Page:Popular Science Monthly Volume 91.djvu/547

 Popular Science Monthly

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��the vast improvements that have been made in motors. Without this enormous techni- cal advance men could not fly with im- punity close to the ground. As the writer prophesied many years ago, the direct result of. this progress is the creation of what may be termed "a second zone of safety." The first zone lies high in the air, far be- y ond the range of anti-aircraft guns. Let the aircraft drop close to the earth, let it all but graze church spires, and it enters this second zone of safety — a zone which becomes safe because of the breathless speed with which the pilot flies. Why did cavalry pa- trols, in the old days, ride up boldly upoh the enemy? Well do I remember how we were surprised in a sham battle in 1892 by the sudden ap- pearance of three "enemy" hussars who craned their necks over a ridge not sixty yards away. Our captain finally managed to blurt out: "Well, somebody shoot at them." But they were gone long before we could reach the stacked rifles. What is .the twenty-miles-an-hour that a cavalry horse can do compared with the ninety- miles an hour expected even of slow flying machines today? Who can hope to hit the small one-hundred-and-thirty-mile-an-hour fighter as he flits over the ground ?

As soon as the airplane developed its full power of flying near the ground as well as high up in the azure, it became a real bird of prey, fighting in the only efficient way that a bird can fieht. which means at close

���Hundreds of captive balloons are used by each of the armies. Artillery officers watch the effect of gunfire from their baskets. Airplanes attack the balloons and drop bombs upon them. The balloons go up in smoke, while the officers descend

��range. This development is simply the automatic outcome of the perfected art of fighting with airplanes — likewise efficient only at close range. After an air-man feels certain of himself, it is second nature to apply the same methods close to the ground

— just as the falcon fights a weasel. And so the "second zone of safe-ty," near the ground, was quite inci- dentally dis- covered.

Alpine hunters must learn how to fight enraged eagles. The troops in the trenches must con- tend with machine gun bullets com- i n g from above. Now do you see why that photograph is an his- toric docu- ment?

��Let Cheese Be Your Principal Meat Substitute

A POUND of cheese supplies more than twice as much energy as a pound of fowl or round steak and almost twice as much protein as the same amount of fowl or ham. It is, pound for pound, more nourishing than any meat. Why, there- fore, do we not use it as a substitute for meat?

According to the Department of Agri- culture we do not appreciate the value of cheese as a food ; we think it is indigestible. Yet more than ninety per cent of the pro- tein of cheese is digested and ninety per cent of its energy is available. For this one reason alone it should form an important part of the daily fare. When cooked it is as easilv digested as any other article of diet.

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