MARINE SCIENCE 43 



in attack as it is in defense, and moreover that is frequently a factor 

 in both tactics and strategy. 



This chapter is now in its final draft and for reasons which I will 

 try to expliiin, it has been a difficult one to edit because we hope to 

 issue this as an unclassified document. 



What has been happening during the last 22 years can be summa- 

 rized as follows : 



As weapon systems have become more and more complex, nature im- 

 poses increasing limitations on their effectiveness. In the modem 

 complex systems one simply cannot ignore the limitations imposed by 

 the environment. Wars are not always fought in fine weather and 

 there exists the equivalent of very bad weather within the sea that is 

 more critical to the performance of most weapon systems employed 

 in undersea warfare than the real weather is to land warfare or aerial 

 warfare. 



Because of security it will not be easy to illustrate this statement by 

 citing specific examples involving advanced design weapon systems. 

 I will have to fall back on early World War II devices, but there 

 exist several excellent classified reports by various other committees 

 and panels that discuss the limitations imposed by nature on weap- 

 on systems of the future as we now envision them. 



In fact, it has become the fate of oceanographers to try to think 

 ahead 15 years or more, so as to be able to explain the effects of en- 

 vironmental factors on systems that have not yet been designed. 

 Thus, to a considerable extent, we have to keep well ahead of reality 

 and at the same time we can only talk about what actually happened 

 15 or more years ago. As you well know, we are living in an age 

 when science and teclinology is making extremely rapid progress. 

 This has largely come through research carried out at university 

 laboratories working in the classifiable fields of science. Oceanog- 

 raphy has had a much shorter and somewhat different history. The 

 engineering phase of oceanography has hardly begmi, but the marine 

 sciences are clearly going to contribute greatly to advanced engineer- 

 ing that strives for greatly improved offensive and defensive capa- 

 bilities. 



I will try next to be somewhat more specific in the case of under- 

 water acoustics, and I think that I can do this best by discussing some 

 of the past history of this subject and by explaining some of the con- 

 tributions made by oceanographers. 



The Chairman. Doctor, would you say, generally speaking, look- 

 ing toward the future in undersea warfare, that the problem of 

 acoustics in one of the primary priorities in a general sense ? 



Mr. IsELiN. Yes. In 1937 I was asked to help out in some tests 

 off Guantanamo, Cuba, of some experimental searchlight-type sonar 

 gear. It had been noticed that frequently during the afternoon the 

 range of detection of a submerged submarine was seriously reduced. 

 It was rather quickly shown in the 1937 operation that warming of 

 the near-surface waters on days when the winds were less strong 

 than usual caused sharp downward refraction of the cone of sound 

 produced by the transducer. In effect, there exists at times thermal 

 hills within the ocean behind which a submarine can hide. 



There is a geography to this near-surface thermal situation and 

 there are also pronounced seasonal and shorter period changes. 



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