. Its speed has brought it, the nickname of "bullet" or 'chaser." A biplane with a 160-horsepower engine has attained a speed of 130 miles an hour. Such a machine can loop the loop and perform other marvelous feats. It requires great skill in handling, for in rising or descending it may swerve suddenly or overturn. It avoids gun fire by the sheer speed by which it moves. This "chaser" type of biplane has proved to be a valuable scout. The German Fokker is the most famous machine of this class. The airplane cannot hover over one spot, neither can she fly at night except at some risk. If a motor fails and the scout has to descend he may crash into tree-tops or against roofs.

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Should a more careful and detailed observation be needed than could be given by these high speed WATCHING Scouts, there is a slower flying biplane THE ENEMY or monoplane which will carry one or more passengers as well as a pilot. The scout takes with him an officer skilled in observation well equipped with glasses and maps. The officer devotes himself entirely to the land below while the pilot

steers. The larger and slower planes are protected by an escort of "chasers."

make maps.

The pilot, when in flight, is too busy a man to As he ascends, the first ten minutes or so are occupied in getting his height. He must see that all instruments are working properly and listen to his engine. Then his eyes must make a ceaseless round of the instruments-the aneroid, airspeed indicator, revolution indicator, oil gauge, petrol gauge, compass and watch. Only occasionally can he look over the side to see if he is in his course. But with a man in the car, or two if possible-for two pairs of eyes are better than one-a machine flying for several hours over the enemy's lines can make a full and accurate survey. Some of these biplanes measure 180 feet from tip to tip. They run great risks in the survey for they are easily taken by the faster machines and they offer a much better target for the enemy's guns.

AIR

For some time after the war opened Germany had the advantage in the number of airplanes and scouts, but in 1917 the Allies obtained control of PATROLS the air along a front of several hundred miles. The Allied armies now employ huge flotillas of airplanes operating up and down the lines. One patrol flies at a height of 6,000 feet, or a little more than a mile, while the higher patrols are from 20,000 feet to 23,000 feet up. It is the duty of the higher patrol to prevent German machines from coming over the line at great height and sweeping down on the Allied patrol flying ten thousand feet below.

The purpose of the two patrols is to prevent any German airmen from crossing the line to obtain photographs and other valuable information concerning the defensive works and artillery and the

movement of troops. If an army is able to control the air they may keep their plans a secret from the enemy. They may move up troops, or build railroads or extend their trenches or build new gun emplacements without giving the enemy an inkling of where the next attack is to be launched.

THE

Then there is the airship or Zeppelin, sometimes called the dirigible, which is large, slow and unwieldy and offers a mark like a haystack ZEPPELIN to the gun-fire from the land. However, the Zeppelin has some points in her favor. She can remain in the air many days. She may hover over a certain spot with her engine stopped and her car motionless, which gives opportunity for detailed observation, or the Zeppelin may hover at the rear of her own lines and with her powerful wireless. plant remain aloft from dawn until dusk. Thus her observers can watch constantly the enemy's battle front and signal any change they may notice in the position of the troops. The airship can also fly safely at night. For destructive raids the Germans at first used only the Zeppelin. She could carry two and one-half tons of shells to a height of two miles. Now the anti-aircraft guns are so accurate and the enemy airplanes so much faster that the slow-flying Zeppelins seldom pass over enemy country except at night.

Much excitement was shown when German Zeppelins attacked London and Paris early in the war. Great precautions were taken to darken these cities at night. Gigantic searchlights and anti-aircraft guns were pointed toward the London sky. One Zeppelin raided London in May, 1915, killing only 6 persons. Another in August killed 10 citizens. À third in September destroyed 37 lives. But if this