It is chiefly by means of the Rio de Is Plata, that those extensive regions 'are drained of their wa ters ; all the streams which have their rise in the eastern declivity of the Chilian Andes, or that de scend from the western ridges of Brasil, being ulti mately carried into the channel of this great river. In the upper part of its course, it is known by the name of the Paraguay, and runs nearly in the centre of the American continent, from N. to S., receiving from the mountains of Brasil -the two great streams of the Parana and the Uruguay, while from the west it receives the Pilcomayo, the Vermejo, and the Sa lado, which flow down the eastern declivity of the Andes.
It was called Rio de la Plata, or River of Silver, by Sebastian Cabot, from his having taken a con siderable booty, in gold and silver, from a body of Indians whom he defeated on its banks, and this imposing title it has ever since retained. This ap pellation, however, though no doubt intended by its author to apply to the whole of the river, is now confined to the channel by which the Paraguay, the Panana, and the Uruguay, pour their united waters into the ocean. This vast estuary of fresh water, which it without a parallel for width and magnifi cence, is 150 miles broad at its mouth, from Cape St Maria, on one side, and Cape St Anthony, on the other. Between Monte Video and the Punta de Piedras, which some have considered its li mits, it is 80 miles in breadth ; and at Buenos Ayres, which is 200 miles from its mouth, its breadth is about SO miles ; and, the shores being low, it is sel dom that they can be seen from opposite sides. This immense inland sea is, however, rendered dangerous for the purposes of navigation, not only by rocks and sand-banks, which are the terror of mariners, and which greatly detract from its utility; but by tempests of wind which, bursting forth from the south-west, sweep over the boundless plains of the Pampas, where they meet with no obstacle to op pose them, and rush down the wide opening of the Plata with unequalled fury. A thunder storm is the general prelude to those destructive blasts, which are known by the name of the Pamper°, ; so that the mariner, being warned of the coming tempest, seeks shelter in some of the neighbouring , ports.
The greater part of the country included with in the viceroyalty of Buenos Ayres, forms, accord-. ing to Aura, a vast plain, of which the uni form level is hardly ever interrupted by hills of a greater elevation than of 90 toises above their base ; and it has been calculated, by barometrical observa tions, that the great river Paraguay, in its progress southward, does not fall above one foot in perpen dicular height between the 18th and 22d parallels of south latitude. In like manner it is asserted, by persons well acquainted with the country, that when the easterly winds occasion the rivers of Buenos Ayres to rise to the height of seven feet above its ordinary level, this rise is perceived in the river Panana at the distance of 60 leagues.
In consequence of this flatness of the country, the rains which fall upon the Cordilleras are stopped when they descend into the plain, and are insensibly eva porated ' • so that 'a number of small rivulets which,.
under a different configuration of the ground, would be collected into rivers, are here checked in their course, and gradually evaporated. Nor can any are or skill ever remedy this physical defect of the coun try; for the same cause which prevents its superflu ous moisture from fprcing its way to the ocean, would equally prevent the conveyance of water by means of any artificial canal. In Buenos Ayres, accord ingly, and in other places situate on the banks of rivers, it is always found necessary to make use of a pump. in order to raise the water to the level of the town.
Rut this peculiarity is, on the other hand, favour. able to the formation of lakes. There being no out let to the superfluous waters which the soil cannot ab sorb, they are necessarily collected in the flat parts of the country, where they spread to a great extent, co vering an immense space, but of no great depth in any part. Most of the lakes which are to be found in this extensive country are of this description. Of these, the celebrated lake of Los Xaiayes is formed by the collected waters which fall during four months from the beginning of November to the end of February in the northern provinces, and in the mountainous districts in which the Paraguay has its sources. This great river, swelled by the tropical rains, soon overflows its banks, and its redundant waters spread to a great extent over the flat country through which it flows. As the quantity of rain which in different years varies considerably, the dimen sions of Lake Xarayes, which is formed by the over flowing of the river, are liable to great uncertainty. In general, however, it is found to extend beyond the 17th degree of south latitude, and about this point its breadth on the east of the river Paraguay is about 66 miles. It preserves the same breadth for about 800 miles to the north, surrounding with its waters several islands which are covered with lofty trees. On the west side of the river, the breadth of the lake is not so considerable. Its whole length, according to the nearest estimate, may be 880 miles, and its breadth on an average 120 miles. But although it spreads over so large a space, it is not navigable in any part except for canoes and small craft. When the rainy season abates, the waters of this lake subside into the channel of the Paraguay, leaving the whole plain perfectly dry, and covered with weeds and other plants. The number of crocodiles in this lake is immense, and in the vi cinity are found tigers, leopards, stags, and monkeys of various kinds; the country also swarms with ants, mosquitoes, and innumerable noxious insects. Dur ing the inundation, the Portuguese, from their set tlements on the Cuyaba, cross the lake in canoes and small barks. There are various other lakes-of the same description in Paraguay, such as that of Aguaracaty in the 25th degree of latitude those which are found to the south and north of the lake -.of Ypoa, situated in the 26th. degree; that of Noun. bucu at the 27th ; an those lieoe the eastern banks of the Paraguay. besides an infinite !smother of others of more or less extent, on the banks of all - the streams and rivulets which run through the vast plains 'of this level country.