f the escarpments. By the study of the adjustment of these
rivers to their valleys, and of the relation of the valleys to the
general structure, Professor W. M. Davis has elaborated a theory of
river classification, and a scheme of the origin of surface-features
which is attractive in its simplicity. The Thames is the one great
river of the division, rising on the Jurassic Belt, crossing the Chalk
country, and finishing its course in the Tertiary London Basin,
towards which, in its prevailing west-to-east direction, it draws its
tributaries from north and south. The other rivers are shorter, and
flow either to the North Sea on the east, or to the English Channel on
the south. With the exception of the Humber, they all rise and pursue
their whole course within the limits of the Eastern Division itself.

The Eastern Division is the richest part of England agriculturally, it
is the part most accessible to trade with the Continent, and that
least adapted for providing refuges for small bodies of men in
conflict with powerful invaders. Hence the latest of the conquerors,
the Saxon and other Germanic tribes, obtained an easy mastery, and
spread over the whole country, holding their own against marauding
Northmen, except on the northern part of the east coast; and even
after the political conquest by the Normans, continuing to form the
great mass of the population, though influenced not a little by the
fresh blood and new ideas they had assimilated. The present population
is so distributed as to show remarkable dependence on the physical
features. The chalk and limestone plateaus are usually almost without
inhabitants, and the villages of these districts occur grouped
together in long strings, either in drift-floored valleys in the
calcareous plateaus, or along the exposure of some favoured stratum at
their base. In almost every case the plain along the foot of an
escarpment bears a line of villages and small towns, and on a good map
of density of population the lines of the geological map may be
readily discerned.

_The Jurassic Belt._--The Jurassic belt is occupied by the counties of
Gloucester, Oxford, Buckingham, Bedford, Northampton, Huntingdon,
Rutland, Lincoln and the North Riding of Yorkshire. The rocks of the
belt may be divided into two main groups: the Lias beds, which come
next to the Triassic plain, and the Oolitic beds. Each group is made
up