ELECTKIC FISH SCREEN 



119 



voltage oflF the screen until 6 p. m., during which period between 3,000 and 4,000 fish 

 went into the protected area. These fish were coaxed out of the protected area by 

 feeding before the screen was electrified again. This accidental interruption of the 

 screen power supply showed two things: First, it is important to have a reUable 

 source of supply, and, second, the screen was effectively keeping the fish out of the 



VARUTION OF ELECTRODE SURFACE VOLTAGE GRADIENT WITH SWCING 



FOR 



PARALLEU CYLINDRICAL ELECTRODES 



IMMERSED IN WATER OF ANY UNIFORM RESISTIVITY 



VOLTAGE ONE VOLT TO NEUTRAL OR TWO VOLTS BETWEEN ELECTRODES 



VOLTACE eKADIENT AT THE. SURFACE OF ^INCH STANDARn Pipe EICCTEOOC 



I 



«■ «■ •> n *• •« S 



t( *l (« M II II 3 



It , r , r I " ft 



Fia. 14 



protected area. Following this interruption the screen was kept electrified continu- 

 ously for 10 days. During this period sunshine and cloudy and rainy weather were 

 experienced. One very hard rain, lasting about 36 hours, occurred on August 25 and 

 26. This afforded an opportunity to see whether weather conditions had any influence 

 on the effectiveness of the screen equipment, and as far as could be observed it did 



