Of these, the Paraguay is the first. This river, which from Corrientes takes the name of Paranã, has its sources between south lat. 13° and 14°, in those ranges which, though of very trifling elevation themselves, appear to connect the lofty mountains of Peru and Brazil, and to constitute the water-shed of some of the principal rivers of South America. From their northern declivities descend some of the most important of the eastern affluents of the Madera, the Tapajos, and other great streams which empty themselves into the Maranon, or Amazons; whilst, on the other hand, all those which pour down towards the south find their way into the bed of the wonderful river I am describing. Many navigable streams join it from the eastward, as it passes through the rich Brazilian territories of Matto Grosso and Cuyabá. Its tributaries from the opposite side are, though perhaps more important, less numerous, the surface of the country being more level; of these the Jaurú is the first of any consequence, the sources of which are close to those of the Guaporé, which runs in the opposite direction into the Madera and Amazons. The short portage which intervenes between the heads of these rivers is all that breaks a continuous water-course from the mouths of the Amazons to that of the Plata, as will be seen on reference to the map. A little below the Jaurú commences a wide region of swamps called the lake or lakes of Xarayes; which, during the periodical inundations of the rivers that descend from the mountains to the north of Cuyabá, is flooded for a vast extent, the waters forming one great inland sea, to the depth of ten or twelve feet, extending between 200 and 300 miles east and west, and upwards of 100 from north to south. As the rainy season passes away, this mass of waters is finally carried off by the Paraguay, which even here, 1200 miles in a direct line from the sea, is navigable for vessels of 40 or 50 tons. The mouth of the Jaurú is in 16° 25´ long. 320° 10´ east of Ferro:--here a marble pyramid is erected to mark the boundary determined upon between the Spaniards and Portuguese by the treaty of 1750. Quiroga, who accompanied Flores, the Spanish commissioner, to determine this point, in descending the Paraguay fixed the latitude of most of the numerous rivers which fall into it before its junction with the Paranã.[50] On the eastern side they afford the means of communication with the gold and diamond districts of Brazil, and lower down with those districts of Paraguay proper which abound in the finest timber, and produce the yerba maté, the article perhaps most in demand of all the rich productions of that favoured country.