Sect. IT. 
RATE OF GROWTH. 
101 
islets are known to be formed, we may feel confident 
that the reef was not three miles wide when the first, 
or most inward ridge, was thrown up ; and, there- 
fore, we must conclude that the reef has grown out- 
wards during the accumulation of the successive ridges. 
Here then, a wall of coral-rock of very considerable 
breadth has been formed by the outw r ard growth of 
the living margin, within a period, during which 
ridges of shells and corals, lying on the bare surface, 
have not decayed. There can be little doubt, from the 
account given by Captain Beechey, that Matilda atoll in 
the Low Archipelago has been converted in the space 
of thirty-four years, from being, as described by the 
crew of a wrecked whaling vessel, a ‘reef of rocks,’ 
into a lagoon-island fourteen miles in length, with 
‘ one of its sides covered nearly the whole way with 
high trees .’ 1 The islets, also, on Keeling atoll, it has 
been shown, have increased in length, and since the 
construction of an old chart, several of them have 
become united into one long islet : but in this case, 
and in that of Matilda atoll, we have no proof that 
the foundation of the islets, namely the reef, has 
increased in breadth, although it must be allowed that 
this is probable. 
I think, therefore, in regard to the possible rate of 
outward growth of coral-reefs, but little importance 
need be attached to the fact that certain reefs in the 
Red Sea have not increased during a long interval of 
time, or to other similar cases, such as that of Ouluthy 
1 Beechey ’s Voyage to the Pacific, ch. vii and viii. 
