volution in natural science, yet does not admit how incomprehensibly
vast have been the past periods of time, may at once close this volume.
Not that it suffices to study the Principles of Geology, or to read
special treatises by different observers on separate formations, and to
mark how each author attempts to give an inadequate idea of the duration
of each formation or even each stratum. A man must for years examine for
himself great piles of superimposed strata, and watch the sea at work
grinding down old rocks and making fresh sediment, before he can hope to
comprehend anything of the lapse of time, the monuments of which we see
around us.

It is good to wander along lines of sea-coast, when formed of moderately
hard rocks, and mark the process of degradation. The tides in most cases
reach the cliffs only for a short time twice a day, and the waves eat
into them only when they are charged with sand or pebbles; for there
is reason to believe that pure water can effect little or nothing in
wearing away rock. At last the base of the cliff is undermined, huge
fragments fall down, and these remaining fixed, have to be worn away,
atom by atom, until reduced in size they can be rolled about by the
waves, and then are more quickly ground into pebbles, sand, or mud.
But how often do we see along the bases of retreating cliffs rounded
boulders, all thickly clothed by marine productions, showing how little
they are abraded and how seldom they are rolled about! Moreover, if
we follow for a few miles any line of rocky cliff, which is undergoing
degradation, we find that it is only here and there, along a short
length or round a promontory, that the cliffs are at the present time
suffering. The appearance of the surface and the vegetation show that
elsewhere years have elapsed since the waters washed their base.

He who most closely studies the action of the sea on our shores, will,
I believe, be most deeply impressed with the slowness with which rocky
coasts are worn away. The observations on this head by Hugh Miller,
and by that excellent observer Mr. Smith of Jordan Hill, are most
impressive. With the mind thus impressed, let any one examine beds of
conglomerate many thousand feet in thickness, which, though probably
formed at a quicker rate than many other deposits, yet, from being
formed of worn and rounded pebbles, each of which bears the stamp of
time, are good to show how slowly the mass has been accumulated. Let
him re