PLATA, RIO DE LA, a large estuary of South America, formed by the confluence of the Rivers Parana and Uruguay. It is about 185 miles in length; and its breadth gradually increases from its head towards the sea. At Buenos Ayres, about 30 miles below the confluence of the two great rivers, it is 29 miles across; at Monte Video, 70 miles farther down, it has expanded to 53 miles; and at its mouth, between Cape San Antonio and Punta de la Ballena, its breadth is about 130 miles. This vast sheet of water is by no means deep: the average depth at the mouth is 10 fathoms; farther up it becomes gradually shallower; and between Monte Video and Buenos Ayres the average depth is only 3 fathoms. The estuary is also much impeded with sand-banks; and the currents are very strong and variable, on account of the immense body of water brought down by the rivers, which drain an area estimated at 1,200,000 square miles; being thus inferior in this respect to the Amazon and Mississippi only. The tides in the La Plata are hardly perceptible; but this is owing not to any real deficiency in their force, but to their being confused, and, as it were, concealed by the other currents. Violent storms frequently agitate the La Plata, chiefly raised by the gales called pamperos, which drive the water in a great volume in one direction. From these causes, the navigation is here so difficult that the estuary has been called El Inferno de los Marineros (Sailors' Hell). The water of the rivers is very long in mingling with that of the ocean; it floats muddy and dark on the surface in an easterly direction; and at the distance of 600 miles from the land it has a velocity of 1 mile an hour, and spreads over a breadth of 800 miles. Of the two great rivers that form the Rio de la Plata, the largest is the Parana, which rises in Brazil not more than 100 miles N.W. of Rio de Janeiro. The upper streams of this river have various names; but at the confluence of the Rio Grande, the longest of them, with the Parnahiba, the combined river takes the name of Parana, which it retains till it merges itself in the Rio de la Plata. The Parana flows southwards, receiving several large affluents, and separates Paraguay from Brazil and La Plata. It then turns to the west, and flows in that direction for 50 miles, still forming the boundary between Paraguay and La Plata. On receiving the Paraguay from the north at Corrientes, it again turns south, and flows through La Plata till it falls into the Rio de la Plata by several branches, forming the island of Martin Garcia and others. The Martin Garcia channel, by which the Parana is entered, is difficult of navigation, and does not admit vessels drawing more than 14 feet of water. The total length of the Parana is 2040 miles,—namely, 500 from the source of the Rio Grande to its confluence with the Parnahiba, 1000 from that point to the union of the Paraguay and Parana, and 540 thence to the Rio de la Plata. It is navigable to Corrientes for ships drawing 7½ feet, and for smaller vessels to Candelaria, 150 miles farther, where rapids occur. The principal affluent of the Parana is the Paraguay, which exceeds, in the volume of its water and in the length and directness of its course, the river that retains the name. It issues from several lakes in the Sierra Diamante in Brazil, and flows southwards, separating La Plata from Brazil and Paraguay. Its principal tributaries are the Pilcomayo and Vermejo, both from the west. Its whole length from its source to Corrientes is about 1890 miles; and it is navigable to Assumption, 200 miles above Corrientes, for vessels drawing 7½ feet. Above this point it is believed to be navigable for smaller vessels for 800 miles, and the Vermejo for 500. The Parana also receives from the west the Salado, which is entirely within the provinces of La Plata, rising in the N.W., flowing S.E., and joining the main stream at Santa Fé. Like all rivers from within the tropics, the Parana has a low and a high season, depending on the periodical rains. The former lasts during the winter and spring of the South-
ern Hemisphere, from June to December, and the latter during the summer and autumn. The difference in the height of the river in these seasons varies at different parts, being about 3 feet where it is wide, 8 feet where narrow, and on an average over the whole about 4 feet. The Uruguay rises in Brazil in the Sierra de Santa Catharina, and flows first west and then south, separating Brazil and Uruguay from La Plata, and falling into the Rio de la Plata, where its blue waters preserve their clearness for miles before they are lost in the muddy current of the Parana. Its whole length is more than 800 miles, and it is navigable for ships drawing 5 or 6 feet for 250 miles. The estuary of La Plata is fitted by nature to be the outlet of a most extensive river trade, though as yet its advantages have been turned to very little account. Goods from foreign countries destined for the interior are generally unshipped at Buenos Ayres, and put on board smaller river craft. But as, until lately, all the river trade was performed by sailing vessels, the means of communication were very imperfect; for no ships could ascend the rivers unless they had not only a wind up the stream, itself not a very frequent occurrence, but one sufficient to impel them against the current running from 2 to 4 miles an hour. At the same time, large steamers could not ascend on account of the shallows. But since the opening of the rivers in 1852 steamers have been introduced, after the model of the Mississippi boats, which will much accelerate and facilitate the conveyance of goods.