5. In the Upper Oolite, of 600 feet in thickness, we have a bed of clay (Kimmeridge clay) 500 feet thick, covered by 100 feet of sandy limestones. The clay lands are difficult and expensive to work, and are chiefly in old pasture. The sandy limestone soils above the clay are also poor, but where they rest immediately upon, and are intermixed with the clay, excellent arable land is produced.
6. The Middle Oolite of 500 feet consists also of a clay (Oxford clay) dark-blue, adhesive, and nearly 1000 feet thick, covered by 100 feet of limestones and sandstones. These latter produce good arable land where the lime happens to abound; the clays form close heavy compact soils, most difficult and expensive to work. The extensive pasture lands of Bedford, Huntingdon, Northampton, Lincoln, Wilts, Oxford, and Gloucester, rest chiefly upon this clay, as do also the fenny tracts of Lincoln and Cambridge.
7. The Lower or Bath Oolite, of 500 feet in thickness, consists of many beds of limestone and sandstone, with about 200 feet of clay in the centre of the formation. The soils are very various in quality, according as the sandstone or limestone predominates. The clays are chiefly in pasture,—the rest is more or less productive, easily worked, arable land. In Gloucester, Northampton, Oxford, the east of Leicester, and in Yorkshire, this formation is found to lie immediately beneath the surface, and a little patch of it occurs also on the south-eastern coast of Sutherland.
6. The Lias is an immense deposit of blue clay from 500 to 1000 feet in thickness, which produces cold, blue, unproductive, clay soils. It forms a long stripe of land from the mouth of the Tees, in Yorkshire, to Lyme Regis in Dorset. It is chiefly in old, and often very valuable pasture.
9. The New Red Sandstone, though only 500 feet in thickness, forms the surface of nearly the whole central plain of England, and stretches north through Cheshire to Carlisle and Dumfries. It consists of red sandstones and marls,—the soils on which are easily and cheaply worked, and form some of the richest and most productive arable lands in the island. In whatever part of the world the red soils of this formation have been met with, they have been found to possess in general the same agricultural capabilities.
10. The Magnesian Limestone, from 100 to 500 feet in thickness, forms a stripe of generally poor thin soil from Durham to Nottingham, capable of improvement as arable land by high farming, but bearing naturally a poor pasture, intermingled with sometimes magnificent furze.
11. The Coal Measures, from 300 to 3000 feet thick, consist of beds of sandstones and dark-blue shales (hard clays), intermingled (interstratified) with beds of coal. Where the sands come to the surface, the soil is thin, poor, hungry, sometimes almost worthless. The shales, on the other hand, produce stiff, wet, almost unmanageable clays;—not unworkable, yet expensive to work, and requiring draining, lime, skill, capital, and a zeal for improvement, to be applied to them, before they can be made to yield the remunerating crops of corn they are capable of producing.
12. To the Millstone Grits of 600 feet or upwards in thickness the same remarks apply. They are often only a repetition of the sandstones and shales of the coal measures, forming in many cases soils still more worthless. When the sandstones prevail, large tracts lie naked, or bear a thin and stunted heath; where the shales abound, the naturally difficult soils of the coal shales again recur. These rocks are generally found on the outskirts of our coal-fields.
13. The Mountain Limestone, 800 to 1000 feet thick, is a hard blue limestone rock, separated here and there into distinct beds by layers of sandstones, of sandy slates, or of blue shales like those of the coal measures. The soil upon the limestone is generally thin, but produces a naturally sweet herbage. When the limestone and clay (shale) adjoin each other, arable land occurs, which is naturally productive of oats, yet, when the climate is favourable, capable of being converted into good wheat land. In the north of England a considerable tract of country is covered by these rocks, but in Ireland they form nearly the whole of the interior of the island.
14. The Old Red Sandstone varies in thickness from 500 to 10,000 feet. It possesses many of the valuable agricultural qualities of the new red, consisting, like it, of red sandstones and marls, which crumble down into rich red soils. Such are the soils of Brecknock, Hereford, and part of Monmouth; of part of Berwick and Roxburgh; of Haddington and Lanark; of southern Perth; of either shore of the Moray Firth; and of the county of Sutherland. In Ireland, also, these rocks abound in Tyrone, Fermanagh, and Monaghan; in Waterford, in Mayo, and in Tipperary. In all these places, the soils they form are generally the best in their several neighbourhoods, though here and there,—where the sandstones are harder, more siliceous and impervious to water,—tracts, sometimes extensive, of heath and bog occur.