The Endless Search 



side of ship's hull ^ 



The Corer 



The corer (above) is a hollow steel 

 tube that can be forced into the 

 sediments covering the sea floor. 

 When the tube is withdrawn it 

 brings up undisturbed samples of 

 sand, clay, volcanic ash, and other 

 deposits. Cores 70 feet long can be 

 made with the Kullenberg corer. 



Echo Sounding 



A continuous profile of the sea floor 

 can be recorded aboard a moving shi| 

 by the echo sounder. The instrument 

 sends out an acoustic signal which 

 is received bacl< as an echo from 

 the sea floor. Depth at any place 

 can be calculated since the velocity 

 of sound in water of different 

 temperature and salinity is l<nown. 

 On the echo sounding record shown 

 left the horizontal lines are at 

 20-fathom intervals; vertical lines 

 are time marks every 5 minutes. 



irr::- 



hydrophones 



anchored 



buoy 



floats have 



been used at 



depths between 



250 & 5000 m 



float (not 

 to scale) 



The Current Float 



The neutrally-buoyant float, designed 

 by J. C. Swallow, is used to measure 

 deep currents. Made of aluminium, it 

 is a free-floating tube sealed 

 at both ends, which is less com- 

 pressible than sea water. Loaded to 

 sink to a predetermined depth, it 

 drifts along with the deep currents. 

 An acoustic transmitter operated by 

 batteries sends out a sound pulse 

 that can be picked up by hydrophones 

 hung over the ship's side. The 

 differences in times of arrival of the 

 float's signal are measured, and, 

 aided by radar bearings from 

 buoys, the float can be tracked. 



Echo Ranging 



An acoustic picture of details of 

 the sea floor can be obtained by 

 the echo ranger. When a fan-shaped 

 acoustic signal is sent out obliquely 

 from the ship a strong echo is 

 returned by any part of the sea 

 floor facing the ship. The acoustic 

 picture at left, which has been 

 interpreted geologically, shows 

 sand (even shading) surrounding 

 a ridge of slates. 



Deep-sea Camera 



The deep-sea camera, developed by 

 A. S. Laughton, is designed to 

 photograph the sea floor. Each 

 time a weight suspended from. the 

 camera unit is allowed to touch 

 bottom, a photograph is taken 

 automatically. (Another illustration 

 appears on page 201.) 



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