Chap. IX. 
GEOLOGICAL EECOED. 
309 
do not appear to have inhabited profound depths, in the 
several formations of Europe and of the United States; 
and from the amount of sediment, miles in thickness, of 
which the formations are composed, we may infer that 
from first to last large islands or tracts of land, whence 
the sediment was derived, occurred in the neighbour¬ 
hood of the existing continents of Europe and North 
America. But we do not know what was the state of 
tilings in the intervals between the successive forma¬ 
tions ; 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 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 se¬ 
condary 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 con¬ 
clude 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 Beefs, led me to 
conclude that the great oceans are still mainly areas of 
