CHAPTER VI THE PLAIN OF THE PAMPAS 161 The limits of the prairie--The rains--The wind and the formation of the clay of the Pampas--The wind and the contour--The zones of colonization on the Pampas--Hunting wild cattle and primitive breeding--The sheep-farms--The ranches--The region of "colonies"--The region of lucerne, maize, and wheat--The combination of agriculture and breeding--The economic mechanism of colonization--The exchanges between the different zones of the Pampas. CHAPTER VII ROADS AND RAILWAYS 209 Roads on the plain--The salt road--The "trade route"--Transport by ox-waggons--_Arrieros_ and _Troperos_--Railways and colonization--The trade in cereals--Home traffic and the reorganization of the system. CHAPTER VIII THE RIVER-ROUTES 234 The use of the river before steam navigation--Floods--The river plain--The bed of the Parana and its changes--The estuary and its shoals--Maritime navigation--The boats on the Parana. CHAPTER IX THE POPULATION 260 The distribution of the population--The streams of emigration to the interior--Seasonal migrations--The historic towns--The towns of the Pampean region--Buenos Aires. BIBLIOGRAPHY 277 INDEX 291 ILLUSTRATIONS PLATE I. THE FALLS OF THE YGUASSU _Frontispiece_ FACING PAGE II. THE ARID ANDES-- PUNTA VACAS, ON THE TRANS-ANDEAN RAILWAY 22 QUEBRADA DE IRUYA 22 III. THE PATAGONIAN ANDES 38 IV. VEGETATION OF THE INTERIOR VALLEYS (ANDES OF THE NORTH-WEST) 48 FOREST ON THE OUTER SLOPE OF THE SUB-ANDEAN CHAINS 48 V. DRY SCRUB OF THE CENTRAL CHACO 58 MARSHES (ESTEROS OR CANADAS) OF THE EASTERN CHACO 58 VI. THE _VALLE_ OF SANTA MARIA, NORTH-WEST OF MOUNT ACONCAGUA 70 THE OASIS OF ANDALGALA 70 VII. THE OASIS DEL RINCON, BELOW SAUJIL (ANDALGALA LINE, PROVINCE OF CATAMARCA) 82 THE MONTE AT EL YESO 82 VIII. A VINEYARD AT SAN JUAN 92 A VINEYARD AT MENDOZA 92