FISH-NET PRESERVATIVES. 33 



Table 12. — Tensile strength of cotton lines exposed in sea water at Woods Hole, Mass. 



Symbol and treatment. 



Unex- 

 posed. 



Number of months exposed-. 



Tensile strength in pounds. 



A — Untreated white line 



L— Dutch metliod 



Q — Copper paiut No. 1 



R— C-opper jiaint No. 2 



X — Petroleum product No. 2 



Y — Copper oleate 15 per cent, benzol 35 per cent, coal tar 50 



per cent 



Z — Copper oleate followed by coal tar 



AA — Copper oleate, alone, 15 per cent gasoline 



(=) 



24.7 

 40.8 

 49.6 



46.5 

 43.6 

 31.0 



1 Average of 00 breaks; every other figure in this table is the average of 15 breaks. 



2 Line was disintegrated and gone. 



The lines treated with petroleum product No. 2, designated X, 

 is scarcely better than the untreated line, A. Tliis result is in keeping 

 with the result obtained with the same preservative at Beaufort. 

 The copper oleate, AA, employed in this case, is strikingly similar 

 to the Dutch method, L, both of which show good preservation, 

 though, as before, these preservatives do not add anything to tlie 

 strength of the lines by a sticky effect on the fibers. Wlien allow- 

 ance is made for this effect in the lines treated with copper paint 

 or the combinations of copper oleate and tar (Q, R, Y, and Z), 

 strildngly similar preservation effect is noticed. As might be 

 expected, the lines treated with copper oleate and tar behave very 

 much like those treated viiih copper paint, since the mixture of copper 

 oleate and tar is very similar to copper paint in composition. Each 

 consists of a form of copper incorporated in a binder — the paints 

 containing copper oxide, the tar mixture containing copper oleate. 

 It should be noticed here, however, that the tar mixtures contain 

 ver}^ much less copper than the copper paints and should accordingly 

 be cheaper, though they preserve fully as well. 



Between the two combinations of tar and copper oleate — that is, 

 the separate application of the copper oleate and tar in the one case 

 and the mixture of the two for application in the other — there is 

 little difference. The combination can be easily and simply applied, 

 since both the copper oleate and tar are soluble in benzol and may 

 be applied cold, rerhaps the separate application of tar and copper 

 oleate is slightly better, though the extra time and labor recpiired to 

 make the two applications would probably more than make up the 

 difference. On the other hand, the separate application maybe 

 employed without the use of benzol by using a gasoline solution of 

 copper oleate and following with tar in the usual way by the hot 

 process. 



These combinations of copper oleate and tar furnish a new possi- 

 bility where nets are exposed to the most extreme conditions for long 

 periods. Straight copper oleate is toxic and preserves to a high 

 degree, but contains nothing in the way of a binder to hold it in the 

 lines. \Vlien combmcd with tar it constitutes a permanent toxic 

 ingredient that will stay in the lines over long periods, although 



