CORRELATION OF THE PREHISTORIC "FLOOR." 277
It appears to me that this change of level, resulting in the
submergence of the low-lying lands of our coasts, may not be so
for back as we might imagine. I think it not improbable that
at is within the tribal memory of the earlier races who inhabited
these islands, and who have now been driven into the West
through the pressure of later immigrants. Legends and tradi-
tions do not arise without some foundation of fact, however
much they may become distorted. It seems reasonable to
suppose (although it is not capable of definite proof) that the
legends of the land of Lyonesse,30 which is traditionally supposed
to have been overwhelmed by the sea, are simply the tribal
memory of the submergence of this Buried Surface, upon which
we now find the weapons, implements, domestic pottery, even
the bones of our ancestors. That the traditions are now chiefly
confined to Cornwall does not imply that the event only took
place there, but that the descendants of those who witnessed
the event have been driven into that district, and have taken
the memory of this terrible calamity with them. Or it may
be, perhaps, that in the eastern parts of England the original
tradition has become fused with the later losses of land due
to erosion, and not to submergence. Some of the traditions
of Wales may possibly refer to the earlier event.
With regard to the geological problem of the time necessary
for the deposition of the tidal silts which overlie the ancient
surface, it must be confessed that we really do not know how
rapidly this may take place under favourable conditions. Our
notions of the slowness of deposition are largely coloured from
the observance of those situations in which not deposition, but
erosion, is actually in progress. Areas of rapid deposition are
necessarily for the most part hidden from our sight. We only
receive hints of what is going on from the silting up of estuaries
and bays, and from the practical difficulties which are ex-
perienced in keeping open navigable channels by dredging
operations, although in such situations the natural scour is
very considerable.
One does not like to give a definite date to the Buried Pre-
historic Surface. Any estimate of its age must be somewhat vague
and uncertain. I do not think that the physical evidence de-
mands a greater antiquity than some five thousand years from
30 W. A. E. Ussher, Geol. Mag., dec. a, vol. vi. (1879), p. 32.