The arrangement of
the particles in layers parallel with the margins of the beins, the regular
recurrence of analogous layers on the opposite sides of the veins (on their
different walls), and, finally, the elongated cellular cavities in the
middle, frequently afford direct evidence of the Plutonic process of
sublimation in metalliferous veins. As the traversing rocks must be of more
recent origin than the traversed, we learn from the relations of
stratification existing between the porphyry and the argentiferous ores in
the Saxon mines (the richest and most important in Germany), that these
formations are at any rate more recent than the vegetable remains found in
carboniferous strata and in the red sandstone.*
[footnote] *Constantin von Veust, 'Ueber die Porphyrgebilde', 1835, s.
89-96; also his 'Belenchtung der Werner'schen Gangtheorie', 1840, s. 6; and
C. von Wissenbach, 'Abbildungen merkwurdiger Gangverhaltnisse', 1836, fig.
12. The ribbon-like structure of the veins is, however, no more to be
regarded of general occurrence than the periodic order of the different
members of these masses.
All the facts connected with our geological hypotheses on the formation of
the earth's crust and the metamorphism of rocks have been unexpectedly
elucidated by the ingenious idea which led to a comparison of the slags or
scoriae of our smelting furnaces with natural minerals, and to the attempt
of reproducing the latter from their elements.
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