54 ' ' MARION ' ' EXPEDITION TO DAVIS STRAIT AND BAFFIN BAY 



By the above two methods the Marlon recorded some 1,700 echo 

 souiidino-s in the Baffin Bay-Davis Strait region betAveen July 19 and 

 September 11, 1928. These soundings were all made along the track 

 indicated on Figure 39. Such a small number of soundings, of course, 



HOW A FATHOMETER MEASURES THE DEPTH 



Figure 40.— This illustrates diagrammatically the sound waves go- 

 in^- out from an oscillator installed in the hull plating of a Imer. 

 They can be seen proceeding to the bottom whence they are re- 

 flected back toward the sea surface. The hydrophone,, near the 



keel picks up the echoes and transmits them electrically to the 

 bridge, where they are amplified. (Courtesy of Submarine Signal 

 Co.). 



can not give a perfect picture of the bathymetry of a large region 

 like that concerned, even if very well distributed along caretully 

 planned lines. In view of the few soundings previously recorded in 

 the deep water of the area, however, they suffice as taken to give 

 much more detailed and positive information about the shelves, 

 slopes, and basins of the region than was hitherto available. 



