Origin of Species Variorum

→ 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

→ 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

con- glomerate

conglomerate

at ten thousand

feet;

feet

~~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.

~~yet~~

~~what~~

~~time~~

~~this~~

~~must~~

~~have~~

~~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

over

any one

area

extensive area

must be extremely slow.

But the amount of denudation which the strata have