The figures are rather less for the Southern, which covers an area that has remained chiefly pastoral and, by means of its Rio Negro line, serves for part of the transport of cattle from Patagonia (cattle-transport on the Southern, average for the years 1913, 1914 and 1916: 17.2 per cent. of the total tonnage, 19 per cent. of total receipts; 1.4 per cent. of tonnage and 6.5 per cent. of receipts). They are higher for the Western, the only system that lies entirely in the Pampean region and has no continuations beyond it, as the Pacific has to Mendoza and the Central to Tucuman. The share of each company in the total traffic varies from year to year according to the harvest. Of the four to ten million tons of cereals carried every year, the greater part--about a third--falls to the Central Argentine, and one-sixth to the Southern. The Central Argentine carries the greater part of the maize and flax, the maize alone representing 26 per cent. of the total tonnage carried by the line, and the flax 5.6 per cent. Of the other lines the Western alone carries any appreciable quantity of maize, which comes from the Junin district (19 per cent. of its tonnage, but only 12 per cent. of its receipts, because of the slight distances the stuff is carried). The transport of wheat is about equally divided amongst the four leading lines, but the proportion of it to total traffic is highest in the case of the Western (34.4 per cent. of total traffic). The Southern is the chief carrier of oats (9.8 per cent. of the total tonnage). The tonnage carried annually is particularly irregular in the case of the Central, on account of the irregularity of the maize crops, and the Pacific, because its lines north-west of Buenos Aires serve a wheat-area that is exposed to drought (wheat carried by the Pacific in 1913, 15.9 per cent. of the total tonnage; in 1914, 27.2 per cent.). The clearing of the cereals gives the Argentine railways a delicate problem in the organization of traffic. The crops of flax, wheat and oats must be cleared in the four to six months following the harvest (December-January). The maize harvest, which is later, is also much slower; it lasts the whole of the autumn. Hence the removal of the maize is spread over a long period, and sometimes the work of one year runs into that of the next. This gives the Central an advantage over the other lines. The wool also must, on account of its great value, be transferred to the ports speedily after the shearing; but this is only a matter of about a hundred thousand tons.[116] [116] The war and the difficulties of marine freightage have lessened the seriousness of the problem of carrying goods rapidly by rail in Argentina.