The per cent saturation of oxygen was computed in 

 accordance with reference 42. 



Outline of Experiment Procedure 



The procedure for taking a measurement can be 

 summarized as follows: 



(1) Fill cavity with sample. 



(2) Wipe side walls and bottom with squeegee. 



(3) Tune generator frequency and the tuning circuit to 

 obtain maximum reading on vacuum tube voltmeter (fig. 4B). 



(4) Decouple transducers until barely full reading is 

 obtained on recorder, and with VTVM sensitivity as high 

 as possible. 



(5) Start recorder at paper speed chosen (100 mm/sec 

 or 30 mm/sec), and interrupt power from the signal gen- 

 erator. 



(6) Tune generator to the two higher modes, repeating 

 steps 3, 4, 5. 



(7) Take plankton and oxygen samples, and measure 

 temperature. 



(8) Record sampling depth and hydrophotometer reading. 

 Calibration of Cavity 



The cavities were calibrated before they were used on 

 the tower and again after the data collection with no change 

 in their acoustic properties indicated. Visual inspection 

 did not disclose any change in the cavities apart from a 

 slight surface discoloration of the stainless steel sheets. 



The calibration was done with the cavities filled with 

 distilled water. The temperature was brought down early 



65 



