298 Christmas Island. 



since upon its summit shallow- water deposits of Eocene age occur, 

 the depth of the floor of the ocean in the neighhourhood can have 

 undergone little alteration since the Eocene times, unless, indeed, 

 it has been lowered equally round the foot of the mountain by 

 a system of cross faults. This Tolcano, like those of Java and 

 Sumatra, etc., probably owes its origin to the movements along the 

 line of the great fault forming the south boundary of the Malayan 

 area in pre-Eocene times. Some post-Eocene movements probably 

 caused the eruptions, the products of which form the base of the 

 Miocene both in Christmas Island and Java, and may have resulted 

 in the deepening of the abyss between the two areas. Movements 

 are still in progress, as the eruptions of the Malayan islands show, 

 and in Christmas Island also two slight earthquakes have been 

 recorded by Mr. A. Clunies Ross within the last few years : the 

 last of these, on October 20th, 1895, was sufficiently severe to 

 loosen great masses of rock from the cliff. This seems to have been 

 felt in the Cocos-Keeling Islands also, a point of some interest, 

 since these islands almost certainly rest on a volcanic peak which 

 may owe its origin to the same causes as that of Christmas Island. 



In the foregoing pages I have frequently spoken of the elevation 

 and depression of the island. This is, of course, merely elevation 

 and depression in reference to the sea-level, and it would probably 

 have been better to have employed the terms suggested by Suess, 

 namely, " negative and positive movements of the shore-line," 

 since in some cases, at least, particularly in the formation of the 

 later cliffs, it seems very probable that it is the general level of 

 the surface of the sea that has been altered, and not merely a local 

 upheaval of a limited land-area that has taken place. 



The above description of the geology of Christmas Island must 

 be regarded merely as a first essay, for owing to the fact that 

 the age of many of the limestones could not be recognized by 

 me on the spot, and to other difficulties referred to above, much 

 remains to be done, and in the light of my present knowledge, 

 both of the localities and of the rocks, if it were possible to revisit 

 the island for even a few days, many questions could be definitely 

 settled which during my former visit puzzled me greatly, after 

 repeated examination. One point of special interest may be 

 referred to, namely, the possibility of finding still earlier, perhaps 

 Cretaceous, limestones beneath the Eocene (or Oligocene) limestone 

 in Sidney's Dale on the west coast. 



