CHAPTER III 



THE RUBBER FORESTS 



The white limestone cliffs at Pongo de Mainique are a bound- 

 ary between two great geographic provinces (Fig. 17). Down val- 

 ley are the vast river plains, drained by broad meandering rivers ; 



Fig. 17 — Regional diagram of the Eastern Andes (here the Cordillera Vileapampa) 

 and the adjacent tropical plains. For an explanation of the method of construction 

 and the symbolism of the diagram see p. 51. 



up valley are the rugged spurs of the eastern Andes and their en- 

 canyoned streams (Fig. 18). There are outliers of the Andes still 

 farther toward the northeast where hangs the inevitable haze of 

 the tropical horizon, but the country beyond them differs in no 

 important respect from that immediately below the Pongo. 



The foot-path to the summit of the cliffs is too narrow and 



22 



