FISH-NET PRESERVATIVES. 9 



Z The lines are first treated with a 15 per cent sohition of copper oleate in gaso- 

 line, allowed to dry and then dipped into a solution of coal tar and benzol, 

 50 per cent each. The lines are then dried as in the case of coal tar (F). 



A A . . . .Copper oleate — 15 per cent concentration in gasoline. Applied same as B. 



LINEN LINES. 



T Untreated, 10-ply 40, Irish flax salmon thread, used as a control. 



U Copper oleate— 12^ per cent concentration in gasoline. This is the same 



preservative as was described under P for cotton line and is applied the 



same as P. 

 V Quercitron and potassium bichromate. This is the same method as was 



described under I for cotton thread. 

 W Dutch method. This is the same method as was described under L for cotton 



line. 

 BB . . . -Petroleum product No. 2. This is the same product as was described under 



X for cotton line and is applied same as X. 

 CO Copper oleate — 15 per cent concentration in gasoline. This is the same 



solution as was described under AA for cotton line and is applied the same 



as the other copper oleate solutions; that is, by dipping the twine into the 



solution and then spreading out to dry. 



METHOD OF TAKING SAMPLES. 



In order that the same amount of line might be used for each 

 sample, and that shrinkage might be measured, it was necessary to 

 measure the samples under constant tension. To measure a line, 

 one end of the line was made fast at one end of a long hall. The line 

 was then paid out for about 100 feet, passed over a small pulley, and 

 made fast to a 2-kg. weight. The line thus stretched out horizontally 

 under a 2-kg. tension was measured ^\dth a steel tape. Trials showed 

 that these measurements could be repeated to within 4 inches for 

 100-foot lengths. After the samples were treated with the several 

 preservatives they were again measured in the same way as before, 

 and the shrinkage was noted. The figures for shrinkage from all 

 series of experiments will be considered together later (p. 50) . 



The accurately measured samples were weighed on the analytical 

 balance before and after treatment by the preservatives and the 

 gain in weight recorded. These gains will also be considered together 

 after the several series of experiments have been considered (p. 46). 

 Where the weight per unit length of any particular sample dis- 

 agreed markedly from the others it was discarded as of over or under 

 size. No doubt the figures contained in this paper show some dis- 

 crepancies or variations that are due to differences in the line itself, 

 but errors of tliis kind are reduced to a minimum by obtaining the 

 average of results from numerous tests. 



Because of the length of samples needed it was impossible to 

 measure them in a room of constant air conditions. After trials with 

 oven-dried samples for weighing it was found best to weigh in the 

 air-dry condition. 



SERIES EXPOSED TO WEATHER CONDITIONS AT WASHINGTON, D. C. 



MATERIALS TESTED. 



Cotton lines were prepared by each of 1 1 different preservatives 

 and preservative methods, namely, copper oleate in tour different 

 concentrations or combinations, B, C, D, and E; coal tar, F; pine tar, 

 G; the two tars in equal parts, H; quercitron and potassium bichro- 



