The vast tract of the pampas, over 300,000 sq. m. in area, is itself distinguishable into several subdivisions, differing in climate and products, although under the same parallel. Proceeding from Buenos Ayres, the first of these sub-re-gions presents for nearly 200 m. an alternate growth of clover and thistles; the next a covering of long grass and brilliant flowers, extending without a weed some 400 m. further westward; the third, reaching to the base of the Andes, one continuous grove of shrubs and small evergreen trees, so evenly set that a horseman may gallop at random between them without inconvenience. Change of season brings little variation in the aspect of the two regions last mentioned; but in the first remarkable mutations occur. During the winter months the thistles and clover are exceedingly rich and strong, and herds of wild cattle are seen browsing in every direction. On the approach of spring the clover disappears, and nothing is distinguishable save an immense forest of giant thistles, tall enough to almost totally obstruct the view, and so closely set and so strong as to form an impenetrable barrier. In summer the thistles give place to a new and luxuriant growth of clover.

The Gran Chaco is a vast and for the most, part unexplored territory, the interior of which is exclusively inhabited by five nomadic tribes, distinct in language, but similar in physical appearance. The southern portion forms an immense desert interspersed with sand pools; the eastern, extensive plains and marshes, with here and there tracts entirely inundated, while the natural features of the northern part are plains of magnificent pasture, dense forests of useful timber, and numerous rivers and lagoons. Some colonies have been founded of late years and bid fair to prosper. The government offers liberal grants of land to settlers. - The Rio de la Plata, with the immense streams which form it, is one of the greatest, and certainly one of the longest, rivers of the western hemisphere. The traveller can take steamer at Montevideo and ascend without interruption to Ouyaba, in Matto Grasso, over 2,000 m. But it is itself rather a vast estuary collecting the waters of large rivers, and pouring into the Atlantic an immense and turbid Hood, which is perceptible more than 100 m. to seaward, and produces a powerful current amid the waters of the ocean to a distance of 200. m. The depth of the Plata is nowise proportionate to its width.

At Montevideo, where the width is 75 m., a series of sand banks narrow the channels and render them of difficult navigation; and at Buenos Ayres, where the shores are 28 m. apart, even vessels of medium draft have to anchor 6 and sometimes 8 or 9 m. from land. Up to 1855 passengers and goods were brought ashore in carts mounted on huge .wheels, that went out to meet the boats at a distanee of two or three cables' length from the water's edge. In that year two handsome piers 1,300 and 1,950 ft. in length were constructed of wood and iron; but when the river is low the old expedient of carts has to be resorted to. Of the two great rivers which unite to form the Plata, the Parana curves from S. to W. on the N. E. border to its junction with the Paraguay, at Tres Bocas, in lat. 27° 14' S., lon. 58o 30' W., whence it flows nearly S. to Rosario, in lat, 33°, then turns S. E., and falls into the Plata by several channels from 25 to 55 m. above Buenos Ayres. The river is navigable for the largest vessels to its junction with the Paraguay, 850 m.; 150 m. higher for small steamers; and 350 m. further up for small boats.

Its chief tributaries in the republic are the Salado, which flows S. E. from the N. W. part of the province of Salta about 6OO m., and empties below Santa Fe, and the Tercero, which flows S. E., receives the Cuarto, and empties about 30 m. above Rosario. The Salado is said to be navigable from the plains of Salta. The Uruguay forms nearly the whole E. boundary of the republic, bordering on the provinces of Entre-Rios and Corrientes, to its embouchure in the Plata by a channel 0 m. wide. This river is usually flooded from June to November, and is navigable for steamers up to Salto Grande, about 200 m. The Paraguay, after a long course through Brazil and on the frontier of Bolivia, forms the dividing line between the Argentine Republic and Paraguay for 350 m. to its confluence with the Parana, 25 m. above Corrientes, receiving in that distance the Pilcomayo and Bermejo. These are both large rivers flowing S. E. through the Gran Chaco, but the former is too shallow for navigation, while the latter has been navigated by steamers for 1,200 m. by its tortuous course. The Colorado or Mendoza, formed by the union of various streams springing from the volcanoes of the Chilian Cordillera, holds a generally S. E. course and flows into the Atlantic at Union bay.

It is navigable for upward of 100 m. from the sea. There is a second Rio Salado in the province of Buenos Ayres, S. of the capital, but it is dry for most of the year. The Negro, which forms the S. boundary of the republic as far W. as lon. 70°, falls into the Atlantic below El Carmen, and has been navigated almost throughout its entire course, or about 500 m. The pampaean plains are drained by innumerable streams, some of considerable volume, whose waters, for the most part saline, spread and are lost in the marshes or salt lakes that abound in those regions. Among them the Primero and Segundo are large but not permanent streams; while the Tercero and Cuarto, already mentioned, are perennial. The plains are interspersed with an infinite number of lakes and lagoons, for the most part salt W. of the Parana and Paraguay, while those E. of these rivers are without exception fresh. In the province of Corrientes is an extensive lake, the Ibera, 130 m. long and 90 m. wide, which gives its name to a marshy territory of considerable area. The Parana is by some geologists supposed to have at an early period taken its course through this lake; and many are of opinion that the latter is now filled by infiltration from the great river, although there exists no visible connection between them.