188 On Coral Reefs and Islands. 
gradual subsiding of the land upon which it stands. ‘The large 
number of instances of distant barriers in the Pacific remove any 
doubt with regard to these conclusions. 'The map of the Feejees 
abounds in them through its eastern part, and we may infer with 
reason that this has been a large area of subsidence, like that 
which is now going on in Greenland. “eg 
Evidence of subsidence still more conclusive, if possible, 1 . 
obtained by actual observation at Metia and some of the elevated 
coral islands. This island is 250 feet in height, full twice the 
coral-growing depth. At another island in the Hervey Group, 
Mangaia, the coral rock is raised 300 feet out of water. — 
The fact of subsidence having actually taken place during the 
formation of many reefs, is therefore put beyond doubt. It must 
form a part of any true theory of reefs, whether it be the crater 
hypothesis or the view here advocated. The latter has this ad- 
vantage, that it explains all the facts, and requires no other ele- 
ment but this single one of subsidence. It rests on a simple fact 
and demands no hypothesis whatever. - 
The manner in which subsidence would operate is shown 1 
the following sketches, representing ideal transverse sections of 
an island and its reefs. In figure 1, if I be the water line, the 
island, like Goro, has a simple fringing reef, f, f:—it is a pres 
her v 
mergence, till If is the water line: then the channel (¢” “’) 
within the barrier is quite broad, as in the island of Nairat 8 
Angau ; on one side (/’) the fringing reef remains, but on sh 
other it has disappeared, owing, perhaps, to some change Cocina! 
e : 
at IV, there are two islets of rock in a wide lagoon, along Wit 
other islets (#” i”) of reef over two peaks which have disap” 
peared. The coral reef-rock by gradual growth has attained & 
great thickness, and envelops nearly the whole of the former 
land. Nanuku, the Argo Reef, and Exploring Isles are here & 
(et al 
* This Journal, [2], vol, xi, p. 366, 
