diameter galvanized pipe. This conclusion is based on unit costs of 

 the materials tested and the results of electrical tests conducted as 

 described in a preceding section. The materials selected for the tests 

 were those of generally low cost and ready availability on the market. 

 Measurements of midpoint voltage gradients and values for relative 

 electrode effectiveness are presented in Table 1. The latter values 

 are based on a figure of 100 percent assigned to the midpoint voltage 

 gradient produced by the 2-inch diameter, galvanized pipe electrode (R-U). 

 This electrode was selected as the standard of comparison in these tests 

 simply because it produced the highest midpoint voltage gradient of 

 those round electrode types tested. Flat electrode materials were tested 

 for comparison with round electrode materials as a matter of academic 

 curiosity only, since mechanical considerations (would seem to) preclude 

 their use in sea lamprey weirs. Where known, unit cost of the round 

 electrode materials was used in the determination of a "cost-efficiency" 

 figure, the magnitude of which was the criterion applied to the final 

 selection of the three most suitable electrode types. Surface dissimilar- 

 ity which is apparently the only difference among the electrical conduit 

 electrodes (R-6 to R-9, Table 1) is probably attributable to minor varia- 

 tions in the manufacturing processes employed. That these differences in 

 type of surface account for different efficiencies was indicated in the 

 test results in that the rough surfaced conduit, having a greater surface 

 area than the smooth surfaced material of the same nominal diameter, 

 exhibited the higher relative effectiveness. It should be stated here 

 that the differences in effectiveness of the various round electrodes 

 tested are not so great but that any of them might be used in arrays with 

 necessary minor adjustments in row and electrode spacing to compensate 

 for variations in effectiveness. In consideration of the desirability 

 of locating electrical sea lamprey weirs in riffle areas where high water 

 velocities may exist and cause considerable electrode deflection, pipe 

 electrodes offer a distinct advantage over those made of electric conduit 

 or thin-wall aluminum tubing. Galvanized steel pipe, having a consider- 

 ably greater weight per unit of length than these other materials, will 

 undergo less deflection for a given water velocity, thereby limiting 

 fluctuations in the intensity of the electrical field. Another probable 

 advantage (though not yet proven in field tests) in the use of galvanized 

 pipe is that of longer protection against complete corrosive deterioration 

 by virtue of its greater wall thickness. 



(5) Electrode mounting 



All of the suspended electrode systems tested proved to be en- 

 tirely satisfactory. In spite of the increased size of the physical 

 structure required, they were a considerable improvement in nearly all 

 respects over the ground-mounted system installed in the Ocqueoc River 

 in 1951. With the suspended systems, localized and general losses of 



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