40 



LORD HOWE ISLA.ND. 



form. It would have taken up far too mucK of our time to Lave attempted 

 to kill these when expanded, without which spirit specimens are of very- 

 little value. 



The Fringing roof itself forms " a simple broad platform, as an extension 

 apparently of the dry land," at both its northern and southern ends where it 

 impinges on the shore at North Bay, and under Mount Ledgbird respectively. 

 There are no less than five channels communicating between the Lagoon and 

 the open sea. Two of these channels are navigable, the northernmost giving 

 five fathoms, and that at the south end seven fathoms. Inside the Lagoon the 

 depth varies from a sixth up to two and a quarter fathoms ; but there are 

 here and there holes, yielding much deeper water. Immediately outside the 

 sea face, the depth varies from one and three quarters fathoms to five 

 fathoms, rapidly descending to fifteen, twenty, and twenty-five fathoms 

 within a comparatively short distance of the reef. The latter at its greatest 

 distance from the shore is about two-thirds of a mile. The seaward edge is 

 but little broken up ; but the Lagoon margin is much more sinuous. The 

 reef varies in width from less than a cable up to four and six cables. The 

 longest section between any two channels penetrating it is over a mile in 

 length. The beach immediately contiguous to the shore ends of the reef is 

 composed of large coral blocks intermingled with others of basalt, and piled 

 up into a regular terrace, extending to a height of from fifteen to twenty 

 feet above high-water mark. This terrace graduates outwards from the 

 shore forming the central ridge of the reef built up of dead coral blocks, 

 and is always bare at from half to three-quarter ebb. Around this central 

 portion is a lower shelf or platform, composed chiefly of dead coral in 

 situ, and always more or less a-wash at low tide. Its surface is furrowed 

 with narrow water channels and excavated into deep pools containing 

 great abundance of life, and many fine living examples of Goslaria dadasUa, 

 E. & S. ?, and Tublpora. The blocks generally are profusely covered 

 with Nullipores. The appearance of the inner portions of the Lord 

 Howe Island reef corresponds well with Dana's description of the shore 



of the Paumotus Islands. He says, ' 



low tide ; there are places where it is 



of water : and the elevated 



;e an embankment preventing 



'Much of it is 

 always covered 

 edge, the only 

 the water from 



jjlatforms of some 

 commonly bare at 

 with a few inches or a foot 

 part exposed, often seems 

 running off."* 



The seas which break over the Lord Howe reef during gales from the 

 westward are very heavy, and simply as a display of nature, remarkably 

 grand. The destruction, however, caused by them does not seem to be 

 particularly heavy, which is perhaps accounted for by the very gradual in- 

 crease in the soundings outside. The two southernmost channels through 

 the reef are opposite the mouths of partially dry freshwater creeks. Doubt- 

 less at times a good deal of floodwater traverses these, but it can hardly be 

 of sufficient continuance or volume to gradually influence these openings. 

 In some well-known fringing reefs the channels are opposite main valleys, 

 and it is supp)osed that the growth of the coral polyp is influenced by the 

 sediment discharged from them. This can scarcely bo so at Lord Howe 

 for the reason given above, the discharge from these creeks being more of 

 the nature of torrent freshets than continuous streams constantly conveying 

 the products of slow denudation to interfere with the healthy existence of 

 the coral polypes. 



* Corals and Coral Islands, 1872 (Engl. Edit.) p. 176. 



