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Page:Popular Science Monthly Volume 90.djvu/771

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��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.

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 fifty thousand feet tons; that is to say, its energy is equal to fifty thousand tons falling from a height of one foot — energy enough to lift two 25, 000- ton battleships to the height of one foot.

Waters Which Exert a Pressure as Great as Dynamite

, Mother Earth is

the greatest of all explosive manufac- turers. Water seep- ing down into the earth's crust and trapped in large quantities in the neighborhood of volcanoes some- times becomes heated to high in- candescence — heated until it is no longer w'ater or steam, but mingled oxygen and hydro- gen, far above the temperature of their dissociation — under a pressure so great that they occupy a space no larger than did the original ,-^^t^ water;

��consequently the entrapped waters exert a pressure as great as the strongest dynamite.

The most notable volcanic explosion that ever occurred in historic time was when that old extinct volcano, Krakatoa, in the straits of Sunda, that had been sleeping for thousands of years, was literally blown into the sky by the pressure of the pent-up gases beneath it.

This great eruption occurred in 1883. More than sixty thousand persons were killed. The captain of a tramp steamer saw a very strange disturbance in the sea, in the direction of the old mountain. Taking his glass he saw a perfect Niagara of water pouring into an enormous fissure that had opened in the earth. He was struck with consternation, and rightly imagining that something ver>' serious was likely soon to happen he put on all steam to escape, and luckily he had reached a point which enabled him to survive the effects of the awful blast when it came.

The Fissure Which Swallowed a Niagara

The vast mass of water which had tumbled into the bowels of the earth was immediately trapped by the closing of the great fissure down which it had poured.; The water was quickly converted by the intense heat into a veritable high explosive, with the result that the massive mountain was literally blown bodily skyward, and fell in huge fragments into the surrounding sea. The shock was so great that it was felt clear through the earth, and an immense tidal wave was set going which encircled the earth. The opposing portions of the great wave, meeting in the lower Atlantic, flowed up even to the coast of France. An atmospheric wave passed around the earth three times. The amount of volcanic mud that was discharged from the mountain during the eruption was more than the muddy Mississippi discharges into the Gulf of Mexico in two hundred years.

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��Sixty twelve-inch naval guns, loaded with several hundred pounds of explosive each, could be fired by electricity one after the other while grandfather's clock is making one tick

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