434 



U. S. BUREAU OF FISHERIES 



SUMMARY OF RESULTS I>f THE POTOMAC RIVER AT WASHINGTON, D. C. 



1. The most important result of this test was the discovery that 

 by removing gear from the water once each month and washing, 

 drying, and treating it with copper oleate the hfe of twine can be 

 more than doubled. 



2. The rare-earths treatment (RE), when used alone, is not very 

 effective as a preservative. 



3. When the treatment is not repeated monthly, the combination 

 of copper oleate and rare earths is somewhat better than copper 

 oleate used alone. 



Fig. 18. — Increase of weight caused by one application of preservative 



INCREASE IN WEIGHT CAUSED BY APPLICATION OF PRESERVATIVES 



In a previous paper on this subject * we discussed the desirability 

 of lightness as a property of textiles used for fisliing gear. In all 

 experiments described in the present work this factor was again 

 accurately measured. The results of these measurements are shown 

 graphically in Figure 18, where the original weight of the line is 

 represented by the height of the rectangle up to 100. The diag- 

 onally hatched part above 100 represents the weight added by the 

 preservative, and the total height of the rectangle represents the total 

 weight of the line after treatment. 



SHRINKAGE CAUSED BY APPLICATION OF PRESERVATIVES 



The measurements of the sample lines before and after treatment 

 revealed any changes in kmgth. The results so obtained are shown 

 graphically in Figure 19. In the case of hemp the lines treated with 



* See footnote 2, p. 409. 



