ca gek 
Another point of such importance in relation to sea-level 
fringing reefs as well as to elevated reefs of all kinds, is 
the nature of the contact with their foundation. It ought 
to be plain to any thoughtful geologist that if this relation 
is uncomformable, subsidence before reef formation is implied, 
while if it is comformable no subsidence and perhaps uplift 
took place. Simple as this principle is, it has been almost 
universally overlooked. Unconformity is most easily recog- 
nized in connection with elevated reefs; but it is not difficult 
to determine even in connection with sea-level fringing reefs. 
It is not necessary to find actual contacts of reef-limestone 
with the underlying rock in order to answer this question. 
It is sufficient to see wether the general form of the surface 
above the level of the reef (whether the reef lie at sea level 
or elevated above it) is a surface of erosion, having hill and 
valley forms, or is a surface of deposition, still having the 
form given to it by uplift from the sea. All the examples 
of reefs that I have seen have strongly uncomformable con- 
tacts. This fact alone gives strong testimony for Darwin’s 
theory of subsidence. 
Please note in this connection that a very common mistake 
has been made by many writers regarding the origin of up- 
lifted reefs, which frequently occur in terraces one above the 
other: They have supposed that such reefs were formed during 
pauses in uplift. If the reefs lie upon a surface of erosion 
with an uncomformable contact, it is clear that the uncon- 
formity requires us to suppose that the foundation mass stood 
at least as high as at present, before the reefs were formed 
upon it, and that it was eroded while in that position, so as 
to be changed from its original form to. the erosional form 
that it possesses beneath the reefs. After this higher stand, 
it must have been submerged at least to the level of the 
highest reef, and then uplifted again to its present attitude. 
Uplifted reefs may therefore be just as well explained as having 
been formed during pauses in the submergence of their foun- 
dation, followed by rapid uplift, as formed during pauses in 
