HAYES— U. S. NAVY MV TYPE OF HYDROPHONE. 387 



In practice the compensator is provided with a separate scale 

 which is caHbrated to give soundings in fathoms. To determine the 

 depth of water the Hstener adjusts the compensator until the pro- 

 peller sounds or submarine signal sounds ofif his own vessel are bi- 

 naurally centered and then reads off the value directly from the 



20 



^0 



60 



80 



/OO 



/ZO 



Fig. 9. 



sounding scale. This operation takes but a few seconds, so that a 

 continuous sounding record can be taken when desired and, as is 

 shown, the record becomes more accurate as the water becomes 

 shallower. 



Sounding in Deep Water. 



The angle of reflection method only gives reliable soundings for 

 depths less than three times the length of the vessel, but if the vessel 

 is equipped with both an MV hydrophone and a proper submarine 

 signal, an intermittent sounding record can be taken in water of any 

 depth. Such soundings are determined by measuring the time re- 

 quired for a sound signal to travel to the bottom and reflect back 

 again to the surface or, in other words, by measuring the time which 

 elapses between the sounding of a signal and the response of its echo 

 on the hydrophone. 



