Page:Popular Science Monthly Volume 88.djvu/192

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��Popular Science Monthly

��balloons must be many" times larger than the heaviest floating mines. At short range they would furnish ideal targets to a Zeppelin's machine- guns. A Zeppelin may easily shade its lights and yet clearly illumin- ate a near object in the air. Let a good marksman with a machine- gun be stationed at each side of the front car, and before any balloon-mine could do any harm, it would be shot' down and fall into a city street.

The Plan Is Feasible in Water

Interconnecting cables such as Mr. Steinmetz proposes, are more satis- factory in water than in the air, where they are liable to slip off upward or downward. If caught by airships below them, the bombs will be drawn together harmlessly be- neath the level of the hull. The chances are that the Zeppelin would gather a trailing mass of wires, empty balloons and live bombs in its wake, to be cut off for the benefit of those be- low. The steel propel- lers would cut the thin wire, and since they are as big and heavy, would hardly be damaged. It would also be easy to shape a Zeppelin so that single wire must slip off wherever it strikes the hull, simply by slanting the outlines of all pro- jections.

It does not look as though the Stein- metz plan would make Zeppelin destruc- tion assured. The three dimensions of the air necessitate the use of mines in large numbers, yet the risk is propor- tionately increased. Here comes the ques- tion of the practical value of the plan.

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����Hooks and flaming bombs as a terror of the air for Zeppe- lins and, indeed, for any den- izens of the air. But is the terror not as great for the houses below?

��Sweeping a Channel for Mines

THE operation of mine sweeping is one of the most dangerous and arduous of the many tasks that fall to the lot of a navy. The dan- gers of mine sweeping are great even in the North Sea and around the Brit- ish Coasts, where there is no active opposition. These dangers are, of course, greatly increased when the ships are con- tinually under fire, as they were in the Dardan- elles.

A mine field consists of a number of mines laid together. It will most effectively block off any particular area of water. A certain number of mines are generally laid at intervals just deep enough to render them invisible to the look-out on board the mine sweep- ers. For such work shal- low draught ships are al- ways employed.

Mine sweepers work generally in pairs. Each ship tows over the stern a wooden apparatus called a kite, fitted with planes which dive beneath the water. The depth to which it dives is regu- lated by the speed of the towing ship. Each of these kites is fitted with a pulley block. A wire rope is passed from the stern of one ship through the pulley on its own kite across the water through the block on the second kite and so up to the stern of the second ship, where it is fastened. Both ships steam ahead at the same speed, the kites dive to the depth corresponding to the particular speed, and the steel rope is stretched out between them. When the rope strikes a mine, it fires it.

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