22 Notices of Memoirs — C. W. Andrews — On Christmas Island. 



of rather fresh-looking corals. In a few places similar limestones 

 form extensive reefs, cut up into deep channels and holes. These 

 reefs, when covered with, thick bush, form almost impenetrable 

 obstacles. 



The Upper Slopes and Terraces. 



As already mentioned, there is beneath the edge of the plateau 

 a steep slope usually covered with talus, but where the rocks 

 cornjDosing it are exposed they are found to consist of foraminiferal 

 and coral limestones, and are often full of angular fragments of 

 older limestones. Beneath this slope is a level terrace varying in 

 width from a few yards to a quarter of a mile or more, and bounded 

 on the seaward side by a second steep declivity, or in places by an 

 actual cliff. The rocks comprising it visually show very distinct 

 traces of coral, and sometimes seem to be entirely composed of it. 

 This slope is absent on the southern side of the island. 



The next terrace also varies considerably in width; on its outer 

 margin there is usually a broad belt of pinnacles of limestone 

 separated by channels. In the neighbourhood of Steep Point, it 

 rises into a rounded hill covered with blocks of phosphate of lime. 

 This hill must have formed a small islet at the time the foot of the 

 second inland cliff was washed by the sea. In other places there is 

 a channel 40 or 50 yards wide running parallel to the edge of the 

 cliff; the inner side is formed by a cliff 30 or 40 feet high, the outer 

 by walls and pinnacles separated by branching channels, the floor of 

 which, like that of the main channel, is perfectly level. Towards 

 the sea there is a steep slope covered with blocks of limestone. 

 When the sea was 350 to 400 feet higher than at present, this 

 channel formed a sort of canal in the reef parallel to the coast. 



Beneath the terrace just described comes the first inland cliff, 

 by far the most conspicuous feature of the island. Usually it has 

 a vertical, or nearly vertical, face, and it is especially well-marked 

 at the headlands. Its summit is from 250 to 300 feet above the sea. 

 In several places about 150 feet above the shore platform there are 

 distinct traces of wave action, the most notable being the presence 

 of caves along this line. In some cases beneath this point, instead 

 of a vertical face, we find a steep slope of limestone with coral in 

 position of growth, apparently the remains of a narrow fringing 

 reef, founded upon and partly composed of talus. That the 

 elevation of this cliff has been of an intermittent character is further 

 shown by the fact that where the slopes of the island are gentle and 

 no high cliff has been formed, there is either a succession of minor 

 cliffs separated by terraces and partly built up of coral rock, or 

 merely a slope with ledges of coral limestone. Although these 

 minor cliffs and ledges may be continuous for some distance in any 

 given locality, they do not always correspond to those found a few 

 miles off. It must also be noted that the geological structure and 

 even the origin of this cliff are not everywhere the same, a point that 

 will be referred to more fully below. 



The shore terrace slopes gently down from the foot of the first 



