The year 1812 was remarkable for the greatest flood in the memory of the natives. Vast quantities of cattle were carried away by it, and when the waters began to subside, and the islands which they had covered became again visible, the whole atmosphere for a time was poisoned by the effluvia from the innumerable carcases of skunks, capiguaras, tigers, and other wild beasts which had been drowned on them. On such occasions it frequently happens that the animals, to save themselves, swim off to the floating masses of canes and brushwood (called by the Spaniards "camelotes"), and are thus carried down the river, and landed in the vicinity of the towns and villages upon the coast. Many strange stories, are told of the unexpected visits of tigers so conveyed from their ordinary haunts to Buenos Ayres and Monte Video. One in my time was shot in my own grounds near Buenos Ayres, and some years before no less than four were landed in one night at Monte Video, to the great alarm of the inhabitants when they found them prowling about the streets in the morning. In the swampy region of Xarayes, where the inundation commences, the ants, which are in vast numbers there, have the sagacity to build their nests in the tops of the trees, far out of reach of the waters; and these nests are made of a kind of adhesive clay, so hard that no cement can be more durable or impervious to the weather.
During the inundation the river is exceedingly turbid, from the great quantity of vegetable substances and mud brought down by it:--the velocity of the stream in the higher and narrower parts of the river at first prevents their deposition, but as it approaches the lower lands, or pampas, where it overflows its bed, these substances are spread over the face of the land, forming a grey slimy soil, which, on the abatement of the waters, is found to increase vegetation in a surprising degree.
A calculation has been made by Colonel Monasterios, author of an excellent paper on this river, printed in the Statistical Register of Buenos Ayres for 1822, that no less than 4000 square leagues of country are annually covered by the waters during the periodical inundations of the Paranã.
From the almost uninterrupted level of the country which intervenes between the eastern ranges of the Cordillera and the Paraguay, many rivers which descend from them are either partially or entirely lost, after long and tortuous meanderings, in swamps and lakes, the waters of which are absorbed by evaporation during the heats of summer. This is strikingly exemplified in the river Pasages, or Salado, which, from the great extent of its course, and the many other streams it collects in its long course from the province of Salta to Santa Fé, would be a river of the first importance, were not the greater part of its waters lost in the level plains through which it runs. The Dulce, which, passing by Tucuman and Santiago, runs parallel to it, is lost in the great lake called the Porongos, in the pampas of the province of Santa Fé. The Primero and Segundo, which rise in the province of Cordova, disappear in the same plains. The Tercero, the most important river of that province, with difficulty finds its way during part of the year to the bed of the Carcaraña, which falls into the Paranã, near San Espiritu, below Santa Fé. The Quarto and the Quinto, and, still further south, the waters of the rivers from Mendoza and San Luis, are lost in the swamps and lakes which form so striking a feature in the maps of that part of the continent.