HAYES— DETECTION OF SUBMARINES. 



35 



The two sets of grooves are so made that their average radius 

 has the ratio 2 : 3 in order that the compensation effected in the sec- 

 ond stage may be one and a half that effected in the first stage which 

 has been shown to be necessary. It remains to be shown that the 



Plate Xlll. a. The Type-H conipensalur, showing structure of grooved 

 plates for compensating twelve acoustical units. 



sound from the two points E and F suffers during the third or bi- 

 naural stage three times the compensation effected in the first stage 

 whenever the top plate is turned. 



The course of the sound from E to the Hstener's ear is: E to H 

 through fixed path in lower plate; H-X-M through compensating 

 groove in upper plate ; M-O-K through fixed groove in lower plate ; 



