ur.

The best authorities do not suppose that the men _originated_ in the
localities where the tools are found; and there is so little known about
the geology of Central Asia (for example) that it is impossible to say
whether tribes may not have wandered from some other places not affected
by the glaciation we have spoken of.

Again, the gravels and brick earths containing the tools are just of the
kind which defy attempts to say how long it took to deposit and arrange
them.

It may be taken as certain, that after the one age ceased and the first
men appeared, the beds in which their relics occur have been raised
violently, and again depressed and subjected to great flushes and floods
of water. The caves have been upheaved, and the gravels are found
chiefly along the valleys of our present rivers, but at a much higher
level, showing that there was both a higher level of the soil itself and
a much greater volume of water.

The Straits of Dover were formed during this period.

But none of these changes required a very long time; and if we can trace
back the later stone age, which shows remains of pottery and other
proofs of greater civilization, to the dawn of the historic period not
more than 4000 or 5000 years ago, there is nothing in the nature of the
changes which, as we have stated, intervened between the palaeolithic
and neolithic periods, that need have occupied more than a thousand or
two of years. Upheavals of strata and disruptions may be the work of
but a short time, or they may be more gradual. And as to the effect of
water, that depends on its volume and velocity; no certain rule can be
given. Our own direct experience shows that very great changes may take
place in a few hundred years.

"The estuaries," remarks Mr. Pattison,[1] "around our south-eastern
coast, which have been filled up in historical times, some within the
last seven hundred years to a height of thirty feet from their
sea-level, by the gradual accumulation of soil, now look like solid
earth in no way differing from the far older land adjoining. The
harbours out of which our Plantagenet kings sailed are now firm,
well-timbered land. The sea-channel through which the Romans sailed on
their course to the Thames, at Thanet, is now a puny fresh-water ditch,
with banks apparently as old as the hills. In Bede's days, in the ninth
century, it was a sea-channel three furlongs wide."

[Footnote 1: "Age and Origin of Man"--Present-Day Tract Se