PRESEEVATION OP PISH NETS 421 



Table 3. — Temperature of the water at Put in Bay, Ohio 



Year and month 



1923 



July-. 



August - - 



September 



October 



November , 



December 



12 3 4 5 6 



NUMBER or MONTHS EXP05EP 



Fig. 7. — Tensile strength of cotton lines at Put in Bay, Ohio 

 TESTS WITH COTTON LINES 



Materials tested. — The preservatives and preservative methods 

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

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

 a proprietary waterproofing (JJ), coal tar (KK), the copper oleate- 

 coal tar mixture (Y), and an untreated control (A). 



Tensile strength. — The tensile strength of the cotton lines exposed 

 at Put in Bay is shown graphically in Figure 7. Here, again, the 

 copper oleate-tar combination is in the lead as a preservative of tensile 

 strength, keeping twine over a six-months period of exposure with only 

 a very slight diminution of tensile strength. The copper oleates and 

 coal tar used separately also preserved well, each of them keeping 

 sample lines so treated in very good condition. Sample lines treated 

 with the quercitron-ammoniacal copper sulphate treatment were 

 completely rotten at the end of five months. In this connection it is 

 very interesting to note that this same preservative method, used in 

 the same water during 1922, kept twine in good condition for six 



