HAYES— U. S. NAVY MV TYPE OF HYDROPHONE. 395 



ily detected by hydrophone soundings as a ship crosses it steaming 

 at full speed. Computations had predicted that the Von Steuben 

 would cross this lOO fathom curve in the vicinity of longitude 70:00 

 about 2 o'clock on a certain afternoon. It so happened that the 

 Von Steuben was actually proceeding on a course indicated by (16) 

 about 10 miles to the northward of the supposed position, so that 

 she would accordingly arrive at this depth some little time prior to 

 expectations. 



The hydrophone operator, who was listening upon the apparatus 

 during the morning, first heard faint sounds from his own ship's 

 propeller, in a depth of about 450 fathoms, at 9 : 25 A.M. A rapid 

 shoaling was subsequently observed and the 100 fathom curve de- 

 tected at 9:45, position (17). At 10:15 the hydrophone gave the 

 depth as 55 fathoms, which observation was checked by the hand- 

 lead. At the same time, position (18), the submarine bell on the 

 Nantucket lightship, distant 37 nautical miles, was heard and a rela- 

 tive bearing of 66 degrees obtained. Subsequent computations 

 gave the value of 67.5 degrees, a close check. This hydrophone 

 bearing together with the sounding data gave a satisfactory "fix" 

 by virtue of which the course of the vessel was changed at (19) and 

 a more satisfactory approach to Ambrose Channel made as shown 

 (20) and (22). 



It is worth noting that the original course of the Von Steuben 

 projected (21) would have carried that vessel towards the Fire 

 Island Shoals, where many unfortunate vessels have gone aground. 



The Submarine Installation. 



A submarine was equipped with electrical MV hydrophone lines 

 and the writer participated in a test cruise on this vessel from New 

 London, Connecticut, to Portland, Maine, and return, for the pur- 

 pose of ascertaining the characteristics of this, the first MV installa- 

 tion of its kind to be made on a submarine. The course of the 

 cruise is drawn upon the chart given in Fig. 10. The entire trip 

 was made by surface running on the Diesel engines, the most unfa- 

 vorable condition for long range listening. Prior to departure a 

 sounding scale had been computed for the compensator in terms of 



