In general, the measured values of sound speed at 

 great depths were found to be less than those computed. 

 Measurements for depths greater than 8000 meters would 

 be very valuable to obtain or verify the depth dependence 

 of sound speed. 



Reference 1 (see list of references at end of report) 

 presents a detailed discussion of sound- speed measure- 

 ments made from the TRIESTE during NEKTON E. Earlier 

 experiments using the bathyscaph in a similar manner are 

 reported in reference 2. 



Sonar Tests 



Dives Nos. 61 and 69 furnished opportunities to test 

 the effectiveness of the AN/SQS-4 and the AN/SQR-8 

 Mod 4 sonars in detecting and following the bathyscaph on 

 its descent and ascent, while maintaining voice communi- 

 cations through the bathyscaph acoustic telephone and two 

 AN/UQC-lB's. Results are omitted because of classifica- 

 tion. 



GRAVITY MEASUREMENTS 



To test the usefulness of the bathyscaph as a platform 

 for obtaining gravity measurements at great ocean depths, 

 K, V. Mackenzie obtained a LaCoste- Romberg Company 

 geodetic gravimeter, model G, to measure the value 

 in situ . This instrument has a range of 6. 000 cm/sec^ 

 with a sensitivity of 1 x lO"'^ cm/sec^. 



During Dive No. 78, gravity measurements at mid- 

 water were attempted. However, the vertical stability 

 and control were insufficient to permit a satisfactory 

 reading. 



Success was achieved on the sea floor at a depth of 

 2286 meters. The value of g was found^ to be 978. 9331 

 cm/sec^ . This compares with a reference value of g 

 at the Ship Repair Facility, Apra Harbor, of 978. 5376 

 cm/sec^. Although this isolated measurement does not 

 contribute significantly to knowledge of the variations of 

 g with depth, it does show the suitability of a manned 

 deep submersible to serve as a stable platform for such 

 delicate instruments. 



33 



