Comparison with 1869 |
|
of the embedded fossils had been less than that of the glacial period, instead of having been really far greater, that
is, is, 1861 1866 1869 1872 | is 1859 1860 |
extending from before the glacial epoch to the present day. |
|
In order to get a perfect gradation between two forms in the upper and lower parts of the same formation, the deposit
will will 1866 1869 | must 1859 1860 1861 1872 |
have
to go on continuously accumulating during a very to go on continuously accumulating during a very 1866 1869 |
gone on accumulating for a very 1859 1860 1861 |
gone on continuously accumulating during a 1872 |
long period,
so that there may be time sufficient so that there may be time sufficient 1866 1869 |
in order to have given sufficient time 1859 1860 |
so that there may have been time sufficient 1861 |
sufficient 1872 |
for the slow process of
modification; modification; 1869 1872 | variation; 1859 1860 1861 1866 |
hence the deposit
will have to will have to 1866 1869 |
will generally have to 1859 1860 1861 |
must 1872 |
be a very thick one; and the species undergoing
change will have to live in change will have to live in 1869 |
modification will have had to live on 1859 1860 1861 |
modification will have to live in 1866 |
change must have lived in 1872 |
the same
district district 1866 1869 1872 | area 1859 1860 1861 |
throughout this
whole time. But we have seen that a thick
formation, formation, 1866 1869 1872 |
fossiliferous formation 1859 1860 |
formation, fossiliferous throughout its thickness, 1861 |
fossiliferous throughout its entire thickness, can accumulate only fossiliferous throughout its entire thickness, can accumulate only 1869 1872 |
can only be accumulated 1859 1860 1861 |
fossiliferous throughout its thickness, can accumulate only 1866 |
during a period of subsidence; and to keep the depth approximately the same, which is necessary
that that 1861 1866 1869 1872 |
in order to enable 1859 1860 |
the same
marine species may marine species may 1866 1869 1872 |
species to 1859 1860 |
species may 1861 |
live on the same space, the supply of sediment must nearly
....... 1866 1869 1872 | have 1859 1860 1861 |
counterbalance counterbalance 1866 1869 1872 | counterbalanced 1859 1860 1861 |
the amount of subsidence. But this same movement of subsidence will
....... 1869 1872 | often 1859 1860 1861 1866 |
tend to
submerge submerge 1866 1869 1872 | sink 1859 1860 1861 |
the area whence the sediment is derived, and thus diminish the supply
whilst the downward movement continues. In fact, this nearly exact balancing between the supply of sediment and the amount of subsidence is probably a rare contingency; for it has been observed by more than one palæontologist, that very thick deposits are usually barren of organic remains, except near their upper or lower limits. |
|
It would seem that each separate formation, like the whole pile of formations in any country, has generally been intermittent in its accumulation. When we see, as is so often the case, a formation composed of beds of different
mineralogical composition, we may reasonably suspect that the process of deposition has been much interrupted, as a change in the currents of the sea and a supply of sediment of a different nature will generally have been due to geographical changes requiring much time.
|
of the embedded fossils had been less than that of the glacial period, instead of having been really far greater, that
is is 1859 1860 | is, 1861 1866 1869 1872 |
extending from before the glacial epoch to the present day. |
|
In order to get a perfect gradation between two forms in the upper and lower parts of the same formation, the deposit
must must 1859 1860 1861 1872 | will 1866 1869 |
have
gone on accumulating for a very gone on accumulating for a very 1859 1860 1861 |
to go on continuously accumulating during a very 1866 1869 |
gone on continuously accumulating during a 1872 |
long period,
in order to have given sufficient time in order to have given sufficient time 1859 1860 |
so that there may have been time sufficient 1861 |
so that there may be time sufficient 1866 1869 |
sufficient 1872 |
for the slow process of
variation; variation; 1859 1860 1861 1866 | modification; 1869 1872 |
hence the deposit
will generally have to will generally have to 1859 1860 1861 |
will have to 1866 1869 |
must 1872 |
be a very thick one; and the species
undergoing undergoing 1859 1860 1861 1869 1872 | under- going 1866 |
modification will have had to live on modification will have had to live on 1859 1860 1861 |
modification will have to live in 1866 |
change will have to live in 1869 |
change must have lived in 1872 |
the same
area area 1859 1860 1861 | district 1866 1869 1872 |
throughout
this this 1859 1860 1861 1866 1869 | the 1872 |
whole time. But we have seen that a thick
fossiliferous formation fossiliferous formation 1859 1860 |
formation, fossiliferous throughout its thickness, 1861 |
formation, 1866 1869 1872 |
can only be accumulated can only be accumulated 1859 1860 1861 |
fossiliferous throughout its thickness, can accumulate only 1866 |
fossiliferous throughout its entire thickness, can accumulate only 1869 1872 |
during a period of subsidence; and to keep the depth approximately the same, which is necessary
in order to enable in order to enable 1859 1860 |
that 1861 1866 1869 1872 |
the same
species to species to 1859 1860 |
species may 1861 |
marine species may 1866 1869 1872 |
live on the same space, the supply of sediment must nearly
have have 1859 1860 1861 | have 1866 1869 1872 |
counterbalanced counterbalanced 1859 1860 1861 | counterbalance 1866 1869 1872 |
the amount of subsidence. But this same movement of subsidence will
often often 1859 1860 1861 1866 | often 1869 1872 |
tend to
sink sink 1859 1860 1861 | submerge 1866 1869 1872 |
the area whence the sediment is derived, and thus diminish the
supply supply 1859 1860 1861 1866 1869 | supply, 1872 |
whilst the downward movement continues. In fact, this nearly exact balancing between the supply of sediment and the amount of subsidence is probably a rare contingency; for it has been observed by more than one palæontologist, that very thick deposits are usually barren of organic remains, except near their upper or lower limits. |
|
It would seem that each separate formation, like the whole pile of formations in any country, has generally been intermittent in its accumulation. When we see, as is so often the case, a formation composed of beds of
different different 1859 1860 1861 1866 1869 | widely different 1872 |
mineralogical composition, we may reasonably suspect that the process of deposition has been
much interrupted, as a change in the currents of the sea and a supply of sediment of a different nature will generally have been due to geographical changes requiring much time. much interrupted, as a change in the currents of the sea and a supply of sediment of a different nature will generally have been due to geographical changes requiring much time. 1859 1860 1861 1866 1869 |
more or less interrupted. 1872 |
|