PISH-NET PRESEBVATIVES. 



35 



flexible than the untreated lines. The lines treated by the Dutch 

 method were also sufficiently flexible. The copper paints, Q and R, 

 tar and copper combinations, Y and Z, and petroleum product No. 2, 

 designated by X, cause marked stiffening, all to about the same 

 extent. Though the lines treated with petroleum product are, by a 

 little, the stiffest, the copper paints also cause marked stiffening, and, 

 upon comparison with the tar-copper-oleate combinations, show 

 slight advantage in favor of the latter. Here, again, the copper 



340 



320 



300 



280 



260 



240 



220 



200 



180 



160 

 «o 



1 140 

 fel20 



ac 



^100 



z 

 80 



60 



40 

 20 



-J UJ 



5 t: 



2 3 4 



NUMBER OFM0NTH5EXP05E0 



Fig. 23.— Wearing quality of cotton lines exposed in sea water at Woods Hole, Mass. 



paints and tar-copper-oleate combinations, being somewhat similar 

 in composition, give similar results. None of these materials would 

 be suitable where flexibility is desired, but they are otherwise ex- 

 cellent preservatives. 



WEARING QUALITY. 



By the method already described, of sawing the lines against 

 themselves (p. 25), the ability of the various lines exposed at Woods 

 Hole to resist mechanical wear, was measured. The results are given 

 in Table 14 and are shown graphically in Figure 23. 



