The welding cable electrodes were 

 made as follows: two equal lengths of cable 

 were clamped together. The insulation was re- 

 moved from the first 30 -inch portion of one 

 cable, then a 6 -inch gap left, and a 30 -inch 

 portion of the other cable was bared. Thus the 

 insulation was removed from alternate 30 -inch 

 portions of the cables, always leaving 6-inch 

 gaps of insulated cable between the bared por- 

 tions, until the desired number of electrodes 

 was obtained . Electrode systems of 12, 18, 

 and 24 feet in length are used most frequently, 

 depending upon the size of the stream to be 

 shocked. Longer systems could be used effec- 

 tively on larger streams. 



the resistivity increased from 104,000 to 148,000 

 ohms when the temperature was reduced from 

 64 to 40° F. 



The results cf applying salt to selected 

 samples showed that relatively few ppm of the 

 salt are required to reduce resistivities by 50 

 percent, particularly among the higher resistiv- 

 ity waters. For example, the resistivity of a 

 sample at 52,000 ohms was reduced 50 percent 

 by 11 ppm of salt; at 76,000 ohms by 8 ppm; at 

 110,000 ohms by 5 ppm; at 220,000 ohms by 3 

 ppm; and at 1,000,000 ohms by less than 1 ppm 

 of salt. The progressive reduction in resistivity 

 was slower in water samples at 40° than at 60° F. 



Solderless terminal lugs are fastened to 

 cable tips on one side of an electrode system. 

 Terminals of this type can be easily and quickly 

 bolted to alternate -polarity terminals on the 

 bottom of the switch -brail. The cable tips at 

 the opposite end of the system are insulated 

 from one another with electrical tape. Dog- 

 chain clasps are used to fasten electrode sys- 

 tems to the brails and thereby systems of differ- 

 ent lengths can be readily substituted on the 

 brails. 



THE EFFECTS OF SALT UPON 

 RESISTIVITY 



The effects of cattle salt applied in 1 ppm 

 amounts to 1 liter samples of water were ob- 

 served in the laboratory. The resistivities of 

 the samples ranged from 48,000 to 1,000,000 

 ohms. With the exception of the latter sample, 

 the resistivities were considered typical of 

 those encountered in soutliern Appalachian trout 

 streams. Measurements of resistivity were 

 made successively following 1 or 2 ppm applica- 

 tions of salt until the accumulated salt in a water 

 sample amounted to 30 ppm (table 1). 



The samples were held in water baths 

 throughout the trials to preserve near -constant 

 temperatures in the test solutions. The influ- 

 ence of water temperature on resistivity was 

 exhibited during preliminary trials wherein the 

 resistivity of one sample increased from 53,000 

 to 57,000 ohms when the temperature changed 

 from 61 to 59° F. In another, the resistivity in- 

 creased from 48,000 to 56,000 when the temper- 

 ature dropped from 64 to 56° F . In a third sample 



These trials demonstrated that decreas' 

 ing advantage is gained by the addition of more 

 salt beyond 12 ppm (figure 1). Regardless of 

 initial resistivities and temperatures of the samples, 

 the application of 30 ppm of salt put final resistiv- 

 ities within a range of 8,000 ohms (14,000 to 22,000 

 ohms). 



The effects of salt on resistivities in large 

 and small streams were observed in both parks 

 during the winter of 1956-57. This season of the 

 year was chosen since water levels and tempera- 

 tures were relatively stable . The more elaborate 

 trials were made on Indian Creek in the Great 

 Smokies since it is a small and rapid trout stream 

 with a closely parallel truck road which facilitated 

 movements from one trial station to another. Salt 

 points and stations were located at convenient 

 sites and immediately preceding a trial, the vol- 

 ume of stream flow, the normal resistivity, and 

 water temperature were measured at each station . 



Typical of the results obtained in Indian 

 Creek and other streams were those observed 

 when a 50-pound block of salt was placed in the 

 water for 15 minutes (table 2). The stream at 

 this point was flowing at 34.4 cfs, the resistivity 

 was 207,000 ohms, and the water temperature was 

 44° F. Sixteen pounds of salt were dissolved from 

 the block in the 15 -minute period. At Station I, 

 100 yards downstream, the resistivity dropped in 

 11 minutes to a low of 54,500 ohms or 26 percent 

 of the original level . It increased abruptly to 

 150,000 ohms 5 minutes after the salt was removed 

 from the stream but did not return to the original 

 level until 27 minutes later. 



