Page:A Treatise on Geology, volume 1.djvu/72

Primary or Palœozoic Strata.
Magnesian or Permian[1] System.
Names of formations.	Thickness in yards.		Subdivisions or groups.	Nature of the deposits.
Magnesian limestone (North of England).	100	$\left\{{\begin{matrix}\ \\\ \\\ \\\ \\\ \\\ \\\ \end{matrix}}\right.$	Knottingley limestone.	Grey laminated limestone.
			Gypseous marls.	Red and white clays, &c.
			Magnesian limestone.	Yellow, granular, &c. limestone.
			Marl slate.	Laminated calcareous beds, with fishes.
			Rothetodteliegende.	Red sandstones and clays.
Carboniferous System.
Coal.	1000	$\left\{{\begin{matrix}\ \\\ \\\ \\\ \\\ \end{matrix}}\right.$	The subdivisions are only locally ascertained.	Strata of sandstone, shale, ironstone, with rare deposits of freshwater limestone.
			Millstone grit	Sandstones, often coarse grained, or pebbly; shales, iron stones, thin limestones.
Carboniferous limestones (N. of England).	900	$\left\{{\begin{matrix}\ \\\ \\\ \end{matrix}}\right.$	Yoredale rocks.	Limestones, sandstones, shales, coals.
			Sear limestones.	Limestones.
			Alternating sandstone, and limestones.	Limestones, sandstones, &c., often red.
Old Red or Devonian System.[2]
Old red sandstone (Herefordshire.)	100 to 3300	$\left\{{\begin{matrix}\ \\\ \\\ \\\ \\\ \end{matrix}}\right.$	Conglomerate group	Conglomerates and sandstones.
			Cornstone group.	Coloured clays and concretionary limestones.
			Tilestone group.	Flagstones and clays. The lower beds pass to the group below.

1. So named by Murchison, from a large Russian district, in which he has found it more fully developed than in England. (Geol. of Russia.)
2. As seen in Herefordshire, &c. In North and South Devon the series is different, as will be explained hereafter.