20 Notices of Memoirs — C. W. Andretcs — On Christmas Island. 



of the high inland cliff which runs round the greater part of the 

 island, rising like a wall above the tall trees growing on the shore 

 terrace. 



If the coast be examined in a boat or from the top of the sea-cliff, 

 it will be seen that a submarine terrace in the shape of a fringing 

 reef is being formed round the greater part of the island. It varies 

 greatly in width, and also in its depths below the surface ; in some 

 places it is partly dry at low-water, in others some fathoms deep. 

 Outside the edge of this reef the water deepens suddenly. 



The greatest length of the island, from North-East Point to Egeria 

 Point, is about 12 miles. The greatest width from north to south is 

 about 9 miles ; the least 3|^ miles. Its area may be roughly stated 

 at 43 square miles. 



The island consists of a centi'al plateau, highest towards the north 

 and east, and descending to the sea on all sides by a succession 

 of terraces, separated by slopes or cliffs. In most places the 

 arrangement of these, from the edge of the plateau downwards, is — 

 (1) a steep slope strewn with blocks; (2) a broad terrace, followed 

 by a similar slope (this seems to be wanting on the south) ; 



(3) a second terrace, terminating in a cliff 200 or 300 feet high ; 



(4) the shore terrace, sloping gently down to the sea-cliff; (5) the 

 present fringing reef. There are, however, many local differences, 

 the more important of which will be noticed below. 



The Central Plateau. 



The edge of the central plateau is roughly parallel to the coast, 

 Teceding farthest from it opposite the principal headlands. It is 

 highest along its northern and eastern borders, where there is 

 a raised rim, the average height of which above the sea is about 

 800 feet. Towards the south it slopes away so that its edge is 

 only from 400 to 450 feet high, but there are some slight elevations 

 above this general level. On the west the upper terraces ai-e 

 replaced by a gentle slope, and even the first inland cliff is not 

 ■well marked except towards North-West and Egeria Points. 



Along the raised rim of the plateau there are a number of hills, 

 the highest of which (Murray Hill) occurs towards North- West 

 Point. It is a nearly flat-topped hill, divided by an oblique valley 

 into a larger and rather higher western portion and a lower eastern 

 one; the greatest height is about 1,170 feet. The summit is formed 

 by masses of dolomitic limestone, and on its lower slopes there are 

 beds of shelly limestone, and a peculiar deposit which seems to be 

 mainly made up of tiny spherules of altered volcanic glass. The 

 outer face is very steep, but towards the south the land first descends 

 gently, then rises a little, finally sinking to the general level of the 

 plateau in a long gradual slope. On the south-western side there 

 are occasionally patches of rounded pebbles, which are of a volcanic 

 nature, and are, perhaps, derived from the bed above mentioned. 

 Similar nodules occur in many places on the higher parts of 

 the island. 



