432 : The Atlantic 



of an aircraft landing system which also required the use of high-fre- 

 quency emissions. Again they observed that their emissions were dis- 

 turbed by an airplane flying within the field. 



It was already known that the Kennelly-Heaviside layer of the 

 atmosphere had the effect of bouncing back or returning certain 

 types of radio signals, high-frequency emission being especially sus- 

 ceptible. It was not necessary to transmit signals from one ship or 

 station to another. Signals could be sent out from one ship in all 

 directions and, when picked up on their return, could be made to 

 show on a luminous screen a pattern of the objects by which they 

 had been deflected in their flight. 



Experimental radar was installed on the USS Leary in April 1937 

 and a finished set was installed on the USS New YorJ^ in December 

 1938. Radar had the advantage of operating day and night through 

 any kind of weather and eventually of bringing in signals and pat- 

 terns over long distances. It gave rise to many various devices for 

 detecting enemy ships and planes of all types and even for training 

 and firing guns at an unseen enemy. 



Surface vessels and aircraft co-operated in the detection and de- 

 struction of enemy submarines, and the battle finally swung in favor 

 of the submarine defenses. However, before this happened the toll 

 of shipping had been tremendous. In 1939 the world tonnage for 

 merchant ships was 68,500,000. Of this amount a half was destroyed 

 in the course of the next five years. Though aircraft and other means 

 gave able assistance in this destruction, the major part of it was at- 

 tributable to the submarines. Finally the defense became an offense. 

 The enemies of the submarines were now not only the destroyers 

 but the destroyer escorts, the frigates and the corvettes. Seaplanes 

 were less in use but they had been replaced by long-range aircraft. 

 Aircraft were no longer confined to flights from land stations but 

 were based on mobile carriers. 



In 1944 this warfare on the submarine had reached such a state of 

 development that two German submarines were sunk for every mer- 

 chantman that they were able to torpedo. This was a ratio that not 

 even the Germans could stand. It is estimated that Germany lost a 

 total of 713 submarines, 100 of which were attributed to mines laid 

 by the British Bomber Command and to other types of destruction 

 where the record was imperfectly known. Of the remaining 613 there 

 was a rough balance between those sunk by ships and those sunk by 

 aircraft. It is interesting to note that in twenty-six cases one sub- 

 marine sank another submarine. 



