CHAPTER 5 

 Sonar and Radar 



Although men have not learned the "language of 

 echoes," they have been remarkably successful in de- 

 signing echolocating instruments which surpass those 

 of animals in many ways but remain quite inferior in 

 other respects. What are these instruments and how do 

 they compare with analogous living mechanisms in the 

 bodies of bats, porpoises, or whirligig beetles? Footsteps 

 and clickers are simple devices that help blind people 

 create more useful echoes, but the receiving instrument 

 is still the human ear. Perhaps blind men will some day 

 learn to exploit the potentialities of the matchless human 

 brain for a better comprehension of the language of 

 echoes. But, in the meantime, it is important to appre- 

 ciate the devices which men have contrived to carry out 

 both the sending and the receiving functions of echoloca- 

 tion. These mechanisms have been developed for very 

 practical, often military, purposes, excelling particularly 

 in the great distances over which they operate. If they 

 utilize sound waves, they are usually called sonar sys- 

 tems. If electromagnetic waves are employed, they are 

 called radar systems. Sonar is used by man almost ex- 



107 



