410 U. S. BUKEAU OF FISHERIES 



CONCLUSIONS 



The principal results and conclusions drawn from the present work 

 are as follows: 



1. The combination of copper oleate with coal tar was the best 

 preservative of tensile strength of those tested. 



2. Both the proprietary waterproofing material and the proprietary 

 wood preservative did some good as preservatives, but neitner one 

 was as effective as copper oleate or coal tar. 



3. At all places where tests were made linen lines, both treated 

 and untreated, were completely rotten in less than two months. 



4. Azulmic acid, a dye tested as a preservative, proved to be of 

 no value for this purpose. 



5. The combination of rare earths and copper oleate was very little 

 better than copper oleate used alone. 



6. Combinations of copper oleate with paraffin, boiled, and raw 

 linseed oil did not preserve tensile strength any better than copper 

 oleate alone. 



7. The copper oleate and linseed oil combinations appeared to 

 wash out less rapidly than copper oleate alone, but did not prevent 

 fouling by marine growth as well. 



8. With the exception of the quercitron-ammoniacal copper- 

 sulphate treatment, the effectiveness of the several preservatives is 

 of the same order on hemp as on cotton. 



9. For hemp lines the copper oleate-coal tar mixture was the best 

 preservative of tensile strength, copper oleate coming second at all 

 places except Fairport, Iowa, where coal tar was second best. 



10. The quercitron-ammoniacal copper-sulphate treatment (L) did 

 not make as good a showing on cotton samples in the 1923 tests as it 

 did in 1922. We do not know of any cause for this other than that 

 due to the variation in water conditions at different localities and in 

 the same locality from one year to another. 



11. The quercitron-ammoniacal copper-sulphate treatment (L) 

 made a very poor showing on hemp samples. The hot-water solution 

 of quercitron seems to damage hemp, causing an exceedingly large 

 diminution of tensile strength, and probably is the cause of the poor 

 results of this treatment on hemp. 



12. In fresh water of the Mississippi River at Fairport, Iowa, 

 sample lines suffered more rapid deterioration than at any other 

 point where tests were made. Coal tar preserved cotton lines at 

 Fairport for three months. Lines treated by all other methods were 

 completely rotten after two months' exposure. 



13. Twine that is removed from the water every 30 days, dried, 

 and treated with copper oleate lasts more than twice as long as that 

 which is treated but once. 



14. In fresh water at Put in Bay, Ohio, results with copper oleate 

 were more satisfactory than in the previous series there. 



15. The results at Put in Bay, Ohio, indicate that the rate of de- 

 terioration of nets not only varies from one locality to another but 

 differs in different years in the same locality. 



