6 Christmas Island — The Sea CUff. 



the greater part of the surface of the reef is covered -svith water 

 less than a foot deep, though there are a few holes of greater 

 depth. In some places there are clumps of a small branching 

 madrepore of considerable extent, the tops of which are exposed 

 for nearly a foot for some time at low-water. Except for these 

 there are only a few small corals in the deeper pools, and the chief 

 inhabitants of this part of the reef are holothuria and small 

 echinoids, which live in holes in the rock. The outer rim is raised 

 from a foot to eighteen inches above the surface of the water of the 

 lagoon. It consists mainly of flat blocks of coral overgrown and 

 cemented together by a thick coating of bright red nullipores, and 

 is cleft by numerous deep fissures and channels, through which the 

 water thrown over it escapes ; it is on the sides of these fissures 

 that the corals seem to flourish best. The reef flat at the northern 

 end of the cove is of much the same character. 



Standing on the nullipore-covered edge of this upper reef, the 

 outer lower reef can be seen through the one or two fathoms of 

 clear water that cover it. Its furfacc is studded with masses 

 of various species of corals, separated by areas of coral sand. As 

 above mentioned, this reef slopes away gently to about 20 fathoms, 

 beyond which the water deepens suddenly. At the southern end 

 of the bay it is interrupted, and at Smith Point no bottom was 

 found with 30 fathoms close to the cliffs. 



A little south of the middle of the cove the reefs are interrupted 

 by a boat-channel forty to fifty yards wide, which runs up to the 

 beach. Its bottom slopes gently down to four or five fathoms, and 

 is composed of coral shingle ; beyond this patches of coral appear, 

 and it passes into the general surface of the lower reef. 



Except at West White Beach and a few small bays with beaches 

 on the east coast, Flying Fish Cove is the only place where any 

 part of the fringing reef is dry at low-water. Round the greater 

 part of the island the foot of the cliff is washed by the sea at all 

 times of the tide, and the fringing reef, if present at all, is from 

 a yard to three or four fathoms below the surface, even at ebb-tide. 

 Here it seems to consist, on its landward side, of a platform formed 

 by the cutting back of the cliff by the sea, while on the seaward 

 portion coral is luxuriant, and is, no doubt, growing outward on 

 the talus resulting from the denudation of the coast. 



The Sea Cliff and Beaches. (Fig. 3.) 



Nearly the whole of the coastline is formed by limestone cliffs, 

 varying in height from about 15 to 150 feet or more. The latter 

 height only occurs at Steep Point, in consequence of certain 

 movements which will be described elsewhere ; in other places tht^ 

 height seldom exceeds 50 feet. The cliffs are nearly everywhere 

 much undercut, and sometimes overhang to the extent of 30 feet 

 or more. There are numerous caves, and occasionally these have 

 openings on the shore terrace at some distance from the sea. 



