simply pressed together and tossed over the side of the ship. A 

 stopwatch is started when it hits the water and stopped when the 

 point source of light disappears and the luminescence remains. 

 The time obtained is an index of transparency. This is an example 

 of the type of expendable instrunnent that we need to develop. 



The INTEGRATING PLANKTON COLLECTOR (fig. 6. 6) is 

 a biological sampling device used for long horizontal tows at various 

 depths behind ships. The inlet tube, on the left, is in the front 

 portion and it fishes --as the term is used -- ahead of the cable. 

 It leads into a hollow chamber that is filled with fresh water. A 

 free piston is shown approxinnately amidships, with water on both 

 sides. A pump is driven by the propeller on the rear, which ex- 

 hausts the volume to the right of the free piston, letting in sea wa- 

 ter at a predetermined rate on the left side. This can be adjusted 

 by gear ratios to fish quantitatively over short distances or long 

 distances. 



A modular concept is illustrated by a series of instruments 

 plugged together as follows: The MODIFIED ROBERTS CURRENT 

 METER (fig. 6. 7) is a fluid-filled instrument and is thus not depth- 

 limited; above it, mounted on the yoke, is a small pre s sure - 

 protected module which measiires depth. Above it, suspending 

 the entire unit, is an electrical swivel. This system is designed 

 to operate on a single conductor, sea return type of cable. The 

 electric plugs, available from several manufacturers, Cein be used 

 very readily to connect and disconnect the modules. These plugs 

 are very simple. They will not leak at any depth in the ocean. 

 In fact, some may be mated successfully under salt water with no 

 trouble for the electronic circuits. 



GLASS SPHERES (fig. 6.8) about three inches in diameter 

 are shown partly to exhibit another concept which we need to keep 

 in mind. We should not fight the ocean but do our best to use it. 

 Hollow glass spheres are used to determine the time at which an 

 instrument reaches the bottom. They are used in a device coupled 

 in series with an instr\iment (fig. 6. 9). When the instriiment 

 reaches the bottom, the heavy weight is released and when the 

 weight falls, a sharp point ruptures the sphere. In deep water this 

 hollow sphere represents a s\ibstantial amount of potential energy. 

 By listening with a hydrophone over the side of the ship or even 

 with the ship's fathometer, one can readily hear when the glass 

 sjdiere implodes. The velocity of sound in water is roughly a 

 mile a second. 



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