496 VIGOTTREUX AND HERSEY [CHAP. 12 



cross-bearings for location. Other work now in progress promises to provide 

 precise ranging procedures that will work over several miles in open ocean (e.g., 

 see Ewing, Worzel and Talwani, 1959). 



H. Other Applications of Sound to Oceanography 



The deep scattering layers of the open ocean are well known as an acoustical 

 manifestation of biological activity in the ocean. This relationship is fully dis- 

 cussed in Chapter 13 and will not be dwelt on here. However, this is representa- 

 tive of several underwater acoustical phenomena which can tell us much about 

 the ocean because of the effect of the ocean on the sound. 



Acoustical telemetering is an obvious application of sound as a technical aid 

 to oceanographers. Dow (1954) employed acoustical telemetering to monitor a 

 pressure-type depth gauge on a plankton net ; he has also successfully used a 

 high-frequency acoustical telemetering link between a remote low-frequency 

 hydrophone and the observing ship (manuscript in preparation). Luskin and 

 others have extended Dow's telemetering hydrophone to a very cleverly 

 conceived bottomed geophone for seismic research. Other similar applications 

 are being developed, and more can easily be imagined. 



We seem gradually to be using sound more and more for such technical 

 duties as measuring distances, monitoring remote procedures, and even tele- 

 metering other data by acoustical means. This much is encouraging, but one 

 cannot but be struck by the contrast between the apparent potential of sound 

 as a scientific tool and the paucity of scientific achievement with it beyond 

 sound and seismology. We can only hope that as oceanographers grow familiar 

 with its use as a technical aid they will come to appreciate its usefulness for 

 other purposes. The chapter on "Sound Production by Marine Animals" 

 (Chapter 14) is to be cited as evidence of progress in this direction. An important 

 unexploited area is that of synoptic observations of water structure. The speed 

 of both ships and airplanes is hopelessly slow for truly synoptic observations ; 

 the speed of sound can provide nearly synoptic quality. Further its propagation 

 is known to be affected by water structures ; several relationships are already 

 well known that could be used for synoptic studies (e.g. the "leakage path" 

 of Hersey et al., 1952). We can hope that these possibilities will be exploited 

 as we all become more familiar with oceanographical acoustics. 



References 



Del Grosso, V. A., 1952. The velocity of sound in sea water at zero depth. U.S. Naval Res. 

 Lab. Rep., 4002. 



Dietz, R. S. and M. J. Sheehy, 1954. Transpacific detection of Myojin volcanic explosions 

 by vmderwater sound. Bull. Oeol. Soc. Amer., 65, 941. 



Dow, W., 1954. Underwater telemetering, a telemetering depth meter. Deep-Sea Res., 2, 

 145. 



Edgerton, H. E. and J. Y. Cousteau, 1959. Underwater camera positioning by sonar. 

 Rev. Sci. Instrum., 30, 1125. 



Ewing, W. M., W. S. Jardetzky and F. Press, 1957. Elastic waves in layered media. McGraw- 

 Hill, New York, 374 pp. 



