During the period from 1875 to 1890 were constructed the main lines which took the place of the old roads from province to province. The Andean railway reached San Luis in 1882 and Mendoza and San Juan in 1885. Branches of the Central Cordoba reached Santiago del Estero in 1884 and Catamarca in 1889. In 1891 the Central Argentine opened a new direct broad-gauge line from Rosario to Tucuman; and almost at the same time the narrow-gauge line of the Central Norte, from Santa Fe to Tucuman, was finished further north. The Tucuman line was continued northward to the foot of the Andes as far as Salta. In the province of Buenos Aires the Bahia Blanca line was opened in 1884. Since 1900 the railways have pushed on to the frontiers and are linked in various directions with those of the adjoining countries. The Cumbre tunnel on the Mendoza trans-Andean was completed in 1910, and traffic with Chile by rail is now permanent. The Salta line was continued in 1908 to the Bolivian tableland. In Mesopotamia, in fine, the north-eastern line reached Posadas in 1911 and effected a junction with the Paraguay line. These details, however, give a very imperfect idea of the history of the development of the Argentine railway system. It has not merely been superimposed upon the old roads, but has, on the other hand, helped to open up and develop new lands, which could not have been colonized without it. As early as 1883 Valiento Noailles, examining the general plan of the system, noticed the profound difference between the railways of Argentine and those of Europe. "In Europe," he said, "the railways are constructed to serve existing centres of production and consumption.... Our Argentine railways are to facilitate colonization." Corresponding to each occupation of a new area of the Pampean plain by the farmer or the breeder is the construction in that area of a new network of lines which are fed by its traffic and in turn help it to increase its production. The more productive the region is, the closer are the meshes of this network. They are wider in the pastoral than in the agricultural areas. The period of the development of the southern lines in the province of Buenos Aires corresponds with the expansion of breeding when the Pampa had been pacified. The railway reached Azul in 1876. The Ayacucho branch was opened in 1880, and continued as far as Tres Arroyos in 1887. The completion of the Bahia Blanca line, via Azul and Olavarria, in 1884, is itself merely one of the dates in this colonizing period. The great period of agricultural colonization at Santa Fe and the construction of the system of lines that serve it begin a little later, and last from 1880 to 1890 (extension of the Central Argentine system, the railways of the province of Santa Fe, and the narrow-gauge railway from Rosario to Cordoba).