158 SOUTH AMERICA— THE ANDES REGIONS. 



on the low divide separating its sources from those of the San Juan, the Atrato 

 loses the aspect of a mountain torrent as soon as it trends round from west to 

 north in a line with the longitudinal axis of its valley. On entering this depression, 

 which was an old marine inlet, it is already navigable for boats, and during the 

 floods even for steamers. 



Swollen by hundreds of affluents both from the Western Cordillera and from 

 the coast range, and farther on by the majestic Rio Sucio from the Paramillo 

 uplands, the Atrato winds in long meanderings, from 400 to 700 yards wide, through 

 the chain of riverine marshes and circular lagoons periodically flooded by its inunda- 

 tions. Its rapid curcents, entirely free from the aquatic growths covering the 

 surface of several of its tributaries, develop a vast network of channels separated 

 by sedge and reeds tall enough to mask their winding banks. A few isolated 

 eminences rise in the midst of the marshy waters along the adjacent plains, and 

 the traveller wonders whether he is sailing on a river or on some shallow 

 inland sea. 



In its lower course the Atrato for some distance skirts the west side of the 

 Gulf of Uraba, and then, turning east, falls into the sea through a many-branching 

 delta, whose alluvial deposits extend considerably beyond the normal coastline. 

 Without reckoning the minor channels, as many as fifteen branches are developed 

 in this alluvial delta. But the position, the size, and even the number of the 

 mouths are yearly modified according to the volume of water and tbe quantity of 

 mud and vegetable matter discharged by the river. 



The peninsular deltaic formation projecting from the west coast is steadily 

 advancing eastwards, and must eventually close the Culata (Sack) of the Gulf 

 of Uraba, leaving only a narrow channel for the streams reaching the coast at 

 this point. Thus the marine inlet is being gradually transformed to a lake, and 

 when visited by the explorer Fidalgo in 1793 the Culata was already fringed 

 with mangroves, and partly covered witb ganialoiales, that is, floating meadows. 

 But the channel was still from 180 to 215 feet deep, whereas, according to the 

 most recent charts, it has now shoaled to from 70 to 160 feet. The Rio Leon 

 (Cuacuba), which discharges into the head of the Sack, may be regarded, like the 

 Rio Suriquilla, as belonging to the basin of the Atrato, which is also joined by 

 several other lateral streams about the delta district. 



Of the numerous branches two only are accessible to sloops and eight to boats. 

 On the bars the depth averages no more than about 6 feet, whereas within 

 these obstructions it is everywhere suificient for large vessels. In some places 

 the plummet reveals as much as 60 or 70 feet, and the only dangers on the main- 

 stream and its navigable affluents are the abrupt windings and the barriers formed 

 by snags, at some points right across the channel. 



The Atrato has often been spoken of as one of the future highways of navi- 

 gation between the Atlantic and Pacific Oceans. In 1793 Fidalgo already 

 mentions the arrastradero (portage) of San Pablo, where a cutting " a little 

 over a mile long " would suffice to connect the two navigable Rios Atrato and 

 San Juan. ' Later Humboldt urged the facility with which this low divide might 



