between the brass strips ; appropriate intermediate 

 voltages were applied to the electrodes. 



Solutions of the partial differential equation 

 for different boundary conditions were obtained 

 by tracing with a probe connected in series with 

 a voltmeter and one tray wall along constant 

 potential lines in the electrolyte. Results were 

 recorded with a pantograph. 



DIRECTION OF FLOW 



Figures 5 through 9 represent longitudinal cross 

 sections of a streambed: the top surface of the 

 figure represents the upper surface of the stream- 

 bed and the bottom, the impermeable stratum. 

 The right and left ends of each figure represent 

 arbitrary vertical planes bounding the reach of 

 streambed considered. The lines of constant 



Figure 5. — Flow net for straight-line-surface potential 

 bla=y2. 



I 7 7 — r — /— -i / 5/ / / — l—l \ 



L rTr^h~N*4Znrh 



X a 



Figure 6. — Flow net for convex parabolic surface potential. 

 484 



Figure 7. — Flow net for concave broken-line-surface 

 potential, illustrating evaluation of As and A0. 



0X0 



Figure 8.— Flow net for sigmoid surface potential. 



♦ IXI 



Figure 9. — Flow net for straight-line .surface potential 

 with impermeable intragravel barrier at x = 0.5o, 



U.S. FISH AND WII.DLIFE SERVICE 



