| → varied forms, and thus a rich 1869 1872 |
| thus a 1859 1860 1861 1866 |
|
| →
throughout the greater part of their thickness
rich
1866 1869 1872 |
| rich 1859 1860 |
| throughout the greater part of their thickness rich 1861 |
|
| ↑ 2 blocks not present in 1861 1866 1869 1872; present in 1859 1860 |
| Thus the geological record will almost necessarily be rendered intermittent.
I feel much confidence in the truth of these views, for they are in strict accordance with the general principles inculcated by Sir C. Lyell; and E. Forbes independently
arrived at a similar conclusion.
|
|
| ↑ 3 blocks not present in 1859 1860 1861 1866 1869 1872; present in |
|
|
|
| → in which it was formed; nor would 1866 1869 1872 |
| supposed to be shallow; 1861 |
|
| → OMIT 1866 1869 1872 |
| would not generally 1861 |
|
|
sediment may be
to any thickness and extent over a shallow bottom, if it continue slowly to subside. In this latter case, as long as the rate of subsidence and
of sediment nearly balance each other, the sea will remain shallow and favourable for
and
→varied forms, and thus a rich
thick enough, when upraised, to resist
amount of
may be formed. |
|
| I am convinced that
our ancient formations, which are
→
throughout the greater part of their thickness
rich
have thus been formed during subsidence. Since publishing my views on this subject in 1845, I have watched the progress of Geology, and have been surprised to note how author after author, in treating of this or that great formation, has come to the conclusion that it was accumulated during subsidence. I may add, that the only ancient tertiary formation on the west coast of South America, which has been bulky enough to resist such degradation as it has as yet suffered, but which will hardly last to a distant geological age, was
deposited during a downward oscillation of level, and thus gained considerable thickness. |
|
| All geological facts tell us plainly that each area has undergone numerous slow oscillations of level, and apparently these oscillations have affected wide spaces.
formations rich in fossils and sufficiently thick and extensive to resist subsequent degradation,
have been formed over wide spaces during periods of subsidence, but only where the supply of sediment was sufficient to keep the sea shallow and to embed and preserve the remains before they had time to decay. On the other hand, as long as the bed of the sea
stationary,
deposits
have been accumulated in the shallow parts, which are the most favourable to life. Still less
this have happened during the alternate periods of elevation; or, to speak more accurately, the beds which were then accumulated will
been destroyed by being upraised and brought within the limits of the coast-action. ↑
↑ |
|
| These remarks apply chiefly to littoral and
deposits. In the case of an extensive and shallow sea, such as that within a large part of the Malay Archipelago, where the depth varies from 30 or 40 to 60 fathoms, a widely extended formation might be formed during a period of
and yet not suffer excessively from denudation during its slow upheaval; but the thickness of the formation could not be great, for owing to the elevatory movement it would be less than the
→in which it was formed; nor would
the deposit
→OMIT
|
