Editorial Comment. 115 
The dead coral on the inner portion of the reef is attacked by 
the solvent action of the sea water and slowly removed. 
Deep-sea corals, mollusks, sea-urchins or other agents may 
assist in building up the foundations on which the reef pro- 
gresses outward, but the principal source of the material must 
be fragments broken from the reef itself. 
Atolls arc explained by the fact that shoals often exist in 
mid-ocean at depths not incompatible with the growth of reef- 
building corals. Corals taking possession of such shoals must 
of necessity construct annular reefs, and the reef once estab- 
lished will grow outward so as to embrace an ever widening- 
area. Solvent action, working upon the dead corals in the 
rear, causes the dimensions of the old lagoon to keep pace with 
the widening circle of growing coral. 
There is nothing incompatible with known phenomena in 
the theory either of Darwin or of Murray. Scientists, not- 
withstanding the absurd charge of the Duke of Argyll, will 
concern themselves onl}^ with ascertaining which corresponds 
most nearly to the facts. Dana, who has traversed the Pacific 
region and made personal observations of all the phenomena, 
presents in his work on Corals and Coral Islands, numerous 
evidences of subsidence, strongly corroborative of Darwin's ex- 
planations. Geike, in his recently prepared text book on ge-. 
ology, states Murray's theory fairly, yet seems to j^lace 
unshaken confidence in the theory of Darwin. 
The magnitude of the operations involved and the length of 
time demanded by Murray's theory are certainly startling. Im- 
agine a barrier reef seventy miles from shore and coming ujd 
from a depth of 1200 or 1500 feet. The reef began near shore. 
Little by little it has crept seaward on a foundation of its own 
fragments. Evei'y inch of progress required the growth and 
destruction of enough coral to build up a foundation from the 
bottom to within twenty or thirty fathoms of the surface. At 
first the depth was not great and the foundations could be easily 
laid, but during the later history of the reef seaward progress 
must have been inconceivably slow. The amount of calcareous 
matter actually secreted by living coials, according to Murray's 
view, was sufficient to solidly fill all the space between the shore 
and the reef. Remember too that corals were not workinsf 
