182 



AMAZONIA AND LA PLATA. 



Westwards, the Organ range is continued by the Serra de Tingua, which has 

 an extreme height of 5,410 feet. This range, being of igneous ori<nn, with 

 obliterated craters, presents a marked contrast to the neighbouring gneiss and 

 gninite mountains. West of the Serra de Tingua, a railway long reo-arded as a 

 marvel of Brazilian enterprise surmounts the Serra do Mar by a series of steep 

 gradients and eighteen tunnels, the highest point reached being 1,356 feet. 

 Farther on towards the S. Paulo frontier the nearly isolated Serra Bocaina has 

 several peaks 5,000 feet high, facing the superb Itatiaya group on the other side 

 of the upper Parahyba valley. On the seaward side of the Serra do Mar a few 



Fig. 74.- Rio de Janeieo Seaboard. 

 Scale 1 : 1,800.000. 



West op Greenwich 



Depths. 



OtolO 

 Fathoms. 



10 to 25 

 Fathoms 



25 to 50 

 Fathoms. 



50 Fathoms 

 and upwards. 



30 Miles. 



narrow heights, rising abruptly above the sea, represent ancient islands now joined 

 to the mainland. Such are the cones encircling Rio de Janeiro Bay, the entrance 

 to which is dominated by Mount Tijuca (3,360 feet), where Agassiz thought traces 

 of former glaciation might be detected. 



Rivers. 



The Parahyba do Sul, or sim[)ly I'arahyba, has its sources close to the sea at 

 the south-east extremity of S. Paulo. It flows first south-west, in the very oppo- 

 .'^ite direction to the course which it afterwards takes to escape from its rocky 



