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Updated: May 25, 2025
Finely laminated sands and clays, with thin layer of lignite, and shells of Cyclas and Valvata, and with Mytilus in some beds. 4. Glacial boulder till. 5. Contorted drift. 6. Gravel overlying contorted drift.
The beds of coal were separated by strata of sandstone or compact clays, and appeared crushed under the weight of overlying strata.
We find where two kinds of rock touch, one overlying the other, and absolute difference in texture and color, and no union between them. How account for their juxtaposition? Rock begat rock, undoubtedly, and the aerial forces played the chief part, but the origin of each kind is hidden in the abyss of geologic time, as is that of the animal species.
The true Pampean deposit, with mammiferous remains, instead of as at Santa Fe overlying conformably the tertiary strata, is here seen at a lower level folding round and between the flat-topped, cliff-bounded hills, formed by a upheaval and denudation of these same tertiary strata.
But it happened that the coal needed to replace the dwindling forests of this small and exceptionally rain-saturated country occurs in low hollow basins overlying clay, and not, as in China and the Alleghanies for example, on high-lying outcrops, that can be worked as chalk is worked in England.
But if, as some geologists suppose, a range of older rocks underlies the Weald, on the flanks of which the overlying sedimentary deposits might have accumulated in thinner masses than elsewhere, the above estimate would be erroneous; but this source of doubt probably would not greatly affect the estimate as applied to the western extremity of the district.
On each side lay shallow sheets of stagnant water overlying a treacherous bottom of semi-fluid mud, which rose above the surface here and there in moist, sweltering banks, mottled over with occasional patches of unhealthy vegetation.
The mucous layer absorbs nutriment from the mass of yelk it encloses; this nutriment has to be transferred to the overlying serous layer, out of which the nervo-muscular system is being developed; and between the two arises a vascular system by which the transfer is effected a system of vessels which continues ever after to be the transferrer of nutriment from the places where it is absorbed and prepared, to the places where it is needed for growth and repair.
For these reasons our choice of a soil for the lowest cost a bushel and probably for a maximum yield should be a rich sandy or sandy loam surface soil overlying a well-drained clay sub-soil. I would prefer one which was originally covered with a heavy growth of beech and maple timber, though I should want it to be "old land" at the time.
When the junctions, however, are carefully examined, it is found that the Plutonic rock intrudes itself in veins, and nowhere covers the fossiliferous strata in large overlying masses, as is so commonly the case with trappean formations.
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