SECT. 1] CONTINtJOtJS BEFLECTION PROFILING 71 



7. Concluding Remarks 



1. Several reflection surveys by continuous profiling methods have shown 

 good agreement with evidence in cores and outcrops. 



2. Sediment penetrations of several thousand feet have been achieved with 

 the more advanced instruments, while even the earliest instruments recorded 

 fine detail. 



3. The principal obstacles to widespread use of the method appear to be : 

 (a) masking by multiple reflections between shallow layers and between the sea 

 surface and bottom, and (b) the probable rapid attenuation or scattering of 

 down-going energy through certain strata such as beds of gravel or shell. 



4. The method appears to offer a great improvement on well known reflection 

 and refraction methods of measuring compressional wave velocities. 



5. Acoustic impedance measurements can probably be made with con- 

 siderable assurance because travel paths of arrivals can be identified and their 

 energy measured. 



6. Absorption in sediments can be measured in some places. 



7. Obvious extensions of the method can be made to study seismic properties 

 and the structure of sediments in deep water with source and receiver at 

 the bottom. 



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