306 W. M. DAVIS 
The same experienced observer later made a more specific state-_ 
ment regarding the Maldives: 
From the outer edge of an encircling reef flat there is generally to seaward 
a gradual slope to 30-50 fathoms in 200-400 yards, succeeded by the steep. 
. ... This slope is essentially the growing area, being covered almost com- 
pletely by living organisms. ... . The outwash of detritus, largely due to 
undercurrents [or to general agitation by wave and current action, with the 
result that the finer sediments are chased about until they finally settle in 
deep water outside the reef where they will not be again disturbed ?], causes a 
raining down of coral masses and sand over the edge of the steep, carrying it 
out and allowing the extension of the whole outer side as a fairy ring.t 
The growth of a reef outward, like a fairy ring, is again mentioned 
by the same author in his elaborate report on the Maldives. A 
later statement by the same author is, “The steep . . . . is built 
up by masses of coral rock from the reef above, its angle represent- 
ing that at which such material comes to rest in sea-water.”3 It is 
interesting to add that the change of slope on the exterior of a reef 
occurs at the same depth as that at which, according to Daly, ‘‘the 
charts of the world show the break of slope”’ (199) on continental 
shelves. 
Lagoon floors of discontinuous reefs.—As to the free border of an 
uninclosed lagoon-floor sector, where the inclosing reef is wanting 
as above mentioned: It is easy to conceive that the lagoon floor 
there represents a more or less aggraded portion of a pre-existent 
platform, elsewhere inclosed by a superposed reef; and it is not 
difficult to explain the origin of the platform by abrasion according 
to the glacial-control theory as stated by Daly, or to leave it un- 
specified, except to say with Vaughan that it is independent of the 
reefs which are growing upon it. But it is also easy to conceive 
that the lagoon floor of today is the more or less aggraded lagoon 
floor of earlier days; that the lagoon floor of earlier days may have 
been deepened during times of rapid subsidence which caused the 
t “The Origin of Coral Reefs .... ,” Amer. Jour. Sci., XVI (1903), 203-13; 
See py 211. 
2The Fauna and Geography of the Maldive and Laccadive Archipelagoes (Cam- 
bridge), I (1903); IL (1906); see I, 175, 182, 183, 317. 
3 “The Indian Ocean,”’ Geogr. Jour., XXVIII (1906), 313-32, 454-55; see p. 455. 
Also ‘‘Submarine Slopes,” ibid., XLV (1915), 202-10. 
