The facts have also a wider bearing, for they teach that
lands separated by a range of deep ocean cannot supply one
another with material for rocks. The existence of an Atlan-
tic ocean continent — an Atlantis — ^has sometimes been assumed
in order to make it a source of the mud, sand and gravel, out
of which the thick sedimentary formations of the Appalachian
region of North America were made. But if this Atlantis
were a reality, there would still have been needed, in addition



GBOLOQIOAL OONOLUaiONS. 389

to the presence of such an ocean continent, a set of f5peight
carriers that could beat off the waves from their accustomed
work, and push aside the ordinary oceanic currents ; or else
Atlantis would get back all its own dirt

VI. ABSENCE OP FOSSILS FROM LIMESTONE STRATA.
Absence of fossils has been mentioned as a frequent char-
acteristic of the fine compact coral reef-rock, and also of the
beach and drift sand-rock or oolite (pp. 153, 194). The rocks
are formed at the sea-level, and in the midst of abundant life,
and yet trituration by the action of the waves and winds has
in many places reduced all to the finest material, so that an em-
bedded shell is seldom to be found in the beach or drift oolite,
and rarely too in much of the fine-grained coral reef-rock.
