EWING: ACOUSTIC PROPERTIES OF THE SEA FLOOR 



So we divide up the sediment column and calculate one of 

 the regression curves. By doing this we get a lot of statistical 

 leverage in a shallow area. We always wind up with a much tighter 

 regression plot than we do in the deep water. 



There is maybe one exception to that, and that is the Bering 

 Sea. There we have 50 or 60 measurements distributed sort of all 

 over the whole basin and they group in quite tightly around regression 

 curves. Whether it's because the Bering Sea is a little more stable 

 oceanographically, I don't know. We're still struggling. 



MR. C. W. SPOFFORD (Office of Naval Research) : On these 

 phase differences, John, is the bottom flat enough that you can con- 

 sider those two rays to be identical in the water column? That is, 

 one ray doesn't spend another 10 meters or so in the bottom in depth 

 which could give you some huge differences here I would think? Is 

 the bottom flat enough to ignore this effect? 



MR. EVJING: I think in the Hatteras abyssal plain it is. Those 

 abyssal plains are the flattest things known in nature as far as I 

 know. VJe cannot measure the slope with an echo sounding system that 

 measures to plus or minus a fathom. 



DR. HERSEY: The grades are typically one in five thousand in 

 the central portion of abyssal plain. 



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