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"MAXIMHURST," MR. MAXIM'S SUMMER PLACE ON LAKE HOPATCONG. The library is shown on the right and the cottage in the back ground. The man standing by the tree is Edwin

Markham, the poet.

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By Wm. R. Stewart

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fact that their makers might reasonably be supposed to be familiar with such agencies. Unsuccessful attempts

wreck the Winter Palace at St. Petersburg, the British houses of Parliament, the Nelson monument at Montreal, the Frederick the Great statue at Washington, and other instances, are readily recalled. Even persons who make a special study of explosives sometimes achieve remarkable failures, as illustrated in the United States dynamite cruiser Vesuvius, and in the test of the Isham shell at Sandy Hook, New York.

There is enough explosive energy in a grateful of coal, if it could be liberated and controlled, to hurl a 1,000-pound projectile through a foot of solid steel. But there can be no explosion without oxygen, and the coal in the grate will not

burn faster than the supply of air which reaches it will permit. If the coal could be furnished all at once with enough air to effect its complete combustion it would explode with as great violence as if it were so much dynamite. Flour mills sometimes blow up from the formation of an explosive mixture of flour dust with atmospheric oxygen, and accidents are common from the use of naphtha and other volatile substances in cleaning clothing, due to the formation of an explosive mixture of the vapors with the air.

An "explosive," it will thus be seen, is a very comprehensive term, being applicable to any combustible substance combined with sufficient oxygen to burn the combustible. The explosive may be either a mechanical mixture or a chemical compound, and the explosion comes when, by whatever agency, its constituent parts are disrupted from one another, or made to react on one another, resulting in the formation of a gas occupying several hundred times more space than the original material, and simultaneously developing a high temperature by which its expansive force is further multiplied. It is estimated that when nitro-gelatin is exploded the volume of gases and heat developed are such that the products of its combustion occupy space equal to 10,000 times the original volume of the body. Some liquid oxygen explosives occupy, when detonated, 15,000 times the original space. Typical of the mechanical mixture explosives are gunpowder and mixtures of finely powdered charcoal and liquid air. These, at elevated temperatures, react on each other and become gaseous. As types of the other class (chemical compounds) are nitroglycerin, liquid acetylene and liquid ozone,

There are two ways of "setting off" an explosive-by burning and by detonation. The former is progressive from one particle to another, like fire in a grate only infinitely more rapidly. As combustion of this kind, from exposed surfaces, requires an appreciable time for the consumption of the explosive body, it is adapted to the purposes of gunpowder. The detonative form of explosion, being simultaneous throughout the mass, is unfitted for use in guns (which would be smashed to pieces) but is adapted to shattering or disruptive purposes, such as blasting and as bursting charges in shells, torpedoes and submarine mines. Substances of the latter sort are termed high explosives.

I have spoken of the safety with which the most dangerous explosives may ordinarily be handled. As an example, a considerable quantity of gun cotton (cellulose, such as pure cotton, treated with nitric acid) may be ignited, and will burn quietly without detonation; but if a suffi

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LIQUID EXPLOSIVES BY THE GALLON.

These bottles contain a liquid which equals in power pure nitro-glycerin, and yet is impossible to explode except by a powerful detonator.

cient mass be ignited the localization of heat and pressure on the surface of the burning body will cause the whole to be detonated, owing to the energy required to displace the products of combustion as rapidly as they are set free. Gun cotton may also be dissolved in acetone and poured on a glass plate and dried, and the product will be a hard substance which will not detonate; but reduce this substance to a powder and it can be exploded. A torpedo filled with wet compressed gun cotton will not explode if a shell should penetrate it and burst in the mass of gun cotton. Even nitro-glycerin

Glonoin Oil. In 1865 a representative of Nobel, the inventor, came to America to try to introduce the material to miners here. He stopped at the Wyoming Hotel, on Greenwich Street, in New York, and running out of funds was obliged to leave his baggage and a large can of the oil at the hotel as security. As made at that time nitro-glycerin was not a very pure nor stable product, and was liable to start decomposing and blow up at any time. A guest at the Wyoming Hotel, using the can of Glonoin Oil one morning as a rest to black his boots, noticed some red fumes escape from it. He called the

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nitric acid and sulphuric acid), yet the nature of the material was then so little understood that frequent explosions occurred at his works, with some fatal results. tendency of pure nitroglycerin to decompose, resulting in violent explosions, brought about its abandonment as a commercial explosive, but when combined with a suitable absorbent, as in the so-called dynamite, this dangerous property is removed.

The fulminating body which is required to

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be attached to a high explosive in order to detonate it is the only ticklish part about a shell or a mine charged with any of the explosive materials now employed. Fulminate of mercury usually is used for this purpose, and is made by dissolving mercury in nitric acid, to which solution, when cool, alcohol is added. Fulminate of mercury is a powerful self-detonating body, because of the weakness. of the chemical bond between the molecules of its constituents, and also because of its high specific gravity, the density of its products of combustion and their confining influences.

It is estimated that fulminate of mer

cury, when exploded in contact with a body, exerts a pressure of more than half a million pounds to the square inch. In other words, the fulminate used as a fuse strikes the high explosive a blow with a force of half a million pounds to the square inch. The explosive wave thus set up is too strong to be resisted by the chemical bonds of the body, and detonation results.

In a shell or a torpedo the fulminate is loaded in a capsule, which is secured rigidly in position a distance to the rear of some dry gun cotton, carried to detonate the shell or torpedo, and from which it is separated by the steel walls of its cham

THE NITRATING HOUSE ON THE UPPER FLOOR.

ber. The projectile can then be exploded only upon receiving a certain amount of retardation (as when it strikes the side of a battleship or fort), causing the plunger body of fulminate to travel forward into the dry gun cotton chamber and explode it. This permits the torpedo or shell to penetrate to a desired depth in water or earthworks before exploding. A torpedo of this description may carry half a ton or more of explosive.

Some notable blasting operations have been

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THE TECHNICAL WORLD MAGAZINE

performed by explosives during recent years, and work accomplished which half a century ago would have been either wholly impossible or prohibitive on account of the immense cost. The largest blast in history was the removal of Hell Gate rock, in the East River, New York, in 1876. This rock had an area of about nine acres. Twenty-four longitudinal and forty-six transverse tunnels, their faces pierced with 12,561 holes three inches in diameter and nine feet deep, were excavated in its interior. In these drill holes were inserted, in all, 240,400 pounds of what was called rack-a-rock powder (coarse-grain ordinary black blasting powder) and 42,331 pounds of dynamite. Water was then admitted to the mine and the blast was fired by electricity. Two hundred and eighty thousand cubic yards of rock were removed by this blast.

In blasting out a rocky obstruction in the Danube River known Gates," a vertical cliff was removed by a as "Iron succession of notable blasts. For one of these a tunnel, three feet by four feet in

size and eighty feet long, was driven incharge of explosives. Twelve tons of to the cliff and widened inside for the 78,000 cubic yards of rock removed. dynamite were detonated at once, and

About five or six years ago in order to secure a supply of rock for the construcgranite mound known as Vesuvius Butte tion of a dam near Teller, Colorado, a was blown up. A horizontal tunnel, with out of the blast, was driven to the center several angles to prevent the blowing of the mound. forming a T, was driven a short distance A transverse tunnel, packed with 32,000 pounds of black poweither way at the center, and this was der. Black powder was used instead of dynamite because it has a less smashing shape. The explosion opened up a crater effect, and preserved the stone in better 72 feet deep and 150 feet in diameter, and broke up 110,000 cubic yards of rock.

In July, 1905, 40,000 pounds of dynamite was exploded in a single charge to break up an obstructing rock known as Henderson's Point, in the Piscatoqua River, opposite Kittery Navy Yard, near

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ISOLATED EXPLOSIVE STORE HOUSE IN THE DEPTHS OF THE WOODS, WHERE SOME SECRET

AND DANGEROUS NITRATING PROCESSES ARE CARRIED ON.

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