A number of different sound source transducer methods have been 

 used: magnetostriction (Sonoprobe, Subsurex), ammonium dihydrogen 

 phosphate (ADP) crystals ("Smith- Cummings- Meichner Apparatus"), 

 electric spark (Subbottom Depth Recorder (SDR), Seismic Profiler), 

 gas explosion (Subbottom Depth Recorder with repeatable acoustic 

 sound source (RASS), Marine Seismic System), eddy current repulsion 

 of a nonmagnetic disk (Sonar Thumper), and barium titanate (Strata- 

 graph). The amplifiers and band- pass filters in all the systems are 

 more or less conventional. Two types of recorders used with some of 

 these systems are the Precision Depth Recorder (PDR) and the 

 Precision Graphic Recorder (PGR). (These recorders are described 

 in Section XI.) 



At present, development of a transmitting transducer is devoted 

 largely to obtaining a high-power, broad-band energy source having 

 a high repetition rate. A short pulse length is required for thin-bed 

 resolution: A one millisecond pulse will resolve strata about 2.5 feet 

 thick. A very short pulse is possible with the Thumper, which is 

 being modified to develop more power. The gas explosion sound source 

 appears to promise maximum power, especially when the energy is 

 directed downward by a wave guide such as used in the Marine Seismic 

 System, 



Progress in the development of continuous-profile equipment sys- 

 tems has been so rapid in recent years that it has been difficult to 

 obtain enough facts to make valid comparisons between the different 

 available systems. Information on known devices is listed in Appendix 

 D, including specific references on each system. All of the instrument 

 systems, except one were checked by one or more persons who either 

 participated in developing the device or performed surveys with it. 

 The one exception is the Marine Seismic System; information for 

 this system was supplied by the manufacturer. A comparative tabula- 

 tion that summarizes the various equipment also is given in Appendix 

 D (Table D-l). 



D. CONCLUSIONS AND RECOMMENDATIONS 



1. Bottom sampling equipment 



Bottom sampling equipment for various survey or bottom analysis 

 requirements are available and considered generally satisfactory for 

 their intended purposes. Where grab samples are required, a large- 

 and small, size Van Veen sampler, a scoopfish, and an orange-peel 

 sampler are considered adequate to handle all anticipated requirements. 

 The triangular, light-weight dredge and the two heavier rectangular 



X-5 



