Inasmuch as a majority of these tropical v/ocds showed no effect, or only- 

 slight evidence of marine borer activity, at 12 months, it apT^ears that 

 this period is too short to permit of a reasonable evaluation of their 

 resistance. At 21; months, on the other hand, species that had deteriorated 

 at quite different rates v;ere no longer distinguishable from one another. 



Consequently, it is suggested that the results of the l6-raonth inspection 

 are most suitable for the purpose of rating the resist nee of individual 

 species in these tests. It is not proposed to attempt to estimate service 

 life of piling or trnbers of structural sizes from these results on small 

 specimens. However, it should be pointed out that Angelique (see Table 2) 

 has an established reputation for long life in marine structures in French 

 Guiana, France, and the Panama Canal. Little pholad and no si'-nificant 

 Teredo damage had occurred after 1$ years of service in marine borer infested 

 waters at Balboa, Canal Zone. 



Interpretation of results shovra in Table 2 for Escivre ilera sp. is assisted 

 by the knowledge that ivianbarklak ( Eschweilera longipe s) and the closely 

 related species, E. subglandulo sa and E. corrugata, are xvidely recognized 

 for their high resistance to marine borers. Manbarklak piles have been 

 reported perfectly sound after 17 years in brackish waters in the Saramacca 

 Canal, Surinam. This species also established the best record of a con- 

 siderable number of species after l5 years of service in an experimental 

 installation at Balboa, Canal Zone. An agency of the Netherlands govern- 

 ment has reported piles of lianbarklak to be still sound after 7$ years' 

 service in the harbor at Nieuvrediep, Holland. 



Edmondson, on the basis of similar specimens, has stated, "a Virood that 

 stands up VTell in Honolulu Harbor, which is a severe testing ground, for 

 one or more years rates honorable mention." (U). Several of the species 

 included in this category in his report are also shown here in a favorable 

 lif^ht either directly or by analogy with closely related species. Among 

 these are Ocotea rubra , Sschyjeilera Sagotiana , Eschweilera blanchetiana , 

 Eschweilera tenax, and Lecythis usitata. 



Best performance among the 2$ tropical woods under test at Harbor Island, 

 Korth Carolina, based upon the results of l6 months' exposure, is shown 

 by the following: 



Acapu ( Vouacapoua americana ) 



ivlorrao (. Eschvreilera blanchetiana ) 



Sapucaia (. Lecythis i^isitata ) 



Angelique ( Dicorynia paraensis ) 



Determa ( Ocotea rubral 



Coco de i'iono ( Escfeveilera tenax ) 



Cumaru Preto ( Taralea sp.) 



Black Kakeralli ( Eschweilera Sagotiana ) 



Natural marine borer resistance of vrood has been ascribed commonly to its 

 silica content. The woods of this study have been analyzed for total ash 

 and silica content in three separate series of tests conducted at the 



T - 8 



