PRESERVATION OF FISH NETS 417 



Harbor. In this case there was only a very shght decrease in tensile 

 strength of any of the samples, even the untreated line lasting for 

 six months with very little decrease in strength. These results 

 indicate that twine undergoes a much more rapid disintegration when 

 continuously submerged in water than it does when periodically 

 submerged. 



SUMMARY OF RESULTS AT BOOTHBAY HARBOR 



1. Duplicate sets of test lines were used, one of which was sus- 

 pended in such a manner as to be continuously submerged in water, 

 the other being suspended so as to be submerged only at high tide. 



2. The periodically submerged samples showed very little deteriora- 

 tion over the six-month period of exposure. 



3. Sample lines subjected to continuous submersion deteriorated 

 much more rapidly than those submerged periodically. 



4. Copper oleate, coal tar, and the copper oleate-coal tar mixture 

 preserved well at Boothbay Harbor. 



5. Action of the water at Boothbay Harbor, Me., was much less 

 severe than at Beaufort, N. C, untreated lines at the former location 

 lasting twice as long as at the latter. 



SERIES EXPOSED IN SEA WATER AT ASTORIA, OREG. 



A series of lines, including cotton, linen, and hemp samples treated 

 with the various materials, was exposed in sea water at the mouth of 

 the Columbia River near Astoria, Oreg., from July 6, 1923, to Janu- 

 ary6, 1924. 



WATER CONDITIONS AT ASTORIA 



Records of the average monthly temperature and salinity of the 

 water at this point are not available. It is known, however, that the 

 temperature during the period of the test varied from about 65° or 

 70° F. during the summer months to about 40° or 45° F. during the 

 winter months. The salinity of the water at this point also varies 

 over a wide range. At very high tide the water reaches a salinity 

 equal to that of full sea water, while at other times, when immense 

 quantities of water come down from inland, it contains scarcely any 

 salt. 



TESTS WITH COTTON LINES 



Materials tested. — The twine used for this series of tests was of the 

 same lot as that described in the preceding experiments — No. 24, 

 cable-laid, hard-finish cotton. The preservatives and preservative 

 methods tested were copper oleate in four variations (EE, FF, GG, 

 and HH), quercitron, followed by ammoniacal cojDper sulphate (L), a 

 proprietary waterproofing (JJ), coal tar (KK), a copper oleate-coal 

 tar mixture (Y), and the untreated cotton line (A) as a control. The 

 lines were measured, weighed, treated with a preservative, and again 

 measured and weighed, as previously described. 



Tensile strength. — The results of tensile-strength measurements are 

 shown graphically in Figure 4. The action of the water on lines 

 exposed at this point was very severe. The untreated line (A), that 

 treated with the quercitron-ammoniacal copper sulphate method (L), 

 and the one treated with the proprietary waterproofing (JJ) were 



