1870.] 421 [Maack. 



Pilcomayo, the Bio Vermejo (the South American Missouri) and 

 the Rio Salado, which flow directly from the northwest to the south- 

 east, and in this way show very clearly the characteristic geograph- 

 ical structure of this Eepublic. 



It is a curious fact that as soon as we have left the southern part of 

 the province of Tucuman, where the elevation is froni 1600 to 1800 

 feet, the land descends suddenly in the province of Santiago del 

 Estero to a height of 500 feet, but in the province of Cordova 

 increases again and reaches in some places even a height of 2600 feet. 

 Then the land descends continually, not only to Buenos Ayres, but 

 further south, to the Magellan strait, except under the 38th degree 

 of south latitude, where the line of descent is interrupted by the 

 chains of Tapalquen, of Tandil, of Volcan and a little farther south- 

 wards by those of Ventana; the former reach a height of 1000, the 

 latter of 3000 feet. 



As I have already stated, the rivers Pilcomayo, Vermejo and 

 Salado, coming from the northwestern mountains, possess fall enough 

 to reach without interruption the Parana ; this is not the case with 

 those many smaller rivers which rise in the mountain-chains of 

 Cordova; their fall, except the Bio Tercero, is very slight, in con- 

 sequence of which they are not able to reach the Parana, and form 

 sometimes very small rivers or what is called by the native people, 

 " arroyos." These arroyos are for a traveller very often great obsta- 

 cles, because they make the ground boggy and impassable; The 

 general direction of all these streams is from the northwest to the 

 southeast. 



But the two large and powerful rivers in Patagonia, namely, the 

 Bio Colorado and the Bio Negro, coming directly from the foot of 

 the Andes, have a very different character. Their direction is from 

 the west across the main land to the east, and, without uniting during 

 their course with any remarkable branch, except the Bio Neuquen 

 with the Bio Negro, they reach the Atlantic Ocean as powerful and 

 navigable rivers, and form in this way a natural passage between the 

 Pacific and Atlantic Oceans. The Bio Negro especially will have 

 an important influence upon the future development of Patagonia, 

 because coal and salt are found in the neighborhood of the sources 

 of its branch " the Neuquen," and also under the same latitude on the 

 other side of the Cordilleras, near Talcahuano, in Chile. Indeed, 

 the navigability of these two large rivers, with the discovery of 

 coal and salt in then' neighborhood, will have an important influence 



