128 AMAZONIA AND LA PLATA. 



extensive sheet of water wliicli discharges into the eastern or lesser branch of the 

 Araguaya. Farther north follow two other islands of similar formation skirting 

 the Serra dos Oayapos, which gradually converges on the river, throwing off trans- 

 verse ridges of gneiss or igneous origin across the stream. Thus are formed the 

 series of cascades and rapids through which the Araguaya descends from the 

 plateaux to the Amazonian plains. In a space of about 18 miles it descends a 

 total incline of 85 feet, and beyond this zone of cataracts the river becomes 

 entangled in rocky gorges, about 500 feet wide, terminating in the Cachoeira 

 Grande ("Great Cataract"), where it falls 50 feet in a distance of 12 miles. 

 Then it pursues a tranquil course to a point where it is abruptly deflected 

 northwards to its confluence with the Tocantins.* 



Below the confluence the united stream, which retains the name of Tocantins, 

 is still obstructed by numerous rapids, one of which at the Tauiry rocks com- 

 pletely arrests the navigation except for boats of light draught at high water in 

 March and April. Even below the last falls of Itaboca the channel is interrupted 

 by sunken reefs, so that the regular navigation stops at the ruined fort of 

 Alcobaça, where at low water the river falls to a depth of about three and a half 

 feet. Here it is distant 130 miles from the system of navigable creeks through 

 which it enters the Para estuary. Hence the whole of Goyaz is deprived of all 

 natural communication with the coast, and its two great watercourses require to 

 be supplemented by canals, roads, or railways before they can be of much use in 

 developing the resources of the country. 



Climate of Goyaz. 



To Goyaz a great diversity of climate is imparted by the course taken by 

 the Tocantins from south to north and along a steeply-inclined slope. From the 

 sources of the Araguaya to the Para estuary the river traverses 17° of southern 

 latitude, and there is a total descent of about 4,000 feet between the crest of the 

 divide in the Serra Goyana and the alluvial coastlands. Thus the lower section 

 of the fluvial basin falls within the Amazonian zone and consequently enjoys a 

 hot moist climate, with but slight vicissitudes between diurnal and periodical 

 temperatures, whereas the upland regions naturally present far greater extremes 

 of heat and cold. Under the influence of the normal south-east trades, or of 

 the south-western winds, the glass here falls at times several degrees below freez- 

 ing-point, especially during the month of August, while the summer heats 

 occasionally exceed 104° Fahr. 



A correspondingly high range occurs between day and night when the wind 

 veers round abruptly from one quarter to the other, and differences of 3G° or even 

 46° have been recorded in less than 24 hours. Summer is ushered in with the 



* Hydrograpliic system of the two rivers : 



