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 agriculture--Its geographical distribution--Terrace agriculture in mountainous islands--Among savage peoples--Fertilizing terrace lands--Economy of level land--Mountain pastures and stock-raising--Life and industry of the summer herdsmen--Communal ownership of mountain pastures--Hay making in high mountains--Winter industries of mountain peoples--Overpopulation and emigration--Preventive checks to increase of population--Religious celibacy--Polyandry--Marauding tendencies in mountaineers--Historical consequences of mountain raiding--Conquest of mountain regions--Political dismemberment of mountain peoples--Types of mountain states--Significance of their small size--Mountain isolation and differentiation--Survival of primitive races in mountains--Diversity of peoples and dialects--Constriction of mountain areas of ethnic survival--Isolation and retardation of mountain regions--Mental and moral qualities of mountain people. CHAPTER XVII. THE INFLUENCES OF CLIMATE UPON MAN