270 



Christmas Island. 



atoll, and to this objection no answer is possible, but since it can be 

 shoTvn that at one time it must have consisted of reefs and islands 

 approximating very nearly to tbose seen in atolls which are regarded 

 as typical, the determination of the nature of the foundations upon 

 which those reefs and islands rested is at least a step in the right 

 direction. From the account that follows, it will be scon that 

 in this case the basis of the island is almost certainly a volcanic 



Fig. 1. — Forest on the Plateau. 



peak the foot of which is now some 2,400 fathoms below the level 

 of the sea, and that on its summit and flanks great accumulations 

 of Tertiary limestones have been deposited, and in some cases are 

 interstratified with the products of the eruptions, probably for the 

 most part submarine, which took place from time to time. The 

 oldest of the volcanic rocks are trachytic, the newer basaltic. The 



