When we study the variations in the numbers of cattle in different parts of the Pampa, by comparing the results of recent Censuses we find that the number has risen rapidly since 1895 in the whole of the eastern area, north of the Sierra de Tandil. The increase is particularly conspicuous north of the Rio Salado, in the dairy district. (Mean density in 1915, 40 to 60 horned cattle per square kilometre.) In the south-west region (wheat belt) the density has always been low (12 per square kilometre), and it shows no tendency to increase. In the north and western region of Buenos Aires (lucerne belt) there has been a rapid increase, especially between 1895 and 1908 (creation of the lucerne farms), and it has not been interrupted since (density 50 to the square kilometre). There is the same increase in the whole area of the lucerne farms in the Cordoba, Santa Fe, and San Luis provinces, where the herds doubled between 1895 and 1908. Only two regions have suffered a reduction: the agricultural area of the centre (Chacabuco, Chivilcoy), where there has been a decrease since 1895, and the maize district (north of Buenos Aires), where cattle-rearing did not diminish until after 1908. * * * * * Agriculture had begun to develop by the end of the eighteenth century in the district round Buenos Aires. D'Azara admits the enormous preponderance of breeding, but mentions that the right bank of the Parana exported flour to the left bank, which was exclusively pastoral. Barrero also observes that between the belt of orchards and lucerne fields, about a league in width, which surrounded Buenos Aires, and the area of the ranches, which did not begin for six or eight leagues, there was an agricultural belt, the district of the _chacras de pan llevar_. The main crop was wheat, and the tillage was chiefly done in the rich soils at the bottom of the valleys, which are called _canadas_ in the local dialect (canada de Moron, canada du Rio Lujan, etc.). It was, however, not at Buenos Aires, but in the Santa Fe province, that modern agricultural colonization began in the nineteenth century. It goes back to the foundation (in 1854) of the colony of Esperanza, west of Santa Fe, from which it was separated by the strip of forest which follows the course of the Salado. European immigrants--Swiss, French, and Piedmontese--had settled there. The early years of colonization at Santa Fe were difficult, and the colonies did not begin to develop rapidly until after 1870. About that date we can distinguish three nuclei of agricultural colonization at Santa Fe. The first group of colonies was settled in the north, on the bank of the Parana. In the centre the Esperanza group advanced steadily westward. A third group of colonies lay along the Central Argentine railway from Rosario to Cordoba.