MARINE WORMS. 347 



teak, 1 Billian or North Borneo ironwood, 2 and cypress pine, 8 

 appear to hold the first place as regards the power of resisting 

 in their natural state the attacks of marine worms. The two 

 latter are referred to as unassailable, while the two first 

 appear, up to a comparatively recent date, to have been 

 considered almost, if not quite, indestructible, although not by 

 any means impenetrable. 



In cold northern waters, this is probably practically correct ; 

 but in tropical or semi-tropical latitudes, experience shows 

 that they are not either unassailable or indestructible. Experi- 

 ments carried out in Malta Harbour, extending over some time, 

 show that greenheart and teak are not invulnerable, but the 

 damage inflicted by the Chelura is of course small compared with 

 that sustained by softer woods immersed in the same water. 



The following, taken from a paper read before the South 

 African Philosophical Society by Mr. E. H. Hammersly Heenan, 

 M.I.C.E., refers to the activity of the marine worm, and the 

 durability of greenheart in South African waters. 



"In 1878, two jetties were erected for the Port Elizabeth 

 Harbour Commissioners, from the designs of Sir I. Coode, 

 V.-P.I.C.E. For the most part iron was used, but it was 

 decided that the seaward ends should be of greenheart, and 

 with this material the work was carried out. 



"An inspection of the jetty made a few years after revealed 

 what at first appeared to be signs of decay in one of the hori- 

 zontal timbers. On cutting into it with an adze, it was found 

 to be completely honeycombed for about one inch in depth with 

 the tunnels of the Teredo. On further examination, it was found 

 that all the horizontal timbers at low water had been attacked 

 in the same way. 



" In the vertical pieces and piles, it was noticed that though 

 the worm had entered them, its progress was small as compared 

 with the horizontal pieces. 



" The timber frame placed as a fender outside the iron 

 portion of the jetty, was also attacked by the Chelura in vast 

 numbers, which had commenced work at the ends of the 

 timbers, or where one piece came in contact with another." 



Rot in Timber. 4 Under the influence of air and moisture, 



1 Stevenson's " Bell Rock Lighthouse." 



1 M.P.T.C.K, vol. ciii. p. 338. 3 Ibid., p. 341. 



Ibid., vol. xli. p. 263. 





