GEOGRAPHY. 31 



To the traveller on the few trails across the mountains no systematic 

 arrangement of the elements composing the Cordillera is perceptible. The 

 range appears to be a j umble of ridges and peaks, with occasional unexpected 

 beautiful little flat-bottomed valleys nestling at their feet. The causes of 

 this irregularity are to be sought in the complex geologic composition and 

 structure of the Cordillera. Not only does the central mountain mass 

 include many different kinds of rocks — effusive and intrusive igneous rocks, 

 schists and other metamorphics, and a great variety of sedimentary rocks — 

 each of which has its own characteristic topographic development, but 

 much of it has been faulted along several different axes and otherwise 

 disturbed. Examples of discordant ridges due to faulting are Loma El 

 Numero, east of Ocoa Bay, and the mountain front north of Azua. Both of 

 these ridges, which run nearly at right angles to one another, are outlined 

 by faults. 



BONAO TRAIL. 



The route across the Cordillera Central most frequently used by travelers 

 between the capital and towns in the Cibao Valley is the Bonao trail. 

 This route leads from Santo Domingo City through Los Alcarrizos and 

 Bonao to La Vega. The Duarte Highway (Carretera Duarte), now under 

 construction, follows this old trail for a considerable distance but departs 

 from it at places in order to take advantage of easier grades. 



Hatillo, 28.5 kilometers from the capital, is in the low hills at the southern 

 border of the Cordillera Central. The approach to Hatillo is over a grad- 

 ually rising, rolling country, much of which is cultivated. The camp at 

 this place marked the end of the part of the Carretera Duarte leading 

 from Santo Domingo City which had been completed by April 1, 1919. 



Between Hatillo and El Madrigal, a settlement of a few scattered houses, 

 the country is rather open. Many of the valleys are steep-sided and the 

 ridges are rather sharp, but the soil is deep and not much rock is exposed. 

 (See PI. V, A and B.) The higher mountains to the west are more rugged. 

 Rio Jaina, where crossed, is clear and rapid, about one meter deep, 90 

 meters wide, and strewn with boulders. Near El Madrigal (see PI. V, C) 

 two terraces at heights of 26 and 49 meters respectively above the river 

 were noted. 



Between El Madrigal and Sabana Grande, which is marked by a single 

 house, the route lies along the valleys of Rio Jaina and Arroyo Guananitos. 

 The valley of Rio Jaina at El Madrigal is nearly 5 kilometers wide and has 

 steep wooded hills on both sides. It is floored with clay, loam, and gravel, 

 and is covered with a fairly dense growth of bushes, interspersed with some- 

 what swampy savannas. Arroyo Guananitos, above La Mata, is a small 

 meandering stream having a fall of 4 or 5 meters per kilometer. Its channel 

 is choked with logs and trees, and terraces of gravel and sand were noted at 

 several places in its valley. The upper part of the valley of Arroyo 



