422 



U. S. BUREAU OF FISHERIES 



months, while that treated with copper oleate in 1922 was rotten at 

 the end of five months. This would indicate that there is a consider- 

 able seasonal variation in the water at this point. Test lines treated 

 with the proprietary waterproofing substance lasted during the entire 

 six months but were of very low tensile strength at the end of the 

 period. 



TESTS WITH MANILA HEMP LINES 



Materials tested. — In addition to the samples of cotton twine there 

 were also included a number of samples of manila hemp treated with 

 the various preservatives. The preservatives and preservative 



2 80 



260 



240 



220 



200 



]80 



160 



140 



120 



100 



80 



60 



40 



EO 



^ 12 3 4 5 6 



^ MUMBER OF MONTHS EXPOSED 



Fig. 8. — Tensile strength of hemp lines at Put in Bay, Ohio 



methods tested were copper oleate in four variations (SS, TT, UU, 

 and W), quercitron and ammoniacal copper sulphate (WW), coal 

 tar (XX), the copper oleate-coal tar mixture (YY), and an untreated 

 control (DD). 



Tensile strength. — The tensile stron£!;th of the manila lines exposed 

 at Put in Bay is shown graphically in Figure 8. The four copper 

 oleates and the copper oleate-coal tar mixture were all of about equal 

 value as preservatives of tensile strength. Lines treated with each of 

 these preservatives lasted through the entire six months with only 

 very slight diminution of strength. Coal tar was not as effective on 

 hemp at Put in Bay as it was at other places. The lines treated with 



