Sect. I. KEELING ATOLL. 25 



the ten previous years. If, during these subterranean 

 disturbances, the atoll did subside, the downward 

 movement must have been very small, as we must con- 

 clude from the fields of dead coral still lipping the 

 surface of the . lagoon, and from the breakers on the 

 western shore not having yet regained the line of their 

 former action. The subsidence must, also, have been 

 preceded by a long period of rest, during which the 

 islets extended to their present size, and the living 

 margin of the reef grew either upwards, or as I believe 

 outwards, to its present distance from the beach. 



Whether this view be correct or not, the above 

 facts are worthy of attention, as showing how severe a 

 struggle is in progress on these low coral-formations 

 between the two nicely balanced powers of land and 

 water. With respect to the future state of Keeling 

 atoll, if left undisturbed, we can see that the islets 

 may still extend in length : but as they cannot resist 

 the surf until it is broken by rolling over a wide space, 

 their increase in breadth must depend on the in- 

 creasing breadth of the reef ; and this must be limited 

 by the steepness of the submarine flanks, which can be 

 added to only by sediment derived from the wear and 

 tear of the coral. From the rapid growth of the coral 

 in the channel cut for the schooner, and from the. 

 several agents at work in producing fine sediment, it 

 might be thought that the lagoon would necessarily 

 become quickly filled up. Some of this sediment, 

 however, is transported into the open sea, as appears 

 from the soundings off the mouth of the lagoon, in- 



