FISH-NET PRESERVATIVES. 



45 



6. Copper oleate alone did not excel in the preservation of cotton 

 lines in this fresh-water series, apparently because it dissolves in 

 fresh water and is removed from the lines. 



7. On linen lines copper oleate preserved better in this series than 

 did the Dutch method — the reverse of the results on cotton lines. 



OTHER CONSIDERATIONS OF IMPORTANCE IN JUDGING 

 VALUE OF PRESERVATIVES. 



VARYING RATE OF DECOMPOSITION OF LINES IN DIFFERENT 



LOCALITIES. 



It is generally understood that lines decompose more rapidly in 

 some localities than in others and more rapidly in summer than in 

 winter, but no quantitative data on the subject have been published. 

 For purposes of comparison the tensile strength records of the un- 

 treated cotton lines exposed in the several series are given in Figure 

 29. It will be noted that the line lasted over the entire six months' 



o WHITE LINE (UNTREATED) 



2 3 



NUMBER OF MONTHS EXPOSED 



Fig. 29. — Varying rate of dccomposilion of cotton lines in different localities. 



period of exposure to v/cather conditions at Washington, D. C, and 

 over the entu-e period of 4^ months at Key West, Fla. At both 

 Woods Hole, Mass., and Beaufort, N. C, the hues were entirely 

 disintegrated and gone at the end of 4 months, though at the end of 

 4 months the line from Woods Hole showed a tensile strength of 

 about 10 pounds and the one from Beaufort of about 3 pounds. 

 In fresh water at Put in Bay the line showed a tensile strength of 

 but about 2 pounds at the end of 2 months and at the end of 3 months 

 was entirely rotten. The average specific gravity of the water at 

 Kev West for the entire period of exposure was 1.025, at Woods 

 Hole 1.023, at Beaufort 1.019, and at Put in Bay about 1.000. Thus, 

 considered roughly, the rate of deterioration of the exposed lines is 

 directly proportional to the specific gravity (salinity) of the water 

 in which they were exposed. 



There is in all probability a relation also between the temperature 

 of the water and the rate at which a line exposed in it will deteriorate; 

 other factors being held constant the rate of deterioration of a line 

 would no doubt bear an inverse relation to the temperature. The 

 temperature records given for the localities of exposure do not show 

 this relation here. Salinity differences complicate the results, and 

 also, because the exposures were made in different seasons at the 

 different places, the fluctuations in temperatui'es are very unlike. 



