HAYES— DETECTION OF SUBMARINES. • 37 



The dimension of the grooves through the compensator are such 

 as to preserve uniformity of cross-section. A third bottom plate is 

 provided and so arranged that by rotating the second plate, which 

 carries the fixed grooves and stethoscope leads, upon this through a 

 small angle either the port or starboard line of receivers can be con- 

 nected through the compensator. 



The three figures in Plate XIII. a give the appearance and con- 

 struction of the Type H Compensator in detail. Plate XIII, b shows 

 the manner of mounting the line of receivers beneath a streamlined 

 protecting blister on the outside of the hull. 



The M-V Tube determines direction by means of variable com- 

 pensation instead of by, rotating the line of receivers and therefore is 

 free from the weaknesses inherent in the M-B Tube and the double 

 M-F Tube. Its focusing effect is superior to either of these devices 

 because of the greater length of its line of receivers. It is more 

 rapid and easy to operate since it only requires the rotation of the 

 compensator plate to center a sound binaurally. And, finally, it can 

 be operated while the boat is moving. The M-V Tube is without 

 doubt the best " on-board " listening device thus far developed. 

 Some idea of its ability to locate a submarine can be gained from 

 Plate XIV. 



The full line curves represent the true course of a submerged 

 submarine. The coordinates of the curves have time for abscissas 

 and angular bearing with respect to the listening boat as ordinates. 

 The round circles represent bearings as determined on an early form 

 of M-V Tube. The speed of the listening boat, a destroyer, is given 

 by the broken line curve at the top of the sheet and the distance in 

 yards of the submarine is marked at various points along the curve. 



The M-V Tube in its later forms makes use of twenty units in- 

 stead of twelve. These installations are capable of giving better 

 results than those recorded in Plate XIV. The possibilities of the 

 M-V Tube will not have been reached until a compensator is devised 

 which will take care of a line of receivers spaced about fifteen inches 

 apart and extending the entire length of the boat upon which it is in- 

 stalled. Experimental results however seem to suggest that the ad- 

 vantage to be gained by extending the line of receivers much beyond 

 forty or fifty feet is scarcely worth striving for. 



