Page:A Treatise on Geology, volume 1.djvu/183

 CHAP. VI.

Further north, viz. in the north-western parts of Yorkshire, the series is still more complicated and varied: as under:—

Pursuing the system to Northumberland, we find the scar limestone broken up into very many parts by inter positions of grits, shale, and abundance of coal; one of the grits being pebbly. Thus the whole method of variation of the system of carboniferous strata becomes known and appears nearly as in the diagram (fig. 18. p. 59.).

We may here notice the remarkable section presented in the Island of Arran, where, according to Murchison and Sedgwick, the new and old red formations are merely separated by a thin zone of limestone and coal, or, as from a careful examination we should be disposed to express it, where only small and diminished members of the mountain limestone formation (in one place yielding coal) appear buried in masses of red conglomerate, sandstone and shale, of very great thickness, there being no certain criterion for deciding that any of this series belongs to the new red sandstone. This