CONTENTS 



The Science Study Series 7 



Preface 9 



1. VOICES OF EXPERIENCE 17 



Echo Experts in the Ocean— Echo Experts in 

 the Air 



2. ECHOES AS MESSENGERS 35 

 The Nature of Sound Waves— Echoes We 

 Seldom Notice— Water Waves and Surface 

 Echoes 



3. AIRBORNE ECHOES OF AUDIBLE 

 SOUNDS 57 



The Acoustics of Clicks and Echoes— The 

 Velocity of Sound Measured by Means of 

 Echoes 



4. THE LANGUAGE OF ECHOES 83 



Orientation Sounds of Bats— Echoes of In- 

 sect Prey— Precision of Echolocation— Bread 

 upon the Waters— Resistance to Jamming 



5. SONAR AND RADAR 107 

 Echoes under Water— Prospecting by Echo- 

 Echoes versus X-rays— Radar— Relative Effi- 

 ciency of Bats and Radar 



13 



