warm seawater 



capacitance bridge 



or 



DC-measuring networl< 



Figure 2. Experimental setup. 



Three panels of each system were exposed in flowing seawater. The 

 baths in which the panels were suspended (Figure 2) were rectangular glass 

 jars 8 inches wide, 11-1/2 inches long, and 8 inches high. Aerated seawater 

 was maintained at 25°C in a reservoir and was allowed to flow into the baths 

 through an inlet tube extending to the bottom at one end of the jar. At the 

 other end of the jar, approximately 2-1/4 inches from the top edge, a hole 

 was drilled to accommodate an outlet tube. The panels were suspended from 

 square fiber glass rods which were placed on the top edge of the jars. The 

 length of the hooks and the level of the seawater was such that the 1 20 cm^ 

 of test surface of each panel was always immersed. 



The AC electrical measurements were made with a capacitance measuring 

 assembly consisting of a capacitance bridge, an audio oscillator, and a tuned 

 amplifier and null detector (General Radio model 1620). The experimental 

 setup is shown schematically in Figure 2, but for the actual measurements, the 

 glass jar of salt water was removed from the source of warm flowing seawater 

 and was placed into a water bath accurately maintained at 25°C. 



