Relief of the sea floor--Mean elevations of the continents--Distribution
of relief--Homologous reliefs and homologous
histories--Anthropo-geography of lowlands--Extensive plains unfavorable
to early development--Conditions for fusion in plains--Retardation due
to monotonous environment--Influence of slight geographic features in
plains--Plains and political expansion--Arid plains--Nomadism--Pastoral
life--Pastoral nomads of Arctic plains--Historical importance of steppe
nomads--Mobility of pastoral nomads--Seasonal migrations--Marauding
expeditions--Forms of defense against nomad depredations--Pastoral life
as a training for soldiers--Capacity for political organization and
consolidation--Centralization versus decentralization in
nomadism--Spirit of independence among nomads--Resistance to
conquest--Curtailment of nomadism--Supplementary agriculture of pastoral
nomadism--Irrigation and horticulture--Scant diet of nomads--Effects of
a diminishing water supply--Checks to population--Trade of
nomads--Pastoral nomads as middlemen--Desert markets--Nomad
industries--Arid lands as areas of arrested development--Mental and
moral qualities of nomads--Religion of pastoral nomads.