64 U. S. BUREAU OF FISHERIES. 



shrinkage, resistance to wear, and flexibility, and by multiplying each 

 by a factor, that, in the case of white line, brings each figure to 100 

 we attach the same weight to the factors, and at the same time 

 refer ail samples to the one standard of excellence for fishing purposes, 

 the new white line. The ideal preservative is that one that most 

 closely keeps its twine like new white line for the longest time, and 

 our composite score by its magnitude indicates the relative ability 

 of the preservatives so to keep the lines. It was not practicable to 

 include in the score resistance to fouling, because exact numerical 

 expression for this factor was lacking. Allowance for it would raise 

 the values for copper oleate and copper paint alike with respect to all 

 the others, for only these two preservatives prevented fouling. 



The new untreated, unexposed cotton line, No. 24, cable-laid, hard- 

 finish, scored in the way described 300, or 100 for each of the three 

 different factors, derived as follows: 



Let 



T=tensile strength in pounds of sample. 



■JT^=weight in pounds per 100 feet. 



T 

 — =brealdns: length in hundreds of feet. 



;S'j=original length, in hundreds of feet, of sample before treating. 

 <S2=length, in hundreds of feet, of sample after treating. 



o m 



-^^Xi;^= breaking length, in hundreds of feet, of sample after treating. 



i^=flexibility=number of swings of pendulum. 

 ^l=number of strokes on wearing machine. 

 For white line: 



^ ==i^i=the factor that brings the shrunken breaking length of 



^X— white line to a value of 100. This white-line factor is 



5i W used in bringing the shrunken breaking length of treated 



line to a common standard. 



-p-=i^2= factor that brings the flexibility of untreated white line 

 to a value of 100. This white-line factor is used for the 

 treated line. 



— J- = i<'3= factor that brings the wearing ability of white line to a 

 ^ value of 100. 



Then, the full score of any sample is the sum of the three separate scores, shrunken 

 breaking length, flexibility, and wearing ability, 



In Table 25 are given the numerical values of the scores of all lines 

 in the Beaufort and Woods Hole series. The same data are pre- 

 sented in graphic form for the several preservatives in Figure 34. 

 It is seen that treatment by any preservative whatsoever causes a 

 reduction in the score. 



