| → natural and domestic varieties 1872 |
| varieties 1859 1860 1861 1866 1869 |
|
| →
Time
, as inferred from the rate of Deposition and extent of Denudation
. 1872 |
|
Time
.—
1859 1860 1861 |
|
Time, as inferred from the rate of Deposition and extent of Denudation
. 1866 |
|
Time, as inferred from the rate of Deposition and extent of Denudation
. 1869 |
|
|
had undergone a vast amount of change; and the principle of competition between organism and organism, between child and parent, will render this a very rare event; for in all cases the new and improved forms of life
tend to supplant the old and unimproved forms. |
|
| By the theory of natural selection all living species have been connected with the parent-species of each genus, by differences not greater than we see between the
→natural and domestic varieties
of the same species at the present day; and these parent-species, now generally extinct, have in their turn been similarly connected with more ancient
and so on backwards, always converging to the common ancestor of each great class. So that the number of intermediate and transitional links, between all living and extinct species, must have been inconceivably great. But assuredly, if this theory be true, such have lived upon
earth. |
|
→
Time
, as inferred from the rate of Deposition and extent of Denudation
.
|
| Independently of our not finding fossil remains of such infinitely numerous connecting links, it may be
that time
have sufficed for so great an amount of organic change, all changes having been effected
It is hardly possible for me
to recall to the
who
not
a practical geologist, the facts leading the mind feebly to comprehend the lapse of time. He who can read Sir Charles Lyell's grand work on the Principles of Geology, which the future historian will recognise as having produced a revolution in natural science,
does not admit how
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
or even
stratum. We can best gain some idea of past time by knowing the agencies at work, and learning how
the surface of the land has been denuded, and how much sediment has been deposited. As Lyell has well 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.
|
