In the years immediately preceding 1914, a sudden revolution upset the cattle traffic on the Neuquen, and the attraction of Buenos Aires took the place of that of the Chilean market. The commercial influence of Buenos Aires was first felt in the wool-market. The _tropas_ of wagons which brought wool to Zapala loaded up, in exchange, with the flour and salt that were needed for sheep-breeding in the pastures of the Cordillera (_pastos dulces_). The import trade followed the path traced by the export trade. The small Chilean wagons which still cross the Cordillera now only bring to the Neuquen the coarse flour of Chile, haricot beans, and wine. They return empty to Chile. After the wool-buyers, the cattle-merchants of Buenos Aires next found their way to the Cordillera. The centres where the sales of cattle for Chile used to be held are now in decay, and have lost part of their population. The cattle are sent to the fattening centres on the Pampa, or to the Bahia Blanca and Buenos Aires markets. Thus we have under our eyes, unexpectedly, in the north of Patagonia a transformation that occurred gradually half a century ago in all the western and north-western parts of Argentina. In its many forms it is the essential fact in the modern history of Argentine colonization. The more distant provinces are detached in succession from foreign markets, and the whole national life is being organized round the great economic focus which the region of the Pampas has become. CHAPTER VI THE PLAIN OF THE PAMPAS 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.