which they afford are
swamps. Neither solid land nor navigable water, their sluggish, passive
surface raises an obstacle of pure inertia to the movements of mankind.
Hence they form one of those natural boundaries that segregate. In
southern England, Ronmey Marsh, reinforced by the Wealden Forest, fixed
the western boundary of the ancient Saxon kingdom of Kent by blocking
expansion in that direction, just as the bordering swamps of the Lea and
Colne rivers formed the eastern and western boundaries of
Middlesex.[729] The Fenland of the Wash, which extended in Saxon days
from the highland about Lincoln south to Cambridge and Newmarket, served
to hem in the Angles of Norfolk and Suffolk on the west, so that the
occupation of the interior was left to later bands who entered by the
estuaries of the Humber and Forth.[730] In northern Germany, the low
cross valleys of the Spree, Havel and Netze rivers, bordered by alder
swamps, were long a serious obstacle to communication, and therefore
became boundaries of districts,[731] just as the Bourtanger Moor drew
the dividing line between Holland and Hanover.

[Sidenote: Swamps as regions of survival.]

Swamp-bordered regions, as areas of natural isolation, guard and keep
intact the people which they hold. Therefore they are regions of
survival of race and language. The scattered islets of the Fens of
England furnished an asylum to the early British Celts from Teutonic
attacks,[732] and later protected them against dominant infusion of
Teutonic blood. Hence to-day in the Fenland and in the district just to
the south we find a darker, shorter people than in the country to the
east or west.[733] Similarly the White Russians, occupying the poor,
marshy region of uncertain watershed between the sources of the Duna,
Dnieper and Volga, have the purest blood of all the eastern Slavs,
though this distinction is coupled with poverty and retarded
culture,[734] a combination that anthropo-geography often reveals.
Wholly distinct from the Russians and segregated from them by a barrier
of swampy forests, we find the Letto-Lithuanians in the Baltic province
of Courland, speaking the most primitive form of flectional languages
classed as Aryan. The isolation which preserved their archaic speech, of
all European tongues the nearest to the Sanskrit, made them the last
European people to accept Christianity.[735] The great race of the
Slavic Wends, who once occupied all northern Germany between the