Page:A Treatise on Geology, volume 1.djvu/219

 CHAP. VI. those of the carboniferous and triassic periods. The cupreous element is attributed to springs flowing from the Ural in the ancient zechstein period: to similar causes we may probably ascribe the copper in the Kupferschiefer of Maarfeld, and in the limestone at a few localities in Yorkshire: the fishes extended in a perfect form on this shale may have been the victims of such infusions.

In Thuringia and Hesse Cassel the zechstein is surmounted by red and spotted sandstones (Lower Bunter) with calamities arenarius, a coal measure plant; these sandstones are referred to the Permian series, which thus becomes triple, viz.:

Lower Bunter. Zechstein. Rotheliegende.

Judging by mineral associations and great structural analogies, Mr. Conybeare united this group of variable strata with the subjacent magnesian limestone; nor is it without a species of divulsion that they can be separated. Yet their organic history is different, and it is by their palæontological relations that the strata are now most successfully gathered into large associations, which can be recognised over distant regions. The red marls and sandstones which compose the trias in Germany form three main groups,—viz.: