368 CORALS AND CORAL ISLANDS. 
In the island of Metia, elevated two hundred and fifty feet, 
the corals below were the same as those now existing, as far 
as we could judge from the fossilized specimens. At the in- 
ner margin of shore reefs, there is the same identity with ex- 
isting genera. We do not claim to have examined the base- 
ment of the coral islands, and offer these facts as the only ev- 
idence on this point that is within reach. We cannot know 
with absolute certainty that the present races of zodphytes 
may not be the successors of others that flourished, on the saine 
sites, even before the Tertiary era in Cretaceous and Jurassic 
times; but as yet have little reason in facts observed, for such 
om 
a conclusion. For a long time volcanic action may have been 
too general and constant over the Pacific, for the growth of 
corals; and this may have continued to interfere till a com- 
paratively late period, if we may judge from the appearance 
of the rocks, even on Tahiti. The subsidence has probably tor 
a considerable period ceased in most, if not all, parts of the 
ocean, and subsequent elevations of many islands and groups 
have taken place. 
V. ELEVATIONS OF MODERN ERAS IN THE PACIFIC, 
Since the period of subsidence discussed in the preceding 
pages, there has been no equally general elevation. Yet va- 
rious parts of the ocean bear evidence of changes confined to 
particular islands, or groups of islands. While the former 
exemplify one of the grander events in the earth’s history, in 
which a large segment of the globe was concerned, the latter 
exhibit its minor changes over limited areas. The instances 
of these changes are so numerous and so widely scattered, that 
they afford convincing evidence of a cessation in the previous 
general subsidence. 
