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1859
1860
1861
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1869
1872

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1859
1860
1861
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1872

has been accumulated. 1859 1860 1861 1866
must have been heaped together. 1872

1 blocks not present in 1859 1860 1861 1866 1872; present in 1869
and although conglomerates have probably been accumulated at a quicker rate than finer sediments, yet from being formed of worn and rounded pebbles, each of which bears the stamp of time, they are good to show how slowly the mass must have been heaped together.

countries! Professor Ramsay has given me the maximum thickness, in most cases from actual measurement, in a few cases from estimate, of each formation in different parts of Great Britain; and this is the result:— Feet. Palæozoic strata (not including igneous beds) .. 57,154 Secondary strata .. .. .. .. .. .. .. 13,190 Tertiary strata .. .. .. .. .. .. .. 2,240 1866
countries! Professor Ramsay has given me the maximum thickness, in most cases from actual measurement, in a few cases from estimate, of each formation in different parts of Great Britain; and this is the result:— Feet. Palæozoic strata (not including igneous beds) .. 57,154 Secondary strata .. .. .. .. .. .. .. 13,190 Tertiary strata .. .. .. .. .. .. .. .. 2,240 1859
countries! Professor Ramsay has given me the maximum thickness, in most cases from actual measurement, in a few cases from estimate, of each formation in different parts of Great Britain; and this is the result:— Feet. Palæozoic strata (not including igneous beds) .. 57,154 Secondary strata .. .. .. .. .. .. .. 13,190 Tertiary strata .. .. .. .. .. .. .. 2,240 1860
countries! Professor Ramsay has given me the maximum thickness, in most cases from actual measurement, in a few cases from estimate, of each formation in different parts of Great Britain; and this is the result:— Feet. Palæozoic strata (not including igneous beds) .. 57,154 Secondary strata .. .. .. .. .. .. .. 13,190 Tertiary strata .. .. .. .. .. .. .. 2,240 1861

periods. 1859 1860 1861 1866 1869
periods of enormous length. 1872

Good observers have estimated that sediment is deposited by the great Mississippi river at the rate of only 600 feet in a hundred thousand years. 1859 1860 1861 1866
The consideration of these various facts impresses the mind almost in the same manner as does the vain endeavour to grapple with the idea of eternity. 1872

has no pretension to strict exactness; 1860 1861 1866
may be quite erroneous; 1859

of which bears the stamp of time,
they are
are
good to show how slowly the mass has been accumulated. In the Cordillera I estimated one
mass
pile
of
con- glomerate
conglomerate
at ten thousand
feet;
feet
in
in
thickness.
thickness.
Let
him
the observer
remember Lyell's profound
remark,
remark
that the thickness and extent of sedimentary formations are the result and measure of the degradation which the earth's crust has elsewhere suffered. And what an amount of degradation is implied by the sedimentary deposits of many countries! Professor Ramsay has given me the maximum thickness, in most cases from actual measurement, in a few cases from estimate, of each formation in different parts of Great Britain; and this is the result:— Feet. Palæozoic strata (not including igneous beds) .. 57,154 Secondary strata .. .. .. .. .. .. .. 13,190 Tertiary strata .. .. .. .. .. .. .. 2,240 — making altogether 72,584 feet; that is, very nearly thirteen and three-quarters British miles. Some of
these
the
formations, which are represented in England by thin beds, are thousands of feet in thickness on the Continent. Moreover, between each successive formation, we have, in the opinion of most geologists,
enormously long
enormously long
blank periods. So that the lofty pile of sedimentary rocks in
Britain,
Britain
gives but an inadequate idea of the time which has elapsed during their
accumulation.
accumulation;
yet
yet
what
what
time
time
this
this
must
must
have
have
consumed!
consumed!
Good observers have estimated that sediment is deposited by the great Mississippi river at the rate of only 600 feet in a hundred thousand years. This estimate has no pretension to strict exactness; yet, considering over what wide spaces very fine sediment is transported by the currents of the sea, the process of accumulation
in
over
any one
area
extensive area
must be extremely slow.
But the amount of denudation which the strata have