But we do not know what was
the state of things in the intervals between the successive
formations; whether Europe and the United States during these
intervals existed as dry land, or as a submarine surface near land, on
which sediment was not deposited, or again as the bed of an open and
unfathomable sea.
Looking to the existing oceans, which are thrice as extensive as the
land, we see them studded with many islands; but not one oceanic
island is as yet known to afford even a remnant of any palaeozoic or
secondary formation. Hence we may perhaps infer, that during the
palaeozoic and secondary periods, neither continents nor continental
islands existed where our oceans now extend; for had they existed
there, palaeozoic and secondary formations would in all probability
have been accumulated from sediment derived from their wear and tear;
and would have been at least partially upheaved by the oscillations of
level, which we may fairly conclude must have intervened during these
enormously long periods. If then we may infer anything from these
facts, we may infer that where our oceans now extend, oceans have
extended from the remotest period of which we have any record; and on
the other hand, that where continents now exist, large tracts of land
have existed, subjected no doubt to great oscillations of level, since
the earliest silurian period. The coloured map appended to my volume
on Coral Reefs, led me to conclude that the great oceans are still
mainly areas of subsidence, the great archipelagoes still areas of
oscillations of level, and the continents areas of elevation.
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