industries--Arid lands as areas of arrested development--Mental and
moral qualities of nomads--Religion of pastoral nomads.


CHAPTER XV. MOUNTAIN BARRIERS AND THEIR PASSES

Man as part of the mobile envelope of the earth--Inaccessibility of
mountains--Mountains as transit regions--Transition forms of relief
between highlands and lowlands--Piedmont belts as boundary
zones--Density of population in piedmont belts--Piedmont towns and
cities--Piedmonts as colonial or backwoods frontiers--Mountain
carriers--Power of mountain barriers to block or deflect historical
movement--Significance of mountain valleys--Longitudinal valleys--Passes
in mountain barriers--Breadth of mountain barriers--Dominant
transmontane routes--Height and form of mountain barriers--Contrasted
accessibility of opposite slopes--Political and ethnic
effects--Persistence of barrier nature--Importance of mountain
passes--Geographic conditions affecting the historical importance of
passes--Passes determine the transmontane routes--Navigable river
approaches to passes--Types of settlement in the valley approaches--Pass
cities and their markets--Pass peoples--Their political importance.


CHAPTER XVI. INFLUENCES OF A MOUNTAIN ENVIRONMENT

Zones of altitude--Politico-economic value of a varied relief--Belief
and climate--Altitude zones of economic and cultural
development--Altitude and density belts in tropical
highlands--Increasing density where altitude confers safety--Geographic
conditions affecting density of mountain population--Terrace