Darwin
adopted the opposite hypothesis, viz., that the land has undergone
extensive and slow depression in those localities in which these
structures exist.
It seems, at first, a startling paradox, to suppose that the land
is less fixed than the sea; but that such is the case is the uniform
testimony of geology. Beds of sandstone or limestone, thousands of feet
thick, and all full of marine remains, occur in various parts of the
earth's surface, and prove, beyond a doubt, that when these beds
were formed, that portion of the sea-bottom which they then occupied
underwent a slow and gradual depression to a distance which cannot have
been less than the thickness of those beds, and may have been very much
greater. In supposing, therefore, that the great areas of the Pacific
and of the Indian Ocean, over which atolls and encircling reefs are
found scattered, have undergone a depression of some hundreds, or,
it may be, thousands of feet, Mr. Darwin made a supposition which had
nothing forced or improbable, but was entirely in accordance with what
we know to have taken place over similarly extensive areas, in other
periods of the world's history. But Mr. Darwin subjected his hypothesis
to an ingenious indirect test. If his view be correct, it is clear that
neither atolls, nor encircling reefs, should be found in those portions
of the ocean in which we have reason to believe, on independent grounds,
that the sea-bottom has long been either stationary, or slowly rising.
Pages:
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200