660 russell. SEDIMENTATION IN NAVAL WARFARE [Ch. 35 



siderably reduce the range of listening gear. World War II patrol 

 reports indicate that our submarines made considerable use of in- 

 formation about the character of the bottom in evading Japanese anti- 

 submarine vessels. 



METHODS AND RESULTS 



The methods of attack on most of the problems listed above are 

 fairly obvious. They are: first, a determination of the factors in- 

 volved and their relative importance by means of laboratory and field 

 experiments; second, accumulation of data on the distribution of the 

 important factors by means of surveys or by compilation of existing 

 data; and, third, presentation of the information in suitable form for 

 operational use by means of charts and manuals. Under wartime pres- 

 sure, much of the first stage sometimes had to be omitted and educated 

 guesses made on the pertinent factors and their relative importance. 

 Thus, stages two and three were often entered without adequate back- 

 ground, and it has been necessary to go back to research and experi- 

 ment to obtain additional information. Such data as have been ac- 

 cumulated during the past few years, however, have shown that most 

 of the guesses were surprisingly good in view of the scanty data on 

 which they were based. 



Experimental Studies 



Operational tests of sonar gear in shallow water, early in World War 

 II, demonstrated the important effect of the bottom on the transmis- 

 sion and scattering of underwater sound. Geologic inference regard- 

 ing the probable effects of various types of bottom was sufficiently con- 

 firmed by preliminary tests to justify the compilation and presentation 

 of information for operational use. Subsequently, detailed field experi- 

 ments were undertaken at the University of California Division of War 

 Research (UCDWR) , the Woods Hole Oceanographic Institution, and 

 the Navy Underwater Sound Laboratory at New London. At San 

 Diego particularly, where a variety of bottom types is available within 

 easy operating range, detailed surveys were made and charts prepared 

 of the distribution of bottom types, and sound transmission and re- 

 verberation measurements were made over these areas. The results 

 (Eckart, n.d. ; Bergmann, n.d.; Spitzer, n.d.) have led to the determina- 

 tion of reflection and scattering coefficients for certain types of bottom, 

 but much yet remains to be learned, and the work is continuing at the 

 Navy Electronics Laboratory and the Marine Physical Laboratory 

 (University of California). Preliminary attempts were also made to 



