36 



HAYES— DETECTION OF SUBMARINES. 



K-W-N through compensator groove in upper plate ; N-R through 

 stethoscope lead to right ear. The sound from F traverses a similar 

 course, viz. : F-H-Z-M-0-K-Y-N-L ending at the left ear. It is 

 readily seen that the compensation effected between E and R and 

 between F and L when the upper plate of the compensator is rotated 



Plate XIII. b. The acoustical M-V installation and protective blister. 



is double that effected between E and {B or A) since in the former 

 case two grooves are connected in series. Thus all the requirements 

 for complete compensation of twelve equally spaced receivers 

 mounted in a line are met. 



