RESISTANCE OF MATERIALS TO MARINE BIOLOGICAL ATTACK 1117 



Lucite rod. In another instance, after 2^ years of exposure at Wrights- 

 ville Beach, there was penetration of a siHcone rubber test rod at a 

 shigle point by a pholad. In this case, the test sample was a soHd rod of 

 the elastomer one inch in diameter. Attack occurred on the cross-sec- 

 tional face of the mud end of the rod. Penetration was to a depth of 

 about 4 mm, and the dimensions of the hole at the point of entry were 

 1.5 by 2.0 mm. Although these examples serve to demonstrate the abihty 

 of pholads to bore into these materials, it should be emphasized again 

 that attack has been confined to single points and is not general on these 

 materials. 



The physical relationship of one material to another can be very im- 

 portant as far as borer attack is concerned. A piece of one of the Lucite 

 rods on which jute roving was wrapped for exposure is shown in Fig. 9. 

 The holes in the rod resulting from penetration by pholads are readily 

 apparent. One of the organisms may be seen protruding from the left- 



Fig. 9 — Section of Lucite rod showing penetration by pholads. One of the mol- 

 lusks can be seen protruding from the left-hand side of the rod. Original magni- 

 fication 2X. 



