eventually be brought nearer to the shore-level, and again subjected to
the wear and tear of the sea; and directly the sea begins to act upon
it, it would of course soon cut up and carry it away, to a greater or
less extent, to be re-deposited further out.

Well, as there is, in all probability, not one single spot on the whole
surface of the earth, which has not been up and down in this way a
great many times, it follows that the thickness of the deposits formed
at any particular spot cannot be taken (even supposing we had at first
obtained correct data as to the rate at which they took place) as
affording reliable information as to the period of time occupied in its
deposit. So that you see it is absolutely necessary from these facts,
seeing that our record entirely consists of accumulations of mud,
superimposed one on the other; seeing in the next place that any
particular spots on which accumulations have occurred, have been
constantly moving up and down, and sometimes out of the reach of a
deposit, and at other times its own deposit broken up and carried away,
it follows that our record must be in the highest degree imperfect, and
we have hardly a trace left of thick deposits, or any definite
knowledge of the area that they occupied, in a great many cases. And
mark this! That supposing even that the whole surface of the earth had
been accessible to the geologist,--that man had had access to every
part of the earth, and had made sections of the whole, and put them all
together,--even then his record must of necessity be imperfect.

But to how much has man really access? If you will look at this Map you
will see that it represents the proportion of the sea to the earth:
this coloured part indicates all the dry land, and this other portion
is the water. You will notice at once that the water covers
three-fifths of the whole surface of the globe, and has covered it in