194 CORAL AND ATOLLS 



of them. I have seen the crumbling masses raised into the 

 coral lighter, and boulder after boulder will be rolled in 

 without any one of them showing the minutest portion of new 

 growth attached to it. To the south and west of Pulu Selma 

 there are still large areas that are only occupied by the re- 

 mains of the corals killed in 1876, and the thirty years that have 

 elapsed seem to have accomplished but little repair when the 

 masses are seen raised to the surface. But before this extreme 

 slowness of repopulation may be taken as a fitting criterion 

 for any estimation of the rate of coral growth, the conditions 

 which have prevailed during the interval of thirty years must 

 be reckoned with. In the first place the algse, of which there 

 were many beds on the adjacent areas untouched by the foul 

 water, have, by reason of their more rapid groAvth and greater 

 hardihood, taken possession of a very large part of the area 

 that suffered the damage. Before the more delicate and 

 slower growing corals could recover their activity, and re- 

 colonise their ground, the algse had invaded it ; and as we 

 have seen, the advent of abundant growth of algse terminates 

 all activity in the coral colonies. When once the seaweeds 

 had fairly settled on the spot, the invariable accompaniment 

 of their growth took place, and sediment began to accumulate 

 in the beds which they had formed. This fact is clearly seen 

 wherever algse are settled — that the lagoon begins to shoal 

 with increased rapidity ; algse in the lagoon play very much 

 the part of the grass on the shore flats, for they enmesh 

 the drift sand and hold it fast. The environment there- 

 fore becomes one of rapid silting, and no environment is more 

 inimical to coral growth. It is, therefore, not alone by reason of 

 the slow growth of the coral that this area has not become 

 repopulated with coral colonies ; for the time that has elapsed 

 since the destruction is ample for very advanced growth to 

 have taken place. 



All over the whole of the southern shallow portion of the 

 lagoon are deeper holes, which show plainly as darker patches 

 in the clear water : and a fair general picture of this part 

 of the lagoon is that of a wide stretch of white sand, wath 



