338 CORALS AND CORAL ISLANDS. 
been longest free from such action, have reefs of considerable 
extent. The island of Maui exemplifies well the same gen- 
eral fact. The island consists of two peninsulas: one the 
eastern, recent volcanic in character, with a large crater at 
summit, and the other, the western, presenting every evidence, 
in its gorges and peaks and absence of volcanic cones, of hav- 
ing become extinct ages since. In conformity with the view 
expressed, the coral reefs are confined almost exclusively to the 
latter peninsula. Other examples are afforded by the Samoan 
or Navigator Islands. Savaii abounds in extinct craters and 
lava streams, and much resembles Hawaii in character; it 
bears proof in every part of being the last seat of the vol- 
canic fires of the Samoan Group. Its reefs are consequently 
few and small: there is but a narrow line on part of the 
northern shores, although on the other islands they are very 
extensive. 
This absence of corals results obviously from the destruc- 
tion of the zodphytes by heat, consequent on volcanic action. 
Submarine eruptions, which are frequent as long as a vol- 
cano near the sea is ijn action, heat the waters and destroy 
whatever of life they may contain. After the eruption of Ki- 
lauea, in 1840, there were numerous dead fish thrown on the 
beach; and many such instances in different regions are on 
record. 
The agencies affecting the growth of coral reefs being be- 
fore the mind, we may proceed to notice the actual distribu- 
tion of reefs through the coral seas. The review given is a 
rapid one, as our present object is simply to explain the 
absence or presence of reefs within the coral reef’ limits, by, 
reference to the above facts. 
In the valuable work by Mr. Darwin, the geographical 
distribution of reefs is treated of at length. The facts here 
