Sect. I. THE GROWTH OF CORAL-REEFS. 
91 
between the great branching corals of the Red Sea and 
those on the reefs of the Maldiva atolls. 
These facts, which in themselves are deserving of 
notice, bear, perhaps, not very remotely on a remarkable 
circumstance which has been pointed out to me by 
Captain Moresby, namely, that with very few excep- 
tions, none of the coral-knolls within the lagoons of Peros 
Banhos, Diego Garcia, and the Great Cliagos Bank (all 
situated in the Cliagos group), rise to the surface of the 
water; whereas, with equally few exceptions, all those 
within Solomon and Egmont atolls in the same group, 
and likewise those within the large southern Maldiva 
atolls, reach the surface. I make these statements, after 
having examined the charts of each atoll. In the lagoon 
of Peros Banhos, which is nearly twenty miles across, 
there is only one single reef which rises to the surface: 
in Diego Garcia there are seven, but several of these lie 
close to the margin of the lagoon, and need scarcely 
have been reckoned : in the Great Cliagos Bank there is 
not one. On the other hand, in the lagoons of some of 
the great southern Maldiva atolls, although thickly 
studded with reefs, every one without exception rises to 
the surface ; and on an average there are less than tw T o 
submerged reefs in each atoll : in the northern atolls, 
however, the submerged lagoon-reefs are not quite so 
rare. The submerged reefs in the Cliagos atolls gene- 
rally have from one to seven fathoms water on them, but 
some have from seven to ten. Most of them are small 
with very steep sides ; 1 at Peros Banhos they rise from 
1 Some of tliese statements were not communicated to me verb- 
