[114] The continuation of many of these lines was contemplated for the future, so as to secure for them at a later date a long-distance traffic. The Resistencia and Formosa lines, which reach the Andes, may compete for traffic with the Rosario and Tucuman lines. In Patagonia, the continuation across the Andes of the line from San Antonio to Lake Nahuel Huapi has been considered. A pass has been found at a height of 4,000 feet. When this plan is carried out, the Trans-Andean from Nahuel Huapi would be in a position to compete successfully with the Trans-Andean from Uspallata, which is condemned by its elevation to remain a passenger line. These plans, still far from realization, do not deprive the Ramos Mejia lines of their character as colonization lines, entirely devoted at present to conveying the timber of the Chaco and the wool of Patagonia. Hence railway construction must be regarded in modern Argentina as one of the aspects of the problem of developing the soil. The railway companies have been compelled to intervene directly in the work of colonization. In 1863 the Central Argentine received from the Government a strip of land three miles wide on each side of the line it was making, between Rosario and Cordoba, on condition that it colonized the land. The company had its own immigration agents and its colonizing staff, and it opened its first colonies west of Rosario between 1870 and 1872. This kind of concession is exceptional in Argentina. On the other hand, the irrigation law of 1909 obliges the railway companies to undertake, on behalf of the Government, the work that is necessary to develop irrigation in the areas they serve, such work being immediately reflected in an increase of population and traffic. In compliance with this law the Southern railway is constructing a canal which will water the whole valley of the Rio Negro below the confluence of the Neuquen. The Central Argentine and the Pacific also have undertaken to construct dams on the Rio Tercero and Rio Quinto, in the provinces of Cordoba and San Luis.