THE OCHANIC CORAL-ISLAND SUBSIDENCE. 409 
part of their interiors may be a consequence of it. A rate of 
sinking exceeding five feet in a thousand years (if the estimate 
on page 253 is right) would have buried islands and reefs to- 
gether 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 movement 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 profoundest facts in the earth’s history prove that 
the oceans have always been oceans. These lands in all proba- 
bility were, for the most part, volcanic islands or summits of 
volcanic ranges, for of this nature are all the islands over the 
interior of either 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 
buried 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 disappeared 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 vallies that prevails 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 stated, that the oceans have always been 
oceans. But while the facts do not imply the existence deep 
