| ↑ 1 blocks not present in 1869 1872; present in 1859 1860 1861 1866 |
| 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.
|
|
| → the coast, 1869 1872 |
| lines of sea-coast, 1859 1860 1861 1866 |
|
| → good evidence 1860 1861 1866 1869 1872 |
| reason to believe 1859 |
|
| → after being reduced 1869 1872 |
| reduced 1859 1860 1861 1866 |
|
| → excellent observers, 1869 |
| many excellent observers— 1872 |
|
|
remarked, the extent and thickness of our sedimentary formations are the result and the measure of the denudation which the earth's crust has elsewhere undergone. Therefore a man should examine for himself the great piles of superimposed strata, and watch the rivulets bringing down mud, and the waves wearing away the sea-cliffs, in order to comprehend something about the duration of past time, the monuments of which we see all around us. ↑
|
|
| It is good to wander along
→the 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
→good evidence
that pure water
nothing in wearing away rock. At last the base of the cliff is undermined, huge fragments fall down, and
remaining fixed, have to be worn
atom by atom,
→after being reduced
in
they can be rolled about by the waves, and then
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
years have elapsed since the waters washed their base. |
|
| We have, however, recently learnt from the observations of Ramsay, in the van of
→excellent observers,
of Jukes, Geikie, Croll, and others, that subaerial
|
