SOUND-RANGING 



77 



dividual sound-ranging locations with the results of a careful 

 survey of the positions; it was found that the estimates of 

 accuracy had been rather too conservative, for in none of the 

 cases examined was the accuracy less than had been claimed 



Centra/ 



Figure 4 



when the report was made and in the majority of the cases 

 it was considerably greater. 



A sound-ranging section consisted of six listening instru- 

 ments at carefully surveyed positions on the ground; each of 

 these instruments was electrically connected with a recording 



