930 REPORT— 1898. 



banks, sometimes rising to a height of 80 feet, and then at Goya descending almost 

 to the river-level, are composed of sandy clay ; hut near Bella Vista are masses of 

 rolled pebhles. Js^ear the boundary line of Corrientes and Entre Eios the hanks 

 of the Parana are very low on both sides of the river, and continue so for nearly 

 100 miles ; hut thence, southward, for 150 miles, the left bank is margined as faV 

 as Diamante by a range of hills from 125 to IGO feet high, at times boldly escarped 

 and presenting a fine geological section. From Diamante the hills trend inland 

 south-east about fifty miles, as far as Victoria, and they probably formed the 

 border of an ancient channel of the river Parana. 



From Santa Fii to the head of the Plata estuary, the right bank of the Parana 

 shows a precipitous blufl" of reddish clay, varying from 25 to 65 feet above mean- 

 river level. It is being gradually undermined, and tumbles in great blocks into the 

 river to add to its volume of silt. 



The Uruguay River flows, almost throughout its course, over a rocky bed, 

 mostly of red sandstone, at times very coarse, and then again of extremely fine 

 composition ; but below La Cruz, in Corrientes, there is much limestone, albeit 

 the sandstone still predominates. The Uruguay is, except in flood, a clear-water 

 stream, and, even at its highest level, carries comparatively bat little silt. 



I have ridden over much of the IBanda Oriental del Uruguay. The southern 

 and western half lies from 150 to 300 feet above sea-level. Darwin is correct in 

 saying : ' It has a gently undulatory surface with a basis of primary rocks, and is in 

 most parts covered up with an unstratified mass, of no great thickness, of reddish 

 Pampean mud.' 



Seco)idari/ Mirers. — I refer again to the very important rivers Grande and 

 Parapiti. Minchin says of them : ' The Pio Grande drains a considerable part of 

 South-eastern Bolivia. It has its sources among the ranges bordering the table- 

 land, and flows for some 400 miles through a deep, narrow gorge, and reaches the 

 plains in latitude 18° 55'. Bending north, it then describes a semicircle, and 

 finallj' runs north-west to join the 31amor^. In its course across the plains, and 

 as far north as latitude 17° 3t)', the river flows through a wide sandy bed, bounded 

 by banks from 16 to 25 feet high. The Parapiti rises at an elevation of 2,030 feet 

 in latitude 19° 59' 18", longitude 63° 4'. At the close of the dry season it flows 

 65 cubic yards per second, and is then absorbed by the sandy region of the plain. 

 In the wet season it runs through a well-defined bed as far as latitude 19° 6', 

 longitude 62° 22', and then spreads through the swampy, forest-covered plain. Its 

 waters, again uniting, cvit through the south range of Chiquitos at Qumome Pass 

 and form Lake Conception.' 



Between 20° and 30° south latitude the arid Andean slopes collect and send 

 south-eastward, across the Gran Chaco, the waters of the three great rivers 

 Vilcomayo, Bermejo, and Salado or Juramento. They are almost without an 

 affluent once they leave the foot of the mountains, where they have their greatest 

 volume. Sometimes they spht into several channels, making narrow and enormous 

 islands in the plain. They are all very crooked, and have uncertain beds, at times 

 changing an old course for a new one miles distant. Thus they erode and tear 

 away great quantities of soft I'ampean material, dissolve it into silt, and pour it 

 into the Paraguay and Parana. Pelleschi, in his admirable work on the Gran 

 Chaco, estimates that 'the soil annually subtracted from the territory of the Chaco 

 by the Bermejo alone equals 6,400,000 cubic yards." 



The rivers Saladillo, Primero, and Segundo provide the water to meet the 

 evaporation from the great inland lake of I'orongos. The Tercero and Cuarto 

 unite, and enter the Parana near Rosario, with a considerable volume of water. 

 The Quinto, with other small rivers, draining the southern spurs of the Cordova 

 range, are absorbed by the thirsty Pampean swamp, La Amarga. 



Some of these rivers carry a large quantity of lime, and many of their westerly 

 affluents carry so much as to have a white colour, thus accounting for the con- 

 siderable number of them called ' Pdo Blanco.' 



A large river system, having many ramifications in the provinces of La Rioja, 

 ilendoza, and San Luis, gathers into lagoons and main channels to find its way 

 to Lake Urre Lauquen, and, in floods, to the Colorado. Pliysical and climatic 



