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Figure 12. — Effect of orude oil mixed with oarboniied sand on the 

 percentage of time oysters remain open and on the total volume of 

 water pumped each day. Oyster No. 1, experimental j and oyster No, 2, 

 control. The control is indicated by open circles. Rubber apron 

 method. July 1 to 16, 1948. 



