[footnote] *Basin-shaped curved strata, which dip and reappear at
measureable distances, although their deepest portions are beyond the reach
of the miner, afford sensible evidence of the nature of the earth's crust at
great depths below its surface. Testimony of this kind possesses,
consequently, a great geognostic interest. I am indebted to that excellent
geognosist, Von Dechen, for the following observations. "The depth of the
coal basin of Liege, at Mont St. Gilles, which I, in conjunction with our
friend Von Oeynhausen, have ascertained to be 3890 feet below the surface,
extends 3464 feet below the surface of the sea, for the absolute height of
Mont St. Gilles certainly does not much exceed 400 feet; the coal basin of
Mons is fully 1865 feet deeper. But all these depths are trifling compared
with those which are presented by the coal strata of Saar-Revier
(Saarbrucken). I have found after repeated examinations, that the lowest
coal stratum which is known in the neighborhood of Duttweiler, near
Bettingen, northeast of Saarlouis, must descend to depths of 20,682 and
22,015 feet (or 3.6 geographical miles) below the level of the sea." This
result exceeds, by more than 8000 feet, the assumption made in the text
regarding the basin of the Devonian strata.
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