116 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Mar. 23, 



The island of San Domingo is one of the large Antilles ; it forms 

 a connecting link with the islands of Cuba and Porto Rico, the three 

 acting as a vast dyke that confines the waters of the Carribbean Sea 

 and Gulf of Mexico as they are forced in by the great Equatorial 

 current, and wliich afterwards escape through the narrow passage 

 between Cuba and the coast of Florida. 



In an economic point of view, the geology of S. Domingo is of 

 interest on account of its mineral riches, and especially its stores of 

 fossil fuel, indicated by numerous outcrops of coal (lignite), which 

 may at a future time be available for the important commercial 

 interests of our country. 



Metamorphic and crystalline rocks are the chief component mate- 

 rials of the central chain of mountains called the Cibao*, from which 

 distinct ridges branch off in some places towards the coast. These 

 mountains rarely exceed 6000 feet in height. 



Secondary (?) formations prevail over the northern and eastern 

 sections of the island, and patches of tertiaries are met with locally 

 along the coasts. Of the tertiary deposits there are two well-defined 

 basins that have been subject to some examination. One occupies 

 the valley of the Lagoons on the south side of the island ; it extends 

 from the Bay of Neyba to Port au Prince, and likewise occupies a 

 large portion of the Central Plains in that vicinity. The other, to- 

 wards the north, embraces the valley of the River Yaqui, from Sant- 

 iago to Manchineel Bay, beyond which it may be traced fringing the 

 coast until it approaches Cape Haytien, a distance of above 100 miles. 



This latter basin will be the object of the present remarks. See 

 Map, fig. 1. 



The valley of the Yaqui is bounded on the north by the Cordillera 

 of Monte Christi, and to the south by the Cibao Mountains. The 

 substratum is composed of an unfossiliferous red sandstone, and the 

 entire distance from Santiago to Monte Christi, about eighty miles, 

 may be considered as an inclined plane or continuous sheet of sand- 

 stone. The stratification of this sandstone, although horizontal in 

 some places, is in general very discordant, and often completely 

 broken up by anticlinal axesf. At Ponton the dip is 25°, W. by N. ; 

 at Esperanza, some four miles to the westward, it is 2.5°, S.W. by 

 S. ; near Rompino the dip is 30°, N.N.W. ; and at St. Lorenzo 

 45°, S.S.W. On the heights near Monte Christi, three miles from 

 the Grange Mountain, it is 17°, N.E. by N. ; under the Grange it 

 is 7°, N.W. by N. 



This sandstone protrudes in small irregular hills, scattered over 

 the plain and more or less modified by the effects of denudation ; 

 and, being but scantily covered with alluvium, it forms a very dry 

 barren district. These small elevations, however, give it an undu- 



* For some remarks on the geology of the mountains of San Domingo, see also 

 Schomburgk's Visit to the Valley of Constanza, Athenaeum Journal, No. 1291. 

 p. 797 et seq. 



t It is a question, whether the disjointed state of the sandstone may not have 

 some relation to the influence of those tremendous earthquakes to which this 

 district is subject. 



