204 W. M. DAVIS 
after long intervals of rest” (130). Because of the frequent 
repetition of this conception we might well speak of Darwin’s 
“theory of intermittent subsidence,”’ and not simply of the ‘“‘theory 
of subsidence.”’ This is well warranted by a striking passage 
in which it is suggested that atoll reefs ““would present a totally 
different appearance from what they do now” if they had long 
remained stationary, and that “‘some renovating agency (namely 
subsidence) comes into play at intervals, and perpetuates their 
original structure” (31). 
Insufficient attention has been given to intermittent subsidence 
as the basis of Darwin’s theory, though he often alluded toit. He 
considered the possibility that an atoll might “be carried down 
by “a. more rapid movement . --.. after a subsidence ols aa 
very slow nature” (104); and he wrote of ‘“‘progressive subsidences, 
perhaps at some periods more rapid than at others’ (107); of. 
“repeated subsidences”’ in the supposed development of the 
Maldives (110); of groups of atolls growing upward “at each 
sinking of the land”’ (126); and he clearly recognized the possibility 
of subsidence at a faster rate than reef upgrowth, not only in the 
account of certain submarine banks which he interpreted as sub- 
- merged atolls, but also in a rarely quoted explanation of certain 
fringing reefs. On the first point he wrote: “There is nothing 
improbable in the death . . . . from the subsidence being great 
or sudden, of the corals on the whole, or on portions of some 
of the atolls” (108); also that ‘‘through further subsidence and 
with the accumulation of sediment, modified by the force of 
ocean currents,’ drowned atolls might ‘‘pass into level banks 
with scarcely any distinguishing character” (114). On the second 
point the following important statement is made: “If during 
the prolonged subsidence of a shore, coral reefs grow for the first 
time on it, or if an old barrier reef were destroyed and submerged 
and new reefs became attached to the land, these would necessarily 
at first belong to the fringing class” (124). Such fringing reefs 
should be regarded as of a new generation; examples of them 
will be given in the next section. The possibility of-intermittent 
elevation as well as intermittent subsidence was also recognized 
by Darwin (145, 146); and mention is made of “elevation having 
