of an alternation of soft marls or clays and hard limestones or
sandstones. The low escarpments of the harder beds of the Lias are the
real, though often scarcely perceptible, boundary between the Triassic
plain and the Jurassic belt. They run along the right bank of the
Trent in its northward course to the Humber, and similarly direct the
course of the Avon southward to the Severn. The great feature of the
region is the long line of the Oolitic escarpment, formed in different
places by the edges of different beds of rock. The escarpment runs
north from Portland Island on the English Channel, curves
north-eastward as the Cotteswold Hills, rising abruptly from the
Severn plain to heights of over 1000 ft.; it sinks to insignificance
in the Midland counties, is again clearly marked in Lincolnshire, and
rises in the North Yorkshire moors to its maximum height of over 1500
ft. Steep towards the west, where it overlooks the low Lias plain as
the Oolitic escarpment, the land falls very gently in slopes of Oxford
Clay towards the Cretaceous escarpments on the south and east.
Throughout its whole extent it yields valuable building-stone, and in
the Yorkshire moors the great abundance of iron ore has created the
prosperity of Middlesbrough, on the plain below. The Lias plain is
rich grazing country, the Oxford Clay forms valuable agricultural
land, yielding heavy crops of wheat. The towns of the belt are
comparatively small, not one attains a population of 75,000, and the
favourite site is on the Lias plain below the great escarpment. They
are for the most part typical rural market-towns, the manufactures,
where such exist, being usually of agricultural machinery, or woollen
and leather goods. Bath, Gloucester, Oxford, Northampton, Bedford,
Rugby, Lincoln and Scarborough are amongst the chief. North of the gap
in the low escarpment in which the town of Lincoln centres, a close
fringe of villages borders the escarpment on the west; and throughout
the belt the alternations of clay and hard rock are reflected in the
grouping of population.

_The Chalk Country._--The dominating surface-feature formed by the
Cretaceous rocks is the Chalk escarpment, the northern edge of the
great sheet of chalk that once spread continuously over the whole
south-east. It appears as a series of rounded hills of no great
elevation, running in a curve from the mouth of the Axe to Flambo