134 
THEORY OE THE FORMATION 
Ch. V. 
insensibly, we may infer, from what we know of the 
conditions favourable to the growth of coral, that the 
living masses bathed by the surf on the margin of the 
reef, will soon regain the surface. The water, however, 
will encroach little by little on the shore, the island 
becoming lower and smaller, and the space between the 
edge of the reef and the beach proportionally broader. 
A section of the reef and island in this state, after a 
subsidence of several hundred feet, is given by the 
dotted lines : coral-islets are supposed to have been 
formed on the new reef, and a ship is anchored in 
the lagoon-channel. This section is in every respect 
that of an encircling barrier-reef, and is, in fact, 
taken E. and W. through the highest point of the 
encircled island of Bolabola, 1 of which a plan is given 
in Plate I., fig. 5. The same section is more clearly 
shown in the following woodcut (No. G) by the un- 
broken lines. The width of the reef and its slope 
both on the outer and inner side, will have been 
determined by the growing powers of the coral, under 
different conditions, for instance, of the force of the 
breakers and currents to which it has been exposed ; 
and the lagoon-channel will be deeper or shallower, in 
proportion to the growth of the delicately branched 
corals within the reef, and to the accumulation of 
sediment ; relatively, also, to the rate of subsi- 
1 The section has been made from the chart given in the Atlas 
of the Voyage of the Coquille. The scale is ‘57 of an inch to a mile. 
The height of the island, according to M. Lesson, is 4,026 feet. The 
deepest part of the lagoon-channel is 162 feet ; its depth is exag- 
gerated in the woodcut for the sake of clearness. 
