Taylor and Wells. — Preservation of Nets and Lines. 43 



ocean water at Key West, Florida, from November to May, 

 showed characteristics quite different from the foregoing. The 

 tensile strength of these 11 samples prepared with different 

 preservatives are shown in Table III and graphically in Fig. 3. 

 Here, the preservatives, except the Dutch method, fall into three 



MONTHS EXPOSE* 



Fig'. 2. — Tensile strength of cotton lines exposed to weather conditions 

 at Washington, D. C. Grouped. 



distinct classes (see Fig. 4) as follows: (1) Coal tar, pine tar, and 

 those two tars mixed (F, G, H) show a preliminary drop in ten- 

 sile strength, followed by a marked increase, which is held almost 

 constant to the end of the period of exposure (18 weeks). (2) 

 All those preserved with copper oleate, with or without oil and 

 cresol, wherein an initial sharp increase in strength is followed 

 by a constant tensile strength through the period of exposure. 

 Both the tars and copper oleates show excellent preservation. 

 (3) Bull's method. Petroleum Product No. 1, and waterproofing 

 material show no particular preserving action at all, as they run 

 essentially the same as the untreated lines. The Dutch method 

 (L) shows characteristics which resemble, in some respects all 

 the other three, and is therefore plotted separately. 



In sharp contrast to the effect of weather conditions in the 

 air at Washington, the lines exposed in sea water at Key West 

 show clearly that toxic preservatives are important and conse- 

 quently we must conclude that the impairment of the lines in 

 sea water is traceable largely to biological causes. The tars 



