HAYES— U. S. NAVY MV TYPE OF HYDROPHONE. 391 



manner the South-West Ledge at the entrance of New London 

 harbor. 



Since ice forms an excellent reflecting medium for submarine 

 sounds, as does also the hollow hull of a vessel, it seems certain that 

 high-pitched oscillator signals should reflect from such surfaces with 

 sufficient intensity to be heard on the hydrophone. In practice the 

 listener would focus the hydrophone dead ahead and send intermit- 

 tent sound signals with the oscillator. If at any time the signal ap- 

 pears binaurally centered, the sound is then being reflected from a 

 surface dead ahead and collision with the same may readily be 

 avoided. 



Several years ago attempts were made to locate icebergs by the 

 echo method but failed for want of a device that could give the 

 direction of the reflected sounds. The MV hydrophone supplies 

 this want and with its aid it is believed that the experiments when 

 repeated will prove successful and introduce a means of preventing 

 such appalling disasters as befell the ill-fated Titanic. 



Character of the Sea-Bottom — Hydrographic Surveys. 



The hand lead and the sounding machine not only give the depth 

 of water but also the character of the sea-bottom. The latter infor- 

 mation oftentimes is as valuable as the former in locating the posi- 

 tion of a vessel. The question, therefore, naturally arises, " Can the 

 hydrophone give any information concerning the character of the 

 sea-bottom ? " 



The answer to this question is " Yes." The character of the 

 reflected propeller sounds varies with change in the character of 

 the sea-bottom both as to intensity and to quality. These variations 

 are so marked that a trained listener needs only to travel back and 

 forth over the same course but a few times before he is able to rec- 

 ognize various regions en route by the character of the propeller 

 sounds. 



While experimenting in Long Island Sound the writer has often 

 noticed a decided change in the intensity of the propeller sounds 

 when the listening vessel was off Saybrook. This change is doubt- 

 less due to the fact that the sea-bottom in this region is covered 



