104 



installed for a number of j-ears on a pier at Long Beach, Calif. Tlie piles there were 

 attacked by Limnorki in scattered spots within a few months. This has been verified 

 by inspection made during the period of this Committee's activity, which also disclosed 

 the fact that a number of the piles upon which the device had been installed were 

 piles which had already been effecti\ely protected from borer attack by creosote 

 treatment. The effectiveness of this scheme is still improved in water where borer 

 action is known to be severe. The minuteness of the crevices capable of sheltering the 

 almost microscopic borer larvae from any impact from such a device, the relati\-ely 

 long time between tidal passages when any given elevation is not effectively covered 

 by such a device, and the utter inadequacy of chain festoons, or any other pendant 

 de\'ice rising and falling with the tide, to protect the submerged portion of the pile, 

 especially that near mud line, where the most severe entrance attack of shipworms 

 occurs, seem on the basis of present knowledge to militate against the success of 

 these de\'ices. Moreover, on the Long Beach pier where they have been longest 

 installed, mechanical wear due to the block ring is materially reducing the effective 

 diameter of the piles between tide levels. 



ELECTROLYSIS 



Electrolysis of the water around the pile, liberating chlorine, which is supposed to 

 kill the teredos in the pile, has been actively promoted for some years but no record of 

 any commercial installation of the scheme has come to the attention of the Committee. 

 Tests conducted by this Committee and described in the chapter on Chemical Research 

 of this report show, briefly, that chlorine in free sea water maintained for seventy-two 

 hours at a concentration so high as to render the breathing of the air around it difficult, 

 caused no more injury to teredos in infested wood than to suspend their feeding 

 activity while the concentration was maintained. In actual application, moreover, the 

 tidal currents would carry the chlorine away and prevent the borers being subjected 

 to its effects to any great extent. Constant repetition of the treatment would in any 

 case be required to take care of the hordes of larvae arriving with every tide. 



DYNAMITING 



Dynamiting in the water around the piles has been tried as a means of killing the 

 borers. A concussion of this kind in water will kill animal life only in its immediate 

 vicinit\-. In any case, constant repetition would be as necessary as in the case of 



electrolysis. 



CREOSOTED WOODEN PILING 



Notwithstanding the countless efforts of the past to evolve protections for timber 

 piling, none has thus far been developed to give better general ser\ice than the creosot- 

 ing process — meaning by better service a longer length of life in relation to cost. The 

 creosote process has been successful not only because of the toxic properties of the 

 oil but because of the method of application. The creosote virtually transforms the 

 exposed timber into a material which for a considerable time repels the borers. The 

 protecting shell is an integral part of the pile, homogeneous with it; no plane of separa- 

 tion exists between it and the untreated interior wood, as in the case of protecting 

 armors attached to a pile surface. Therefore none of the normal influences acting on 

 the pile can cause the protecting shell to be forced off or to fall away; where flexibility 

 is required, the shell will act with other portions of the pile and no rupture should 

 develop as in the case of piles built up of heterogeneous parts. 



The greatest difficulty- in the use of the average surface armor is that of keeping 



