The Patagonian plain, however, is, in appearance at any rate, a different and much older formation, namely the Tertiary, an extensive gravel bed which possibly extends under the whole Quaternary deposit of the Pampa. But exposures occur of both varieties of this formation, i.e., the Patagonian and the Guaraman, in the banks of the Parana and elsewhere. It is supposed to have been contributed chiefly by Glacial action.
THE RIVER URUGUAY.
The river system of Argentina, which is perhaps the most remarkable physical feature of the country, next demands our attention. All the Argentine rivers find their way into the Atlantic, but all are insignificant compared with the marvellous confluence of mighty streams in the Plate estuary. The Parana rises in far-away Brazilian mountains, and is already a noble stream when it reaches the north-eastern confines of Paraguay. Flowing southward it then, for more than 100 miles, serves as the boundary between Paraguay and Brazil, and from the point where it is joined by the Iguazu River it becomes an Argentine stream, and, inclining more and more to the west, it is now the boundary between Argentine and Paraguay. At Corrientes it unites with the Paraguay River and flows almost due south, running into the Plate estuary at the same point as the Uruguay. Few rivers can match the Parana in majesty; at Rosario it is 20 miles wide, and would give the impression of the broad sea were it not for the cluster of poplar-clad islands which intercept the view. In thus tracing the course of the Parana we have mentioned only a few of the innumerable streams of the system in which it takes the most conspicuous part; the waters drain the south of Brazil, the whole of Uruguay and Paraguay, the fertile districts of Argentina, and even portions of Bolivia. The Parana—the Nile of the West—debouches through fourteen channels; it has a drainage area of 1,198,000 square miles, and the discharge of each twenty-four hours is sufficient to create a lake a mile square and 1,650 feet deep.[8] Subordinate to the Parana are several Argentine systems which deserve mention. The provinces of Corrientes and Entre Rios, called the Argentine Mesopotamia, are drained by the Corrientes, the Saranai, and the Gualeguay, which last falls eventually not into the Parana but the Pavon, a curious channel which runs parallel with the lower course of the great river for a considerable distance.
RIVER LANDING STAGE.
The northernmost part of the country is drained by the Pilcomayo and the Vermejo, which both fall into the Paraguay. The Vermejo has a course of 1,300 miles. The Salado meanders through the Gran Chaco, and is the only perennial river in that region. Owing to the western dryness and the curious contour of the Gran Chaco and the Pampa, many of the rivers are unable to make headway and find a channel to carry them to the sea. Thus the Rio Dulce which, with innumerable small tributaries, drains a large area round about Tucuman, ends in a morass named Porongos, which is connected in flood-time with the great lake of Mar Chiquita—Little Sea. In like manner the Mendoza river loses itself in arid country.