FISH-NET PRESERVATIVES. 59 



tar. In the trials, however, they fail to show any prescrvin": quality 

 worth considering. The tensile strength of lines treated by them 

 rapidly diminishes on exposure, the stiffness is greatly increased, and 

 the wearing quality, while good in the unexposed lines, rapidly dis- 

 appears on exposure. The failure of these materials was equally rapid 

 on cotton and linen lines. 



GILSONITE. 



This material, also called Uintaite, coming as it does from the Uinta 

 Mountains of Utah, is an asphalt, similar to Trinidad asphalt. It is 

 sold under a proprietary name as a net dip, and this proprietary 

 product was the one tested in this work. It is a black sirupy liquid 

 of a bituminous odor. When applied to cotton twdne, it dries in about 

 24 hours, leaving the lines colored dark brown or black and of a stiff- 

 ness as great as that produced by tar or copper paint. It increased 

 the weight of No. 24 cotton twine when dipped 48 per cent, which is 

 similar to the increase caused by tar. 



As might be expected from the results already given, which show 

 that mere waterproofing or covering lines is not in itself adequate to 

 preserving them against deterioration on exposure, gilsonite fails to 

 show any preserving effect. At Beaufort, where it was exposed, it was 

 little better than no preservation as far as tensile strength was con- 

 cerned. In resistance to mechanical wear gilsonite compared well at 

 first vrith. other preservatives, but this resistance soon disappeared 

 on exposure of the samples. This substance, if fortified with copper 

 oleate or some other toxic material, might be effective; but if it costs 

 much more than tar, little if any advantage would be gained by sub- 

 stituting it for tar. Because of general failm-e and disintegration of 

 lines treated by it gilsonite may be dismissed as of no value as a net 

 preservative. 



COPPER OLEATE. 



In our experiments this substance is tested for the first time as a net 



Ereservative. It has been tried in various concentrations and com- 

 inations, and, as far as our experiments go, it shows characteristics 

 that should make it valuable for preserving nets. If tensile strength 

 of lines after exposure is alone taken as a measure of its preserving 

 effect, copper oleate gave good results, though not always the best. 

 In the Key West series it kept the lines up to their original strength 

 for four and one-half montt^. At Beaufort the only preservatives 

 that resisted six months' exposure were copper oleate, copper paint, 

 and the Dutch method. Because of a binding effect on the fibers the 

 tensile strength of the lines treated with copper paint was greater than 

 that of Unas treated with copper oleate. At Woods Hole again all 

 those lines that endured six months had copper in some form in them. 

 Those preservatives that contained a protecting body in addition to 

 the copper lasted better than those treated with copper oleate alone. 

 At Put in Ba\' in fresh water copper oleate alone did not give encourag- 

 ing results, but combined with tar as a binder it gave excellent results. 

 The copper oleate without binder seems to disappear from the lines 

 rather rapidly in the fresh water of Lake Erie. In none of the fore- 

 going experiments was copper oleate applied a second time to the 

 sample. The amount of copper per yard of line was very small in 



