As the time required for the projectile to be thrown from a twelve-inch cannon is only about the sixtieth of a second, sixty of these huge guns could be placed side by side and fired by electricity one after the other, while grandfather’s clock is making but one tick.
Our ideas of duration are but relative. We have seen that the combustion in a cannon, though very rapid to our senses, is actually very slow indeed as compared with the much more rapid combustion of a high explosive; and great as is the speed of the detonative wave, yet the speed of the earth in its orbit is four times as great.
If a celestial giant with a huge dynamite bomb the size of the earth itself were to approach the earth in its flight through space, and detonate the bomb immediately behind the earth, it would take half an hour for the bomb to explode, that is to say, it would take half an hour, or thirty minutes, for the explosive wave to pass through the eight thousand miles of its diameter. As the speed of the earth in its orbit is four times as great as that of the explosive wave, the earth would rush away, leaving the bomb about thirty thousand miles behind by the time it had completely exploded. If the interstellar ether were a high explosive mixture and were to be set off by the bomb, the earth would pass on clear around the sun, and while coming back, about six months later, would meet the explosive wave still going. It would require nearly a year for such a detonative wave to reach our sun from the earth.
We have seen that if the earth were a ball of dynamite, it would require half an hour to explode. If the sun were a mass of dynamite it would require about two and a half days to explode.
We frequently hear the theory advanced that planets and suns sometimes explode from pent-up forces within them, and that our earth might possibly blow up. Now, the force exerted by a high explosive is dependent entirely upon the pressure capable of being exerted by the gases liberated by the explosion. The pressure exerted by the most powerful high explosives has been estimated to be about 500,000 pounds to the square inch. Consequently, were the whole molten interior of the earth to be replaced with dynamite and detonated, the explosion that would follow would not lift the earth’s crust. The superincumbent weight of the earth’s crust is greater than would be the pressure exerted by the dynamite.
If it were possible to throw a projectile from the earth to the nearest fixed star, Alpha Centauri, it would take about four years for the light of the flash to reach that star. The sound, if it could travel through ether, would reach there about four million years later. The projectile, traveling more than twice as fast as sound, would reach there in about two million years.
When one of our big twelve-inch cannon is fired, the projectile, weighing a thousand pounds, has a muzzle energy, stated in mechanical terms, of about 50,000 foot tons, that is to say, its energy is equal to 50,000 tons falling from a height of one foot—energy enough to lift two 25,000-ton battleships to the height of a foot.
As the projectile weighs half a ton, the energy is equal to that which would be developed by dropping the projectile from a height of more than twenty miles, making no account of the resistance of the atmosphere.
Dropping upon a piece of armorplate too hard and thick for the projectile to penetrate, the heat developed would be sufficient to melt 750 pounds of cast iron.
When one of these projectiles is fired from the gun directly against twelve-inch armorplate, which the projectile is capable of penetrating, the hard-tempered steel plate in front of the projectile is fuzed or rendered plastic from the heat generated by the energy of the impact, and is forced like wax from the path of the projectile.
There are many popular errors regarding the action of explosive materials. One of the most notable is the opinion that the action of dynamite is downward, and that if a body of high explosive be detonated on the surface of the earth the main effect is downward.
The exact opposite is the truth. When a mass of explosive is detonated, it is converted practically instantly into a ball of incandescent gases and vapors under very high pressure. When confined the gases act to disrupt their container.
When a large steel projectile is charged with a high explosive, like picric acid, and the explosive detonated, the walls of the projectile are not only broken but they are also torn, twisted and shredded, and so quick is the action that the inner surface of the metal is compressed and densified against the outer metal.
For this reason it is easy to tell from the character of the fragments of a projectile whether or not a high explosive or an explosive of inferior power was employed, that is to say, whether or not the explosion was of high order or of low order.
There is one false belief about the action of high explosives that has been about the hardest of any to kill, and the cost of killing it has been very expensive. Furthermore, it possesses more lives than the proverbial nine-lived cat. This belief is that five hundred pounds or so of dynamite exploded upon a warship or upon coast fortifications would destroy ship or fortifications, and that a few of such large bombs of dynamite dropped in a city would lay the city in ruins.
Upon the advent of the aeroplane and the dirigible balloon, it was confidently believed that the aerial bomb would quickly become the most destructive implement of warfare. It was prophesied that should war come between England and Germany, London would soon be reduced to a heap of ruins by bombs dropped from the German Zeppelins.
Several years before the European War broke out, I predicted that Zeppelin bombs would not and could not by any possibility work very wide destruction, and events have since vindicated my prediction. I pointed out the fact that should a hundred Zeppelins visit the city of London, once a day, for a year, returning to their base without mishap, and each Zeppelin succeed in destroying two buildings, the destruction would just about keep up with the growth of that city, for they build in London sixty thousand houses a year.
We all remember the destructive powers that were predicted for the fifteen-inch Zalinski pneumatic dynamite guns that were mounted at Sandy Hook and at San Francisco at enormous Government expense. These guns were capable of throwing with compressed air about six hundred pounds of nitrogelatin to a distance of from a mile-and-a-half to two miles. It was popularly believed that one of these bombs striking upon a huge armorclad warship would utterly destroy it.
Also two of these guns were mounted in a sort of cruiser called the Vesuvius. During the Spanish War the Vesuvius was taken down to Cuba, and in one action several of the huge bombs were thrown upon the earthworks and fortifications of the Spanish. They succeeded merely in mussing up the green, grassy effect. They did no material damage, for the reason that the action of the explosive was nearly all upward into the air.
When the pneumatic dynamite gun was promulgated, it was popularly believed that all high explosives were exceedingly sensitive, and that it was necessary to get them out of the gun very gently if they were to be thrown from ordnance.
The writer was the first to dispel this folly, through the invention of Maximite, a high explosive which will stand not only the shock of being fired from heavy guns at high velocities, but which will also, without exploding, stand the far greater shock of penetrating the heaviest armorplate—armorplate as heavy as the projectile will stand to pass through without breaking up.
While I was working upon Maximite and trying to get the Government to adopt it, Congress appropriated the money for building an eighteen-inch gun for testing a shell invented by Louis Gathmann, which was intended to destroy battleships by exploding the shell on the outside of their heavy armorplate, it being believed that if five hundred pounds of guncotton were to be fired against the side of an armored ship and exploded, the whole side of the ship would be blown in and the vessel destroyed.
The gun employed by Gathmann was essentially the same type of gun as that previously designed by me, and explained in a lecture by me before the Royal United Service Institution of Great Britain in 1897, and illustrated in a book of mine published the same year by Eyre & Spottiswoode, British