Popular Science Monthly 



245 



25 Miles 



18 i Miles 



14 Miles 



IO4 Miles 



0~ ^ 



Position Wo 3 

 Carqo.^subina;:^ 

 rine bridge 

 15 Ft. above 

 water 



8 Miles 



5| Miles 



Horiion 65 Miles 



Position No 2 

 Cargo subma- 

 rine bridge 

 5 Ft. above 

 water 



^- 



Position No I 

 _ Carqo subz.- 

 marine per- 

 iscope 15 Ft. 

 above water 



Military submarine 



lying in wait for approach- 

 ing vessels; periscope 15 Ft. 

 above water Submerged 

 speed -10 knots 



and Keeps the Big Ship in View While She Is Herself Unseen 



direct course than if slie were intercepting a fast 

 Mauretania. Assume that this approaching slow- 

 speed craft had no solid opaque portion extending 

 over fifteen feet above the surface of the water, as 

 in the case of the cargo submarine shown in posi- 

 tion 3. She would pass the waiting submarine 

 below the horizon, and the intervening round of the 

 sea surface would prevent the submarine from 

 seeing her. She would pass by unseen and in 

 safety. In the various positions here shown, the 

 submarine is assumed to have a submerged speed 

 of ten knots. It is evident that practically one 

 hundred per cent safety would be secured, could 



land. I can see no sense in building 

 million dollar ships, loading them with 

 several million dollars worth of cargo and 

 sending them out to be sacrificed, when 

 absolute immunity from attack can be 

 secured at an additional first cost of not 

 over two hundred and fifty thousand 

 dollars per ship, or about eight per cent of 

 the value of the ship and cargo (less than 

 the present immense insurance rate on one 

 voyage to England). For a supposedly 

 inventive and progressive people, we are 





Area of der-.qsi 



'ai 1"'' *^6a of possible > 



/ interception 



Diagram position No a 

 cargo submarine. 

 5peed lo Knots 



Without Danger of Being Torpedoed 



in position No. 3. This increases the danger area 

 to about three hundred and thirty square miles, 

 about three times the danger area shown in position 

 No. 1. But as the area to be covered by the military 

 submarine on the high seas far from land is also 

 much greater, the real danger would be propior- 

 tionately less than the lower visibility in a more 

 thickly infested zone might lead one to suppose. 



cargo-carrying submarines cross the ocean and 

 remain invisible during the entire journey. This is, 

 of course, impossible, because there is no means of 

 supplying sufficient power for long under-water 

 voyages without drawing on the upper air. But 

 the diagram shows that a cargo-carrying sub- 

 marine running awash, with her periscope and 

 air-intakes alone above the water line, may ap- 

 proach within about five and three-quarter miles of 

 any waiting military submarine without danger 

 of being seen; for her betraying wake would 

 be far, far below the horizon of the most 

 watchful, ruthless enemy submarine afloat. 



curiously prejudiced. Here are the Ger- 

 mans with their reputation for stolidity 

 and slow-thinking successfully attacking 

 very much the same problem with a 

 boldness and an imagination which they 

 themselves attribute to Americans. And 

 we — we seem to be paralyzed by a con- 

 servatism inherited from our English 

 ancestors. 



The truth is -that the submarine is a 



mystery to our shipping men. It takes a 



combination of liberal-mindedness and 



special knowledge to set a fleet 



of merchant submarines afloat. 



Despite the example of the 



Deutschland, despite the enor- 



\ mous profits which that ves- 



:,~l~ sel admittedly made for her 



'" / owners, we still go on building 



/ surface ships, many of which 



must inevitably succumb to 



German submarines. 



When our shipping men and 

 our naval authorities realize 

 the importance of invisibility and learn 

 that the submarine is the least visible of 

 all vessels, perhaps the rational solution 

 of the problem here advocated will be 

 attempted. The only effort at present 

 used to secure invisibility is to be 



