Page:Popular Science Monthly Volume 90.djvu/736

 Hiding a Ship in Smoke

England equips her liners with an apparatus to produce a smoke screen which hides them from submarines

��OCEAN liners flying the flag of England are now being fitted with the smoke ! screen apparatus invented by the

'British Admiralty as a protection against submarine attack. Several ships equipped with the apparatus have already docked in American ports.

On each side of the afterbridge, where there is always an officer on watch, two funnel-shaped ventilators are placed, from which dense clouds of chemical smoke belch. The ventilators are rotated by a ratchet mechanism which is controlled by electric wires from the bridge of the ship. The smoke, which is thick and heavy, is forced out of the ventilators by a blower in a long ribbon, from two to five miles in length and a hundred feet high. ' It is well-nigh impossible to drive or force smoke or dense vapor against the wind by mechanical means. Consequently, the smoke screen is at the mercy of the wind. The seven diagrams ac- companying this article vividly illustrate this. In No. i and No. 3 the smoke ribbon is shown trailing straight away from the ship, leaving both sides and the bow of the vessel ex- posed. In No. 4 the apparatus gives but scant pro-. . tectlon, while No. 5 shows nearly one half of one side obscured. In No. 7, which

��shows the wind and ship traveling in the same direction, the screen is very effective, enveloping the ship from bow to stern in a thick pall of smoke. The method of smoke- screening a line of battleships by torpedo boat destroyers is shown in No. 6. Both the battleships and the destroyers, travel- ing at approximately thirty knots, maneu- ver for a favorable wind direction before the destroyers belch their smoke. With the smoke screen or shield to cover them the fleet conceal&its movements. Ordinarily the number of destroyers varies with the number of battleships, but not necessarily so.

Although the captain on the bridge is able to rotate the ventilators, he can not throw a screen of smoke around his vessel if the wind is against him. This is brought out very clearly by diagram No. 2, which shows how a submarine could choose its own position and wait for its victim.

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SMOKE SCREEN FOR BATTLESHIPS

���Two ventilators rotated by a ratchet device are placed one on each side of the afterbridge. The smoke is either generated in the ship's fire box by burning oil or naphtha, or in a smudge pot

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