118 CORAL REEFS. 



spongy sort of stone. The greater part of the 

 surface of this mound is quite flat, and near the 

 level of low water. At its edges it commonly slopes 

 gradually down to a depth of two, three, or four 

 fathoms, and then pitches suddenly with a very 

 rapid slope into deep water, twenty, or two hundred 

 fathoms, as the case may be. The surface of the 

 reef when exposed, looks like a great flat of sand- 

 stone, with a few loose slabs lying about, or here 

 and there an accumulation of dead, broken coral 

 branches, or a bank of dazzling white sand. It is, 

 however, chequered with holes and hollows more or 

 less deep, in which small living corals are growing, 

 or has, perhaps, a large portion always covered with 

 two or three feet of water ; and here are fields of 

 corals, either clumps of branching madrepores, or 

 round stools and blocks of meandrina and astraea, 

 both dead and living. 



" Proceeding from this central flat towards the 

 ridge, living corals become more and more abundant ; 

 as we get towards the windward side, we encounter 

 the surf of the breakers long before we can reach 

 the extreme verge of the reef; and among these 

 breakers we see immense blocks, often two or three 

 yards or more in diameter, lying loose upon the 

 reef. If we approach the lee edge of the reef, we 

 find it covered with living corals, commonly mean- 

 drina, astrsea, and madrepore, in about equal abun- 

 dance, all glowing with rich colours, bristling with 

 branches, or studded with great knobs and blocks. 



