The earth is being constantly bombarded with meteorites, usually of very small size. But the earth is armor-plated with its envelope of air. The impact of meteorites upon this envelope, at the enormous speed at which they are traveling through space, is fatal to them, and they are dashed to pieces and consumed upon it, as though it were a solid shield of hardest tempered steel. It is seldom, indeed, that a meteorite has sufficient size and mass to penetrate through the atmosphere to the earth's surface. Were it not for the protection offered by the earth's envelope of air, every living thing upon its surface would be very soon destroyed by the meteoric bombardment from the heavens. A minute particle of meteoric dust, traveling at celestial velocity, would be more deadly than a bullet from a shoulder-rifle.
When a projectile is fired from a gun, it encounters the same atmospheric resistance, in proportion to its velocity and mass, as is encountered by a meteorite, the resistance increasing in a ratio something like the square of the velocity. When a battleship fires a 12-inch shot at another war-vessel ten miles away, the velocity is greatly reduced during flight, for an enormous amount of energy is consumed in punching a 12-inch hole ten miles long through the atmosphere. Gravitation, also, is drawing the projectile toward the earth with a constant pull of half a ton, to counteract which the trajectory must be made an upward curve. This makes the path longer, and consumes additional energy in raising the projectile to the top of the trajectory.
If a projectile could be thrown from a gun at a velocity equal to that of a meteor, it would blaze like the sun during flight, for the metal upon its surface would be fused and gasefied by the resistance and friction of the air. It would not make any difference whether it were made of the toughest, hardest tempered steel, or whether it were made of soft iron. The velocity would be so great that it would pass through the heaviest armor-plate without appreciable reduction of speed. If the projectile were of lead, it would require armor-plate of a greater thickness to stop it than if it were of steel, for the reason that its mass or weight for its bulk would be greater.
Distance and the intervening air are our most efficient protection. No armored defense now employed is wholly effectual, except the range be long. By consequence, then, future naval battles will be decided more and more by speed and size of guns, rather than by armored protection.
Were two modern dreadnoughts to battle at as close range as did the Monitor and the Merrimac, immediate destruction would be mutual. They would cripple each other more in four minutes than did the Monitor and the Merrimac in the four long hours during which they pounded each other.
The Alabama and Kearsarge fought for more than an hour, within bowshot of each other, before the Alabama was destroyed. Were two of the biggest and most heavily armored battleships in the world to fight today at as close range, one or the other of them would be destroyed in a very few minutes.
The projectiles fired from the monster naval guns now weigh many times as much as those thrown from the guns of either the Monitor or the Merrimac, and these huge projectiles have also a multiplied velocity. The total thickness of the armor of the Monitor's turret was ten inches. An iron wall of the character used in Ericsson's turret, five feet in thickness, would not afford adequate protection against our modern, monster guns.
Of course, the character of armor-plate has been vastly improved since that time. Instead of being merely soft iron, as was that of the Monitor, armor-plate is now made of the hardest and toughest tempered steel that science can produce. So, also, is the projectile. The projectile has far more than held its own. It is necessary, therefore, that the most heavily armored ships, as well as those unarmored, must fight today at long range, depending mainly upon skilled marksmanship and power and range of guns, rather than upon armored protection. A battle at close range between two huge modern dreadnoughts would be as deadly to both combatants as a duel between two men standing close together, face to face, holding pistols at each other's breast.
When a chemical engineer makes an invention, and needs money for its exploitation, he first interests capitalists by letting them see the invention practised on a laboratory scale, embodying essentially the same conditions as would be involved in the larger commercial application. Similarly, we may get a very just and dependable idea of the relative efficiency of guns and armor-plate on a naval-battle scale, by taking into consideration what would be the result of a lesser conflict, embodying essentially the same conditions.
Suppose two men were to fight a duel, one wearing armor capable of protecting him as efficiently against rifle balls as the heaviest armor carried by any warship today is capable of protecting it against modern cannon-fire; the other wearing no armor, and being thereby enabled to run much faster than his armor-clad opponent. Obviously, if the unarmored man had a gun of longer range than that carried by the protected man, he would be able to keep out of range of his enemy's gun, while still keeping him well within range. Thus he would be able to continue firing at him until he killed him, without in return being hit at all.