CANNON. Imagine a machine that could pick up an automobile full of people and throw it ten or fifteen miles! The monster cannon Ott modern battleships and in coast defense forts hurl shells as heavy as that. What's more, at the end of their journey these shells have enough power to pierce a foot or so of steel armor plate and blow up a ship.
Imagine now a 330 pound steel messenger leaving Independence Hall in Philadelphia, soar ing into the air more than four times as high as the highest mountain, and about two minutes later blow ing off the top of the Woolworth tower in New York City. This will give you an idea of the performance of the famous " 75-mile" gun with which the Germans bombarded Paris during the World War of 1914-18.
More big guns are used on battleships than on land, for their immense weight makes it difficult to move them from place to place with enough speed to be useful. Modern armies are chiefly equipped with light and heavy field guns, ranging from three to five inches in caliber, and with the short-barrelled mortars and howitzers of six-, eight-, and ten inch bore used in high-angle fire.
The tendency in the navies of the world, however, is toward larger and larger guns of extreme length to give maximum range and pene trating power. Fourteen-inch and even sixteen-inch guns from 40 to 60 feet long and firing shells weigh ing from 2,200 to 2,600 pounds over a range of more than 20 miles form the regular arma ment of the newer and larger vessels of the United States navy, and of the coast-defense forts. Great Britain carries her naval guns up to 18 inches.
Nevertheless, the largest cannon ever used in battle was a land gun devised by the French during the World War. It had a bore of 20 inches, a barrel 76 feet long, and fired a shell weighing 3,200 pounds. The destructive effect of this weapon sur passed even the famous "Big Bertha" siege guns with which the Germans shattered the steel and concrete garrison and put the fort permanently out of action.
The "75-mile" gun mentioned before was looked upon as a freak weapon, designed to spread terror rather by its unexpected and startling range than by the destructive effect of its fire.
It was only 8% inches in caliber, and its 330-pound shell carried only 33 pounds of explosives.
However, the velocity of the shell as it left the muzzle of the gun was probably the greatest ever achiev ed by any man-propelled object 5,000 feet per second. If it could have maintained this rate of speed, which amounts to more than 3,400 miles an hour, it would have en circled the earth in about seven hours.
The shells fired by modern cannon follow in general the same pattern—hollow cylinders of steel with sharp-pointed heads, filled with high explosive which is set off by a percussion fuse as soon as the shell strikes any solid object; around the shell near the base is a brass band to catch in the grooves of the rifling and impart the necessary "spin" to the projectile. Smaller guns use "fixed ammunition," like huge rifle cartridges; but the larger guns load their shell and powder sepa rately. The smaller guns are usually fired by percussion or fric tion fuses; the larger ones by electricity.
The armor-piercing shell used by the big naval guns is an ex ception to the standard construc tion. It has been discovered that , a sharp-pointed projectile tends to crumble when it strikes the tough thick metal skin which protects our battleships. For this reason, a broad blunt cap of soft steel is fitted over the hard sharp nose of the shell; and then to re duce the air resistance of this blunt cap, a thin hollow "dummy" point is added. When the projectile strikes the armor plate, the dummy point is smashed and crumbles away, allowing the soft cap to hit the plate. This crashes into the metal and spreads out like a wedge, preparing the way for the hard point, which plows through, drilling a clean hole. The fuse is arranged so the shell will explode after it has reached the interior of the ship.