418 



U. S. BUREAU OP FISHERIES 



completely rotten at the end of two months, the two preservatives 

 apparently doing very little good. Here it will be notea that tar is a 

 better preservative than copper oleate, but the copper oleate-coal tar 

 mixtm'c is much better than either tar or copper oleate used separately. 

 The results are in keeping with results obtained with the same pre- 

 servatives at Beaufort, N. C. 



TESTS WITH LINEN LINES 



Materials tested. — In this series of experiments samples of linen 

 lines were also included. The linen selected for this purpose was 

 10-ply 40 ''Irish flax salmon thread," loose-laid, such as is used for 

 gill netting for salmon on the Pacific coast. The preservatives and 

 preservative methods tested on this material were copper oleate in 

 lour variations (NN, 00, PP, and QQ), quercitron, followed by 





12 3 4 



NUMBER OF MONTHS EXPOSED 



Fig. 4.— Tensile strength of cotton lines at Astoria, Oreg. 



ammoniacal copper sulphate (W), copper sulphate (RR), and the 

 untreated sample (T) . 



Tensile strength. — The results of the measurements of tensile 

 strength are shown graphically in Figure 5. Here the samples 

 treated with copper oleate led at the end of one month, the sample 

 treated with quercitron and ammoniacal copper sulphate coming 

 second, and that treated with copper sulphate alone coming third. 

 The untreated sample was completely rotten at the end of one month. 

 At the end of two months all samples were completely rotten and 

 had fallen from the frames. These results bear out conclusions 

 drawn from previous tests — that is, that linen thread disintegrates 

 much more rapidly than cotton under the same conditions in salt 

 water. 



