It is not easy, in the absence of documents, to attempt to give for Patagonia as a whole a detailed description of the pastoral industry, and to follow step by step on the spot its efforts to adjust itself to the natural conditions. But the analysis may be attempted in regard to the region between San Antonio and Lake Nahuel Huapi south of the Rio Negro,[71] the valley of the Rio Negro, and the tableland which stretches westward between the Neuquen and the Limay. This part of Patagonia is now easily accessible, and it is entered by two parallel railways. One starts from San Antonio on the Atlantic, and goes westward to Lake Nahuel Huapi. It has (1914) reached Maquinchao, on the tableland, mid-way across the Andes. The other starts from Bahía Blanca. At Choele Choel it enters the valley of the Rio Negro, and ascends it as far as the confluence of the Neuquen. Then it goes 130 miles westward as far as Zapala, at the foot of the first sub-Andean chains. Each of these lines is ambitious to attract the trans-Andeans. At all events, they are in a hurry to reach the humid zone at the foot of the Andes, which could maintain a busier traffic than the desolate tableland.
The railway from San Antonio, and the road which is a continuation of it west of Maquinchao, cover a distance of 320 miles from the Atlantic to the Andes, and cross five distinct regions. The first is the coastal plain, composed of horizontal marine Tertiary sedimentary rocks, both of sand and clay. The plain rises slowly toward the west, and it attains a height of 650 feet at a distance of seventy miles from the coast. This coastal platform divides, on the north-west, the enclosed hollow of the Bajo del Gualicho from the Gulf of San Antonio. Its surface is very even. The gravel on it has formed a sort of conglomerate, and in spite of appearances, this gravelly soil is not bad for vegetation. It quickly absorbs the rain-water, which thus escapes evaporation. The vegetation is comparatively rich. There are no springs, but the autumn rains sustain manantiales in the marly surface, and these do not dry up until the spring. During the summer the plain is deserted, and there is no water. But the flocks return in the winter and remain there until spring. There is very little snow, as the temperature is moderate. In spite of the density of the pastoral population in winter, the pasturage is not injured. The grass grows plentifully amongst the thickets. This is because the flocks leave the district before the season when the grasses flower and reproduce, so the next generation is secured. Part of the flocks which winter on the coastal plain pass the summer in the south-west, on the high basaltic tablelands of Somuncura. However, the whole of the surface of the tableland cannot be used permanently, or during the entire summer. There is plenty of water in spring, when the snows have melted. In the middle of the summer the flocks collect round the permanent springs, and they scatter once more over the mountain pastures during the autumn rains, before they return to the plain.
The second region is that of Valcheta. From Aguada Cecilia to Corral Chico the railway follows for sixty miles the edge of the outpour of lava from the south, which covers the Tertiary clays. In front of the basalt cliff the land dips in the north toward a closed depression, the Bajo de Valcheta, the bottom of which consists of clays impregnated with salt. Tertiary marine strata surround this hollow in the west and north, where they divide it from the Bajo del Gualicho, but here they form only a thin skin which covers the crystalline platform. The line of contact of the basalt and the Tertiary marls is marked by a series of good springs, and these give rise to permanent streams, such as the Arroyo Valcheta and the Nahuel Niyeu. At first they flow in a narrow valley crowned by basalts, with peaty prairies at the bottom, then over Tertiary marls, and, in the latitude of the railways, they pass into a gorge cut through the granites before losing themselves to the north in the salitral. A small agricultural oasis is sustained by the waters of the Valcheta.
The site of Valcheta has an exceptional importance in the story of Patagonian colonization. It marks a necessary stage in the Indian track from the Atlantic to Nahuel Huapi, which is now followed by the line of the railway. Musters halted there. The track from Choele Choel, on the Rio Negro, to the southern coast and the Santa Cruz also passed by there. It was so much used, says Ezcurra, that the hoofs of the horses had hollowed it.[72] The Argentine village dates from 1890. At first it lived by supplying fodder to the convoys of wagons which carried the wool. The railway has suppressed this traffic, and the only outlet of the oasis to-day is the small port of San Antonio, where the wool is shipped, and where the district is unsuitable for any kind of cultivation.
Like the coast region, the Valcheta district seems marked out by its moderate altitude to serve as winter pasture. In point of fact, it is used during the whole year. The springs do not dry up in summer. The streams which flow from the south toward the Bajo de Valcheta are permanent. In addition, a few wells have been bored in the Tertiary strata. Contrary to experience on the coast, therefore, cattle can be kept here during the summer. There is less chance for the grasses to reproduce, and the pasture tends to become impoverished.
The third zone, 130 miles from the coast, is that of the tableland of the Cerros Colorados, where low masses of red granite rise like an archipelago amongst the Tertiary formations deposited in the intervening depressions. In the west its altitude rises from 650 to 1,300 feet. It is one of the poorest parts of the tableland, and the size of the flock is reduced to 600 head to the square league. The naked rock crops up, not covered, as it is further east, by a bed of gravel. In the valleys there is little water, and it lies very deep. There are no periodical removals of the animals. Winter and summer they remain within range of a few poor springs, which are caused by various outcrops of lava of limited extent; and they leave these, and wander over the tableland, only in the rainy season.
Beyond the Cerros Colorados the line rises rapidly, and at Maquinchao it reaches the basin of Lake Carilaufquen. This occupies the bottom of a closed depression, at an altitude of 3,000 feet, dominated on every side by a plateau of lava, toward which, in the south, a number of important valleys run (Nahuel Niyeu, Quetriquile, Maquinchao). These valleys rise in the south in the basalt plateau, at a height of 4,000 and 4,700 feet, and have no running water except at their upper ends. South of Carilaufquen they open upon a broad plain, round which there is a sombre cornice of lava, about 350 feet high. Water has collected on the plain, which consists of alluvial beds redistributed by wind: angular pebbles from the terraces, fine dust from the mallinas, and sand from the dunes round the lake.
This region is much better than that of the Cerros Colorados. There are many springs at the base of the lava-flows, on the sides of the valleys, and it has as yet not been necessary to look for the subterranean sheets which accompany some of the valleys. The elevated basin of the Quetriquile, though it is only occupied by intrusos, seems to have a particularly high pastoral density, and, I am told, feeds 500,000 sheep. In the western part of the region the spring is late, and there is risk of snow during the lambing season. There are, however, no rams there; the lambs are brought from Maquinchao. This arrangement of special zones for the multiplication of the flock enables them rapidly to improve the breed. Here again there are no removals of the animals to a great distance in order to use the pasture. The vegetation of the valleys suffered from the continuous presence of the flocks during the years of drought before 1914; the reproduction of useful grasses was prevented. There is, however, less danger here than on the Cerros Colorados, because the mallinas are extensive, and they suffice for feeding the sheep during the periods when the manantiales of the tableland dry up, and the animals are confined to the valleys.