Ch. V. 
OF CORAL-REEFS. 
155 
same or closely adjoining areas ? How are such reefs 
related to each other in form and position,— for 
instance, do neighbouring groups of atolls, and the 
separate atolls in each group, hear the same relation 
to each other as do ordinary islands ? Although coral- 
s 
reefs which have just begun to re-grow, after having 
been killed by too rapid a subsidence, would at first 
belong to the fringing class, yet, as a general rule, 
reefs of this class indicate that the land has either 
long remained at a stationary level, or has been up- 
raised. Of a stationary level it is hardly possible 
to find any evidence except of a negative kind ; but 
of recent elevation, upraised marine remains afford 
a sure proof : it may therefore be asked, do fringed 
coasts often afford such evidence ? Do the areas 
which have subsided, as shown by the presence of 
atolls and barrier-reefs, and the areas which have 
either remained stationary or have been upraised, 
as indicated by fringing-reefs, bear any determinate 
relation to each other ? Is there any relation between 
the areas of recent subsidence or elevation, and the 
presence of active volcanic vents ? These several 
questions will be considered in the following chapter. 1 
1 I may take this opportunity of briefly considering the appear- 
ance which would probably be presented by a vertical and deep 
section across a coral formation (referring chiefly to an atoll) formed 
by the upward growth of coral during successive subsidences. This 
is a subject worthy of attention, as a means of comparison with 
ancient coral strata. The circumferential parts would consist of 
massive species in a vertical position, with their interstices filled up 
with detritus; but this would be the part most subject to subsequent 
denudation and removal. It is useless to speculate how large a 
