40 American Fisheries Society. 



PACTORS WHICH MADE UP THE QUAI.ITY OF LINES, AND METHODS OF 



MEASURING THEM. 



Merely to subject lines to the action of water with no more 

 definite means of testing them than a visual examination after- 

 ward, with perhaps a measurement of breaking strength, would 

 be quite insufficient for the purpose of judging the several ef- 

 fects of preservatives. A cotton or linen line has numerous prop- 

 erties or qualities which make it suitable for fish nets. These 

 properties or qualities must be separately measured as accurately 

 as possible, and any changes in them during exposure to work- 

 ing conditions quantitatively determined. It is therefore neces- 

 sary to resolve the quality of a line into its several factors, and 

 to consider how these may be measured. It was in this field 

 where the greatest difficulty was encountered, as methods of 

 measuring these factors had to be devised, machines invented, 

 made, and tested. 



The factors of importance in the present connection are 

 (1) breaking strength; (2) resistance to mechanical wear or 

 abrasion ; (3) stiffness of the line as affected by the preservative ; 

 (4) shrinkage caused by the application of the preservative; (5) 

 increase in weight caused by the application of a preservative; 

 and (6) color imparted by the preservative. These factors will 

 be discussed separately. Such matters as cost, and labor in ap- 

 plication of the several preservatives, will be considered else- 

 where. 



BREAKING STRENGTH. 



This factor is, of course, the force or pull required to break 

 the sample of line. It is measured on a tensile strength testing 

 machine; the one used for the present work was a "Scott" ma- 

 chine at the U. S. Bureau of Standards, which Bureau cooperated 

 with the Bureau of Fisheries in doing this part of the work. The 

 machine is little more than a pair of fasteners which are at- 

 tached to each end of the sample which is 8 or 10 inches long, 

 and a mechanism for producing a pull which is exerted slowly 

 on the sample by means of an electric motor. As the pull in- 

 creases, a weight is lifted on a pendulous lever until the sample 

 breaks. When the line breaks, the lever with weight is stopped 

 in its position, whereupon a reading is taken which shows the 

 force in pounds required to break the sample. As the jaws pull 



