THE EIOS SAN JUAN AND PATIA. 159 



be pierced at the Easpadura gorge, and towards the middle of the present century 

 Trautwine, Porter, Michler, Selfridge, and other explorers suggested the 

 tunnelling and cutting of the coast range between the Pacific and the Truando 

 or the Napipi affluent of the Atrato. But all these schemes were abandoned 

 after the adoption of the Panama route; nor have they been revived since 

 the failure of that disastrous undertaking. 



The Atrato itself, which might have such paramount importance as an inter- 

 national highway, is scarcely utilised for the local traffic. It is visited by a 

 few steamers, and ascended by barges, which take from 36 to 42 days to reach 

 Quibdo in its upper valley. This stagnation is due to the insalubrious climate 

 of its valley, and the almost total absence of civilised populations along its 

 banks. 



The San Juan and Patia Basins. 



On the Pacific slope south of Panama the only important watercourses are 

 the San Juan and the Patia. Although not more than about 190 miles long, the 

 San Juan presents with its affluents over 300 miles of navigable waters for 

 steamers, barges, and canoes. Unfortunately, the bars at the mouths of its delta 

 just above Buenaventura have depths of not more than from 5 to 7 feet. The 

 mean discharge is estimated by Yergara y Velasco at 50,000 cubic feet per 

 second, which exceeds that of any other South American river on the Pacific slope. 



South of the San Juan follow several other coast streams, such as the Dagua, 

 the Micai, the Iscuande, and the Patia, this last ranking next to the San Juan in 

 volume. It rises east of the Western Cordillera in the Colombia group close to 

 the Cauca, the Magdalena, and the Caqueta. The Sotara, or main headstream, 

 descends from the Sotara volcano south-westwards, receiving the Mayo, Juanambu, 

 Guaitara, and other affluents, from the Western, and especially from the Central 

 Cordillera. The Guaitara, Avhose headwaters descend from the Paste volcano 

 and the Tuquerres plateau, is remarkable for its extremely deep and narrow 

 valley, excavated to a depth of 3,000 feet in the limestone cliffs, which are 

 perfectly level above, having been deposited in marine waters at an epoch ante- 

 cedent to the appearance of the surrounding trachytic rockso 



The Rio Carchi, main headstream of the Guaitara, has been chosen as the 

 limit of the conterminous republics of Colombia and Ecuador. At the Pio 

 Blanco confluence the Carchi is crossed on the route from Popayan to Quito by 

 the famous Rumichaca natural bridge, a block of siliceous limestone wedged in 

 between two granite walls. Although formerly known as the " Inca's Bridge," 

 this natural curiosity owes nothing to the hand of man. 



After collecting nearly all its tributaries, the Patia plunges into the intricacies 

 of the Western Cordillera, traverses the Minama gorge, not more than 130 feet 

 wide, and debouches on the lower plains through a series of swirling rapids. 

 Beyond the confluence of the copious Telembi, from the Ecuador frontier, the 

 majestic stream rolls seawards in long meanderings through the alluvial plains 

 studded with marshes and now abandoned fluvial beds. Its delta, like that of the 



