humanity most easily moves, determine within certain limits the
direction of its flow, the velocity and volume of its current. Every new
flood tends to fit itself approximately into the old banks, seeks first
these lines of least resistance, and only when it finds them blocked or
pre-empted does it turn to more difficult paths.

[Sidenote: Regions of historical similarity.]

Geographical environment, through the persistence of its influence,
acquires peculiar significance. Its effect is not restricted to a given
historical event or epoch, but, except when temporarily met by some
strong counteracting force, tends to make itself felt under varying
guise in all succeeding history. It is the permanent element in the
shifting fate of races. Islands show certain fundamental points of
agreement which can be distinguished in the economic, ethnic and
historical development of England, Japan, Melanesian Fiji, Polynesian
New Zealand, and pre-historic Crete. The great belt of deserts and
steppes extending across the Old World gives us a vast territory of rare
historical uniformity. From time immemorial they have borne and bred
tribes of wandering herdsmen; they have sent out the invading hordes
who, in successive waves of conquest, have overwhelmed the neighboring
river lowlands of Eurasia and Africa. They have given birth in turn to
Scythians, Indo-Aryans, Avars, Huns, Saracens, Tartars and Turks, as to
the Tuareg tribes of the Sahara, the Sudanese and Bantu folk of the
African grasslands. But whether these various peoples have been Negroes,
Hamites, Semites, Indo-Europeans or Mongolians, they have always been
pastoral nomads. The description given by Herodotus of the ancient
Scythians is applicable in its main features to the Kirghis and Kalmuck
who inhabit the Caspian plains to-day. The environment of this dry
grassland operates now to produce the same mode of life and social