They were intended to wrap around and tear down the enemy's masts. Cannister, consisting of a great quantity of small bullets in a metal can which was broken by the force of the explosion, and grape-shot, consisting of a number of larger bullets held together in a frame until they left the muzzle, were among the early projectiles which continued to be used until after the Civil War.
Accuracy of fire, long range, and deep penetration were impossible in the old smooth-bore guns, firing round shot. They depended on the smashing effect of heavy weights coming down from aloft in a high curve, or upon the shattering force of fire at point blank range, as when ships grappled with each other, their rails almost touching.
What Rifling Did for Marksmanship A new era in gunnery developed, however, with the discovery and effective use of the principle of rifling, which enabled the guns to fire long missiles without having them turn over and over in the air (see Fire arms). This change took place in the middle of the 19th century at about the same time that armored ships were first built. Improved methods for setting off the explosive charge contained in the shells and the successful application of the breech-loading system, coupled with the discovery of smokeless powder and the mastery of such high explosives as gun-cotton and nitroglycerin, contributed in turn toward making artil lery the powerful and destructive weapon it is today.
Modern gun-fire is an exact science. The naval engagements in the early part of the World War proved that warships must be prepared to fight most of their battles at from five to ten miles' range.
Guessing at distances is therefore out of the question, and the gunner of today relies on an intricate system of " fire control," aided by delicate instruments called " range-finders" and the expert calculations of master mathematicians.
Field gunners use a method called "indirect fire" to strike objects beyond their sight over the brow of a hill; anti-aircraft gunners can calculate in a few seconds how fast a tiny speck in the sky is moving, how high up it is, whether it is rising or falling; and they are able to burst their shells around that speck with surprising accuracy.
Each year sees some new addition to the power of cannon. Land forts have already been proved useless before artillery fire, and those mighty sea-fortresses, the modern "dreadnoughts," cannot carry armor so heavy but that a gun will be found to pierce it.