PRESERVATION OF FISH NETS 



427 



TESTS WITH COTTON LINES 



Materials tested. — The preservatives and preservative methods 

 tested on cotton Hnes were copper oleate in four variations (EE, FF, 

 GG, and HH), the quercitron-ammoniacal copper sulphate method 

 (L), the proprietary waterproofing (JJ), coal tar (KK), the copper 

 oleate-coal tar combination (Y), a proprietary wood preservative 

 (LL), azulmic acid (MM), and the untreated control (A). 



Tensile strength. — The results of the tensile-strength measurements 

 are shown graphically in Figure 11. Deterioration of twine sub- 

 merged at this point was extremely rapid. Sample lines treated with 



NUMBER OF MONTHS EXPOSED 



Fig. 12. — Flexibility of cotton lines exposed at Fairport, Iowa 



coal tar (KK) lasted only four months; all others were completely 

 disintegrated at the end of two months. Lines treated with the 

 copper oleates (EE, FF, GG, and HH), those treated with the cop- 

 per oleate-coal tar mixture (Y), and those treated with the pro- 

 prietary wood preservative (LL) were completely rotten at the end 

 of two months' exposure. AzuLmic acid (MM), the quercitron- 

 ammoniacal copper sulphate method (L), and the proprietary water- 

 proofing (JJ) were here of no value as preservatives. Samples 

 treated with the last three materials, together with the untreated 

 sample, were completely rotten at the end of one month. 



