of inland waterways—­Rivers and railroads—­Natural unity of every river system—­In arid lands as common source of water supply—­Tendency towards ethnic and cultural unity in a river valley—­Identity of country with river valley—­Rivers as boundaries of races and peoples—­Rivers as political boundaries—­Fluvial settlements and peoples—­Boatman tribes or castes—­River islands as protected sites—­River and lake islands as robber strongholds—­River peninsulas—­River islands as sites of trading posts and colonies—­Swamps as barriers and boundaries—­Swamps as regions of survivals—­Swamps as places of refuge—­The spirit of the marshes—­Economic and political importance of lakes—­Lakes as nuclei of states—­Lakes as fresh-water seas.

CHAPTER XII.  CONTINENTS AND THEIR PENINSULAS

Insularity of the land-masses—­Classification of land-masses according to size and location—­Effect of the size of land-masses—­Independence due to location versus independence due to size—­Continental convergence and ethnic kinship—­Africa’s location—­The Atlantic abyss—­Geographical character of the Pacific—­Pacific affinities of North America—­The Atlantic face of America as the infant Orient of the world—­The Atlantic abyss in the movements of peoples—­Races and continents—­Contrast of the northern and southern continents—­Effects of continental structure upon historical development—­Structure of North and South America—­Cultural superiority of Pacific slope Indians—­Coast articulations of continents—­Importance of size in continental articulations—­Peninsular conditions most favorable to historical development—­The continental base of peninsulas—­Continental base a zone of transition—­Continental base the scene of invasion and war—­Peninsular extremities as areas of isolation—­Ethnic unity of peninsulas—­Peninsulas as intermediaries.

CHAPTER XIII.  ISLAND PEOPLES

Physical relationship between islands and peninsulas—­Character of insular flora and fauna—­Paradoxical influences of island habitat on man—­Conservative and radical tendencies born of isolation and accessibility—­Islands as nurseries and disseminators of distinctive civilizations—­Limitation of small area in insular history—­Sources of ethnic stock of islands on nearest mainland.  Ethnic divergence with increased isolation—­Differentiation of peoples and civilizations in islands—­Differentiation of language—­Unification of race in islands—­Remoter sources of island populations—­Double sources—­Mixed population of small thalassic isles—­Significant location of island way stations—­Thalassic islands as goals of maritime expansion—­Political detachability of islands—­Insular weakness based upon small area—­Island fragments of broken empires—­Area and location as factors in political autonomy of islands—­Historical effects of island isolation in primitive retardation—­Later stimulation of development—­Excessive isolation—­Protection