that alternating shear stresses, caused by wind or moon, in a Coriolis 

 field may build up such a velocity field. On the other hand, it may 

 somehow be induced by major currents such as the Gulf Stream. These 

 possibilities, however, must remain speculative until more attention 

 is given the problem. 



The structure of the field of horizontal motion is important 

 because it probably determines the vertical fluctuating velocities. 

 So far, these vertical turbulent motions were postulated to explain 

 vertical diffusion, and gradients in the horizontal motion were then 

 postulated as necessary to maintain them. There remains the possibility 

 that the relation between horizontal motion and vertical diffusion is 

 not quite so indirect. 



In effect, ideas derived from studies of turbulent motion in 

 shear flow have led to a picture of an ocean in which the role of shear 

 flow is uncertain^ Despite this, it is probable that the approach used 

 was simple enough for the limits established on the motion to be valid 

 to within an order of magnitude. 



Much continued experimental work on "ambient" oceanic turbulence 

 is obviously needed, but, if the present results are any indication, 

 this research will be difficult. Diffusion measurements on a large 

 scale are particularly convenient because they can be made on material 

 introduced naturally, or artificially well in advance of the gradient 

 measurements. The outlook for making direct measurements of the turbu- 

 lent velocities or associated pressure fluctuations is discouraging. 

 Fluctuations in the horizontal velocity of the order of a centimeter 

 per second over a day would be difficult to separate from periodic tidal 



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