of Edinburgh, Session 1879 - 80 . 
517 
many groups ; for instance in the Fiji Islands, where fringing reefs, 
harrier reefs, and atolls, all occur in close proximity, and where all 
the other evidence seems to point to elevation, or at least a long 
period of rest. In instances like the Gambier group, the reefs 
situated on the seaward side of the outer islands would grow more 
vigorously than those towards the interior ; they would extend in 
the direction of the shallower water, and ultimately would form a 
continuous harrier around the whole group. The distinguishing 
feature of the views now advanced is that they do away with the 
great and general subsidences required by Darwin’s theory,* and are 
in harmony with Dana’s views of the great antiquity and permanence 
of the great ocean basin, which all recent deep-sea researches 
appear to support. 
Summary . — It was shown (1) that foundations have been pre- 
pared for barrier reefs and atolls by the disintegration of volcanic 
islands, and by the building up of submarine volcanoes by the deposi- 
tion on their summits of organic and other sediments. 
(2.) That the chief food of the corals consists of the abundant 
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 all the greater depths of the ocean. 
(3.) That when coral plantations build up from submarine 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 by the action of the carbonic 
acid dissolved in sea- 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 
these features would exist alike in areas of slow elevation, of rest, or 
of slow subsidence. 
In conclusion it was pointed out that all the causes here appealed 
* “We may conclude that immense areas have subsided, to an amount suffi- 
cient to bury not only any formerly existing lofty- table-land, but even the 
heights formed by fractured strata and erupted matter. ” — ‘ ‘ Coral Reefs, ” p. 190. 
