38 GEOLOGICAL RECONNAISSANCE OF THE DOMINICAN REPUBLIC. 



The Azua Plain is hot and semiarid. The rainfall is somewhat greater 

 than the vegetation would indicate, but as much of it is torrential the run- 

 off is excessive, so that much of the water is lost. A large part of the plain 

 is overgrown with thickets of cacti and mesquite, which make travel across 

 it tedious and painful except along beaten trails. A low, shrubby cactus, 

 guazabara, is particularly annoying. The soil is fertile and responds 

 readily to irrigation. 



Azua, the only large town in the neighborhood, is 5 kilometers inland 

 from its port on Bahia de Ocoa, with which it is connected by an improved 

 highway and a narrow-gauge railroad. South of the town are several large 

 sugar plantations. A wagon road passable by automobiles furnishes an 

 outlet from the fertile Valley of San Juan to Azua, and another wagon road 

 leads from Azua across El Numero to Ban! and thence to the capital. 

 The trail to Barahona by way of Quita Coraza is usually traveled at night 

 in order to avoid the heat and the glare of midday. A little-used trail 

 across the Sierra de Martin Garcia furnishes a difficult alternate route to 

 Barahona. 



SIERRA DE NEIBA. 



The Sierra de Neiba is a range of high mountains lying south of the valley 

 of San Juan and forming the boundary between the provinces of Azua and 

 Barahona. The western extension of these mountains forms the central 

 range of Haiti. The east end of the Sierra de Neiba is separated from the 

 Sierra de Martin Garcia by Rio Yaque del Sur. South of the mountains 

 is the deep trough of Enriquillo Basin. 



The Sierra de Neiba is composed chiefly of ridges of limestone ranging in 

 altitude from 1,000 to 1,500 meters above sea level and having a fairly even 

 profile, only a few peaks projecting above it, in this respect differing 

 markedly from the rugged Cordillera Central. This uniformity gives a 

 clue to the geological composition and structure of the range, which is formed 

 of tilted blocks of hard limestone and other bedded rocks. 



SIERRA DE MARTIN GARCIA. 



East of the Sierra de Neiba and separated from it by Rio Yaque del 

 Sur is the Sierra de Martin Garcia, a short mountain range culminating in 

 Monte Busu at an altitude of 1,340 meters above sea level. The range ter- 

 minates in a row of hills, the Cerros de la Terraza, on the shore of the Carib- 

 bean Sea. The Sierra de Martin Garcia overlooks the Azua Plain on the 

 north and Neiba Bay on the south, and partly shuts off Enriquillo Basin on 

 the west. From the vicinity of Azua or Barahona the Sierra de Martin 

 Garcia looms up as a lofty, rugged mountain. It is composed in part of 

 limestones similar to those of the Sierra de Neiba. 



