From so great a surface in temperate latitudes issue the various constituent streams which !ultimately unite and form the wide estuary known as the bay of Rio de la Plata. This inlet opens to the Atlantic Ocean between S. lat. 35° and and long. 21° E. from Washington City, and is from the confluence of the Paraguay and Uraguay to the Atlantic 200, with a width varying from 30 to 150 miles wide.
In their general characters, the eastern and western confluents of the Plate vary essentially; the Parana and its branches are rather rapid currents, but the flow is gentle, or indeed sluggish, of tho Paraguay and all its western tributaries. Such distinction of feature arises from the general structure of the continent of South America. Rising as has been observed, by a rapid ac clivity from the Pacific Ocean to the table land of the Andes, the short rivers flowing from so great an eleva tion westward, are brief in their courses, but rapid tor rents until near their recipient. The streams again, which are discharged eastward, also are poured down the steeps with great velocity and frequent cataracts, until reaching the eastern verge of the Andes they en ter on a plain, over which their channels are excessively -.vinding and deeply cut, but currents necessarily slug gish.
The central plain of South America stretches with variant breadth, from the north-western sources of the Orinoco, to Patagonia, some places wooded, but in others presenting on the basin of Orinoco, the grassy tracts of Casanare, and Llanos of Cundinamarca and Pilcomayo ; and again the wide spread Pampas of Bue nos Ayres.
Crossing the central plain, the continent eastward from the•basins of the Amazon and Plate, rises into a table land less elevated and less extensive than the Andes, but distinct, and from which the river currents fall with considerable force. The Amazon, flowing from the Andes, may be said to pierce the eastern plateau, and enter the Atlantic by a wide ravine between the Brazil ian system of mountains and that of Guyana ; but the tributary waters of the Plate issuing from the eastern and western plateaus, flow towards each other, unite in the heart of the continent, and continue over the central plain to the Atlantic.
Considering the Parana as the principal stream, a Spanish author observes, that " one of the peculiarities which most interests the curiosity of the observer, is the nature of its periodical inundations, very much resem bling those of the Nile. In fact, we believe that there
is not on the globe two other rivers, the qualities of which are more analogous to each other. Both have their sources in the torrid zone ; and nearly equidistant from the equator, although in different hemispheres. Both disembogue themselves almost on the same lati tude, directing their course towards their respective poles. Both are navigable for many leagues, and pos sess each their cataracts. Each of them has its periods of increase in the respective seasons, which cause it to rise in its channel, and inundate an immense tract of country." With the preceding points of resemblance, it may he observed that the contrasts between the Nile and Rio de la Plata are equally striking. The Nile enters the final recipient by an extensive Delta, the Plate by a wide bay, and whilst the African river is environed in all the lower part of its basin by arid sandy plains, the Plate and Parana, with their confluents, drain an almost invariable fertile tract.
As a basin of navigation, that of the Plate possesses advantages fully commensurate, in a comparative view, with its relative extent. At the lowest depth, there is 15 or 16 English feet of water in the mouth of the Pa rana, and a much greater depth below in the bay, or above in the river. Vessels of 300 tons burthen are built above the junction of the Pataguay and Pilcotnayo, and navigated to Europe and elsewhere. The Parana proper, the Salado, Rio Grande, Uraguay, Paraguay, and many others, present navigable channels from 200, to near 2000 miles, following the sinuosities of the rivers.
Beyond the basin of the Plate spreads a triangular slope from S. lat. 36° to 52°, being a continuation south ward of the great plain of the Andes. The latter sec tion is least known, and in the existing state of settle ment and civilization in South America, the least im portant of the Atlantic portion of that continent. The Saladillo, Colorado, Cusu Leuvu, Camarones, and some other rivers, traverse the slope south from Buenos Ayres, but are mostly yet inhabited by savages, and as far as known not generally well calculated for civilized settlement. This tract is succeeded to the southward by another equally savage, and much more naturally rugged and inclement, and Patagonia, with the adjacent island of Tierra del Fuego, closes South America, by the most Austral continental protrusion of the earth.