Circuitry for the control of power to the electromechanical 

 weir and for protection of personnel against electrical shock was also 

 installed in the generator cabin (Fig. 3). 



In detail, this electrical weir was simple. It consisted 

 of three rows of 23, 2-inch 0. D., non-buoyant aluminum electrodes with 

 a spacing of 3-1./2 feet between rows and h feet between electrodes in a 

 row. Each electrode was anchored to the bed of the stream by means of 

 a U-foot steel pin driven into the bottom (Fig. h) . The electrode was 

 attached to the steel anchor pin by a spring-loaded hinge, which per- 

 mitted movement of the electrode through an arc of 60 degrees only in a 

 downstream direction. A plastic plug isolated the electrode (electri- 

 cally) from the hinge, steel anchor pin, and the stream bed. 



The center row of electrodes was made the common connection 

 for a voltage source of 110 volts AC for the upstream row of electrodes, 

 and 55 volts AC for the downstream row of electrodes (Fig. 2). It was 

 possible by means of a variable voltage transformer (variac), to raise 

 or lower these two voltages simultaneously, while maintaining the 2 s 1 

 voltage ratio between the upper and lower rows. The above indicated 

 voltage levels were arbitrarily selected as a starting point for the 

 tests simply because they seemed ample to block the upstream migrating 

 sea lampreys, and yet were not excessively wasteful of power. They fur- 

 ther represented voltages which could be introduced into the stream with 

 a minimum of equipment should ordinary line power be utilized. 



The purpose of the low voltage field on the downstream side 

 of the array was to act as a non-lethal warning area for the game fish 

 while allowing the sea lampreys to penetrate to the high voltage field, 

 which was expected to have a lethal, paralyzing, or diverting effect on 

 them. 1/ 



The array of electrodes was installed diagonally across the 

 stream and a conventional weir-trap was installed between each end of 

 the array and the stream bank. These traps were bordered on their 

 streamward sides by wooden baffle walls covered with a metal screen 

 which acted as an electrical shunt in preventing the extension of the 

 fringe field into the trap area. 



After initial tests of the electrical weir had indicated that 

 some game fish were being turned back downstream, a direct current 

 guiding field, powered by a 100 volt, continuous, DC power supply was 

 installed and tested. It consisted of an anode above the upstream trap 



1/ Comments on the reactions of migrant sea lampreys to electrical 

 fields in the water are presented in a subsequent section. 



