4. CONTINUOUS REFLECTION PROFILING 



J. B. Hersey 



1. Introduction 



A continuous seismic -reflection apparatus consists of a sound source and a 

 nearby hydrophone receiver which are towed through the water while operating 

 exactly as the conventional echo -sounding instrument does ; the source sends 

 out sound pulses at regular intervals ; the receiver receives subsequent echoes 

 reflected from the bottom of the ocean and from reflectors below the bottom. 



Ship 

 underway 



Hydrophone moved away or 

 towards spark source 



Fig. 1. (a) Continuous profiling for normal incidence reflections, (b) Procedure for oblique 

 reflection profiles. 



The echoes are then converted to electrical signals and fed ultimately to a 

 graphic recorder like those commonly used in echo-sounding. (The basic 

 operation is illustrated in Fig. 1.) Both single-frequency and broad-spectrum 

 sound sources have been used. Either are short pulses of sound radiated on a 

 precise schedule that is controlled by the graphic recorder. Since different 



[MS received July, 1960] 47 



