26 tr. S. BUREAU OF FISHERIES. 



is kept hot while the net is put into it. It is left in until the knots have had 

 time to he thoroughly penetrated ; then taken out, drained, and the moist net 

 packed in a vessel till next morning, when it is taken out and dried very 

 tlioroughly. As soon as completely dry it is ready to iecei\t> the same treat- 

 ment again, and so on until it has had 6 to 8 treatments, hetween each two of 

 which it is thoroughly dried out, care being taken that the interior of knots is 

 soaked at each treatment and dried with each drying. 



The net, perfectly dried, is now brought under raw linseed oil — 1 pound of 

 oil for each pound of net. The oil is kept as cold as possible. The excess of 

 oil is drained off in a vessel with a false bottom. This done, the net is laid out 

 in a held to dry, which drying takes two or three weeks or more. :Much rain 

 will injure the net, but under no circumstances should the net ever be heaped 

 up until absolutely dry, even if it does rain. If it is heaped up it is certain 

 to heat, and, aside from the danger of fire, it may be ruined by the heat 

 generated. 



There is no doubt that this is an excellent preserving method for 

 nets and deserves all the esteem in which it has been held for so many 

 years. But, because of its laboriousness and the present cost of linseed 

 oil, it is not at all likely to receive consideration under present con- 

 ditions in the United States. Neither is it ever}' fisherman that has 

 idle land on which he can lay out nets for three weeks or more to dry. 

 Nor is the method necessary in many cases, for if the figures by 

 Lindeman and Bull, given above, are reliable, the threads may be 

 as well preserved by catechu or other tan, followed by a mordant, 

 at much less cost and labor. The threads of hemp, preserA'ed with 

 catechu and mordant, were reduced in strength from 13.7 to 12.1 

 between first and third tests (28 weeks) ; preserved with catechu, 

 mordanted, and then oiled, the figures are 10.9 and 13.2, or an ap- 

 parent increase in strength. AYith cotton the results wore similar, 

 only both appeared to become stronger. But it will be noticed that 

 the oiled nets are 50 per cent or more heavier than the other and the 

 breaking length is correspondingl}' shorter. 



Nets oiled with linseed oil are stiff er and harder than nets not oiled ; 

 in some cases, such as the gill nets for shad, this would be a serious 

 objection; but for nets that stay constantly' in the water, such as 

 trammel or moored nets, oiling might be well justified. Cunningham 

 said he left oiled nets in the water two months and found no diminu- 

 tion in strength in that time. Barclay (1905) concludes that im- 

 proved tanning methods are good where there is opportimity for 

 occasional drying of nets, but where there is no opportunity for 

 drying it may be desirable to oil the nets after they are tanned or 

 " barked." 



TAR. 



Preservation of nets by tar is the principal method used in the 

 United States. The nets are simply passed througli hot tar. freed 

 from excess, and partially dried. On use the drying continues until 

 the tar is hard and tough. Of this method Cunningham says : 



This method of treating a net is very cheap and tested by tb.e niothod above 

 described — breaking tests — on pieces of net exposed in a harbor, the preserva- 

 fon is very perfect. A piece of net lost scarcely any strength after two months in 

 the water, and, moreover, a ttlrred net is distinctly stronger than a cutched 

 net, because the dry tar increases the strength of the cotton fibers by gluing 

 them together. .Vs' an antidote to putrefaction coal tar is perfect, no septic 

 organisms being able to live in it. The fibers of the cotton, being covered by 

 the tar, do not come actually into contact with water. For these reasons tar 

 is an excellent preservative for coarse nets for i-ough use, such as trawl nets. 



