Page:Popular Science Monthly Volume 92.djvu/530

 Hiding Ships with Paint

How protective coloring causes Fritz much waste of torpedoes. It is camouflage at its best

��Bv Robert G. Skerrett

��THE gun afloat, whether upon a naval craft or an armed merchantman, drives the submarine to cover be- neath the waves when it approaches its prey close enough to discharge the tor- pedo. The U-boat commander must, therefore, keep track of his moving target. At best, a periscope is a poor substitute for the naked eye or the binocular vision made possible by good field glasses. The periscope is one-eyed, and this entails very definite and unsatisfactory limitations. These facts must be kept in mind in order to evaluate the real purpose of ma- rine camouflage.

Marine camouflage differs radically from camouflage ashore where the charac- ter of the background facilitates conceal- ment. It is a simple thing to cloak a gun with a screen of foliage or to mottle it with paint so that its contours disappear. The ship afloat, except through the agency of a smoke screen, cannot veil its identity. Under certain conditions of light, the vessel stands vividly silhou- etted against the sky, and even when the atmospheric contrast is not so sharp, the ship can be seen rather distinctly though painted a single tone of gray.

Atmospheric gray and paint-brush gray are two fundamentally different things so far as vision or visibility is concerned. The latter is the product principally of black and white pigments, while the at- mospheric gray is a vibratory effect re- sulting from the movement of red, green, and violet rays of light. The quality of this gray alters from hour to hour as one or the other of these chromatic rays pre- dominates, and, manifestly, no single pigmentary gray could accommodate itself to these changes. Finally, the character of a ship is indicated by her body form and her upper works — details that are emphasized by high lights and strongly contrasting shadows.

The submarine in the barred zones seeks to close in upon its quarry during

��the dusk of early morning, or the close of day or after nightfall, especially if the moon helps to make the enemy craft discernible. The camoufleur therefore tries to reduce the visibility of vessels during the periods of dim or half light, and, curiously enough, the more scien- tific of these men employ really vivid coloring for the purpose. They paint their ships with apparently meaningless splotches of strong pink, blue, and green. The patches become prominent agreeably to the predominating light ray at the time, and serve to obliterate those famil- iar details or forms for which the observer looks. Not only that, but normally shaded areas are purposely painted light, and the visual effect is flat and confusing. There is dazzle and loss of definition in fairly strong light, and, during periods of twilight, atmospheric vibration induces a gray tone that is so nearly akin to the sea background that craft painted in this marked fashion actually become invisible at a mile!

Upon the field of a periscope there are a number of horizontal lines as well as vertical ones. The horizontal lines are spaced to represent a prescribed height at distances say of 1,000, 2,000, or 3.000 yards, while the vertical lines are spaced to indicate definite intervals at those different distances so as to determine the speed of a vessel passing across them. The U-boat commander, in order to launch his torpedo with a fair chance of hitting his target, must know how far off the enemy ship is, whether her course is bringing her closer or taking her away, and approximately how fast she is moving. With these factors fairly gaged, the tor- pedo is pointed far enough ahead of the target to allow for its time of flight and the advance of the enemy craft.

The commander of the submarine must also be able to measure the height of his quarry from her true waterline to the top of her smokestack, which is a reasonably

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