42 GEOLOGICAL RECONNAISSANCE OF THE DOMINICAN REPUBLIC. 



Haitian border and north of the main watershed. The Amina, Mao, 

 and Cana carry a considerable volume of clear, pure water. Rio Gurabo is 

 a smaller, sluggish stream, but is the only source of drinking water for the 

 villages along its banks. Rio Guayubin and the watercourses west of it 

 are mere arroyos, dry most of the time but raging torrents in wet weather. 



SOUTH SLOPE OF THE CORDILLERA CENTRAL. 



The drainage from the south slope of the Cordillera Central falls into 

 three principal groups — the through-flowing streams of the coastal plain, 

 the basin of the Rio Yaque del Sur, and the headwaters of the Artibonite. 



Many large rivers cross the coastal plain and enter the Caribbean Sea, 

 most of them in directions normal to the coast. Though none of these are 

 ong in comparison to the rivers in other parts of the island, yet because of 

 the large rainfall in this region they carry a surprisingly large volume of 

 water and are subject to sudden floods. The larger rivers of the coastal 

 plain, named from east to west, are the Chavon, the Soco, the Macoris and 

 its principal tributaries (the Magua and the Iguamo), the Ozama, the Jaina, 

 the Nigua, the Nizao, and the Ocoa. Many of the smaller streams, such as 

 Rio Bani, have broad, boulder-strewn beds capable of carrying a large 

 volume of flood water. The Ozama and the Macoris are navigable for 

 some distance above their mouths. 



Rio Yaque del Sur, one of the three largest rivers, rises on the south 

 flank of El Rucillo not far from the source of Rio Yaque del Norte. Its 

 principal tributaries are Rio del Medio, a brawling torrent that twists 

 through a deep gorge between Monte La Fortuna and Monte Culo de Maco ; 

 Rio de las Cuevas, whose milky waters, anastomosing over a broad, boulder- 

 strewn bed, come from the direction of Monte Tina; and Rio San Juan, 

 which drains a large mountainous area and the east end of the valley of San 

 Juan. The Yaque receives no large tributaries below the mouth of Rio 

 San Juan. It cuts across the end of the Sierra de Neiba, runs back of the 

 Sierra de Martin Garcfa, and builds its delta at the head of the Bahia de 

 Neiba. 



Riviere Artibonite, formed by the confluence near the Haitian border of 

 Rio Macasia and Rio Guayajayuco, flows westward across Haiti and drains 

 the western part of the valley of San Juan and its continuation, the central 

 plain of Haiti, as well as part of the Cordillera Central. Along the Haitian 

 boundary the Guayajayuco flows through a deep canon cut in shales and 

 slates. This river system shows anomalies that offer interesting problems 

 to be solved when accurate maps and more detailed knowledge of the 

 geology are available. 



CORDILLERA SEPTENTRIONAL. 



The divide between the drainage basins of the Cibao Valley and the 

 Atlantic coast is the high ridge that forms the south front of the Cordillera 

 Septentrional. From the south slope of this ridge small streams flow south- 



