16 



U. S. BUREAU OF FISHEEIES. 



diminution in strength after treatment was apparently due to the 

 lubricating effect. The variations of copper oleate showed no con- 

 siderable differences between themselves. 



5. Coal tar, pine tar, and the mixture of the two preserved the 

 tensile strength unimpaired for four and one-half months. 



6. The tars also increased the tensile strength by sticking the fibers 

 of the twine together. 



7. No growth of marine plants or animals was attached to any of 

 the lines at Key West. 



SERIES EXPOSED IN SEA WATER AT BEAUFORT, N. C. 



The exposures were made in the water of Beaufort harbor, at the 

 wharf of the U. S. Fisheries Biological Laboratory, from February 

 15 to August 15, 1922. 



WATER CONDITIONS AT BEAUFORT. 



The water temperature and salinity for the six months are given in 

 Table 6. Here both salinity and temperature vary more than thev 

 do at Key West, the water being at times considerably diluted with 

 fresh water. There is abundant growth of barnacles, hydroids, ascid- 

 ians, sea anemones, and other attached marine growths. 



Table 6. — Water conditions at Beaufort, N. C. 



TESTS WITH COTTON LINES. 



The lines to be exposed were measured and weighed by the meth- 

 ods already described (p. 9). After treatment they were again 

 measured and weighed and differences noted, as shrinkage and 

 increase of weight, respectively. These factors will be considered 

 later. In this series of experiments two new tests were introduced, 

 namely, tests of flexibility and of wearing quality, as influenced by 

 the preservatives. These factors will be discussed in connection 

 with the data obtained concerning them. 



MATERIALS TESTED. 



The cotton twine used here was, as before, No. 24 cable-laid, 

 hard-finish cotton, in individual samples, each 100 feet long. 



The preservatives and preservative methods were as follows: 

 Coal, pine, and mixed tar, F, G, and H, as in the previous experi- 

 ments; quercitron and potassium bichromate, I; petroleum, product 



