RESISTANCE OF MATERIALS TO MARINE BIOLOGICAL ATTACK 1121 



ally close contact. The radial extent of this sulfiding in the bottom end 

 of the rod which was embedded in the sediment, as compared to the top 

 or water end, is shown in Fig. 14. It must be emphasized that there has 

 been no indication to date of any adverse effect on the physical properties 

 of plastics which have been sulfided in this way. 



VI. CABLE SAMPLES FROM SERVICE 



The samples of submarine cables which have been examined to the 

 present time represent both telegraph and telephone cables. The samples 

 of telegraph cable have been obtained through the cooperation of the 

 Western Union Telegraph Company. It takes considerable time to as- 

 semble a large number of specimens during the course of routine repair 

 operations. As a result, although some 22 different samples, the majority 

 from the North Atlantic, have been examined, it is possible to make only 



Fig. 13 — Sulfiding of Poly(Viu3'l Cliloricle) plastic test rod beneath barnacles. 

 The black, circular border and center area represent sulfiding at points of excep- 

 tionally close contHct. Original magnification 2X. Photo bj^ J. B. DeCoste. 



