Taylor and Wells. — Preservation of Nets and Lines. 51 



tial rise that it is excellent. The differences are not, however, 

 of great value in themselves. The important thing is to observe 

 how much deterioration takes place on long exposure. 



3. The toxic or biological action of the preservative used. 

 If a line on treatment, drops in tensile strength from 40 to 35 

 pounds, and holds the 35 pounds six months, it is still in good 

 condition ; but if it increases at once in strength to 45 pounds 

 and begins to lose its great strength in 60 days through the 

 detrimental action of microorganisms, it may be totally worthless 

 in 6 months. Furthermore, the increase in strength caused by 

 heavy-body preservatives is always associated with a corres- 

 pondingly great increase in stiffness and wiriness, as will be seen 

 later. This marked loss does, in fact, occur in the tars, for after 

 the volatile or soluble creosote is gone, the lines rapidly deterior- 

 ate. It is thus plainly to be seen that the principal detrimental 

 agency is decomposition, and therefore the most important func- 

 tion of the preservative is to prevent this by means of a toxic 

 ingredient that is insoluble in water and non-volatile in air. 



It is at this point that criticism can be made of the English, 

 Norwegian, and Dutch experiments, in which the experiments 

 extended over only a short time, usually two months. Some of 

 Bull's experiments covered eleven weeks. It will be seen from 

 the graphs and figures presented herewith that the real differ- 

 ences do not come out very strikingly until three or four months 

 of exposure, and six months are necessary to get a good test. 



RESISTANCE TO MECHANICAL WEAR OR ABRASION. 



It is impossible to say definitely what are the greatest 

 enemies of lines. Breakage by pull against snags, and by the 

 struggles of large fish, are important, of course ; bacterial decom- 

 position appears to be very important. Mechanical wear or 

 abrasion caused by dragging the seines or lines over the gun- 

 wales of boats, or by the rubbing of the lines against each other 

 in handling them, is no doubt also very important. Diminish- 

 ing ability to withstand mechanical wear is, like tensile strength, 

 an indicator of the general quality of the line, and if it can be 

 rated quantitatively will give not only some measure of the 

 general condition of any particular sample, but by imitating the 

 wear that it is subjected to in actual use, will give a measure 

 of this particular factor — ability to withstand abrasion. 



