APPENDIX II. 
286 
These facts point out the removal of matter which is going 
on in the lagoons and lagoon channels.’ 
Elevation, not subsidence, is to he expected in a volcanic 
region, as there is an a priori reason for attributing the 
phenomena of coral reefs — as resting on volcanic foun- 
dations — to elevation rather than to subsidence. The 
former hypothesis appears to Mr. Murray to accord with all 
the facts indicated by the published charts of coral-reefs, 
and thus is considered by him preferable to the latter. 
Mr. Murray’s general conclusions may be briefly enun- 
ciated as follows : — 
1. That foundations have been prepared for barrier-reefs 
and atolls by the disintegration of volcanic islands, and by 
the building up of submarine volcanoes,’ and by the depo- 
sition on their summits of organic and other sediments. 
2. That the chief food of the corals consists of the abun- 
dant pelagic life of the tropical regions, and the extensive 
solvent action of sea-water is shown by the removal of the 
carbonate of lime shells of these surface organisms from 
the greater depths of the ocean. 
3. That when coral plantations build up from sub- 
marine banks they assume an atoll form, owing to the 
more abundant supply of food to the outer margins and 
the removal of dead coral-rock from the interior portions 
by currents and the action of the carbonic acid dissolved 
in the water. 
4. That barrier-reefs have built out from the shore on a 
foundation of volcanic debris or on a talus of coral blocks, 
coral sediment and pelagic shells, and the lagoon channel 
is formed in the same way as a lagoon. 
5. That it is not necessary to call in subsidence to 
explain any of the characteristic features of barrier-reefs 
or atolls, and that all their features would exist alike in 
areas of slow elevation, of rest, or of slow subsidence. 
