46 HAYES— DETECTION OF SUBMARINES. 



these devices in peace times as well as in war times is but imperfectly 

 realized, but it is a safe prediction that the future will find them a 

 distinct safeguard to navigation. 



The Value of the Submarine Sound Detector as an Instrument of 

 Warfare is not to be measured by the number of " U-boats " that by 

 its aid have been located and damaged or sunk but rather by the re- 

 sulting curtailment of their radius of operation and the effect on the 

 morale of their officers and crews. The U-boat in operation was 

 never safe after the perfection of the submarine detector. When 

 traveling at sufficient speed to cover any distance it could be heard 

 and accurately located at a range of several miles. The same was 

 true whenever it lay on the surface charging its batteries. It. could, 

 in some localities, lie at rest on the bottom or if the depth prevented 

 this it could run very slowly, about one and a fourth knots, at a 

 depth of from lOO to 200 feet and thus be reasonably free from de- 

 tection but under such conditions it was comparatively harmless. 



Submarine sound detectors promise to become a distinct aid to 

 navigation during conditions of low visibility. Its aid is two-fold : 

 first, approaching vessels can usually be heard and located in time 

 to avoid collision and second, harbor entrances can be safely made 

 by taking bearings on properly placed submarine signals. 



The U. S. S. destroyer Parker while maneuvering in the North 

 Sea in a dense fog reported that she avoided two collisions in one 

 day by locating an approaching boat with her listening gear. 



Some idea of the aid which can be given in entering a harbor is 

 shown by the results of recent experiments. By means of an elec- 

 trical MV-Tube on one of our transports, the writer recently located 

 the Nantucket Light-ship within two degrees at a distance of 2)7 

 nautical miles by picking up its submarine bell signal, and this was 

 accomplished while the transport was steaming at 15 knots. Had 

 the transport slowed down to Ys speed the bell could without doubt 

 have been heard at a range of over 50 miles. While entering New 

 York Harbor from one to three bell signals could be heard and ac- 

 curately located at any time and as a result the vessel could have 

 safely entered harbor in a dense fog. 



It would seem that navigation during conditions of low visibility 

 can be made perfectly safe if each boat is equipped with a good sub- 



