[69] In spite of their importance we must regard as mere episodes in the story of Patagonian colonization the influx of population caused on the eastern coast by the discovery of placer-gold at Cape Virgenes and on the Atlantic coast of Tierra del Fuego (1884), and the discovery of petroleum at Rivadavia (1907) in the course of drilling in search of water. Rivadavia is already, with its 3,000 inhabitants, one of the chief centres in Patagonia.
[70] The search for possible routes for cattle in the districts that were not yet colonized helped in the study of Patagonia. Moyano was doing this when he explored the route from Santa Cruz to Lake Nahuel Huapi.
[71] This was the area studied by the Commission of which Bailey Willis was chairman.
[72] Pedro Ezcurra, "Camino indio entre los rios Negro y Chubut: la travesia de Valcheta," Bol. Instit. Geog. Argent., xix. 1898, pp. 134-38.
[73] The district of the Rio Negro is not the only part of Patagonia which faces the problem of increasing the winter pasture. Attention has been drawn to the possibility of enlarging the lucerne farms in the district of Colonia Sarmiento, south of Lake Musters, and making this a great wintering area for the Santa Cruz flocks.
[74] The work now (1914) in hand will reduce the risk of floods, and will enable them to enlarge considerably the extent of the tilled land. The Cuenca Vidal, which opens amongst the sandstone, below the level of the valley, on the tableland to the north of the Neuquen, will be arranged so as to absorb the flood-water, and it will feed a canal which will serve the left bank over an area of 100 miles. The waters of the Limay will be available for the lower valley.
[75] As a matter of fact, of recent years there has been a practice on this slope of disguising the smuggling of animals under the name of "transhumation," as the removal of the sheep facilitated it and helped to maintain it. The shepherds got certificates exaggerating the number of their sheep from the Chilean officials before they crossed the frontier, and under cover of these they came back to Chile with additions to their flocks which they had bought on Argentine territory.
[76] On the left bank of the Salado, west of the Resistencia railway, a great gulf of low prairie penetrates into the forest of the Chaco in the north, almost as far as 28° S. lat., but it has rather the character of one of the floodable clearings of the Chaco (esteros) than of the temperate Pampa.
[77] Argentine Mesopotamia, which is a continuation of the Pampean region from the climatological point of view, is also, even in its northern part, without the rigorous dry seasons of the Chaco. Ascending the Paraná, from Corrientes to Posadas, just as in passing from Córdoba to Buenos Aires, one notices that the winter minimum decreases, and a secondary maximum appears in the spring. The predominance of the spring rains, which is a characteristic of southern Brazil, is conspicuous on the middle Uruguay. On the lower part of that river the rain-system approaches that of Buenos Aires, with maxima in spring and autumn, a principal minimum in winter, and a secondary minimum in summer.
[78] While the Pampean deposits lie immediately on the crystalline and Paleozoic formations in the sierras of the lower Colorado and of the central Pampa, in the south of the province of Buenos Aires and in Uruguay, they are, on the eastern edge of the Sierra de Córdoba, separated from it by red sandstones and conglomerates of uncertain age, perhaps synchronous with the continental red sandstones of Corrientes which outcrop east of the Paraná and have been known since D'Orbigny's time as "granitic sandstones."