86 J. D. Dana—Oceanie Coral Island Subsidence. 
The probability is, therefore, that both the central Atlantic 
and Indian Oceans were regions of this subsidence, like the 
central Pacific, and that the absence of islands over a large 
part of their interiors may be a consequence of it. rate of 
sinking exceeding five feet in a thousand years (if my estimate 
from the growth of corals is right) would have buried islands 
and reefs together in the ocean; while, with a slower rate, the 
reefs might have kept themselves at the water’s surface. So 
small may have been the difference of rate in the great move- 
ment that covered the Pacific with coral islands, but left the 
Indian Ocean a region of comparatively barren waters, with 
some “half-drowned” atolls, and the central Atlantic almost 
wholly a blank. 
While thus seeming to prove that all the great oceans have their 
buried lands, we are far from establishing that these lands were 
oceanic continents. For as the author has elsewhere shown, the 
rofoundest facts in the earth’s history prove that the oceans 
ocean that are not of coral origin. 
The course of argument leads us to the belief that a very 
large number of islands, more than has been supposed, lie bur- 
ied in the ocean. Coral islands give us the location of many of 
these lands; but still we know little of the extent to which the 
earth’s ranges of heights, or at least of volcanic peaks, have dis- 
appeared through oceanic subsidence. Recent dredgings and 
soundings have proved that the bottom of the oceanic basin 
has little of the diversity of mountain chains and valleys that 
prevail over the continents; and, through this observation (and 
also by the discovery that some ancient types of animal life, 
supposed to have been long extinct, are perpetuated there), they 
have afforded new demonstration of the proposition, above sta- 
ted, that the oceans have always been oceans. But while the facts 
do not imply the existence deep in the ocean of many granitic 
mountain chains, they do teach that there are long ranges, 
or lines, of volcanic ridges and peaks, and some of these es 
be among the discoveries of future dredging expeditions. 
range of deep-sea cones, or sunken voleanic islands, would be 
as interesting a discovery as a deep-sea sponge or coral, even if 
it should refuse, excepting perhaps a mere fragment, to come to 
the surface in the dredge. 
e may also accept, with some confidence, the conclusion 
that atolls and barrier reefs originated in the same great bal- 
ance-like movement of the earth's crust that gave elevation and 
cold, in the Glacial era, to high-latitude lands. If so, the 
tropics and the colder latitudes were performing their several 
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