114 



BULLETIN OF THE BUREAU OF FISHERIES 



The above observations show the necessity, when using an electric screen for 

 protecting an opening, of having the equipotential surfaces parallel with the plane 

 of the opening and the lines of electric-current flow perpendicular to this plane. 



LINES OF CURRENT FLOW AND EQUI POTCNTI AL SURFACES 



FOK 

 TWO par;»lle.l gr/^tinss of parallel CYUNCRICALELECTRCDES 



IMMERSED IN WATER OF ANY UMIFORM RESISTIVITY 



Fig. 10 



When in swift water fish hold their bodies parallel with the direction of stream 

 flow for ease in swimming. This fact must also be taken account of when installing 

 an electric screen. The lines of electric-current flow must be parallel with the direc- 

 tion of water flow and the equipotential surfaces at right angles to the direction of 

 water flow. 



