Page:Popular Science Monthly Volume 92.djvu/260

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��Popular Science Monthly

���>. — Line of vision

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��Sarlace of Ocean

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��Position No6- Smoke appears 200 Ft. above water

��Position No 5 Lusitania type surface 5hijp;top of smoke stack 100 Ft. above water

��Position No. 4. Merchant tramp., surface ship; top" of smoke stack 40 Ft above water

��How the Submarine Takes Advantage of Her Low-Lying Hull

��This diagram, shows the comparative visibility of vessels when seen from a military submarine and gives the distances at which the various parts of a large ocean steamer such as the Mauretania, with smoke-stacks extending one hundred feet above the surface of the sea, would be visible to a distant observer fifteen feet above the surface. Assume that the Mauretania is making her maxi- mum speed of about twenty-five knots. By re- ferring to the diagram it is seen that her upper works become visible above the horizon at a dis- tance of eighteen and three-eighth miles from the periscope of the submarine. By using his range

She eluded not only the hundreds of vessels which swarm in the waters sur- rounding Great Britain and which are constantly on the watch for submarines, not only the seaplanes and dirigibles which patrol the British coast, but also the British cruisers on the Atlantic sea- board of the United States. No vessel spoke her on the way. She entered

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��and direction finder, the submarine commander can determine the course of the vessel and figure out just when and where he can intercept her (position No. 5). In the case of a slow tramp, the smoke from the stack will first betray her approach. Her smokestacks are probably not over forty feet above the water level; therefore, if she were making the same course as the high-speed ship, it would be observed by referring to position No. 4 and the data there given, that the submarine at a speed of ten knots has more time to get nearer the course of the approaching ship and can have more time to calculate the enemy's speed of approach and

Baltimore and New London with dra- matic unexpectedness, unloaded her coal- tar dyes, shipped a new cargo of nickel and other German necessities, and calmly sailed for home.

In my judgment the only way in which we can thwart the submarine, the only way in which we can continue to send much-needed fuel, food and supplies to our Allies is the construction of large merchant submarines like the Deutsche

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��Vioqram poiifion Kos Luiitania type. Speed J5 knoti

Why a Cargo- Carrying Submarine Can Cross the Atlantic Ocean

��Diagram position No ♦ merchant tramp. Speed 10 knots

��Diaqrann position No i cargo submarine. Speed II Knots

��A cargo-carrying subm irinc. traveling with a freeboard of five feet wouM become visilile to a submarine lying in ambusli when she approached within eight miles. This iiureases tlic area from one hundred and three sfinaro miles as shown in position No. 1, to two huiulrcd and one square miles as shown in position N'o. 2. In comparison with the usual tyjre of surfaci- cirKo-iarrvinK ship —

��a tramp, for instance. — the submariiio freighter is siife; for she has the ability to submerge in less tiian two tuiinite.>!. Moreover, it is hardly likely that sill- will be attacked without warning for fear she might be a friendly military submarine. When far from land, she could navigate entirely on the surface with a freeboard of fifteen feet, in which condition she can make a speed of eleven knots as

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