CHAPTER VIL 



THE TOC.^'TINS BASIN-STATE OF GOTAZ. 



IHE Tocantins hydrogrciphic system is closely connected with that of 

 the Amazons. If, as seems probable, a continuous subsidence of 



the old marine bed has given access to the Atlantic waters, 

 causing them to flood the lands at present occupied by the 

 Amazonian gulf, the Tocantins must at one time have communi- 

 cated directly with the Amazons through a confluence lying to the east of Marajo 

 Island. It was thus a simple affluent of the great river. In any case it flows 

 from the same slope as the Xingu, the l^apajoz, and the other southern tributaries 

 of the main stream, and its course is developed in the same direction. 



But the Tocantins, rising in the very heart of the Brazilian orographic system, 

 is conterminous about the region of its sources with two other large fluvial basins, 

 those of the S. Francisco and the Parana. Hence it has been proposed to found 

 a new capital of the federal republic on this dividing line near the diverging 

 point of three great rivers. 



There is no coincidence between the political frontiers of Goyaz and the natural 

 limits of the Tocantins catchment basin. Goyaz, the superficial area of which may 

 be approximately estimated at about 800,000 square miles, occupies south of the 

 Pyreneos divide part of the southern slope draining to the Parana, and towards 

 the west it comprises no more than one-half of the Araguaya Valley ; the channel 

 of this river in fact forms its frontier towards Matte Grosso and Amazonia. 



The drainage area itself is otherwise very sharply defined. An oval- 

 shaped cirque is developed round the sources of the two main branches — 

 Tocantins and Araguaya — and this cirque is closed northwards by the rocky 

 ridges where are formed the last fluvial cataracts. The outer walls of this vast 

 amphitheatre are formed, if not by distinct mountain ranges, at least by the 

 escarpments of a plateau. Towards the east especially the edge of the basin 

 rises in scarps of bold relief, which have even received the name of serras 

 ("ranges"), from the aspect which they present towards the valley. Such are 

 the Serra das Mangabeiras, the Serra do Douro, da Tabatinga, and do Paranan. 



In reality these heights consist of chcqjcidoes, fragments of a sandstone plateau 

 at a mean elevation of 1,300 feet, above which rise at intervals cubic masses about 

 165 feet higher, with a few intervening depressions of corresponding depth- 



