not be expected, since nothing is known about the length 

 of time required for decaying plant material to stabilize 

 nuclei, nor about the possible production of new nuclei due 

 to the decay processes. 



The observations presented here are in many ways 

 similar to the description given by Skudrzyk. ''" The explan- 

 ation presented in this reference is based on a continuous 

 production of bubbles, but the experiments were performed 

 at frequencies of the order of 100 kc/s. Bubbles close to 

 resonance will have such a small diameter that it is diffi- 

 cult to verify by visual inspection whether bubbles of this 

 size are present. A frequency of 100 kc/s corresponds to 

 about 0. 065 mm diameter. 



Serial Sequence of Measurements 



One series of measurements was taken through the 

 night of 2-3 August 1960, in an attempt to identify variables 

 of importance to the sound attenuation other than the oxygen 

 content and the count of particulate matter (fig. 31). The 

 samples were taken in the layer of lowest light transmission 

 as indicated by the hydrophotometer. Changes in the differ- 

 ent counts reflects not only changes in the density of the 

 layer with highest turbidity, but also the influence of sur- 

 face waves and internal waves during the sampling period. 

 These changes must therefore be interpreted with some 

 caution. 



The samples are supersaturated with oxygen at atmos- 

 pheric pressure, and the change in concentration through 

 the night is not very great. The upper 15-20 feet were 

 supersaturated through the whole series, and there was 

 no pronounced layer of maximum oxygen concentration. 

 The layer of maximum oxygen content did not coincide with 

 the layer of maximum turbidity. 



,; Ref. 4, p. 869-870 



95 



