FISH-NET PRESERVATIVES. 31 



the other preservatives failed to bring their respective lines through 

 six months' exposure. 



3. The effects of sea water at Beaufort were more severe than 

 those at Key West, Fla., though temperatures at Beaufort were 

 somewhat lower than those at Key West. 



4. A method of and device for determining the flexibility of lines 

 and changes therein brought about by the application of preserva- 

 tives were devised, tested, and used. A description and discussion of 

 this method and device are given (p. 20). 



5. In diminisliing the flexibility of the cotton lines the tars, pe- 

 troleum residues, and gilsonite had the greatest effect, the copper 

 paints had a large effect, the tanning methods caused some stiffen- 

 mg, and copper oleate had less effect than any other preservative 

 studied. 



6. A machine for determining the abiUty of lines to endure mechan- 

 ical wear or abrasion was devised, tested, and used. A description 

 and discussion of this device are given (p. 25). 



7. In wearing ability the copper paints, which made such a good 

 showing in preserving tensile strength, were at a great disadvantage. 

 The lines treated with these and those treated with quercitron and 

 potassium bichromate wore very poorly; those treated by the Dutch 

 method wore rather better than those treated with copper paints or 

 by quercitron and potassium bichromate ; those treated with tar re- 

 sisted mechanical abrasion well at first, but this quality was lost on 

 exposure along with the disappearing tensile strength. The copper 

 oleates, when applied as preservatives, enabled the lines to resist 

 mechanical abrasion better than any of the preservatives. 



8. All lines, except those treated with copper paint or copper oleate, 

 were fouled by marine growths in four months at Beaufort. The 

 lines treated by the Dutch method, which also contained copper, 

 were slightly fouled. The lines treated by quercitron and potassium 

 bichromate and those treated with a petroleum product were very 

 heavily fouled. Copper oleate and copper paint effectually prevent 

 fouling. 



9. Of the linen lines only those treated with copper oleate or by the 

 Dutch method endured four months' exposure at Beaufort. Of these 

 two copper oleate was more efficacious and much easier to apply. 



10. Linen lines deteriorated in sea water at Beaufort more rapidly 

 than cotton lines, whether preserved or not. 



SERIES EXPOSED IN SEA WATER AT WOODS- HOLE, MASS. 



Beginning June 9 and extending to December 9, 1922, a period of 

 six months, a series of lines preserved with various materials was 

 exposed in sea water at Woods Hole, Mass. 



WATER CONDITIONS AT WOODS HOLE. 



The water conditions at Woods Hole were different from those at 

 either Key West or Beaufort, being cooler. The temperature and 

 specific gravities that prevailed at Woods Hole during the period of 

 test are shown in Table 11. The samples were suspended under the 

 dock at the station of the U. S. Bureau of Fisheries Biological Labor- 

 atory. The water is full sea water, and the samples were subjected 

 to the regular ebb and flow of the tide. 



36199°— 23 3 



