The granules
composing the sandstones of many formations have been separated rather by
friction against the erupted volcanic or Plutonic rock than destroyed by the
erosive force of a neighboring sea. The existence of these friction
'conglomerates', which are met with in enormous masses in both hemispheres,
testifies the intensity of the force with which the erupted rocks have been
propelled from the interior through the earth's crust. This detritus has
subsequently been taken up by the waters, which have then deposited it in
the strata which it still covers."*
[footnote] *Leop. von Buck, 'Geognost. Briefe', s. 75-82, where it is also
shown why the new red sandstone (the 'Todtliegende' of the Thuringian flotz
formation) and the coal measures must be regarded as produced by erupted
porphyry.
Sandstone formations are found imbedded in all strata, from the lower
silurian transition stone to the beds of the tertiary formations, superposed
on the chalk. They are found on the margin of the boundless plains of the
New Continent, both within and without the tropics, extending like
breast-works along the ancient shore, against which the sea once broke its
foaming waves.
p 270
If we cast a glance on the geographical distribution of rocks, and their
relations in space, in that portion of the earth's crust which is accessible
to us, we shall find that the most universally distributed chemical
substance is 'silicic acid', generally in a variously-colored and opaque
form.
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